Spring Boot探究之旅--启动分析
刚接触SpringBoot，感觉挺方便的，不用配置那么多乱七八糟的配置，很方便！酒饱思淫欲，得陇望蜀一下，看看SpringBoot到底怎么做到这么方便的。
首先呢，先来看个SpringBoot的hello world：
项目文件结构如下：
POM.xml如下：
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion> <groupId>com.jdktomcat</groupId>
<artifactId>spring-boot-hello</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging> <name>spring-boot-hello</name>
<description>Demo project for Spring Boot</description> <parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.3.7.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent> <properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties> <dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency> <dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies> <build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build> </project>
程序主入口类：
package com.jdktomcat; import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication; /**
* 测试
*
* @author Administrator
*/
@SpringBootApplication
public class HelloApplication { public static void main(String[] args) {
SpringApplication.run(HelloApplication.class, args);
}
}
控制器类：
package com.jdktomcat.web; import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController; /**
* 测试控制器
*
* @author Administrator
*/
@RestController
public class HelloController { @RequestMapping("/hello")
public String index(@RequestParam(value = "id", required = true) Integer id) {
return "Hello World " + id;
} }
控制器测试类：
package com.jdktomcat; import com.jdktomcat.web.HelloController;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.SpringApplicationConfiguration;
import org.springframework.http.MediaType;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.web.WebAppConfiguration;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.test.web.servlet.request.MockMvcRequestBuilders;
import org.springframework.test.web.servlet.setup.MockMvcBuilders;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap; import static org.hamcrest.CoreMatchers.equalTo;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status; @RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = HelloApplication.class)
@WebAppConfiguration
public class HelloApplicationTests { private MockMvc mvc; @Before
public void setUp() {
mvc = MockMvcBuilders.standaloneSetup(new HelloController()).build();
} @Test
public void hello() throws Exception {
MultiValueMap<String, String> params = new LinkedMultiValueMap();
params.set("id", "45");
mvc.perform(MockMvcRequestBuilders.get("/hello")
.params(params)
.accept(MediaType.APPLICATION_JSON))
.andExpect(status().isOk())
.andExpect(content().string(equalTo("Hello World 45")));
} }
环境配置文件：
###application.properties#####
spring.application.name=hello
server.port=8885
spring.profiles.active=dev info.app.name=spring-boot-hello
info.app.version=v1.0.0 #endpoints.info.enabled=false
####application-dev.properties#####
server.port=8881
####application-prod.properties#####
server.port=8882
####application-test.properties#####
server.port=8883
然后跑起来看看效果：
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v1.3.7.RELEASE) 2018-07-18 15:21:42.588 INFO 3552 --- [ main] com.jdktomcat.HelloApplication : Starting HelloApplication on DESKTOP-01R8JI0 with PID 3552 (D:\workspace\github\spring-cloud-in-action\spring-boot-hello\target\classes started by Administrator in D:\workspace\github\spring-cloud-in-action)
2018-07-18 15:21:42.591 INFO 3552 --- [ main] com.jdktomcat.HelloApplication : The following profiles are active: dev
2018-07-18 15:21:42.638 INFO 3552 --- [ main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@76494737: startup date [Wed Jul 18 15:21:42 CST 2018]; root of context hierarchy
2018-07-18 15:21:44.021 INFO 3552 --- [ main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with port(s): 8881 (http)
2018-07-18 15:21:44.031 INFO 3552 --- [ main] o.apache.catalina.core.StandardService : Starting service Tomcat
2018-07-18 15:21:44.032 INFO 3552 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet Engine: Apache Tomcat/8.0.36
2018-07-18 15:21:44.116 INFO 3552 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2018-07-18 15:21:44.117 INFO 3552 --- [ost-startStop-1] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 1482 ms
2018-07-18 15:21:44.435 INFO 3552 --- [ost-startStop-1] o.s.b.c.e.ServletRegistrationBean : Mapping servlet: 'dispatcherServlet' to [/]
2018-07-18 15:21:44.438 INFO 3552 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'metricFilter' to: [/*]
2018-07-18 15:21:44.439 INFO 3552 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'characterEncodingFilter' to: [/*]
2018-07-18 15:21:44.439 INFO 3552 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
2018-07-18 15:21:44.439 INFO 3552 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'httpPutFormContentFilter' to: [/*]
2018-07-18 15:21:44.439 INFO 3552 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'requestContextFilter' to: [/*]
2018-07-18 15:21:44.439 INFO 3552 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'webRequestLoggingFilter' to: [/*]
2018-07-18 15:21:44.439 INFO 3552 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'applicationContextIdFilter' to: [/*]
