1.ioc核心功能bean的配置与获取api

有以下四种

(来自精通spring4.x的p175)

常用的是前三种

第一种方式

<?xml version="1.0" encoding="GBK"?> <beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.springframework.org/schema/beans" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd"> <!-- 指定class属性，通过构造方法创建Bean实例 --> <bean id="person" class="com.mao.gouzao.Person"> </bean> </beans> public static void main( String[] args ) { ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml"); System.out.println(ctx.getBean("person")); } 

第二种方式

定义

@Service public class UserServiceImpl { public void test(){ System.out.println(666); } }

获取

@Autowired private static UserServiceImpl userService;

第三种方式

定义

@Configuration public class MainConfig { @Bean public Person person(){ return new Person(); } }

注意: 通过@Bean的形式是使用的话，bean的默认名称是方法名，若Bean(value="bean＂的名称")那么bean的名称是指定的

去容器中读取Bean的信息（传入配置类）

获取

public static void main( String[] args ) { AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(MainConfig.class); System.out.println(ctx.getBean("person")); }

2.如何实现的

1.基于Java类配置的实现方式源码分析

1.就执行了这两句代码

AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(MainConfig.class); System.out.println(ctx.getBean("person"));

先看看，打开构造器源码：

public AnnotationConfigApplicationContext(Class<?>... annotatedClasses) { this(); register(annotatedClasses); refresh(); }

2.首先不急，主角儿AnnotationConfigApplicationContext 它有父类，因为类初始化顺序的关系，会先初始化父类，所以得看父类，一直看到最后父类为DefaultResourceLoader

DefaultResourceLoader，很明显是用来加载资源的，倒数第二个AbstractApplicationContext的无参构造中也是初始化一个加载资源相关：

Ok，再来看最后一个父类GenericApplicationContext了，父类默认初始化使用下面这个无参的

public GenericApplicationContext() { this.beanFactory = new DefaultListableBeanFactory(); }

这里是创建了springioc体系中的一个重要的类DefaultListableBeanFactory，DefaultListableBeanFactory非常关键里面实现了ioc相关很多功能，可以提供给我们的AnnotationConfigApplicationContext使用（后面会看到）

3.ok父类都看完了，那就回到我们的主角儿AnnotationConfigApplicationContext了

我们来看它的构造器刚刚是什么代码（回归本身）：

public AnnotationConfigApplicationContext() { this.reader = new AnnotatedBeanDefinitionReader(this); this.scanner = new ClassPathBeanDefinitionScanner(this); }

就两行。

4.先看第一句this.reader = new AnnotatedBeanDefinitionReader(this);

进去

public AnnotatedBeanDefinitionReader(BeanDefinitionRegistry registry) { this(registry, getOrCreateEnvironment(registry)); }

它再次调用自己的构造器

这里还涉及了一个方法getOrCreateEnvironment(registry)

很明显这个方法从名字看就知道是有缓存的意思，获取或创建，如果是第一次则创建 第二次则就是获取了，第二次拿的第一次缓存的。如下：

 private static Environment getOrCreateEnvironment(BeanDefinitionRegistry registry) { Assert.notNull(registry, "BeanDefinitionRegistry must not be null"); if (registry instanceof EnvironmentCapable) { return ((EnvironmentCapable) registry).getEnvironment(); } return new StandardEnvironment(); }

ok，继续看，刚刚是从构造器到另一个构造器了：

 public AnnotatedBeanDefinitionReader(BeanDefinitionRegistry registry, Environment environment) { Assert.notNull(registry, "BeanDefinitionRegistry must not be null"); Assert.notNull(environment, "Environment must not be null"); this.registry = registry; this.conditionEvaluator = new ConditionEvaluator(registry, environment, null); AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry); }

ConditionEvaluator是计算conditon的解析器（后面会讲），这里很明显主要逻辑在 AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);

