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; } }
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。