2018-07-18 15:21:44.606 INFO 3552 --- [ main] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@76494737: startup date [Wed Jul 18 15:21:42 CST 2018]; root of context hierarchy
2018-07-18 15:21:44.666 INFO 3552 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/hello]}" onto public java.lang.String com.jdktomcat.web.HelloController.index(java.lang.Integer)
2018-07-18 15:21:44.668 INFO 3552 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error]}" onto public org.springframework.http.ResponseEntity<java.util.Map<java.lang.String, java.lang.Object>> org.springframework.boot.autoconfigure.web.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
2018-07-18 15:21:44.668 INFO 3552 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],produces=[text/html]}" onto public org.springframework.web.servlet.ModelAndView org.springframework.boot.autoconfigure.web.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)
2018-07-18 15:21:44.695 INFO 3552 --- [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2018-07-18 15:21:44.695 INFO 3552 --- [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2018-07-18 15:21:44.728 INFO 3552 --- [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2018-07-18 15:21:45.003 INFO 3552 --- [ main] o.s.b.a.e.mvc.EndpointHandlerMapping : Mapped "{[/env/{name:.*}],methods=[GET],produces=[application/json]}" onto public java.lang.Object org.springframework.boot.actuate.endpoint.mvc.EnvironmentMvcEndpoint.value(java.lang.String)
2018-07-18 15:21:45.003 INFO 3552 --- [ main] o.s.b.a.e.mvc.EndpointHandlerMapping : Mapped "{[/env || /env.json],methods=[GET],produces=[application/json]}" onto public java.lang.Object org.springframework.boot.actuate.endpoint.mvc.EndpointMvcAdapter.invoke()
2018-07-18 15:21:45.003 INFO 3552 --- [ main] o.s.b.a.e.mvc.EndpointHandlerMapping : Mapped "{[/autoconfig || /autoconfig.json],methods=[GET],produces=[application/json]}" onto public java.lang.Object org.springframework.boot.actuate.endpoint.mvc.EndpointMvcAdapter.invoke()
2018-07-18 15:21:45.004 INFO 3552 --- [ main] o.s.b.a.e.mvc.EndpointHandlerMapping : Mapped "{[/mappings || /mappings.json],methods=[GET],produces=[application/json]}" onto public java.lang.Object org.springframework.boot.actuate.endpoint.mvc.EndpointMvcAdapter.invoke()
2018-07-18 15:21:45.004 INFO 3552 --- [ main] o.s.b.a.e.mvc.EndpointHandlerMapping : Mapped "{[/info || /info.json],methods=[GET],produces=[application/json]}" onto public java.lang.Object org.springframework.boot.actuate.endpoint.mvc.EndpointMvcAdapter.invoke()
2018-07-18 15:21:45.007 INFO 3552 --- [ main] o.s.b.a.e.mvc.EndpointHandlerMapping : Mapped "{[/dump || /dump.json],methods=[GET],produces=[application/json]}" onto public java.lang.Object org.springframework.boot.actuate.endpoint.mvc.EndpointMvcAdapter.invoke()
2018-07-18 15:21:45.007 INFO 3552 --- [ main] o.s.b.a.e.mvc.EndpointHandlerMapping : Mapped "{[/trace || /trace.json],methods=[GET],produces=[application/json]}" onto public java.lang.Object org.springframework.boot.actuate.endpoint.mvc.EndpointMvcAdapter.invoke()
2018-07-18 15:21:45.008 INFO 3552 --- [ main] o.s.b.a.e.mvc.EndpointHandlerMapping : Mapped "{[/health || /health.json],produces=[application/json]}" onto public java.lang.Object org.springframework.boot.actuate.endpoint.mvc.HealthMvcEndpoint.invoke(java.security.Principal)
2018-07-18 15:21:45.008 INFO 3552 --- [ main] o.s.b.a.e.mvc.EndpointHandlerMapping : Mapped "{[/metrics/{name:.*}],methods=[GET],produces=[application/json]}" onto public java.lang.Object org.springframework.boot.actuate.endpoint.mvc.MetricsMvcEndpoint.value(java.lang.String)
2018-07-18 15:21:45.008 INFO 3552 --- [ main] o.s.b.a.e.mvc.EndpointHandlerMapping : Mapped "{[/metrics || /metrics.json],methods=[GET],produces=[application/json]}" onto public java.lang.Object org.springframework.boot.actuate.endpoint.mvc.EndpointMvcAdapter.invoke()
2018-07-18 15:21:45.009 INFO 3552 --- [ main] o.s.b.a.e.mvc.EndpointHandlerMapping : Mapped "{[/configprops || /configprops.json],methods=[GET],produces=[application/json]}" onto public java.lang.Object org.springframework.boot.actuate.endpoint.mvc.EndpointMvcAdapter.invoke()
2018-07-18 15:21:45.009 INFO 3552 --- [ main] o.s.b.a.e.mvc.EndpointHandlerMapping : Mapped "{[/beans || /beans.json],methods=[GET],produces=[application/json]}" onto public java.lang.Object org.springframework.boot.actuate.endpoint.mvc.EndpointMvcAdapter.invoke()
2018-07-18 15:21:45.151 INFO 3552 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Registering beans for JMX exposure on startup
2018-07-18 15:21:45.159 INFO 3552 --- [ main] o.s.c.support.DefaultLifecycleProcessor : Starting beans in phase 0
2018-07-18 15:21:45.278 INFO 3552 --- [ main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8881 (http)
2018-07-18 15:21:45.283 INFO 3552 --- [ main] com.jdktomcat.HelloApplication : Started HelloApplication in 3.342 seconds (JVM running for 4.37)
首先简单分析一下启动日志：
首先会启动一个java进程，然后根据配置进行加载资源。接着初始化启动另外一个单独线程完成根web服务上下文初始化，并初始化对应的filter过滤器。
在主线程中，加载各种组件完成整个上下文初始化。和Spring正常启动类似。
接着看一下其内部实现方式是什么样子的：
追踪程序主入口类执行过程：（SpringApplication）
/**
* Run the Spring application, creating and refreshing a new
* {@link ApplicationContext}.