接下来AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);是重中之重，终于开始有大段逻辑了！之前都是各种继承跳转！

registerAnnotationConfigProcessors源码实现如下

public static Set<BeanDefinitionHolder> registerAnnotationConfigProcessors( BeanDefinitionRegistry registry, Object source) { DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry); if (beanFactory != null) { if (!(beanFactory.getDependencyComparator() instanceof AnnotationAwareOrderComparator)) { beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE); } if (!(beanFactory.getAutowireCandidateResolver() instanceof ContextAnnotationAutowireCandidateResolver)) { beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver()); } } Set<BeanDefinitionHolder> beanDefs = new LinkedHashSet<BeanDefinitionHolder>(4); if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(ConfigurationClassPostProcessor.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)); } if (!registry.containsBeanDefinition(AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(AutowiredAnnotationBeanPostProcessor.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME)); } if (!registry.containsBeanDefinition(REQUIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(RequiredAnnotationBeanPostProcessor.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, REQUIRED_ANNOTATION_PROCESSOR_BEAN_NAME)); } // Check for JSR-250 support, and if present add the CommonAnnotationBeanPostProcessor. if (jsr250Present && !registry.containsBeanDefinition(COMMON_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(CommonAnnotationBeanPostProcessor.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, COMMON_ANNOTATION_PROCESSOR_BEAN_NAME)); } // Check for JPA support, and if present add the PersistenceAnnotationBeanPostProcessor. if (jpaPresent && !registry.containsBeanDefinition(PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(); try { def.setBeanClass(ClassUtils.forName(PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, AnnotationConfigUtils.class.getClassLoader())); } catch (ClassNotFoundException ex) { throw new IllegalStateException( "Cannot load optional framework class: " + PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, ex); } def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)); } if (!registry.containsBeanDefinition(EVENT_LISTENER_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(EventListenerMethodProcessor.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_PROCESSOR_BEAN_NAME)); } if (!registry.containsBeanDefinition(EVENT_LISTENER_FACTORY_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(DefaultEventListenerFactory.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_FACTORY_BEAN_NAME)); } return beanDefs; }

挺长，先看第一部分：

 DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry); if (beanFactory != null) { if (!(beanFactory.getDependencyComparator() instanceof AnnotationAwareOrderComparator)) { beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE); } if (!(beanFactory.getAutowireCandidateResolver() instanceof ContextAnnotationAutowireCandidateResolver)) { beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver()); } }

很明显这是从registry里拿DefaultListableBeanFactory ，还记得前面讲主角儿AnnotationConfigApplicationContext的父类GenericApplicationContext吗？在它的无参构造中就创建了DefaultListableBeanFactory。现在到这个registry里去拿，而这个registry就是前面用this传过来的主角儿AnnotationConfigApplicationContext自然就有DefaultListableBeanFactory了。后面的逻辑就是null判断和设置比较器和解析器到里面了。

Set<BeanDefinitionHolder> beanDefs = new LinkedHashSet<BeanDefinitionHolder>(4); if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(ConfigurationClassPostProcessor.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)); } if (!registry.containsBeanDefinition(AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(AutowiredAnnotationBeanPostProcessor.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME)); } if (!registry.containsBeanDefinition(REQUIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(RequiredAnnotationBeanPostProcessor.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, REQUIRED_ANNOTATION_PROCESSOR_BEAN_NAME)); } // Check for JSR-250 support, and if present add the CommonAnnotationBeanPostProcessor. if (jsr250Present && !registry.containsBeanDefinition(COMMON_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(CommonAnnotationBeanPostProcessor.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, COMMON_ANNOTATION_PROCESSOR_BEAN_NAME)); } // Check for JPA support, and if present add the PersistenceAnnotationBeanPostProcessor. if (jpaPresent && !registry.containsBeanDefinition(PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(); try { def.setBeanClass(ClassUtils.forName(PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, AnnotationConfigUtils.class.getClassLoader())); } catch (ClassNotFoundException ex) { throw new IllegalStateException( "Cannot load optional framework class: " + PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, ex); } def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)); } if (!registry.containsBeanDefinition(EVENT_LISTENER_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(EventListenerMethodProcessor.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_PROCESSOR_BEAN_NAME)); } if (!registry.containsBeanDefinition(EVENT_LISTENER_FACTORY_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(DefaultEventListenerFactory.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_FACTORY_BEAN_NAME)); } return beanDefs;

创建了一个set集合保存BeanDefinitionHolder（BeanDefinition是）。后面就非常多的if判断。这都是判断啥呢？

 if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(ConfigurationClassPostProcessor.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)); }

判断registry中是否存在一个个的常量定义的东西。那这些常量是什么呢？打开一看：

 public static final String CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME = "org.springframework.context.annotation.internalConfigurationAnnotationProcessor";

