Spring MVC -- Spring MVC入门
本篇博客首先介绍Spring MVC的优点，然后介绍Spring MVC的基本组件，包括DispatcherServlet，并学习如何开发一个“传统风格”的控制器，这是在Spring 2.5版本之前开发控制器的唯一方式。之所以介绍传统方式，是因为我们可能不得不在基于旧版Spring的遗留代码上工作。对于新的应用，我们可以采用基于注解的控制器。
此外，还会介绍Sping MVC配置，大部分的Spring MVC应用会采用一个XML文档来定义应用中所用到的bean（Spring管理的对象称为bean）。更多Spring MVC配置文件的信息可以参考博客Spring MVC -- Spring框架入门（IoC、DI以及XML配置文件）。
一 Spring MVC的优点
若采用Spring MVC框架开发一个应用程序，我们通常要负责编写一个DispatcherServlet（实际上就是一个Servlet控制器，实现了抽象类HttpServlet）和控制类（注意这里的控制类不是指的Servlet控制器，而是指实现了Controller接口的类，后面会详细介绍）。其中，DispatcherServlet必须能够做一下事情：
- 根据URL调用相应的action；
- 实例化正确的控制器类；
- 根据页面请求参数值来构造表单bean；
- 调用控制器对象的相应方法；
- 转到一个试图（jsp页面）。
幸运的是，Spring MVC是一个包含了DispatcherServlet的MVC框架。它调用控制器方法并转发到视图。使用Spring MVC的第一个好处是，不需要编写DispatcherServlet。以下是Spring MVC具有的能加速开发的功能的列表：
- Spring MVC提供了一个DispatcherServlet，无需额外开发；
- Spring MVC使用了基于XML的配置文件，可以编辑，而无需重新编译应用程序；
- Spring MVC实例化控制器，并根据用户输入来构造bean；
- Spring MVC可以自动绑定用户输入，并正确地转换数据类型。例如，Spring MVC能自动解析字符串，并设置float或decimal类型的属性；
- Spring MVC可以校验用户输入，若校验不通过，则重定向回输入表单。输入校验是可选的，支持编程方式及声明方式。关于这一点，Spring MVC内置了常见的校验器；
- Spring MVC是Spring框架的一部分，可以利用Spring提供的其它能力；
- Spring MVC支持国际化和本地化，支持根据用户区域显示多国语言；
- Spring MVC支持多种视图技术。最常见的jsp技术以及其他技术包括Velocity和FreeMarker。
二 Spring MVC基本组件
1、Spring MVC的DispatcherServlet
在Spring MVC -- MVC设计模式(演示4个基于MVC框架的案例)中我们创建了一个简单的基于MVC框架的Web应用，应用中包括一个充当调度员的控制器(servlet或者是filter)。基于Spring MVC，则无需如此。Spring MVC中自带了一个开箱即用的DispatcherServlet，该servlei全名是org.springframework.web.servlet.DispacterServlet。源码如下，有兴趣可以看一下：
/*
* Copyright 2002-2019 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/ package org.springframework.web.servlet; import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import java.util.stream.Collectors;
import javax.servlet.DispatcherType;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory; import org.springframework.beans.factory.BeanFactoryUtils;
import org.springframework.beans.factory.BeanInitializationException;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.i18n.LocaleContext;
import org.springframework.core.annotation.AnnotationAwareOrderComparator;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.support.PropertiesLoaderUtils;
import org.springframework.core.log.LogFormatUtils;
import org.springframework.http.server.ServletServerHttpRequest;
import org.springframework.lang.Nullable;
import org.springframework.ui.context.ThemeSource;
import org.springframework.util.ClassUtils;
import org.springframework.util.StringUtils;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.request.ServletWebRequest;
import org.springframework.web.context.request.async.WebAsyncManager;
import org.springframework.web.context.request.async.WebAsyncUtils;
import org.springframework.web.multipart.MultipartException;
import org.springframework.web.multipart.MultipartHttpServletRequest;
import org.springframework.web.multipart.MultipartResolver;
import org.springframework.web.util.NestedServletException;
import org.springframework.web.util.WebUtils; /**
* Central dispatcher for HTTP request handlers/controllers, e.g. for web UI controllers
* or HTTP-based remote service exporters. Dispatches to registered handlers for processing
* a web request, providing convenient mapping and exception handling facilities.
*
* <p>This servlet is very flexible: It can be used with just about any workflow, with the
* installation of the appropriate adapter classes. It offers the following functionality
* that distinguishes it from other request-driven web MVC frameworks:
*
* <ul>
* <li>It is based around a JavaBeans configuration mechanism.
*
* <li>It can use any {@link HandlerMapping} implementation - pre-built or provided as part
* of an application - to control the routing of requests to handler objects. Default is
* {@link org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping} and
* {@link org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping}.
* HandlerMapping objects can be defined as beans in the servlet's application context,
* implementing the HandlerMapping interface, overriding the default HandlerMapping if
* present. HandlerMappings can be given any bean name (they are tested by type).
*
* <li>It can use any {@link HandlerAdapter}; this allows for using any handler interface.
* Default adapters are {@link org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter},
* {@link org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter}, for Spring's
* {@link org.springframework.web.HttpRequestHandler} and
* {@link org.springframework.web.servlet.mvc.Controller} interfaces, respectively. A default
* {@link org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter}
* will be registered as well. HandlerAdapter objects can be added as beans in the
* application context, overriding the default HandlerAdapters. Like HandlerMappings,
* HandlerAdapters can be given any bean name (they are tested by type).
*
* <li>The dispatcher's exception resolution strategy can be specified via a
* {@link HandlerExceptionResolver}, for example mapping certain exceptions to error pages.
* Default are
* {@link org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver},
* {@link org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver}, and
* {@link org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver}.
* These HandlerExceptionResolvers can be overridden through the application context.
* HandlerExceptionResolver can be given any bean name (they are tested by type).
*
* <li>Its view resolution strategy can be specified via a {@link ViewResolver}
* implementation, resolving symbolic view names into View objects. Default is
* {@link org.springframework.web.servlet.view.InternalResourceViewResolver}.
* ViewResolver objects can be added as beans in the application context, overriding the
* default ViewResolver. ViewResolvers can be given any bean name (they are tested by type).
*
* <li>If a {@link View} or view name is not supplied by the user, then the configured
* {@link RequestToViewNameTranslator} will translate the current request into a view name.
* The corresponding bean name is "viewNameTranslator"; the default is
* {@link org.springframework.web.servlet.view.DefaultRequestToViewNameTranslator}.
*
* <li>The dispatcher's strategy for resolving multipart requests is determined by a
* {@link org.springframework.web.multipart.MultipartResolver} implementation.
* Implementations for Apache Commons FileUpload and Servlet 3 are included; the typical
* choice is {@link org.springframework.web.multipart.commons.CommonsMultipartResolver}.
* The MultipartResolver bean name is "multipartResolver"; default is none.
*
* <li>Its locale resolution strategy is determined by a {@link LocaleResolver}.
* Out-of-the-box implementations work via HTTP accept header, cookie, or session.
* The LocaleResolver bean name is "localeResolver"; default is
* {@link org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver}.
*
* <li>Its theme resolution strategy is determined by a {@link ThemeResolver}.
* Implementations for a fixed theme and for cookie and session storage are included.
* The ThemeResolver bean name is "themeResolver"; default is
* {@link org.springframework.web.servlet.theme.FixedThemeResolver}.
* </ul>
*
* <p><b>NOTE: The {@code @RequestMapping} annotation will only be processed if a
* corresponding {@code HandlerMapping} (for type-level annotations) and/or
* {@code HandlerAdapter} (for method-level annotations) is present in the dispatcher.</b>
* This is the case by default. However, if you are defining custom {@code HandlerMappings}
* or {@code HandlerAdapters}, then you need to make sure that a corresponding custom
* {@code RequestMappingHandlerMapping} and/or {@code RequestMappingHandlerAdapter}
* is defined as well - provided that you intend to use {@code @RequestMapping}.
*
* <p><b>A web application can define any number of DispatcherServlets.</b>
* Each servlet will operate in its own namespace, loading its own application context
* with mappings, handlers, etc. Only the root application context as loaded by
* {@link org.springframework.web.context.ContextLoaderListener}, if any, will be shared.
*
* <p>As of Spring 3.1, {@code DispatcherServlet} may now be injected with a web
* application context, rather than creating its own internally. This is useful in Servlet
* 3.0+ environments, which support programmatic registration of servlet instances.
* See the {@link #DispatcherServlet(WebApplicationContext)} javadoc for details.
*
* @author Rod Johnson
* @author Juergen Hoeller
* @author Rob Harrop
* @author Chris Beams
* @author Rossen Stoyanchev
* @see org.springframework.web.HttpRequestHandler
* @see org.springframework.web.servlet.mvc.Controller
* @see org.springframework.web.context.ContextLoaderListener
*/
@SuppressWarnings("serial")
public class DispatcherServlet extends FrameworkServlet { /** Well-known name for the MultipartResolver object in the bean factory for this namespace. */
public static final String MULTIPART_RESOLVER_BEAN_NAME = "multipartResolver"; /** Well-known name for the LocaleResolver object in the bean factory for this namespace. */
public static final String LOCALE_RESOLVER_BEAN_NAME = "localeResolver"; /** Well-known name for the ThemeResolver object in the bean factory for this namespace. */
public static final String THEME_RESOLVER_BEAN_NAME = "themeResolver"; /**
* Well-known name for the HandlerMapping object in the bean factory for this namespace.
