Servlet和springMVC
什么是Servlet?
- Servlet是使用Java语言编写的运行在服务器端的程序。狭义的Servlet是指Java语言实现的一个接口，广义的Servlet是指任何实现了这个Servlet接口的类，一般情况下，人们将Servlet理解为后者。Servlet 主要用于处理客户端传来的 HTTP 请求，并返回一个响应，它能够处理的请求有doGet()和doPost()等方法
- Servlet由Servlet容器提供，所谓的Servlet容器是指提供了Servlet 功能的服务器（本书中指Tomcat）,Servlet容器将Servlet动态地加载到服务器上。与HTTP 协议相关的Servlet使用HTTP请求和HTTP响应与客户端进行交互。因此，Servlet容器支持所有HTTP协议的请求和响应。Servlet应用程序的体系结构如图所示。<<javaWeb程序设计教程>>
什么是SpringMVC?
- Spring MVC一开始就定位于一个较为松散的组合，展示给用户的视图（View）、控制器返回的数据模型（Model）、定位视图的视图解析器（ViewResolver）和处理适配器（HandlerAdapter）等内容都是独立的。换句话说，通过Spring MVC很容易把后台的数据转换为各种类型的数据，以满足移动互联网数据多样化的要求。例如，Spring MVC可以十分方便地转换为目前最常用的JSON数据集，也可以转换为PDF、Excel和XML等。加之Spring MVC是基于Spring基础框架派生出来的Web框架，所以它天然就可以十分方便地整合到Spring框架中，而Spring整合Struts2还是比较繁复的.
- mvc架构设计:处理请求先到达控制器（Controller），控制器的作用是进行请求分发，这样它会根据请求的内容去访问模型层（Model）；在现今互联网系统中，数据主要从数据库和NoSQL中来，而且对于数据库而言往往还存在事务的机制，为了适应这样的变化，设计者会把模型层再细分为两层，即服务层（Service）和数据访问层（DAO）；当控制器获取到由模型层返回的数据后，就将数据渲染到视图中，这样就能够展现给用户了
图取自于<<深入浅出springboot2.x>>书籍
思考和疑问
早些年的时候,使用servlet开发web程序, 一般都是继承HttpServlet接口,请求访问时直接根据类名调用.但这样写的结果是,一个类只能处理一个请求.项目结构大概长这样
使用SpringMVC框架后,只需要配置简单的@RequestMapping("")就可以找到对应的方法,原来的servlet呢? 对springMVC的了解还是不够详细,所以
继续探讨以下几个问题
1.SpringMVC如何代替Servlet?
可以看到DispatcherServlet继承自HttpServlet, 前端控制器其实就相当于一个Servlet.
2. SpringMVC的工作流程?
图取自于<<深入浅出springboot2.x>>书籍
基于springboot开发使得SpringMVC的使用更为简便,可以通过Spring Boot的配置来定制这些组件的初始化
/*
* 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 a
* {@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 queryString = request.getQueryString();
String queryClause = (StringUtils.hasLength(queryString) ? "?" + queryString : "");
String dispatchType = (!request.getDispatcherType().equals(DispatcherType.REQUEST) ?
"\"" + request.getDispatcherType().name() + "\" dispatch for " : "");
String message = (dispatchType + request.getMethod() + " \"" + getRequestUri(request) +
queryClause + "\", 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) {
// Exception (if any) is already handled..
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);
}
else 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;
} }DispatcherServlet
@Controller表明这是一个控制器，然后@RequestMapping代表请求路径和控制器（或其方法）的映射关系，它会在Web服务器启动Spring MVC时，就被扫描到HandlerMapping的机制中存储，之后在用户发起请求被DispatcherServlet拦截后，通过URI和其他的条件，通过HandlerMapper机制就能找到对应的控制器（或其方法）进行响应。只是通过HandlerMapping返回的是一个HandlerExecutionChain对象
-
/*
* Copyright 2002-2020 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.util.ArrayList;
import java.util.List; 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.lang.Nullable;
import org.springframework.util.CollectionUtils;
import org.springframework.util.ObjectUtils; /**
* Handler execution chain, consisting of handler object and any handler interceptors.
* Returned by HandlerMapping's {@link HandlerMapping#getHandler} method.