* @param args the application arguments (usually passed from a Java main method)
* @return a running {@link ApplicationContext}
*/
public ConfigurableApplicationContext run(String... args) {
StopWatch stopWatch = new StopWatch();
stopWatch.start();
ConfigurableApplicationContext context = null;
configureHeadlessProperty();
SpringApplicationRunListeners listeners = getRunListeners(args);
listeners.started();
try {
ApplicationArguments applicationArguments = new DefaultApplicationArguments(
args);
context = createAndRefreshContext(listeners, applicationArguments);
afterRefresh(context, applicationArguments);
listeners.finished(context, null);
stopWatch.stop();
if (this.logStartupInfo) {
new StartupInfoLogger(this.mainApplicationClass)
.logStarted(getApplicationLog(), stopWatch);
}
return context;
}
catch (Throwable ex) {
handleRunFailure(context, listeners, ex);
throw new IllegalStateException(ex);
}
}
其中代码中最重要的是context = createAndRefreshContext(listeners, applicationArguments);这个是创建并刷新上下文，与Spring核心相类似。接着进去看一下该方法的实现有何不同。
private ConfigurableApplicationContext createAndRefreshContext(
SpringApplicationRunListeners listeners,
ApplicationArguments applicationArguments) {
ConfigurableApplicationContext context;
// Create and configure the environment
ConfigurableEnvironment environment = getOrCreateEnvironment();
configureEnvironment(environment, applicationArguments.getSourceArgs());
listeners.environmentPrepared(environment);
if (isWebEnvironment(environment) && !this.webEnvironment) {
environment = convertToStandardEnvironment(environment);
} if (this.bannerMode != Banner.Mode.OFF) {
printBanner(environment);
} // Create, load, refresh and run the ApplicationContext
context = createApplicationContext();
context.setEnvironment(environment);
postProcessApplicationContext(context);
applyInitializers(context);
listeners.contextPrepared(context);
if (this.logStartupInfo) {
logStartupInfo(context.getParent() == null);
logStartupProfileInfo(context);
} // Add boot specific singleton beans
context.getBeanFactory().registerSingleton("springApplicationArguments",
applicationArguments); // Load the sources
Set<Object> sources = getSources();
Assert.notEmpty(sources, "Sources must not be empty");
load(context, sources.toArray(new Object[sources.size()]));
listeners.contextLoaded(context); // Refresh the context
refresh(context);
if (this.registerShutdownHook) {
try {
context.registerShutdownHook();
}
catch (AccessControlException ex) {
// Not allowed in some environments.
}
}
return context;
}
从代码上来看，与常见的Spring初始化上下文差不多，没什么特殊之处。
下面来看一下SpringBoot如何这么方便的：
仔细观察HelloApplication类定义中，可以发现一个不一样的地方，多了一个注解@SpringBootApplication，点开看一下其定义：
/*
* Copyright 2012-2015 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
*
* http://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.boot.autoconfigure; import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target; import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration;
import org.springframework.core.annotation.AliasFor; /**
* Indicates a {@link Configuration configuration} class that declares one or more
* {@link Bean @Bean} methods and also triggers {@link EnableAutoConfiguration
* auto-configuration} and {@link ComponentScan component scanning}. This is a convenience
* annotation that is equivalent to declaring {@code @Configuration},
* {@code @EnableAutoConfiguration} and {@code @ComponentScan}.
*
* @author Phillip Webb
* @author Stephane Nicoll
* @since 1.2.0
*/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@Configuration
@EnableAutoConfiguration
@ComponentScan
public @interface SpringBootApplication { /**
* Exclude specific auto-configuration classes such that they will never be applied.
* @return the classes to exclude
*/
Class<?>[] exclude() default {}; /**
* Exclude specific auto-configuration class names such that they will never be
* applied.
* @return the class names to exclude
* @since 1.3.0
*/
String[] excludeName() default {}; /**
* Base packages to scan for annotated components. Use {@link #scanBasePackageClasses}
* for a type-safe alternative to String-based package names.
* @return base packages to scan
* @since 1.3.0
*/
@AliasFor(annotation = ComponentScan.class, attribute = "basePackages")
String[] scanBasePackages() default {}; /**
* Type-safe alternative to {@link #scanBasePackages} for specifying the packages to
* scan for annotated components. The package of each class specified will be scanned.
* <p>
* Consider creating a special no-op marker class or interface in each package that
* serves no purpose other than being referenced by this attribute.
* @return base packages to scan
* @since 1.3.0
*/
@AliasFor(annotation = ComponentScan.class, attribute = "basePackageClasses")
Class<?>[] scanBasePackageClasses() default {}; }
呦！看到了吧，有一个@EnableAutoConfiguration注解，从其名称上来看就像是我们想要的钥匙。接着看看他的实现：
/*
* Copyright 2012-2015 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
*
* http://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.boot.autoconfigure; import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target; import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.context.embedded.EmbeddedServletContainerFactory;
import org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory;
import org.springframework.context.annotation.Conditional;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.core.io.support.SpringFactoriesLoader; /**
* Enable auto-configuration of the Spring Application Context, attempting to guess and
* configure beans that you are likely to need. Auto-configuration classes are usually
* applied based on your classpath and what beans you have defined. For example, If you
* have {@code tomcat-embedded.jar} on your classpath you are likely to want a
* {@link TomcatEmbeddedServletContainerFactory} (unless you have defined your own
* {@link EmbeddedServletContainerFactory} bean).