* Only used when "detectAllHandlerMappings" is turned off.
* @see #setDetectAllHandlerMappings
*/
public static final String HANDLER_MAPPING_BEAN_NAME = "handlerMapping"; /**
* Well-known name for the HandlerAdapter object in the bean factory for this namespace.
* Only used when "detectAllHandlerAdapters" is turned off.
* @see #setDetectAllHandlerAdapters
*/
public static final String HANDLER_ADAPTER_BEAN_NAME = "handlerAdapter"; /**
* Well-known name for the HandlerExceptionResolver object in the bean factory for this namespace.
* Only used when "detectAllHandlerExceptionResolvers" is turned off.
* @see #setDetectAllHandlerExceptionResolvers
*/
public static final String HANDLER_EXCEPTION_RESOLVER_BEAN_NAME = "handlerExceptionResolver"; /**
* Well-known name for the RequestToViewNameTranslator object in the bean factory for this namespace.
*/
public static final String REQUEST_TO_VIEW_NAME_TRANSLATOR_BEAN_NAME = "viewNameTranslator"; /**
* Well-known name for the ViewResolver object in the bean factory for this namespace.
* Only used when "detectAllViewResolvers" is turned off.
* @see #setDetectAllViewResolvers
*/
public static final String VIEW_RESOLVER_BEAN_NAME = "viewResolver"; /**
* Well-known name for the FlashMapManager object in the bean factory for this namespace.
*/
public static final String FLASH_MAP_MANAGER_BEAN_NAME = "flashMapManager"; /**
* Request attribute to hold the current web application context.
* Otherwise only the global web app context is obtainable by tags etc.
* @see org.springframework.web.servlet.support.RequestContextUtils#findWebApplicationContext
*/
public static final String WEB_APPLICATION_CONTEXT_ATTRIBUTE = DispatcherServlet.class.getName() + ".CONTEXT"; /**
* Request attribute to hold the current LocaleResolver, retrievable by views.
* @see org.springframework.web.servlet.support.RequestContextUtils#getLocaleResolver
*/
public static final String LOCALE_RESOLVER_ATTRIBUTE = DispatcherServlet.class.getName() + ".LOCALE_RESOLVER"; /**
* Request attribute to hold the current ThemeResolver, retrievable by views.
* @see org.springframework.web.servlet.support.RequestContextUtils#getThemeResolver
*/
public static final String THEME_RESOLVER_ATTRIBUTE = DispatcherServlet.class.getName() + ".THEME_RESOLVER"; /**
* Request attribute to hold the current ThemeSource, retrievable by views.
* @see org.springframework.web.servlet.support.RequestContextUtils#getThemeSource
*/
public static final String THEME_SOURCE_ATTRIBUTE = DispatcherServlet.class.getName() + ".THEME_SOURCE"; /**
* Name of request attribute that holds a read-only {@code Map<String,?>}
* with "input" flash attributes saved by a previous request, if any.
* @see org.springframework.web.servlet.support.RequestContextUtils#getInputFlashMap(HttpServletRequest)
*/
public static final String INPUT_FLASH_MAP_ATTRIBUTE = DispatcherServlet.class.getName() + ".INPUT_FLASH_MAP"; /**
* Name of request attribute that holds the "output" {@link FlashMap} with
* attributes to save for a subsequent request.
* @see org.springframework.web.servlet.support.RequestContextUtils#getOutputFlashMap(HttpServletRequest)
*/
public static final String OUTPUT_FLASH_MAP_ATTRIBUTE = DispatcherServlet.class.getName() + ".OUTPUT_FLASH_MAP"; /**
* Name of request attribute that holds the {@link FlashMapManager}.
* @see org.springframework.web.servlet.support.RequestContextUtils#getFlashMapManager(HttpServletRequest)
*/
public static final String FLASH_MAP_MANAGER_ATTRIBUTE = DispatcherServlet.class.getName() + ".FLASH_MAP_MANAGER"; /**
* Name of request attribute that exposes an Exception resolved with an
* {@link HandlerExceptionResolver} but where no view was rendered
* (e.g. setting the status code).
*/
public static final String EXCEPTION_ATTRIBUTE = DispatcherServlet.class.getName() + ".EXCEPTION"; /** Log category to use when no mapped handler is found for a request. */
public static final String PAGE_NOT_FOUND_LOG_CATEGORY = "org.springframework.web.servlet.PageNotFound"; /**
* Name of the class path resource (relative to the DispatcherServlet class)
* that defines DispatcherServlet's default strategy names.
*/
private static final String DEFAULT_STRATEGIES_PATH = "DispatcherServlet.properties"; /**
* Common prefix that DispatcherServlet's default strategy attributes start with.
*/
private static final String DEFAULT_STRATEGIES_PREFIX = "org.springframework.web.servlet"; /** Additional logger to use when no mapped handler is found for a request. */
protected static final Log pageNotFoundLogger = LogFactory.getLog(PAGE_NOT_FOUND_LOG_CATEGORY); private static final Properties defaultStrategies; static {
// Load default strategy implementations from properties file.
// This is currently strictly internal and not meant to be customized
// by application developers.
try {
ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, DispatcherServlet.class);
defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);
}
catch (IOException ex) {
throw new IllegalStateException("Could not load '" + DEFAULT_STRATEGIES_PATH + "': " + ex.getMessage());
}
} /** Detect all HandlerMappings or just expect "handlerMapping" bean?. */
private boolean detectAllHandlerMappings = true; /** Detect all HandlerAdapters or just expect "handlerAdapter" bean?. */
private boolean detectAllHandlerAdapters = true; /** Detect all HandlerExceptionResolvers or just expect "handlerExceptionResolver" bean?. */
private boolean detectAllHandlerExceptionResolvers = true; /** Detect all ViewResolvers or just expect "viewResolver" bean?. */
private boolean detectAllViewResolvers = true; /** Throw a NoHandlerFoundException if no Handler was found to process this request? *.*/
private boolean throwExceptionIfNoHandlerFound = false; /** Perform cleanup of request attributes after include request?. */
private boolean cleanupAfterInclude = true; /** MultipartResolver used by this servlet. */
@Nullable
private MultipartResolver multipartResolver; /** LocaleResolver used by this servlet. */
@Nullable
private LocaleResolver localeResolver; /** ThemeResolver used by this servlet. */
@Nullable
private ThemeResolver themeResolver; /** List of HandlerMappings used by this servlet. */
@Nullable
private List<HandlerMapping> handlerMappings; /** List of HandlerAdapters used by this servlet. */
@Nullable
private List<HandlerAdapter> handlerAdapters; /** List of HandlerExceptionResolvers used by this servlet. */
@Nullable
private List<HandlerExceptionResolver> handlerExceptionResolvers; /** RequestToViewNameTranslator used by this servlet. */
@Nullable
private RequestToViewNameTranslator viewNameTranslator; /** FlashMapManager used by this servlet. */
@Nullable
private FlashMapManager flashMapManager; /** List of ViewResolvers used by this servlet. */
@Nullable
private List<ViewResolver> viewResolvers; /**
* Create a new {@code DispatcherServlet} that will create its own internal web
* application context based on defaults and values provided through servlet
* init-params. Typically used in Servlet 2.5 or earlier environments, where the only
* option for servlet registration is through {@code web.xml} which requires the use
* of a no-arg constructor.
* <p>Calling {@link #setContextConfigLocation} (init-param 'contextConfigLocation')
* will dictate which XML files will be loaded by the
* {@linkplain #DEFAULT_CONTEXT_CLASS default XmlWebApplicationContext}
* <p>Calling {@link #setContextClass} (init-param 'contextClass') overrides the
* default {@code XmlWebApplicationContext} and allows for specifying an alternative class,
* such as {@code AnnotationConfigWebApplicationContext}.
* <p>Calling {@link #setContextInitializerClasses} (init-param 'contextInitializerClasses')
* indicates which {@code ApplicationContextInitializer} classes should be used to
* further configure the internal application context prior to refresh().
* @see #DispatcherServlet(WebApplicationContext)
*/
public DispatcherServlet() {
super();
setDispatchOptionsRequest(true);
} /**
* Create a new {@code DispatcherServlet} with the given web application context. This
* constructor is useful in Servlet 3.0+ environments where instance-based registration
* of servlets is possible through the {@link ServletContext#addServlet} API.