是个类的全路径，如果registry里面没有就执行最后一句（前两句都是给最后一句服务的）：

beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME));

也就是判断有没有这个类，没有就添加这个类进去，这这个类是用来解析配置注解的处理器。

还有个 public static final String AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME = "org.springframework.context.annotation.internalAutowiredAnnotationProcessor";

综合所见，这段代码后半部分其实就是注册spring支持的各种注解的解析器的逻辑

这个对应是用来解析自动装配注解的

最后如下：

 public static Set<BeanDefinitionHolder> registerAnnotationConfigProcessors( BeanDefinitionRegistry registry, Object source) { //获取之前创建的DefaultListableBeanFactory，检查null并塞入相关组件 DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry); if (beanFactory != null) { if (!(beanFactory.getDependencyComparator() instanceof AnnotationAwareOrderComparator)) { beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE); } if (!(beanFactory.getAutowireCandidateResolver() instanceof ContextAnnotationAutowireCandidateResolver)) { beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver()); } } Set<BeanDefinitionHolder> beanDefs = new LinkedHashSet<BeanDefinitionHolder>(8); //注册一个配置类@Configuration解析器的bean定义（ConfigurationClassPostProcessor） if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(ConfigurationClassPostProcessor.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)); } //设置AutoWired注解解析器的bean定义信息 if (!registry.containsBeanDefinition(AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(AutowiredAnnotationBeanPostProcessor.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME)); } //注册解析@Required 注解的处理器 if (!registry.containsBeanDefinition(REQUIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(RequiredAnnotationBeanPostProcessor.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, REQUIRED_ANNOTATION_PROCESSOR_BEAN_NAME)); } //检查是否支持JSR250规范，如何支持注册 解析JSR250规范的注解 // Check for JSR-250 support, and if present add the CommonAnnotationBeanPostProcessor. if (jsr250Present && !registry.containsBeanDefinition(COMMON_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(CommonAnnotationBeanPostProcessor.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, COMMON_ANNOTATION_PROCESSOR_BEAN_NAME)); } //检查是否支持jpa，若支持注册解析jpa规范的注解 // Check for JPA support, and if present add the PersistenceAnnotationBeanPostProcessor. if (jpaPresent && !registry.containsBeanDefinition(PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(); try { def.setBeanClass(ClassUtils.forName(PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, AnnotationConfigUtils.class.getClassLoader())); } catch (ClassNotFoundException ex) { throw new IllegalStateException( "Cannot load optional framework class: " + PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, ex); } def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)); } //注册解析@EventListener的注解解析器 if (!registry.containsBeanDefinition(EVENT_LISTENER_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(EventListenerMethodProcessor.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_PROCESSOR_BEAN_NAME)); } if (!registry.containsBeanDefinition(EVENT_LISTENER_FACTORY_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(DefaultEventListenerFactory.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_FACTORY_BEAN_NAME)); } //最后带着这一堆spring支持的功能的解析器返回（实际上刚刚分析的过程中压根没用到这个返回值，那是为什么呢？值得注意的是 原来它是把这些搞到registry里去了，综上， 注入这堆注解解析器 到registry 也就是DefaultListableBeanFactory中！） return beanDefs; }

好，以上这部分分析结束，回到主角儿AnnotationConfigApplicationContext，之前我们是从它的构造器：

 public AnnotationConfigApplicationContext() { this.reader = new AnnotatedBeanDefinitionReader(this); this.scanner = new ClassPathBeanDefinitionScanner(this); }

中分析的第一句终于把这个reader完毕了，接下来分析第二句咯。

名字可以看出是类路径下的扫描器，开始查看源码！

 public ClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry) { this(registry, true); }

继续跟进

 public ClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry, boolean useDefaultFilters) { this(registry, useDefaultFilters, getOrCreateEnvironment(registry)); }

第一个registry 还是之前说的DefaultListableBeanFactory传的this,第二个也就是 传了个true，是否使用默认的filter，选择了是。第三个之前讲过了，有则用没有则创建，缓存。继续跟

 public ClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry, boolean useDefaultFilters, Environment environment, ResourceLoader resourceLoader) { Assert.notNull(registry, "BeanDefinitionRegistry must not be null"); this.registry = registry; if (useDefaultFilters) { registerDefaultFilters(); } setEnvironment(environment); setResourceLoader(resourceLoader); }