* <p>
* Auto-configuration tries to be as intelligent as possible and will back-away as you
* define more of your own configuration. You can always manually {@link #exclude()} any
* configuration that you never want to apply (use {@link #excludeName()} if you don't
* have access to them). You can also exclude them via the
* {@code spring.autoconfigure.exclude} property. Auto-configuration is always applied
* after user-defined beans have been registered.
* <p>
* The package of the class that is annotated with {@code @EnableAutoConfiguration} has
* specific significance and is often used as a 'default'. For example, it will be used
* when scanning for {@code @Entity} classes. It is generally recommended that you place
* {@code @EnableAutoConfiguration} in a root package so that all sub-packages and classes
* can be searched.
* <p>
* Auto-configuration classes are regular Spring {@link Configuration} beans. They are
* located using the {@link SpringFactoriesLoader} mechanism (keyed against this class).
* Generally auto-configuration beans are {@link Conditional @Conditional} beans (most
* often using {@link ConditionalOnClass @ConditionalOnClass} and
* {@link ConditionalOnMissingBean @ConditionalOnMissingBean} annotations).
*
* @author Phillip Webb
* @author Stephane Nicoll
* @see ConditionalOnBean
* @see ConditionalOnMissingBean
* @see ConditionalOnClass
* @see AutoConfigureAfter
*/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import(EnableAutoConfigurationImportSelector.class)
public @interface EnableAutoConfiguration { /**
* Exclude specific auto-configuration classes such that they will never be applied.
* @return the classes to exclude
*/
Class<?>[] exclude() default {}; /**
* Exclude specific auto-configuration class names such that they will never be
* applied.
* @return the class names to exclude
* @since 1.3.0
*/
String[] excludeName() default {}; }
通过其注释来看：Spring上下文自动配置，尝试着猜和配置你想要使用的bean0。大致使用SpringFactoriesLoader机制以及条件注解来实现的。
按照文档看一下EnableAutoConfigurationImportSelector实现类：
/*
* Copyright 2012-2015 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
*
* http://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.boot.autoconfigure; import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set; import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanClassLoaderAware;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.boot.autoconfigure.condition.ConditionEvaluationReport;
import org.springframework.boot.bind.PropertySourcesPropertyValues;
import org.springframework.boot.bind.RelaxedDataBinder;
import org.springframework.boot.bind.RelaxedPropertyResolver;
import org.springframework.context.EnvironmentAware;
import org.springframework.context.ResourceLoaderAware;
import org.springframework.context.annotation.DeferredImportSelector;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.AnnotationAttributes;
import org.springframework.core.annotation.Order;
import org.springframework.core.env.ConfigurableEnvironment;
import org.springframework.core.env.Environment;
import org.springframework.core.io.ResourceLoader;
import org.springframework.core.io.support.SpringFactoriesLoader;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils; /**
* {@link DeferredImportSelector} to handle {@link EnableAutoConfiguration
* auto-configuration}. This class can also be subclassed if a custom variant of
* {@link EnableAutoConfiguration @EnableAutoConfiguration}. is needed.
*
* @author Phillip Webb
* @author Andy Wilkinson
* @author Stephane Nicoll
* @see EnableAutoConfiguration
* @since 1.3.0
*/
@Order(Ordered.LOWEST_PRECEDENCE - 1)
public class EnableAutoConfigurationImportSelector implements DeferredImportSelector,
BeanClassLoaderAware, ResourceLoaderAware, BeanFactoryAware, EnvironmentAware { private ConfigurableListableBeanFactory beanFactory; private Environment environment; private ClassLoader beanClassLoader; private ResourceLoader resourceLoader; @Override
public String[] selectImports(AnnotationMetadata metadata) {
try {
AnnotationAttributes attributes = getAttributes(metadata);
List<String> configurations = getCandidateConfigurations(metadata,
attributes);
configurations = removeDuplicates(configurations);
Set<String> exclusions = getExclusions(metadata, attributes);
configurations.removeAll(exclusions);
configurations = sort(configurations);
recordWithConditionEvaluationReport(configurations, exclusions);
return configurations.toArray(new String[configurations.size()]);
}
catch (IOException ex) {
throw new IllegalStateException(ex);
}
} /**
* Return the appropriate {@link AnnotationAttributes} from the
* {@link AnnotationMetadata}. By default this method will return attributes for
* {@link #getAnnotationClass()}.
* @param metadata the annotation metadata
* @return annotation attributes
*/
protected AnnotationAttributes getAttributes(AnnotationMetadata metadata) {
String name = getAnnotationClass().getName();
AnnotationAttributes attributes = AnnotationAttributes
.fromMap(metadata.getAnnotationAttributes(name, true));
Assert.notNull(attributes,
"No auto-configuration attributes found. Is " + metadata.getClassName()
+ " annotated with " + ClassUtils.getShortName(name) + "?");
return attributes;
} /**
* Return the source annotation class used by the selector.