* <p>Using this constructor indicates that the following properties / init-params
* will be ignored:
* <ul>
* <li>{@link #setContextClass(Class)} / 'contextClass'</li>
* <li>{@link #setContextConfigLocation(String)} / 'contextConfigLocation'</li>
* <li>{@link #setContextAttribute(String)} / 'contextAttribute'</li>
* <li>{@link #setNamespace(String)} / 'namespace'</li>
* </ul>
* <p>The given web application context may or may not yet be {@linkplain
* ConfigurableApplicationContext#refresh() refreshed}. If it has <strong>not</strong>
* already been refreshed (the recommended approach), then the following will occur:
* <ul>
* <li>If the given context does not already have a {@linkplain
* ConfigurableApplicationContext#setParent parent}, the root application context
* will be set as the parent.</li>
* <li>If the given context has not already been assigned an {@linkplain
* ConfigurableApplicationContext#setId id}, one will be assigned to it</li>
* <li>{@code ServletContext} and {@code ServletConfig} objects will be delegated to
* the application context</li>
* <li>{@link #postProcessWebApplicationContext} will be called</li>
* <li>Any {@code ApplicationContextInitializer}s specified through the
* "contextInitializerClasses" init-param or through the {@link
* #setContextInitializers} property will be applied.</li>
* <li>{@link ConfigurableApplicationContext#refresh refresh()} will be called if the
* context implements {@link ConfigurableApplicationContext}</li>
* </ul>
* If the context has already been refreshed, none of the above will occur, under the
* assumption that the user has performed these actions (or not) per their specific
* needs.
* <p>See {@link org.springframework.web.WebApplicationInitializer} for usage examples.
* @param webApplicationContext the context to use
* @see #initWebApplicationContext
* @see #configureAndRefreshWebApplicationContext
* @see org.springframework.web.WebApplicationInitializer
*/
public DispatcherServlet(WebApplicationContext webApplicationContext) {
super(webApplicationContext);
setDispatchOptionsRequest(true);
} /**
* Set whether to detect all HandlerMapping beans in this servlet's context. Otherwise,
* just a single bean with name "handlerMapping" will be expected.
* <p>Default is "true". Turn this off if you want this servlet to use a single
* HandlerMapping, despite multiple HandlerMapping beans being defined in the context.
*/
public void setDetectAllHandlerMappings(boolean detectAllHandlerMappings) {
this.detectAllHandlerMappings = detectAllHandlerMappings;
} /**
* Set whether to detect all HandlerAdapter beans in this servlet's context. Otherwise,
* just a single bean with name "handlerAdapter" will be expected.
* <p>Default is "true". Turn this off if you want this servlet to use a single
* HandlerAdapter, despite multiple HandlerAdapter beans being defined in the context.
*/
public void setDetectAllHandlerAdapters(boolean detectAllHandlerAdapters) {
this.detectAllHandlerAdapters = detectAllHandlerAdapters;
} /**
* Set whether to detect all HandlerExceptionResolver beans in this servlet's context. Otherwise,
* just a single bean with name "handlerExceptionResolver" will be expected.
* <p>Default is "true". Turn this off if you want this servlet to use a single
* HandlerExceptionResolver, despite multiple HandlerExceptionResolver beans being defined in the context.
*/
public void setDetectAllHandlerExceptionResolvers(boolean detectAllHandlerExceptionResolvers) {
this.detectAllHandlerExceptionResolvers = detectAllHandlerExceptionResolvers;
} /**
* Set whether to detect all ViewResolver beans in this servlet's context. Otherwise,
* just a single bean with name "viewResolver" will be expected.
* <p>Default is "true". Turn this off if you want this servlet to use a single
* ViewResolver, despite multiple ViewResolver beans being defined in the context.
*/
public void setDetectAllViewResolvers(boolean detectAllViewResolvers) {
this.detectAllViewResolvers = detectAllViewResolvers;
} /**
* Set whether to throw a NoHandlerFoundException when no Handler was found for this request.
* This exception can then be caught with a HandlerExceptionResolver or an
* {@code @ExceptionHandler} controller method.
* <p>Note that if {@link org.springframework.web.servlet.resource.DefaultServletHttpRequestHandler}
* is used, then requests will always be forwarded to the default servlet and a
* NoHandlerFoundException would never be thrown in that case.
* <p>Default is "false", meaning the DispatcherServlet sends a NOT_FOUND error through the
* Servlet response.
* @since 4.0
*/
public void setThrowExceptionIfNoHandlerFound(boolean throwExceptionIfNoHandlerFound) {
this.throwExceptionIfNoHandlerFound = throwExceptionIfNoHandlerFound;
} /**
* Set whether to perform cleanup of request attributes after an include request, that is,
* whether to reset the original state of all request attributes after the DispatcherServlet
* has processed within an include request. Otherwise, just the DispatcherServlet's own
* request attributes will be reset, but not model attributes for JSPs or special attributes
* set by views (for example, JSTL's).
* <p>Default is "true", which is strongly recommended. Views should not rely on request attributes
* having been set by (dynamic) includes. This allows JSP views rendered by an included controller
* to use any model attributes, even with the same names as in the main JSP, without causing side
* effects. Only turn this off for special needs, for example to deliberately allow main JSPs to
* access attributes from JSP views rendered by an included controller.
*/
public void setCleanupAfterInclude(boolean cleanupAfterInclude) {
this.cleanupAfterInclude = cleanupAfterInclude;
} /**
* This implementation calls {@link #initStrategies}.
*/
@Override
protected void onRefresh(ApplicationContext context) {
initStrategies(context);
} /**
* Initialize the strategy objects that this servlet uses.
* <p>May be overridden in subclasses in order to initialize further strategy objects.
*/
protected void initStrategies(ApplicationContext context) {
initMultipartResolver(context);
initLocaleResolver(context);
initThemeResolver(context);
initHandlerMappings(context);
initHandlerAdapters(context);
initHandlerExceptionResolvers(context);
initRequestToViewNameTranslator(context);
initViewResolvers(context);
initFlashMapManager(context);
} /**
* Initialize the MultipartResolver used by this class.
* <p>If no bean is defined with the given name in the BeanFactory for this namespace,
* no multipart handling is provided.
*/
private void initMultipartResolver(ApplicationContext context) {
try {
this.multipartResolver = context.getBean(MULTIPART_RESOLVER_BEAN_NAME, MultipartResolver.class);
if (logger.isTraceEnabled()) {
logger.trace("Detected " + this.multipartResolver);
}
else if (logger.isDebugEnabled()) {
logger.debug("Detected " + this.multipartResolver.getClass().getSimpleName());
}
}
catch (NoSuchBeanDefinitionException ex) {
// Default is no multipart resolver.
this.multipartResolver = null;
if (logger.isTraceEnabled()) {
logger.trace("No MultipartResolver '" + MULTIPART_RESOLVER_BEAN_NAME + "' declared");
}
}
} /**
* Initialize the LocaleResolver used by this class.
* <p>If no bean is defined with the given name in the BeanFactory for this namespace,
* we default to AcceptHeaderLocaleResolver.
*/
private void initLocaleResolver(ApplicationContext context) {
try {
this.localeResolver = context.getBean(LOCALE_RESOLVER_BEAN_NAME, LocaleResolver.class);
if (logger.isTraceEnabled()) {
logger.trace("Detected " + this.localeResolver);
}
else if (logger.isDebugEnabled()) {
logger.debug("Detected " + this.localeResolver.getClass().getSimpleName());
}
}
catch (NoSuchBeanDefinitionException ex) {
// We need to use the default.
this.localeResolver = getDefaultStrategy(context, LocaleResolver.class);
if (logger.isTraceEnabled()) {
logger.trace("No LocaleResolver '" + LOCALE_RESOLVER_BEAN_NAME +
"': using default [" + this.localeResolver.getClass().getSimpleName() + "]");
}
}
} /**
* Initialize the ThemeResolver used by this class.
* <p>If no bean is defined with the given name in the BeanFactory for this namespace,
* we default to a FixedThemeResolver.
*/
private void initThemeResolver(ApplicationContext context) {
try {
this.themeResolver = context.getBean(THEME_RESOLVER_BEAN_NAME, ThemeResolver.class);
if (logger.isTraceEnabled()) {
logger.trace("Detected " + this.themeResolver);
}
else if (logger.isDebugEnabled()) {
logger.debug("Detected " + this.themeResolver.getClass().getSimpleName());
}
}
catch (NoSuchBeanDefinitionException ex) {
// We need to use the default.
this.themeResolver = getDefaultStrategy(context, ThemeResolver.class);
if (logger.isTraceEnabled()) {
logger.trace("No ThemeResolver '" + THEME_RESOLVER_BEAN_NAME +
"': using default [" + this.themeResolver.getClass().getSimpleName() + "]");
}
}
} /**
* Initialize the HandlerMappings used by this class.
* <p>If no HandlerMapping beans are defined in the BeanFactory for this namespace,
* we default to BeanNameUrlHandlerMapping.
*/
private void initHandlerMappings(ApplicationContext context) {
this.handlerMappings = null; if (this.detectAllHandlerMappings) {
// Find all HandlerMappings in the ApplicationContext, including ancestor contexts.
Map<String, HandlerMapping> matchingBeans =
BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false);
if (!matchingBeans.isEmpty()) {
this.handlerMappings = new ArrayList<>(matchingBeans.values());
// We keep HandlerMappings in sorted order.
AnnotationAwareOrderComparator.sort(this.handlerMappings);
}
}
else {
try {
HandlerMapping hm = context.getBean(HANDLER_MAPPING_BEAN_NAME, HandlerMapping.class);
this.handlerMappings = Collections.singletonList(hm);
}
catch (NoSuchBeanDefinitionException ex) {
// Ignore, we'll add a default HandlerMapping later.