*
* @author Juergen Hoeller
* @since 20.06.2003
* @see HandlerInterceptor
*/
public class HandlerExecutionChain { private static final Log logger = LogFactory.getLog(HandlerExecutionChain.class); private final Object handler; @Nullable
private HandlerInterceptor[] interceptors; @Nullable
private List<HandlerInterceptor> interceptorList; private int interceptorIndex = -1; /**
* Create a new HandlerExecutionChain.
* @param handler the handler object to execute
*/
public HandlerExecutionChain(Object handler) {
this(handler, (HandlerInterceptor[]) null);
} /**
* Create a new HandlerExecutionChain.
* @param handler the handler object to execute
* @param interceptors the array of interceptors to apply
* (in the given order) before the handler itself executes
*/
public HandlerExecutionChain(Object handler, @Nullable HandlerInterceptor... interceptors) {
if (handler instanceof HandlerExecutionChain) {
HandlerExecutionChain originalChain = (HandlerExecutionChain) handler;
this.handler = originalChain.getHandler();
this.interceptorList = new ArrayList<>();
CollectionUtils.mergeArrayIntoCollection(originalChain.getInterceptors(), this.interceptorList);
CollectionUtils.mergeArrayIntoCollection(interceptors, this.interceptorList);
}
else {
this.handler = handler;
this.interceptors = interceptors;
}
} /**
* Return the handler object to execute.
*/
public Object getHandler() {
return this.handler;
} /**
* Add the given interceptor to the end of this chain.
*/
public void addInterceptor(HandlerInterceptor interceptor) {
initInterceptorList().add(interceptor);
} /**
* Add the given interceptor at the specified index of this chain.
* @since 5.2
*/
public void addInterceptor(int index, HandlerInterceptor interceptor) {
initInterceptorList().add(index, interceptor);
} /**
* Add the given interceptors to the end of this chain.
*/
public void addInterceptors(HandlerInterceptor... interceptors) {
if (!ObjectUtils.isEmpty(interceptors)) {
CollectionUtils.mergeArrayIntoCollection(interceptors, initInterceptorList());
}
} private List<HandlerInterceptor> initInterceptorList() {
if (this.interceptorList == null) {
this.interceptorList = new ArrayList<>();
if (this.interceptors != null) {
// An interceptor array specified through the constructor
CollectionUtils.mergeArrayIntoCollection(this.interceptors, this.interceptorList);
}
}
this.interceptors = null;
return this.interceptorList;
} /**
* Return the array of interceptors to apply (in the given order).
* @return the array of HandlerInterceptors instances (may be {@code null})
*/
@Nullable
public HandlerInterceptor[] getInterceptors() {
if (this.interceptors == null && this.interceptorList != null) {
this.interceptors = this.interceptorList.toArray(new HandlerInterceptor[0]);
}
return this.interceptors;
} /**
* Apply preHandle methods of registered interceptors.
* @return {@code true} if the execution chain should proceed with the
* next interceptor or the handler itself. Else, DispatcherServlet assumes
* that this interceptor has already dealt with the response itself.
*/
boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {
HandlerInterceptor[] interceptors = getInterceptors();
if (!ObjectUtils.isEmpty(interceptors)) {
for (int i = 0; i < interceptors.length; i++) {
HandlerInterceptor interceptor = interceptors[i];
if (!interceptor.preHandle(request, response, this.handler)) {
triggerAfterCompletion(request, response, null);
return false;
}
this.interceptorIndex = i;
}
}
return true;
} /**
* Apply postHandle methods of registered interceptors.
*/
void applyPostHandle(HttpServletRequest request, HttpServletResponse response, @Nullable ModelAndView mv)
throws Exception { HandlerInterceptor[] interceptors = getInterceptors();
if (!ObjectUtils.isEmpty(interceptors)) {
for (int i = interceptors.length - 1; i >= 0; i--) {
HandlerInterceptor interceptor = interceptors[i];
interceptor.postHandle(request, response, this.handler, mv);
}
}
} /**
* Trigger afterCompletion callbacks on the mapped HandlerInterceptors.
* Will just invoke afterCompletion for all interceptors whose preHandle invocation
* has successfully completed and returned true.