* @return the annotation class
*/
protected Class<?> getAnnotationClass() {
return EnableAutoConfiguration.class;
} /**
* Return the auto-configuration class names that should be considered. By default
* this method will load candidates using {@link SpringFactoriesLoader} with
* {@link #getSpringFactoriesLoaderFactoryClass()}.
* @param metadata the source metadata
* @param attributes the {@link #getAttributes(AnnotationMetadata) annotation
* attributes}
* @return a list of candidate configurations
*/
protected List<String> getCandidateConfigurations(AnnotationMetadata metadata,
AnnotationAttributes attributes) {
return SpringFactoriesLoader.loadFactoryNames(
getSpringFactoriesLoaderFactoryClass(), getBeanClassLoader());
} /**
* Return the class used by {@link SpringFactoriesLoader} to load configuration
* candidates.
* @return the factory class
*/
protected Class<?> getSpringFactoriesLoaderFactoryClass() {
return EnableAutoConfiguration.class;
} /**
* Return any exclusions that limit the candidate configurations.
* @param metadata the source metadata
* @param attributes the {@link #getAttributes(AnnotationMetadata) annotation
* attributes}
* @return exclusions or an empty set
*/
protected Set<String> getExclusions(AnnotationMetadata metadata,
AnnotationAttributes attributes) {
Set<String> excluded = new LinkedHashSet<String>();
excluded.addAll(asList(attributes, "exclude"));
excluded.addAll(Arrays.asList(attributes.getStringArray("excludeName")));
excluded.addAll(getExcludeAutoConfigurationsProperty());
return excluded;
} private List<String> getExcludeAutoConfigurationsProperty() {
if (getEnvironment() instanceof ConfigurableEnvironment) {
Excludes excludes = new Excludes();
RelaxedDataBinder binder = new RelaxedDataBinder(excludes,
"spring.autoconfigure.");
binder.bind(new PropertySourcesPropertyValues(
((ConfigurableEnvironment) getEnvironment()).getPropertySources()));
return excludes.getExclude();
}
RelaxedPropertyResolver resolver = new RelaxedPropertyResolver(getEnvironment(),
"spring.autoconfigure.");
String[] exclude = resolver.getProperty("exclude", String[].class);
return (Arrays.asList(exclude == null ? new String[0] : exclude));
} private List<String> sort(List<String> configurations) throws IOException {
configurations = new AutoConfigurationSorter(getResourceLoader())
.getInPriorityOrder(configurations);
return configurations;
} private void recordWithConditionEvaluationReport(List<String> configurations,
Collection<String> exclusions) throws IOException {
ConditionEvaluationReport report = ConditionEvaluationReport
.get(getBeanFactory());
report.recordEvaluationCandidates(configurations);
report.recordExclusions(exclusions);
} protected final <T> List<T> removeDuplicates(List<T> list) {
return new ArrayList<T>(new LinkedHashSet<T>(list));
} protected final List<String> asList(AnnotationAttributes attributes, String name) {
String[] value = attributes.getStringArray(name);
return Arrays.asList(value == null ? new String[0] : value);
} @Override
public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
Assert.isInstanceOf(ConfigurableListableBeanFactory.class, beanFactory);
this.beanFactory = (ConfigurableListableBeanFactory) beanFactory;
} protected final ConfigurableListableBeanFactory getBeanFactory() {
return this.beanFactory;
} @Override
public void setBeanClassLoader(ClassLoader classLoader) {
this.beanClassLoader = classLoader;
} protected ClassLoader getBeanClassLoader() {
return this.beanClassLoader;
} @Override
public void setEnvironment(Environment environment) {
this.environment = environment;
} protected final Environment getEnvironment() {
return this.environment;
} @Override
public void setResourceLoader(ResourceLoader resourceLoader) {
this.resourceLoader = resourceLoader;
} protected final ResourceLoader getResourceLoader() {
return this.resourceLoader;
} /**
* Bindable object used to get excludes.