}
} // Ensure we have at least one HandlerMapping, by registering
// a default HandlerMapping if no other mappings are found.
if (this.handlerMappings == null) {
this.handlerMappings = getDefaultStrategies(context, HandlerMapping.class);
if (logger.isTraceEnabled()) {
logger.trace("No HandlerMappings declared for servlet '" + getServletName() +
"': using default strategies from DispatcherServlet.properties");
}
}
} /**
* Initialize the HandlerAdapters used by this class.
* <p>If no HandlerAdapter beans are defined in the BeanFactory for this namespace,
* we default to SimpleControllerHandlerAdapter.
*/
private void initHandlerAdapters(ApplicationContext context) {
this.handlerAdapters = null; if (this.detectAllHandlerAdapters) {
// Find all HandlerAdapters in the ApplicationContext, including ancestor contexts.
Map<String, HandlerAdapter> matchingBeans =
BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerAdapter.class, true, false);
if (!matchingBeans.isEmpty()) {
this.handlerAdapters = new ArrayList<>(matchingBeans.values());
// We keep HandlerAdapters in sorted order.
AnnotationAwareOrderComparator.sort(this.handlerAdapters);
}
}
else {
try {
HandlerAdapter ha = context.getBean(HANDLER_ADAPTER_BEAN_NAME, HandlerAdapter.class);
this.handlerAdapters = Collections.singletonList(ha);
}
catch (NoSuchBeanDefinitionException ex) {
// Ignore, we'll add a default HandlerAdapter later.
}
} // Ensure we have at least some HandlerAdapters, by registering
// default HandlerAdapters if no other adapters are found.
if (this.handlerAdapters == null) {
this.handlerAdapters = getDefaultStrategies(context, HandlerAdapter.class);
if (logger.isTraceEnabled()) {
logger.trace("No HandlerAdapters declared for servlet '" + getServletName() +
"': using default strategies from DispatcherServlet.properties");
}
}
} /**
* Initialize the HandlerExceptionResolver used by this class.
* <p>If no bean is defined with the given name in the BeanFactory for this namespace,
* we default to no exception resolver.
*/
private void initHandlerExceptionResolvers(ApplicationContext context) {
this.handlerExceptionResolvers = null; if (this.detectAllHandlerExceptionResolvers) {
// Find all HandlerExceptionResolvers in the ApplicationContext, including ancestor contexts.
Map<String, HandlerExceptionResolver> matchingBeans = BeanFactoryUtils
.beansOfTypeIncludingAncestors(context, HandlerExceptionResolver.class, true, false);
if (!matchingBeans.isEmpty()) {
this.handlerExceptionResolvers = new ArrayList<>(matchingBeans.values());
// We keep HandlerExceptionResolvers in sorted order.
AnnotationAwareOrderComparator.sort(this.handlerExceptionResolvers);
}
}
else {
try {
HandlerExceptionResolver her =
context.getBean(HANDLER_EXCEPTION_RESOLVER_BEAN_NAME, HandlerExceptionResolver.class);
this.handlerExceptionResolvers = Collections.singletonList(her);
}
catch (NoSuchBeanDefinitionException ex) {
// Ignore, no HandlerExceptionResolver is fine too.
}
} // Ensure we have at least some HandlerExceptionResolvers, by registering
// default HandlerExceptionResolvers if no other resolvers are found.
if (this.handlerExceptionResolvers == null) {
this.handlerExceptionResolvers = getDefaultStrategies(context, HandlerExceptionResolver.class);
if (logger.isTraceEnabled()) {
logger.trace("No HandlerExceptionResolvers declared in servlet '" + getServletName() +
"': using default strategies from DispatcherServlet.properties");
}
}
} /**
* Initialize the RequestToViewNameTranslator used by this servlet instance.
* <p>If no implementation is configured then we default to DefaultRequestToViewNameTranslator.
*/
private void initRequestToViewNameTranslator(ApplicationContext context) {
try {
this.viewNameTranslator =
context.getBean(REQUEST_TO_VIEW_NAME_TRANSLATOR_BEAN_NAME, RequestToViewNameTranslator.class);
if (logger.isTraceEnabled()) {
logger.trace("Detected " + this.viewNameTranslator.getClass().getSimpleName());
}
else if (logger.isDebugEnabled()) {
logger.debug("Detected " + this.viewNameTranslator);
}
}
catch (NoSuchBeanDefinitionException ex) {
// We need to use the default.
this.viewNameTranslator = getDefaultStrategy(context, RequestToViewNameTranslator.class);
if (logger.isTraceEnabled()) {
logger.trace("No RequestToViewNameTranslator '" + REQUEST_TO_VIEW_NAME_TRANSLATOR_BEAN_NAME +
"': using default [" + this.viewNameTranslator.getClass().getSimpleName() + "]");
}
}
} /**
* Initialize the ViewResolvers used by this class.
* <p>If no ViewResolver beans are defined in the BeanFactory for this
* namespace, we default to InternalResourceViewResolver.
*/
private void initViewResolvers(ApplicationContext context) {
this.viewResolvers = null; if (this.detectAllViewResolvers) {
// Find all ViewResolvers in the ApplicationContext, including ancestor contexts.
Map<String, ViewResolver> matchingBeans =
BeanFactoryUtils.beansOfTypeIncludingAncestors(context, ViewResolver.class, true, false);
if (!matchingBeans.isEmpty()) {
this.viewResolvers = new ArrayList<>(matchingBeans.values());
// We keep ViewResolvers in sorted order.
AnnotationAwareOrderComparator.sort(this.viewResolvers);
}
}
else {
try {
ViewResolver vr = context.getBean(VIEW_RESOLVER_BEAN_NAME, ViewResolver.class);
this.viewResolvers = Collections.singletonList(vr);
}
catch (NoSuchBeanDefinitionException ex) {
// Ignore, we'll add a default ViewResolver later.
}
} // Ensure we have at least one ViewResolver, by registering
// a default ViewResolver if no other resolvers are found.
if (this.viewResolvers == null) {
this.viewResolvers = getDefaultStrategies(context, ViewResolver.class);
if (logger.isTraceEnabled()) {
logger.trace("No ViewResolvers declared for servlet '" + getServletName() +
"': using default strategies from DispatcherServlet.properties");
}
}
} /**
* Initialize the {@link FlashMapManager} used by this servlet instance.
* <p>If no implementation is configured then we default to
* {@code org.springframework.web.servlet.support.DefaultFlashMapManager}.
*/
private void initFlashMapManager(ApplicationContext context) {
try {
this.flashMapManager = context.getBean(FLASH_MAP_MANAGER_BEAN_NAME, FlashMapManager.class);
if (logger.isTraceEnabled()) {
logger.trace("Detected " + this.flashMapManager.getClass().getSimpleName());
}
else if (logger.isDebugEnabled()) {
logger.debug("Detected " + this.flashMapManager);
}
}
catch (NoSuchBeanDefinitionException ex) {
// We need to use the default.
this.flashMapManager = getDefaultStrategy(context, FlashMapManager.class);
if (logger.isTraceEnabled()) {
logger.trace("No FlashMapManager '" + FLASH_MAP_MANAGER_BEAN_NAME +
"': using default [" + this.flashMapManager.getClass().getSimpleName() + "]");
}
}
} /**
* Return this servlet's ThemeSource, if any; else return {@code null}.
* <p>Default is to return the WebApplicationContext as ThemeSource,
* provided that it implements the ThemeSource interface.
* @return the ThemeSource, if any
* @see #getWebApplicationContext()
*/
@Nullable
public final ThemeSource getThemeSource() {
return (getWebApplicationContext() instanceof ThemeSource ? (ThemeSource) getWebApplicationContext() : null);
} /**
* Obtain this servlet's MultipartResolver, if any.
* @return the MultipartResolver used by this servlet, or {@code null} if none
* (indicating that no multipart support is available)
*/
@Nullable
public final MultipartResolver getMultipartResolver() {
return this.multipartResolver;
} /**
* Return the configured {@link HandlerMapping} beans that were detected by
* type in the {@link WebApplicationContext} or initialized based on the
* default set of strategies from {@literal DispatcherServlet.properties}.
* <p><strong>Note:</strong> This method may return {@code null} if invoked
* prior to {@link #onRefresh(ApplicationContext)}.
* @return an immutable list with the configured mappings, or {@code null}
* if not initialized yet
* @since 5.0
*/
@Nullable
public final List<HandlerMapping> getHandlerMappings() {
return (this.handlerMappings != null ? Collections.unmodifiableList(this.handlerMappings) : null);
} /**
* Return the default strategy object for the given strategy interface.
* <p>The default implementation delegates to {@link #getDefaultStrategies},
* expecting a single object in the list.
* @param context the current WebApplicationContext
* @param strategyInterface the strategy interface
* @return the corresponding strategy object
* @see #getDefaultStrategies
*/
protected <T> T getDefaultStrategy(ApplicationContext context, Class<T> strategyInterface) {
List<T> strategies = getDefaultStrategies(context, strategyInterface);
if (strategies.size() != 1) {
throw new BeanInitializationException(
"DispatcherServlet needs exactly 1 strategy for interface [" + strategyInterface.getName() + "]");
}
return strategies.get(0);
} /**
* Create a List of default strategy objects for the given strategy interface.