*/
void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, @Nullable Exception ex)
throws Exception { HandlerInterceptor[] interceptors = getInterceptors();
if (!ObjectUtils.isEmpty(interceptors)) {
for (int i = this.interceptorIndex; i >= 0; i--) {
HandlerInterceptor interceptor = interceptors[i];
try {
interceptor.afterCompletion(request, response, this.handler, ex);
}
catch (Throwable ex2) {
logger.error("HandlerInterceptor.afterCompletion threw exception", ex2);
}
}
}
} /**
* Apply afterConcurrentHandlerStarted callback on mapped AsyncHandlerInterceptors.
*/
void applyAfterConcurrentHandlingStarted(HttpServletRequest request, HttpServletResponse response) {
HandlerInterceptor[] interceptors = getInterceptors();
if (!ObjectUtils.isEmpty(interceptors)) {
for (int i = interceptors.length - 1; i >= 0; i--) {
HandlerInterceptor interceptor = interceptors[i];
if (interceptor instanceof AsyncHandlerInterceptor) {
try {
AsyncHandlerInterceptor asyncInterceptor = (AsyncHandlerInterceptor) interceptor;
asyncInterceptor.afterConcurrentHandlingStarted(request, response, this.handler);
}
catch (Throwable ex) {
if (logger.isErrorEnabled()) {
logger.error("Interceptor [" + interceptor + "] failed in afterConcurrentHandlingStarted", ex);
}
}
}
}
}
} /**
* Delegates to the handler's {@code toString()} implementation.
*/
@Override
public String toString() {
Object handler = getHandler();
StringBuilder sb = new StringBuilder();
sb.append("HandlerExecutionChain with [").append(handler).append("] and ");
if (this.interceptorList != null) {
sb.append(this.interceptorList.size());
}
else if (this.interceptors != null) {
sb.append(this.interceptors.length);
}
else {
sb.append(0);
}
return sb.append(" interceptors").toString();
} }HandlerExecutionChain对象包含一个处理器（handler）。这里的处理器是对控制器（controller）的包装，因为我们的控制器方法可能存在参数，那么处理器就可以读入HTTP和上下文的相关参数，然后再传递给控制器方法。而在控制器执行完成返回后，处理器又可以通过配置信息对控制器的返回结果进行处理。从这段描述中可以看出，处理器包含了控制器方法的逻辑，此外还有处理器的拦截器（interceptor），这样就能够通过拦截处理器进一步地增强处理器的功能。得到了处理器（handler），还需要去运行，但是我们有普通HTTP请求，也有按BeanName的请求，甚至是WebSocket的请求，所以它还需要一个适配器去运行HandlerExecutionChain对象包含的处理器，这就是HandlerAdapter接口定义的实现类。可以看到在Spring MVC中最常用的HandlerAdapter的实现类，这便是HttpRequestHandlerAdapter。通过请求的类型，DispatcherServlet就会找到它来执行Web请求的HandlerExecutionChain对象包含的内容，这样就能够执行我们的处理器（handler）了。只是HandlerAdapter运行HandlerExecutionChain对象这步还比较复杂，我们这里暂时不进行深入讨论，放到后面再谈。在处理器调用控制器时，它首先通过模型层得到数据，再放入数据模型中，最后将返回模型和视图（ModelAndView）对象，这里控制器设置的视图名称设置为“user/details”，这样就走到了视图解析器（ViewResolver），去解析视图逻辑名称了。在代码清单中可以看到视图解析器（ViewResolver）的自动初始化。为了定制InternalResourceViewResolver初始化，可以在配置文件application.properties中进行配置
- 在Spring Boot的机制下定制InternalResourceViewResolver这个视图解析器的初始化，也就是在返回视图名称之后，它会以前缀（prefix）和后缀（suffix）以及视图名称组成全路径定位视图。例如，在控制器中返回的是“user/details”，那么它就会找到/WEB-INF/jsp/user/details.jsp作为视图（View）。严格地说，这一步也不是必需的，因为有些视图并不需要逻辑名称，在不需要的时候，就不再需要视图解析器工作了
- 视图解析器定位到视图后，视图的作用是将数据模型（Model）渲染，这样就能够响应用户的请求。这一步就是视图将数据模型渲染（View）出来，用来展示给用户查看。按照我们控制器的返回，就是/WEB-INF/jsp/user/details.jsp作为我们的视图
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