*/
static class Excludes { private List<String> exclude = new ArrayList<String>(); public List<String> getExclude() {
return this.exclude;
} public void setExclude(List<String> excludes) {
this.exclude = excludes;
} } }
其中getCandidateConfigurations方法中调用SpringFactoriesLoader.loadFactoryNames()静态方法，接着看下去，可以发现，其实就是加载META-INF/spring.factories里面的内容而已，
再来看一下spring.factories内容：
# Initializers
org.springframework.context.ApplicationContextInitializer=\
org.springframework.boot.autoconfigure.logging.AutoConfigurationReportLoggingInitializer # Application Listeners
org.springframework.context.ApplicationListener=\
org.springframework.boot.autoconfigure.BackgroundPreinitializer # Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration,\
org.springframework.boot.autoconfigure.aop.AopAutoConfiguration,\
org.springframework.boot.autoconfigure.amqp.RabbitAutoConfiguration,\
org.springframework.boot.autoconfigure.MessageSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.PropertyPlaceholderAutoConfiguration,\
org.springframework.boot.autoconfigure.batch.BatchAutoConfiguration,\
org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration,\
org.springframework.boot.autoconfigure.cassandra.CassandraAutoConfiguration,\
org.springframework.boot.autoconfigure.cloud.CloudAutoConfiguration,\
org.springframework.boot.autoconfigure.context.ConfigurationPropertiesAutoConfiguration,\
org.springframework.boot.autoconfigure.dao.PersistenceExceptionTranslationAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchAutoConfiguration,\
org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.mongo.MongoDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.mongo.MongoRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.solr.SolrRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration,\
org.springframework.boot.autoconfigure.data.rest.RepositoryRestMvcAutoConfiguration,\
org.springframework.boot.autoconfigure.data.web.SpringDataWebAutoConfiguration,\
org.springframework.boot.autoconfigure.freemarker.FreeMarkerAutoConfiguration,\
org.springframework.boot.autoconfigure.gson.GsonAutoConfiguration,\
org.springframework.boot.autoconfigure.h2.H2ConsoleAutoConfiguration,\
org.springframework.boot.autoconfigure.hateoas.HypermediaAutoConfiguration,\
org.springframework.boot.autoconfigure.hazelcast.HazelcastAutoConfiguration,\
org.springframework.boot.autoconfigure.hazelcast.HazelcastJpaDependencyAutoConfiguration,\
org.springframework.boot.autoconfigure.integration.IntegrationAutoConfiguration,\
org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.JndiDataSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.XADataSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.JmsAutoConfiguration,\
org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.JndiConnectionFactoryAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.activemq.ActiveMQAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.artemis.ArtemisAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.hornetq.HornetQAutoConfiguration,\
org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration,\
org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAutoConfiguration,\
org.springframework.boot.autoconfigure.jersey.JerseyAutoConfiguration,\
org.springframework.boot.autoconfigure.jooq.JooqAutoConfiguration,\
org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration,\
org.springframework.boot.autoconfigure.mail.MailSenderAutoConfiguration,\
org.springframework.boot.autoconfigure.mail.MailSenderValidatorAutoConfiguration,\
org.springframework.boot.autoconfigure.mobile.DeviceResolverAutoConfiguration,\
org.springframework.boot.autoconfigure.mobile.DeviceDelegatingViewResolverAutoConfiguration,\
org.springframework.boot.autoconfigure.mobile.SitePreferenceAutoConfiguration,\
org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongoAutoConfiguration,\
org.springframework.boot.autoconfigure.mongo.MongoAutoConfiguration,\
org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration,\
org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration,\
org.springframework.boot.autoconfigure.reactor.ReactorAutoConfiguration,\
org.springframework.boot.autoconfigure.security.SecurityAutoConfiguration,\
org.springframework.boot.autoconfigure.security.SecurityFilterAutoConfiguration,\
org.springframework.boot.autoconfigure.security.FallbackWebSecurityAutoConfiguration,\
org.springframework.boot.autoconfigure.security.oauth2.OAuth2AutoConfiguration,\
org.springframework.boot.autoconfigure.sendgrid.SendGridAutoConfiguration,\
org.springframework.boot.autoconfigure.session.SessionAutoConfiguration,\
org.springframework.boot.autoconfigure.social.SocialWebAutoConfiguration,\
org.springframework.boot.autoconfigure.social.FacebookAutoConfiguration,\
org.springframework.boot.autoconfigure.social.LinkedInAutoConfiguration,\
org.springframework.boot.autoconfigure.social.TwitterAutoConfiguration,\
org.springframework.boot.autoconfigure.solr.SolrAutoConfiguration,\
org.springframework.boot.autoconfigure.velocity.VelocityAutoConfiguration,\
org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration,\
org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration,\
org.springframework.boot.autoconfigure.transaction.jta.JtaAutoConfiguration,\
org.springframework.boot.autoconfigure.web.DispatcherServletAutoConfiguration,\
org.springframework.boot.autoconfigure.web.EmbeddedServletContainerAutoConfiguration,\
org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration,\
org.springframework.boot.autoconfigure.web.HttpEncodingAutoConfiguration,\
org.springframework.boot.autoconfigure.web.HttpMessageConvertersAutoConfiguration,\
org.springframework.boot.autoconfigure.web.MultipartAutoConfiguration,\
org.springframework.boot.autoconfigure.web.ServerPropertiesAutoConfiguration,\
org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration,\
org.springframework.boot.autoconfigure.websocket.WebSocketAutoConfiguration,\
org.springframework.boot.autoconfigure.websocket.WebSocketMessagingAutoConfiguration # Template availability providers
org.springframework.boot.autoconfigure.template.TemplateAvailabilityProvider=\
org.springframework.boot.autoconfigure.freemarker.FreeMarkerTemplateAvailabilityProvider,\
org.springframework.boot.autoconfigure.mustache.MustacheTemplateAvailabilityProvider,\
org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAvailabilityProvider,\
org.springframework.boot.autoconfigure.thymeleaf.ThymeleafTemplateAvailabilityProvider,\
org.springframework.boot.autoconfigure.velocity.VelocityTemplateAvailabilityProvider,\
org.springframework.boot.autoconfigure.web.JspTemplateAvailabilityProvider
看到没，直接预定义了好多配置类，随意打开一个看一下，
/*
* Copyright 2012-2015 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
*
* http://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.boot.autoconfigure.amqp; import com.rabbitmq.client.Channel; import org.springframework.amqp.core.AmqpAdmin;
import org.springframework.amqp.rabbit.connection.CachingConnectionFactory;
import org.springframework.amqp.rabbit.connection.ConnectionFactory;
import org.springframework.amqp.rabbit.connection.RabbitConnectionFactoryBean;
import org.springframework.amqp.rabbit.core.RabbitAdmin;
import org.springframework.amqp.rabbit.core.RabbitMessagingTemplate;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import; /**
* {@link EnableAutoConfiguration Auto-configuration} for {@link RabbitTemplate}.