* <p>The default implementation uses the "DispatcherServlet.properties" file (in the same
* package as the DispatcherServlet class) to determine the class names. It instantiates
* the strategy objects through the context's BeanFactory.
* @param context the current WebApplicationContext
* @param strategyInterface the strategy interface
* @return the List of corresponding strategy objects
*/
@SuppressWarnings("unchecked")
protected <T> List<T> getDefaultStrategies(ApplicationContext context, Class<T> strategyInterface) {
String key = strategyInterface.getName();
String value = defaultStrategies.getProperty(key);
if (value != null) {
String[] classNames = StringUtils.commaDelimitedListToStringArray(value);
List<T> strategies = new ArrayList<>(classNames.length);
for (String className : classNames) {
try {
Class<?> clazz = ClassUtils.forName(className, DispatcherServlet.class.getClassLoader());
Object strategy = createDefaultStrategy(context, clazz);
strategies.add((T) strategy);
}
catch (ClassNotFoundException ex) {
throw new BeanInitializationException(
"Could not find DispatcherServlet's default strategy class [" + className +
"] for interface [" + key + "]", ex);
}
catch (LinkageError err) {
throw new BeanInitializationException(
"Unresolvable class definition for DispatcherServlet's default strategy class [" +
className + "] for interface [" + key + "]", err);
}
}
return strategies;
}
else {
return new LinkedList<>();
}
} /**
* Create a default strategy.
* <p>The default implementation uses
* {@link org.springframework.beans.factory.config.AutowireCapableBeanFactory#createBean}.
* @param context the current WebApplicationContext
* @param clazz the strategy implementation class to instantiate
* @return the fully configured strategy instance
* @see org.springframework.context.ApplicationContext#getAutowireCapableBeanFactory()
* @see org.springframework.beans.factory.config.AutowireCapableBeanFactory#createBean
*/
protected Object createDefaultStrategy(ApplicationContext context, Class<?> clazz) {
return context.getAutowireCapableBeanFactory().createBean(clazz);
} /**
* Exposes the DispatcherServlet-specific request attributes and delegates to {@link #doDispatch}
* for the actual dispatching.
*/
@Override
protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
logRequest(request); // Keep a snapshot of the request attributes in case of an include,
// to be able to restore the original attributes after the include.
Map<String, Object> attributesSnapshot = null;
if (WebUtils.isIncludeRequest(request)) {
attributesSnapshot = new HashMap<>();
Enumeration<?> attrNames = request.getAttributeNames();
while (attrNames.hasMoreElements()) {
String attrName = (String) attrNames.nextElement();
if (this.cleanupAfterInclude || attrName.startsWith(DEFAULT_STRATEGIES_PREFIX)) {
attributesSnapshot.put(attrName, request.getAttribute(attrName));
}
}
} // Make framework objects available to handlers and view objects.
request.setAttribute(WEB_APPLICATION_CONTEXT_ATTRIBUTE, getWebApplicationContext());
request.setAttribute(LOCALE_RESOLVER_ATTRIBUTE, this.localeResolver);
request.setAttribute(THEME_RESOLVER_ATTRIBUTE, this.themeResolver);
request.setAttribute(THEME_SOURCE_ATTRIBUTE, getThemeSource()); if (this.flashMapManager != null) {
FlashMap inputFlashMap = this.flashMapManager.retrieveAndUpdate(request, response);
if (inputFlashMap != null) {
request.setAttribute(INPUT_FLASH_MAP_ATTRIBUTE, Collections.unmodifiableMap(inputFlashMap));
}
request.setAttribute(OUTPUT_FLASH_MAP_ATTRIBUTE, new FlashMap());
request.setAttribute(FLASH_MAP_MANAGER_ATTRIBUTE, this.flashMapManager);
} try {
doDispatch(request, response);
}
finally {
if (!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
// Restore the original attribute snapshot, in case of an include.
if (attributesSnapshot != null) {
restoreAttributesAfterInclude(request, attributesSnapshot);
}
}
}
} private void logRequest(HttpServletRequest request) {
LogFormatUtils.traceDebug(logger, traceOn -> {
String params;
if (isEnableLoggingRequestDetails()) {
params = request.getParameterMap().entrySet().stream()
.map(entry -> entry.getKey() + ":" + Arrays.toString(entry.getValue()))
.collect(Collectors.joining(", "));
}
else {
params = (request.getParameterMap().isEmpty() ? "" : "masked");
} String query = StringUtils.isEmpty(request.getQueryString()) ? "" : "?" + request.getQueryString();
String dispatchType = (!request.getDispatcherType().equals(DispatcherType.REQUEST) ?
"\"" + request.getDispatcherType().name() + "\" dispatch for " : "");
String message = (dispatchType + request.getMethod() + " \"" + getRequestUri(request) +
query + "\", parameters={" + params + "}"); if (traceOn) {
List<String> values = Collections.list(request.getHeaderNames());
String headers = values.size() > 0 ? "masked" : "";
if (isEnableLoggingRequestDetails()) {
headers = values.stream().map(name -> name + ":" + Collections.list(request.getHeaders(name)))
.collect(Collectors.joining(", "));
}
return message + ", headers={" + headers + "} in DispatcherServlet '" + getServletName() + "'";
}
else {
return message;
}
});
} /**
* Process the actual dispatching to the handler.
* <p>The handler will be obtained by applying the servlet's HandlerMappings in order.
* The HandlerAdapter will be obtained by querying the servlet's installed HandlerAdapters
* to find the first that supports the handler class.
* <p>All HTTP methods are handled by this method. It's up to HandlerAdapters or handlers
* themselves to decide which methods are acceptable.
* @param request current HTTP request
* @param response current HTTP response
* @throws Exception in case of any kind of processing failure
*/
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
HttpServletRequest processedRequest = request;
HandlerExecutionChain mappedHandler = null;
boolean multipartRequestParsed = false; WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request); try {
ModelAndView mv = null;
Exception dispatchException = null; try {
processedRequest = checkMultipart(request);
multipartRequestParsed = (processedRequest != request); // Determine handler for the current request.
mappedHandler = getHandler(processedRequest);
if (mappedHandler == null) {
noHandlerFound(processedRequest, response);
return;
} // Determine handler adapter for the current request.
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler()); // Process last-modified header, if supported by the handler.
String method = request.getMethod();
boolean isGet = "GET".equals(method);
if (isGet || "HEAD".equals(method)) {
long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
return;
}
} if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
} // Actually invoke the handler.
mv = ha.handle(processedRequest, response, mappedHandler.getHandler()); if (asyncManager.isConcurrentHandlingStarted()) {
return;
} applyDefaultViewName(processedRequest, mv);
mappedHandler.applyPostHandle(processedRequest, response, mv);
}
catch (Exception ex) {
dispatchException = ex;
}
catch (Throwable err) {
// As of 4.3, we're processing Errors thrown from handler methods as well,
// making them available for @ExceptionHandler methods and other scenarios.
dispatchException = new NestedServletException("Handler dispatch failed", err);
}
processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
}
catch (Exception ex) {
triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
}
catch (Throwable err) {
triggerAfterCompletion(processedRequest, response, mappedHandler,
new NestedServletException("Handler processing failed", err));
}
finally {
if (asyncManager.isConcurrentHandlingStarted()) {
// Instead of postHandle and afterCompletion
if (mappedHandler != null) {
mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
}
}
else {
// Clean up any resources used by a multipart request.
if (multipartRequestParsed) {
cleanupMultipart(processedRequest);
}
}
}
} /**
* Do we need view name translation?
*/
private void applyDefaultViewName(HttpServletRequest request, @Nullable ModelAndView mv) throws Exception {
if (mv != null && !mv.hasView()) {
String defaultViewName = getDefaultViewName(request);
if (defaultViewName != null) {
mv.setViewName(defaultViewName);
}
}
} /**
* Handle the result of handler selection and handler invocation, which is
* either a ModelAndView or an Exception to be resolved to a ModelAndView.
*/
private void processDispatchResult(HttpServletRequest request, HttpServletResponse response,
@Nullable HandlerExecutionChain mappedHandler, @Nullable ModelAndView mv,
@Nullable Exception exception) throws Exception { boolean errorView = false; if (exception != null) {
if (exception instanceof ModelAndViewDefiningException) {
logger.debug("ModelAndViewDefiningException encountered", exception);
mv = ((ModelAndViewDefiningException) exception).getModelAndView();
}
else {
Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null);
mv = processHandlerException(request, response, handler, exception);
errorView = (mv != null);
}
} // Did the handler return a view to render?
if (mv != null && !mv.wasCleared()) {
render(mv, request, response);
if (errorView) {
WebUtils.clearErrorRequestAttributes(request);
}
}
else {
if (logger.isTraceEnabled()) {
logger.trace("No view rendering, null ModelAndView returned.");
}
} if (WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
// Concurrent handling started during a forward
return;
} if (mappedHandler != null) {
mappedHandler.triggerAfterCompletion(request, response, null);
}
} /**
* Build a LocaleContext for the given request, exposing the request's primary locale as current locale.
* <p>The default implementation uses the dispatcher's LocaleResolver to obtain the current locale,
* which might change during a request.