这部分代码前面就是赋值、注册默认的filters、设置从registry拿的环境设置、最后设置ResourceLoader

一部分一部分的看，先看registerDefaultFilters();

 /** * Register the default filter for {@link Component @Component}. * <p>This will implicitly register all annotations that have the * {@link Component @Component} meta-annotation including the * {@link Repository @Repository}, {@link Service @Service}, and * {@link Controller @Controller} stereotype annotations. * <p>Also supports Java EE 6's {@link javax.annotation.ManagedBean} and * JSR-330's {@link javax.inject.Named} annotations, if available. * */ @SuppressWarnings("unchecked") protected void registerDefaultFilters() { this.includeFilters.add(new AnnotationTypeFilter(Component.class)); ClassLoader cl = ClassPathScanningCandidateComponentProvider.class.getClassLoader(); try { this.includeFilters.add(new AnnotationTypeFilter( ((Class<? extends Annotation>) ClassUtils.forName("javax.annotation.ManagedBean", cl)), false)); logger.debug("JSR-250 'javax.annotation.ManagedBean' found and supported for component scanning"); } catch (ClassNotFoundException ex) { // JSR-250 1.1 API (as included in Java EE 6) not available - simply skip. } try { this.includeFilters.add(new AnnotationTypeFilter( ((Class<? extends Annotation>) ClassUtils.forName("javax.inject.Named", cl)), false)); logger.debug("JSR-330 'javax.inject.Named' annotation found and supported for component scanning"); } catch (ClassNotFoundException ex) { // JSR-330 API not available - simply skip. } }

方法注释可以看到 意思是，注册这些默认的filter，@Component、@Repository、@Controller才会起作用

然后方法内部就注入添加Component.class进去了，让@Component起作用，而@Repository、@Controller本身都被打了@Component 是子注解，所以也连带起作用

后面部分就是判断jsr250 330相关注解了

到此看完了，回到上层上层去，至此

 public AnnotationConfigApplicationContext(DefaultListableBeanFactory beanFactory) { super(beanFactory); this.reader = new AnnotatedBeanDefinitionReader(this); this.scanner = new ClassPathBeanDefinitionScanner(this); }

中的第二句我们也大致看完了，至此一个构造器看完了。大功告成.......了，一半。。。发现这个构造器是无参的，而我们之前用的两句代码：

AnnotationConfigApplicationContext annotationConfigApplication = new AnnotationConfigApplicationContext (MainConfig.class);Person person2 = (Person)annotationConfigApplication.getBean("person2");

中主角AnnotationConfigApplicationContext用的带class的构造器啊，看来没完，原来这个构造器还有上层调用，在这：

 public AnnotationConfigApplicationContext(Class<?>... annotatedClasses) { this(); register(annotatedClasses); refresh(); }

这里才是最开始那两行代码的第一次调用处。我们把this()；看完了！

接下来看第二句register(annotatedClasses);，不断跟进

 public void register(Class<?>... annotatedClasses) { Assert.notEmpty(annotatedClasses, "At least one annotated class must be specified"); this.reader.register(annotatedClasses); }

不断跟进到这

 public void registerBean(Class<?> annotatedClass, String name, Class<? extends Annotation>... qualifiers) { AnnotatedGenericBeanDefinition abd = new AnnotatedGenericBeanDefinition(annotatedClass); if (this.conditionEvaluator.shouldSkip(abd.getMetadata())) { return; } ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd); abd.setScope(scopeMetadata.getScopeName()); String beanName = (name != null ? name : this.beanNameGenerator.generateBeanName(abd, this.registry)); AnnotationConfigUtils.processCommonDefinitionAnnotations(abd); if (qualifiers != null) { for (Class<? extends Annotation> qualifier : qualifiers) { if (Primary.class == qualifier) { abd.setPrimary(true); } else if (Lazy.class == qualifier) { abd.setLazyInit(true); } else { abd.addQualifier(new AutowireCandidateQualifier(qualifier)); } } } BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(abd, beanName); definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry); BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry); }

原来这句代码是把传入的配置类里的bean全给注册了。至此第二句完毕。至于最后第三句核心，留给下篇文章。一起加油！