* <p>
* This configuration class is active only when the RabbitMQ and Spring AMQP client
* libraries are on the classpath.
* <P>
* Registers the following beans:
* <ul>
* <li>{@link org.springframework.amqp.rabbit.core.RabbitTemplate RabbitTemplate} if there
* is no other bean of the same type in the context.</li>
* <li>{@link org.springframework.amqp.rabbit.connection.CachingConnectionFactory
* CachingConnectionFactory} instance if there is no other bean of the same type in the
* context.</li>
* <li>{@link org.springframework.amqp.core.AmqpAdmin } instance as long as
* {@literal spring.rabbitmq.dynamic=true}.</li>
* </ul>
* <p>
* The {@link org.springframework.amqp.rabbit.connection.CachingConnectionFactory} honors
* the following properties:
* <ul>
* <li>{@literal spring.rabbitmq.port} is used to specify the port to which the client
* should connect, and defaults to 5672.</li>
* <li>{@literal spring.rabbitmq.username} is used to specify the (optional) username.
* </li>
* <li>{@literal spring.rabbitmq.password} is used to specify the (optional) password.
* </li>
* <li>{@literal spring.rabbitmq.host} is used to specify the host, and defaults to
* {@literal localhost}.</li>
* <li>{@literal spring.rabbitmq.virtualHost} is used to specify the (optional) virtual
* host to which the client should connect.</li>
* </ul>
* @author Greg Turnquist
* @author Josh Long
* @author Stephane Nicoll
*/
@Configuration
@ConditionalOnClass({ RabbitTemplate.class, Channel.class })
@EnableConfigurationProperties(RabbitProperties.class)
@Import(RabbitAnnotationDrivenConfiguration.class)
public class RabbitAutoConfiguration { @Bean
@ConditionalOnProperty(prefix = "spring.rabbitmq", name = "dynamic", matchIfMissing = true)
@ConditionalOnMissingBean(AmqpAdmin.class)
public AmqpAdmin amqpAdmin(ConnectionFactory connectionFactory) {
return new RabbitAdmin(connectionFactory);
} @Autowired
private ConnectionFactory connectionFactory; @Bean
@ConditionalOnMissingBean(RabbitTemplate.class)
public RabbitTemplate rabbitTemplate() {
return new RabbitTemplate(this.connectionFactory);
} @Configuration
@ConditionalOnMissingBean(ConnectionFactory.class)
protected static class RabbitConnectionFactoryCreator { @Bean
public CachingConnectionFactory rabbitConnectionFactory(RabbitProperties config)
throws Exception {
RabbitConnectionFactoryBean factory = new RabbitConnectionFactoryBean();
if (config.getHost() != null) {
factory.setHost(config.getHost());
factory.setPort(config.getPort());
}
if (config.getUsername() != null) {
factory.setUsername(config.getUsername());
}
if (config.getPassword() != null) {
factory.setPassword(config.getPassword());
}
if (config.getVirtualHost() != null) {
factory.setVirtualHost(config.getVirtualHost());
}
if (config.getRequestedHeartbeat() != null) {
factory.setRequestedHeartbeat(config.getRequestedHeartbeat());
}
RabbitProperties.Ssl ssl = config.getSsl();
if (ssl.isEnabled()) {
factory.setUseSSL(true);
if (ssl.getAlgorithm() != null) {
factory.setSslAlgorithm(ssl.getAlgorithm());
}
factory.setKeyStore(ssl.getKeyStore());
factory.setKeyStorePassphrase(ssl.getKeyStorePassword());
factory.setTrustStore(ssl.getTrustStore());
factory.setTrustStorePassphrase(ssl.getTrustStorePassword());
}
factory.afterPropertiesSet();
CachingConnectionFactory connectionFactory = new CachingConnectionFactory(
factory.getObject());
connectionFactory.setAddresses(config.getAddresses());
return connectionFactory;
} } @ConditionalOnClass(RabbitMessagingTemplate.class)
@ConditionalOnMissingBean(RabbitMessagingTemplate.class)
protected static class MessagingTemplateConfiguration { @Bean
public RabbitMessagingTemplate rabbitMessagingTemplate(
RabbitTemplate rabbitTemplate) {
return new RabbitMessagingTemplate(rabbitTemplate);
} } }
到这里，想必大家已经可以有些明白SpringBoot实现自动配置原理了。就是根据条件注解，如（@ConditionalOnClass，@ConditionalOnProperty，@ConditionalOnMissingBean等）。
最后呢，还有一个问题就是，自动配置所需要的第三方组件是怎么引用进来的呢？这就需要了解一下SpringBoot的各种starter依赖了，之前pom文件中引入了好几个starter依赖，
其详情如下：
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.3.7.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent> <properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties> <dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
</dependencies>
spring-boot-starter-parent.pom:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<version>1.3.7.RELEASE</version>
<relativePath>../../spring-boot-dependencies</relativePath>
</parent>
<artifactId>spring-boot-starter-parent</artifactId>
<packaging>pom</packaging>
<name>Spring Boot Starter Parent</name>
<description>Spring Boot Starter Parent</description>
<url>http://projects.spring.io/spring-boot/</url>
<organization>
<name>Pivotal Software, Inc.</name>
<url>http://www.spring.io</url>
</organization>
<properties>
<java.version>1.6</java.version>
<resource.delimiter>@</resource.delimiter> <!-- delimiter that doesn't clash with Spring ${} placeholders -->
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<maven.compiler.source>${java.version}</maven.compiler.source>