* @param request current HTTP request
* @return the corresponding LocaleContext
*/
@Override
protected LocaleContext buildLocaleContext(final HttpServletRequest request) {
LocaleResolver lr = this.localeResolver;
if (lr instanceof LocaleContextResolver) {
return ((LocaleContextResolver) lr).resolveLocaleContext(request);
}
else {
return () -> (lr != null ? lr.resolveLocale(request) : request.getLocale());
}
} /**
* Convert the request into a multipart request, and make multipart resolver available.
* <p>If no multipart resolver is set, simply use the existing request.
* @param request current HTTP request
* @return the processed request (multipart wrapper if necessary)
* @see MultipartResolver#resolveMultipart
*/
protected HttpServletRequest checkMultipart(HttpServletRequest request) throws MultipartException {
if (this.multipartResolver != null && this.multipartResolver.isMultipart(request)) {
if (WebUtils.getNativeRequest(request, MultipartHttpServletRequest.class) != null) {
if (request.getDispatcherType().equals(DispatcherType.REQUEST)) {
logger.trace("Request already resolved to MultipartHttpServletRequest, e.g. by MultipartFilter");
}
}
else if (hasMultipartException(request)) {
logger.debug("Multipart resolution previously failed for current request - " +
"skipping re-resolution for undisturbed error rendering");
}
else {
try {
return this.multipartResolver.resolveMultipart(request);
}
catch (MultipartException ex) {
if (request.getAttribute(WebUtils.ERROR_EXCEPTION_ATTRIBUTE) != null) {
logger.debug("Multipart resolution failed for error dispatch", ex);
// Keep processing error dispatch with regular request handle below
}
else {
throw ex;
}
}
}
}
// If not returned before: return original request.
return request;
} /**
* Check "javax.servlet.error.exception" attribute for a multipart exception.
*/
private boolean hasMultipartException(HttpServletRequest request) {
Throwable error = (Throwable) request.getAttribute(WebUtils.ERROR_EXCEPTION_ATTRIBUTE);
while (error != null) {
if (error instanceof MultipartException) {
return true;
}
error = error.getCause();
}
return false;
} /**
* Clean up any resources used by the given multipart request (if any).
* @param request current HTTP request
* @see MultipartResolver#cleanupMultipart
*/
protected void cleanupMultipart(HttpServletRequest request) {
if (this.multipartResolver != null) {
MultipartHttpServletRequest multipartRequest =
WebUtils.getNativeRequest(request, MultipartHttpServletRequest.class);
if (multipartRequest != null) {
this.multipartResolver.cleanupMultipart(multipartRequest);
}
}
} /**
* Return the HandlerExecutionChain for this request.
* <p>Tries all handler mappings in order.
* @param request current HTTP request
* @return the HandlerExecutionChain, or {@code null} if no handler could be found
*/
@Nullable
protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
if (this.handlerMappings != null) {
for (HandlerMapping mapping : this.handlerMappings) {
HandlerExecutionChain handler = mapping.getHandler(request);
if (handler != null) {
return handler;
}
}
}
return null;
} /**
* No handler found -> set appropriate HTTP response status.
* @param request current HTTP request
* @param response current HTTP response
* @throws Exception if preparing the response failed
*/
protected void noHandlerFound(HttpServletRequest request, HttpServletResponse response) throws Exception {
if (pageNotFoundLogger.isWarnEnabled()) {
pageNotFoundLogger.warn("No mapping for " + request.getMethod() + " " + getRequestUri(request));
}
if (this.throwExceptionIfNoHandlerFound) {
throw new NoHandlerFoundException(request.getMethod(), getRequestUri(request),
new ServletServerHttpRequest(request).getHeaders());
}
else {
response.sendError(HttpServletResponse.SC_NOT_FOUND);
}
} /**
* Return the HandlerAdapter for this handler object.
* @param handler the handler object to find an adapter for
* @throws ServletException if no HandlerAdapter can be found for the handler. This is a fatal error.
*/
protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException {
if (this.handlerAdapters != null) {
for (HandlerAdapter adapter : this.handlerAdapters) {
if (adapter.supports(handler)) {
return adapter;
}
}
}
throw new ServletException("No adapter for handler [" + handler +
"]: The DispatcherServlet configuration needs to include a HandlerAdapter that supports this handler");
} /**
* Determine an error ModelAndView via the registered HandlerExceptionResolvers.
* @param request current HTTP request
* @param response current HTTP response
* @param handler the executed handler, or {@code null} if none chosen at the time of the exception
* (for example, if multipart resolution failed)
* @param ex the exception that got thrown during handler execution
* @return a corresponding ModelAndView to forward to
* @throws Exception if no error ModelAndView found
*/
@Nullable
protected ModelAndView processHandlerException(HttpServletRequest request, HttpServletResponse response,
@Nullable Object handler, Exception ex) throws Exception { // Success and error responses may use different content types
request.removeAttribute(HandlerMapping.PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE); // Check registered HandlerExceptionResolvers...
ModelAndView exMv = null;
if (this.handlerExceptionResolvers != null) {
for (HandlerExceptionResolver resolver : this.handlerExceptionResolvers) {
exMv = resolver.resolveException(request, response, handler, ex);
if (exMv != null) {
break;
}
}
}
if (exMv != null) {
if (exMv.isEmpty()) {
request.setAttribute(EXCEPTION_ATTRIBUTE, ex);
return null;
}
// We might still need view name translation for a plain error model...
if (!exMv.hasView()) {
String defaultViewName = getDefaultViewName(request);
if (defaultViewName != null) {
exMv.setViewName(defaultViewName);
}
}
if (logger.isTraceEnabled()) {
logger.trace("Using resolved error view: " + exMv, ex);
}
if (logger.isDebugEnabled()) {
logger.debug("Using resolved error view: " + exMv);
}
WebUtils.exposeErrorRequestAttributes(request, ex, getServletName());
return exMv;
} throw ex;
} /**
* Render the given ModelAndView.
* <p>This is the last stage in handling a request. It may involve resolving the view by name.
* @param mv the ModelAndView to render
* @param request current HTTP servlet request
* @param response current HTTP servlet response
* @throws ServletException if view is missing or cannot be resolved
* @throws Exception if there's a problem rendering the view
*/
protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception {
// Determine locale for request and apply it to the response.
Locale locale =
(this.localeResolver != null ? this.localeResolver.resolveLocale(request) : request.getLocale());
response.setLocale(locale); View view;
String viewName = mv.getViewName();
if (viewName != null) {
// We need to resolve the view name.
view = resolveViewName(viewName, mv.getModelInternal(), locale, request);
if (view == null) {
throw new ServletException("Could not resolve view with name '" + mv.getViewName() +
"' in servlet with name '" + getServletName() + "'");
}
}
else {
// No need to lookup: the ModelAndView object contains the actual View object.
view = mv.getView();
if (view == null) {
throw new ServletException("ModelAndView [" + mv + "] neither contains a view name nor a " +
"View object in servlet with name '" + getServletName() + "'");
}
} // Delegate to the View object for rendering.
if (logger.isTraceEnabled()) {
logger.trace("Rendering view [" + view + "] ");
}
try {
if (mv.getStatus() != null) {
response.setStatus(mv.getStatus().value());
}
view.render(mv.getModelInternal(), request, response);
}
catch (Exception ex) {
if (logger.isDebugEnabled()) {
logger.debug("Error rendering view [" + view + "]", ex);
}
throw ex;
}
} /**
* Translate the supplied request into a default view name.
* @param request current HTTP servlet request
* @return the view name (or {@code null} if no default found)
* @throws Exception if view name translation failed
*/
@Nullable
protected String getDefaultViewName(HttpServletRequest request) throws Exception {
return (this.viewNameTranslator != null ? this.viewNameTranslator.getViewName(request) : null);
} /**
* Resolve the given view name into a View object (to be rendered).
* <p>The default implementations asks all ViewResolvers of this dispatcher.
* Can be overridden for custom resolution strategies, potentially based on
* specific model attributes or request parameters.
* @param viewName the name of the view to resolve
* @param model the model to be passed to the view
* @param locale the current locale
* @param request current HTTP servlet request
* @return the View object, or {@code null} if none found
* @throws Exception if the view cannot be resolved
* (typically in case of problems creating an actual View object)
* @see ViewResolver#resolveViewName
*/
@Nullable
protected View resolveViewName(String viewName, @Nullable Map<String, Object> model,
Locale locale, HttpServletRequest request) throws Exception { if (this.viewResolvers != null) {
for (ViewResolver viewResolver : this.viewResolvers) {
View view = viewResolver.resolveViewName(viewName, locale);
if (view != null) {
return view;
}
}
}
return null;
} private void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response,
@Nullable HandlerExecutionChain mappedHandler, Exception ex) throws Exception { if (mappedHandler != null) {
mappedHandler.triggerAfterCompletion(request, response, ex);
}
throw ex;
} /**
* Restore the request attributes after an include.
* @param request current HTTP request
* @param attributesSnapshot the snapshot of the request attributes before the include
*/
@SuppressWarnings("unchecked")
private void restoreAttributesAfterInclude(HttpServletRequest request, Map<?, ?> attributesSnapshot) {
// Need to copy into separate Collection here, to avoid side effects
// on the Enumeration when removing attributes.
Set<String> attrsToCheck = new HashSet<>();
Enumeration<?> attrNames = request.getAttributeNames();
while (attrNames.hasMoreElements()) {
String attrName = (String) attrNames.nextElement();
if (this.cleanupAfterInclude || attrName.startsWith(DEFAULT_STRATEGIES_PREFIX)) {
attrsToCheck.add(attrName);
}
} // Add attributes that may have been removed
attrsToCheck.addAll((Set<String>) attributesSnapshot.keySet()); // Iterate over the attributes to check, restoring the original value
// or removing the attribute, respectively, if appropriate.
for (String attrName : attrsToCheck) {
Object attrValue = attributesSnapshot.get(attrName);
if (attrValue == null) {
request.removeAttribute(attrName);
}
else if (attrValue != request.getAttribute(attrName)) {
request.setAttribute(attrName, attrValue);
}
}
} private static String getRequestUri(HttpServletRequest request) {
String uri = (String) request.getAttribute(WebUtils.INCLUDE_REQUEST_URI_ATTRIBUTE);
if (uri == null) {
uri = request.getRequestURI();
}
return uri;
} }
要使用这个servlet，需要在部署描述符文件(web.xml)中使用servlet和servlet-mapping元素来配置它，如下所示：
<servlet>
<servlet-name>springmvc</servlet-name>
<servlet-class>
org.springframework.web.servlet.DispatcherServlet
</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet> <servlet-mapping>
<servlet-name>springmvc</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
servlet元素内的load-on-startup元素是可选的，如果它存在，则它将在应用程序启动时装载该servlet并调用它的init()方法。若它不存在，则在该servlet第一个请求时加载它。
DispatcherServlet将使用Spring MVC诸多默认的组件。此外，初始化时，它会寻找在应用程序的WEB-INF目录下的一个配置文件，该配置文件的命名规则如下：
servletName-servlet.xml
其中，servletName是部署描述符中的DispatcherServlet的名称（上面配置的 <servlet-name>springmvc</servlet-name>）。如果这个servlet的名称是springmvc，则应在应用程序目录的WEB-INF下对应的文件时springmvc-servlet.xml。
此外，也可以把Spring MVC的配置文件放在应用程序目录中的任何地方，只要告诉DispatcherServlet在哪里可以找到该文件。我们使用servlet声明下的一个init-param元素来做到这一点。init-param元素拥有一个值为contextConfigLocation的param-name元素，其param-value元素则包含配置文件的路径。例如，可以利用init-param元素将默认的文件名和文件路径更改为/WEB-INF/config/simple-config.xml。
<servlet>
<servlet-name>springmvc</servlet-name>
<servlet-class>
org.springframework.web.servlet.DispatcherServlet
</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/config/simple-config.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet> <servlet-mapping>
<servlet-name>springmvc</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
2、Controller接口
在Spring 2.5之前，开发一个控制器的唯一方法是实现org.springframework.web.servlet.mvc.Controller接口。源码如下：
/*
* Copyright 2002-2016 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/ package org.springframework.web.servlet.mvc; import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import org.springframework.lang.Nullable;
import org.springframework.web.servlet.ModelAndView; /**
* Base Controller interface, representing a component that receives
* {@code HttpServletRequest} and {@code HttpServletResponse}
* instances just like a {@code HttpServlet} but is able to
* participate in an MVC workflow. Controllers are comparable to the
* notion of a Struts {@code Action}.
*
* <p>Any implementation of the Controller interface should be a
* <i>reusable, thread-safe</i> class, capable of handling multiple
* HTTP requests throughout the lifecycle of an application. To be able to
* configure a Controller easily, Controller implementations are encouraged
* to be (and usually are) JavaBeans.
*
* <h3><a name="workflow">Workflow</a></h3>
*
* <p>After a {@code DispatcherServlet} has received a request and has
* done its work to resolve locales, themes, and suchlike, it then tries
* to resolve a Controller, using a
* {@link org.springframework.web.servlet.HandlerMapping HandlerMapping}.
* When a Controller has been found to handle the request, the
* {@link #handleRequest(HttpServletRequest, HttpServletResponse) handleRequest}
* method of the located Controller will be invoked; the located Controller
* is then responsible for handling the actual request and — if applicable
* — returning an appropriate
* {@link org.springframework.web.servlet.ModelAndView ModelAndView}.
* So actually, this method is the main entry point for the
* {@link org.springframework.web.servlet.DispatcherServlet DispatcherServlet}
* which delegates requests to controllers.
*
* <p>So basically any <i>direct</i> implementation of the {@code Controller} interface
* just handles HttpServletRequests and should return a ModelAndView, to be further
* interpreted by the DispatcherServlet. Any additional functionality such as
* optional validation, form handling, etc. should be obtained through extending
* {@link org.springframework.web.servlet.mvc.AbstractController AbstractController}
* or one of its subclasses.
*
* <h3>Notes on design and testing</h3>
*
* <p>The Controller interface is explicitly designed to operate on HttpServletRequest
* and HttpServletResponse objects, just like an HttpServlet. It does not aim to
* decouple itself from the Servlet API, in contrast to, for example, WebWork, JSF or Tapestry.
* Instead, the full power of the Servlet API is available, allowing Controllers to be
* general-purpose: a Controller is able to not only handle web user interface
* requests but also to process remoting protocols or to generate reports on demand.
*
* <p>Controllers can easily be tested by passing in mock objects for the
* HttpServletRequest and HttpServletResponse objects as parameters to the
* {@link #handleRequest(HttpServletRequest, HttpServletResponse) handleRequest}
* method. As a convenience, Spring ships with a set of Servlet API mocks
* that are suitable for testing any kind of web components, but are particularly
* suitable for testing Spring web controllers. In contrast to a Struts Action,
* there is no need to mock the ActionServlet or any other infrastructure;
* mocking HttpServletRequest and HttpServletResponse is sufficient.
*
* <p>If Controllers need to be aware of specific environment references, they can
* choose to implement specific awareness interfaces, just like any other bean in a
* Spring (web) application context can do, for example:
* <ul>
* <li>{@code org.springframework.context.ApplicationContextAware}</li>
* <li>{@code org.springframework.context.ResourceLoaderAware}</li>
* <li>{@code org.springframework.web.context.ServletContextAware}</li>
* </ul>
*
* <p>Such environment references can easily be passed in testing environments,
* through the corresponding setters defined in the respective awareness interfaces.
* In general, it is recommended to keep the dependencies as minimal as possible:
* for example, if all you need is resource loading, implement ResourceLoaderAware only.
* Alternatively, derive from the WebApplicationObjectSupport base class, which gives
* you all those references through convenient accessors but requires an
* ApplicationContext reference on initialization.
*
* <p>Controllers can optionally implement the {@link LastModified} interface.
*
* @author Rod Johnson
* @author Juergen Hoeller
* @see LastModified
* @see SimpleControllerHandlerAdapter
* @see AbstractController
* @see org.springframework.mock.web.MockHttpServletRequest
* @see org.springframework.mock.web.MockHttpServletResponse
* @see org.springframework.context.ApplicationContextAware
* @see org.springframework.context.ResourceLoaderAware
* @see org.springframework.web.context.ServletContextAware
* @see org.springframework.web.context.support.WebApplicationObjectSupport
*/
@FunctionalInterface
public interface Controller { /**
* Process the request and return a ModelAndView object which the DispatcherServlet
* will render. A {@code null} return value is not an error: it indicates that
* this object completed request processing itself and that there is therefore no
* ModelAndView to render.