<maven.compiler.target>${java.version}</maven.compiler.target>
</properties>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
<exclusions>
<exclusion>
<groupId>commons-logging</groupId>
<artifactId>commons-logging</artifactId>
</exclusion>
</exclusions>
</dependency>
</dependencies>
</dependencyManagement>
<build>
<!-- Turn on filtering by default for application properties -->
<resources>
<resource>
<directory>${basedir}/src/main/resources</directory>
<filtering>true</filtering>
<includes>
<include>**/application.yml</include>
<include>**/application.properties</include>
</includes>
</resource>
<resource>
<directory>${basedir}/src/main/resources</directory>
<excludes>
<exclude>**/application.yml</exclude>
<exclude>**/application.properties</exclude>
</excludes>
</resource>
</resources>
<pluginManagement>
<plugins>
<!-- Apply more sensible defaults for user projects -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<configuration>
<archive>
<manifest>
<mainClass>${start-class}</mainClass>
<addDefaultImplementationEntries>true</addDefaultImplementationEntries>
</manifest>
</archive>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<configuration>
<includes>
<include>**/*Tests.java</include>
<include>**/*Test.java</include>
</includes>
<excludes>
<exclude>**/Abstract*.java</exclude>
</excludes>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<configuration>
<failOnMissingWebXml>false</failOnMissingWebXml>
<archive>
<manifest>
<mainClass>${start-class}</mainClass>
<addDefaultImplementationEntries>true</addDefaultImplementationEntries>
</manifest>
</archive>
</configuration>
</plugin>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<configuration>
<mainClass>${start-class}</mainClass>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-resources-plugin</artifactId>
<version>2.6</version>
<configuration>
<delimiters>
<delimiter>${resource.delimiter}</delimiter>
</delimiters>
<useDefaultDelimiters>false</useDefaultDelimiters>
</configuration>
</plugin>
<plugin>
<groupId>pl.project13.maven</groupId>
<artifactId>git-commit-id-plugin</artifactId>
<version>2.1.11</version>
<executions>
<execution>
<goals>
<goal>revision</goal>
</goals>
</execution>
</executions>
<configuration>
<verbose>true</verbose>
<dateFormat>yyyy-MM-dd'T'HH:mm:ssZ</dateFormat>
<generateGitPropertiesFile>true</generateGitPropertiesFile>
<generateGitPropertiesFilename>${project.build.outputDirectory}/git.properties</generateGitPropertiesFilename>
</configuration>
</plugin>
<!-- Support our own plugin -->
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>${spring-boot.version}</version>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
<configuration>
<mainClass>${start-class}</mainClass>
</configuration>
</plugin>
<!-- Support shade packaging (if the user does not want to use our plugin) -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-shade-plugin</artifactId>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>${spring-boot.version}</version>
</dependency>
</dependencies>
<configuration>
<keepDependenciesWithProvidedScope>true</keepDependenciesWithProvidedScope>
<createDependencyReducedPom>true</createDependencyReducedPom>
<filters>
<filter>
<artifact>*:*</artifact>
<excludes>
<exclude>META-INF/*.SF</exclude>
<exclude>META-INF/*.DSA</exclude>
<exclude>META-INF/*.RSA</exclude>
</excludes>
</filter>
</filters>
</configuration>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>shade</goal>
</goals>
<configuration>
<transformers>
<transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
<resource>META-INF/spring.handlers</resource>
</transformer>
<transformer implementation="org.springframework.boot.maven.PropertiesMergingResourceTransformer">
<resource>META-INF/spring.factories</resource>
</transformer>
<transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
<resource>META-INF/spring.schemas</resource>
</transformer>
<transformer implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer" />
<transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
<mainClass>${start-class}</mainClass>
</transformer>
</transformers>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</pluginManagement>
</build>
</project>
其定义了springboot工程结构及常用配置依赖之类的，所有的SpringBoot工程均适用。
spring-boot-starter-web.pom:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starters</artifactId>
<version>1.3.7.RELEASE</version>
</parent>
<artifactId>spring-boot-starter-web</artifactId>
<name>Spring Boot Web Starter</name>
<description>Spring Boot Web Starter</description>
<url>http://projects.spring.io/spring-boot/</url>
<organization>
<name>Pivotal Software, Inc.</name>
<url>http://www.spring.io</url>
</organization>
<properties>
<main.basedir>${basedir}/../..</main.basedir>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-validation</artifactId>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
</dependency>
</dependencies>
</project>
总结一下：Spring Boot为开发者提供了各种解决方案模板，只需要按照模板填充业务逻辑即可，不需要过分关注各种组件之间耦合，尽可能解放开发人员技术压力。
同样，我们也可以仿造现有模板来定制模板实现特定的业务场景与新组件。
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