* @param request current HTTP request
* @param response current HTTP response
* @return a ModelAndView to render, or {@code null} if handled directly
* @throws Exception in case of errors
*/
@Nullable
ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception; }
这个接口公开了一个handleRequest()方法，下面是该方法的签名：
ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception;
其实现类可以访问对应请求的HttpServletRequest 和HttpServletResponse 还必须返回一个ModelAndView 对象，它包含视图路径或视图路径和模型。
Controller接口的实现类只能处理一个单一动作(action)，而一个基于注解的控制器可以同时支持多个请求处理动作，并且无需实现任何接口（下一篇博客会介绍）。
三 第一个Spring MVC应用
本节的示例应用程序springmvc-intro1展示了基本的Spring MVC应用。该应用程序和Spring MVC -- MVC设计模式(演示4个基于MVC框架的案例)中的appdesign1应用非常相似，专用于展示Spring MVC是如何工作的。springmvc-intro1包含两个控制器类，类似于appdesign1中的控制器类。
1、目录结构
目录结构如下：
注意：WEB-INF/lib目录包含了Spring MVC所需要的所有jar文件。特别需要注意的是spring-webmvc-5.1.6.RELEASE.jar包含了DispacterServlet类。还要注意Spring MVC依赖于Apache Commons Logging组件，没有它，Spring MVC应用程序就无法正常工作。这些jar包的下载可以参考博客Spring MVC -- Spring框架入门（IoC、DI以及XML配置文件）。
该示例应用的所有jsp页面都存放在/WEB-INF/jsp目录下，这样就可以避免直接通过浏览器访问，但是控制器仍然可以转发请求到这些页面。
2、部署描述符(web.xml文件)和Spring MVC配置文件
部署描述符(web.xml文件)：
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.1"
xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd">
<servlet>
<servlet-name>springmvc</servlet-name>
<servlet-class>
org.springframework.web.servlet.DispatcherServlet
</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet> <servlet-mapping>
<servlet-name>springmvc</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping> </web-app>
这里告诉了Servlet/JSP容器，我们将使用Spring MVC的DispatcherServlet，并通过url-pattern元素值配置为“/”，将所有的URL映射到该servlet。由于servlet元素下没有init-param元素，所以Spring MVC的配置文件在/WEB-INF文件夹下，并按照通常的命名约定：
Spring MVC配置文件(springmvc-servlet.xml)：
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd"> <bean name="/input-product" class="controller.InputProductController"/>
<bean name="/save-product" class="controller.SaveProductController"/> </beans>
这里声明了InputProductController和SaveProductController两个控制器，并分别映射到/input-product和/save-product。
3、Controller类
springmvc-intro1应用程序有InputProductController和SaveProductController这两个控制器，分别实现了Controller接口。
InputProductController类：
package controller; import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.Controller; public class InputProductController implements Controller { private static final Log logger = LogFactory
.getLog(InputProductController.class); @Override
public ModelAndView handleRequest(HttpServletRequest request,
HttpServletResponse response) throws Exception {
logger.info("InputProductController called");
return new ModelAndView("/WEB-INF/jsp/ProductForm.jsp");
} }
InputProductController类的handleRequest()方法只是返回一个ModelAndView ，包含一个视图，但没有模型。因此，该请求将被转发到/WEB-INF/jsp/ProductForm.jsp页面。
SaveProductController类：
package controller; import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.Controller; import domain.Product;
import form.ProductForm; public class SaveProductController implements Controller { private static final Log logger = LogFactory
.getLog(SaveProductController.class); @Override
public ModelAndView handleRequest(HttpServletRequest request,
HttpServletResponse response) throws Exception {
logger.info("SaveProductController called");
//创建表单类 保存表单提交的信息
ProductForm productForm = new ProductForm();
// populate action properties
productForm.setName(request.getParameter("name"));
productForm.setDescription(request.getParameter("description"));
productForm.setPrice(request.getParameter("price")); // create model 创建Product模型对象
Product product = new Product();
product.setName(productForm.getName());
product.setDescription(productForm.getDescription());
try {
product.setPrice(Float.parseFloat(productForm.getPrice()));
} catch (NumberFormatException e) {
} // insert code to save Product return new ModelAndView("/WEB-INF/jsp/ProductDetails.jsp", "product",
product);
} }
SaveProductController类的handleRequest()方法中，首先用请求参数创建一个ProductForm对象，然后它根据ProductForm对象创建Product对象。由于ProductForm的price属性是一个字符串，而其在Product类对应的是一个float，此处类型转换是必要的。
SaveProductController类的handleRequest()方法最后返回的ModelAndView模型包含了视图的路径、模型名称以及模型（Product对象）。该模型将提供给目标视图，用于界面显示。
其中ProductForm类如下：
package form;
public class ProductForm {
private String name;
private String description;
private String price;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public String getPrice() {
return price;
}
public void setPrice(String price) {
this.price = price;
}
}
Product类如下：
package domain;
import java.io.Serializable; public class Product implements Serializable {
private static final long serialVersionUID = 748392348L;
private String name;
private String description;
private float price; public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public float getPrice() {
return price;
}
public void setPrice(float price) {
this.price = price;
}
}
4、视图
springmvc-intro1应用程序包含两个jsp页面：ProductForm.jsp页面和ProductDetails页面：
ProductForm.jsp：
<!DOCTYPE html>
<html>
<head>
<title>Add Product Form</title>
<style type="text/css">@import url(css/main.css);</style>
</head>
<body> <div id="global">
<form action="save-product" method="post">
<fieldset>
<legend>Add a product</legend>
<p>
<label for="name">Product Name: </label>
<input type="text" id="name" name="name"
tabindex="1">
</p>
<p>
<label for="description">Description: </label>
<input type="text" id="description"
name="description" tabindex="2">
</p>
<p>
<label for="price">Price: </label>
<input type="text" id="price" name="price"
tabindex="3">
</p>
<p id="buttons">
<input id="reset" type="reset" tabindex="4">
<input id="submit" type="submit" tabindex="5"
value="Add Product">
</p>
</fieldset>
</form>
</div>
</body>
</html>
ProductDetails.jsp：
<!DOCTYPE html>
<html>
<head>
<title>Save Product</title>
<style type="text/css">@import url(css/main.css);</style>
</head>
<body>
<div id="global">
<h4>The product has been saved.</h4>
<p>
<h5>Details:</h5>
Product Name: ${product.name}<br/>
Description: ${product.description}<br/>
Price: $${product.price}
</p>
</div>
</body>
</html>
ProductDetails页面通过EL表达式语言访问product对象的各种属性。
main.css：
#global {
text-align: left;
border: 1px solid #dedede;
background: #efefef;
width: 560px;
padding: 20px;
margin: 100px auto;
}
form {
font:100% verdana;
min-width: 500px;
max-width: 600px;
width: 560px;
}
form fieldset {
border-color: #bdbebf;
border-width: 3px;
margin:;
}
legend {
font-size: 1.3em;
}
form label {
width: 250px;
display: block;
float: left;
text-align: right;
padding: 2px;
}
#buttons {
text-align: right;
}
#errors, li {
color: red;
}
5、测试应用
将项目部署到tomcat服务器，然后启动服务器，假设示例应用运行在本机的8000端口上，则可以通过如下URL访问应用：
http://localhost:8008/springmvc-intro1/input-product
会看到如下产品表单页面：
在表单中输入相应的值后单击Add Product按钮，会在下一页中看到产品属性：
注意：price应该输入一个合法数字，不然就会设置为float型默认值0.0。
四 视图解析器
Spring MVC中的视图解析器复制解析视图。可以通过在XML配置文件中定义一个ViewResolver来配置视图解析器，如下：
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd"> <bean name="/input-product" class="controller.InputProductController"/>
<bean name="/save-product" class="controller.SaveProductController"/>
<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/WEB-INF/jsp/"/>
<property name="suffix" value=".jsp"/>
</bean>
</beans>
视图解析器配置有前缀和后缀两个属性。这样一来，view路径将缩短。例如：仅需提供“myPage”，而不必再将视图路径设置为/WEB-INF/jsp/myPage.jsp，视图解析器将会自动增加前缀和后缀。
以springmvc-intro2应用为例，该例子和springmvc-intro1应用类似，只是调整了配置文件的名称和路径。此外，它还配置了默认的视图解析器，为所有视图路径增加前缀和后缀：
我们可以看一下InputProductController的代码：
package controller; import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.Controller; public class InputProductController implements Controller { private static final Log logger = LogFactory.getLog(InputProductController.class); @Override
public ModelAndView handleRequest(HttpServletRequest request,
HttpServletResponse response) throws Exception {
logger.info("InputProductController called");
return new ModelAndView("ProductForm");
} }
我们可以看到返回的视图名由springmvc-intro1中的/WEB-INF/jsp/ProductForm.jsp变成了ProductForm。
此外，在springmvc-intro2中，Spring MVC配置文件springmvc-config.xml被移动到/WEB-INF/config目录下。为了让Spring MVC可以正确加载到该配置文件，需要将文件路径配置到Spring MVC的DispatcherServlet。springmvc-intro2的web.xml配置文件如下：
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.1"
xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd">
<servlet>
<servlet-name>springmvc</servlet-name>
<servlet-class>
org.springframework.web.servlet.DispatcherServlet
</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/config/springmvc-config.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet> <servlet-mapping>
<servlet-name>springmvc</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>
需要特别注意的是web.xml文件中的init-param元素。如果要使用非默认配置文件的命名和路径，需要使用名为contextConfigLocation的init-param，其值应为配置文件在应用中的相对路径。
五 总结
下面我们来总结一下使用Spring MVC框架的Web应用，用户通过浏览器请求服务器的响应流程，我们以URL：http://localhost:8008/springmvc-intro1/input-product为例：
- 请求首先被应用程序的web.xml文件拦截，通过url-pattern元素值配置为“/”，将所有的URL映射到Spring MVC的DispatcherServlet；
<servlet>
<servlet-name>springmvc</servlet-name>
<servlet-class>
org.springframework.web.servlet.DispatcherServlet
</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet> <servlet-mapping>
<servlet-name>springmvc</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
- DispatcherServlet在第一次加载时会调用init()方法进行初始化，会寻找Spring MVC配置文件；
- 通过配置文件中的bean元素，将URL映射到控制器类；
<bean name="/input-product" class="controller.InputProductController"/>
- 执行控制器的handleRequest方法，并返回一个ModelAndView。
public ModelAndView handleRequest(HttpServletRequest request,
HttpServletResponse response) throws Exception {
logger.info("InputProductController called");
return new ModelAndView("/WEB-INF/jsp/ProductForm.jsp");
}
本篇博客是Spring MVC的入门介绍，我们学习了一个简单的Spring MVC应用。在Srping MVC中，我们无需编写自己的DispatcherServlet，并通过实现控制器接口来编写控制器，这是传统风格的控制器。从Spring 2.5版本开始，Spring提供了一个更好的开发控制器的方式，如采用注解。下一篇博客将会详细介绍。
参考文章
[1]Spring MVC学习指南
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