一、依赖注入ApplicationContext
方法一、@Autowired
创建一个User，内部使用ApplicationContext
@Component public class User { @Autowired private ApplicationContext applicationContext; public void show() { System.out.println("User:"+applicationContext.getClass()); } }
使用
public static void main(String[] args) { AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext("com.lhx.spring.kuozhan"); System.out.println(context.getBean("user")); // System.out.println(context.getBean("createUser")); User bean = (User) context.getBean("user"); bean.show(); context.close(); }
方法二、实现ApplicationContextAware接口
@Component public class Book implements ApplicationContextAware{ private ApplicationContext ApplicationContext; @Override public void setApplicationContext(ApplicationContext applicationContext) throws BeansException { this.ApplicationContext=applicationContext; } public void show() { System.out.println("book:"+ApplicationContext.getClass()); } }
1）内部原理
接口BeanPostProcessor，内部方法，每一个bean初始化都会被执行
bean初始化属性完毕后，即依赖装配完成之后，postProcessBeforeInitialization
bean初始化在属性设置之后，Bean init之后触发的，postProcessAfterInitialization
作用：回调，返回代理对象等
如在postProcessBeforeInitialization中返回其他代理对象。
构建一个默认实现【两个方法不能返回null】
package com.lhx.spring.kuozhan; import org.springframework.beans.BeansException; import org.springframework.beans.factory.config.BeanPostProcessor; import org.springframework.stereotype.Component; @Component public class EchoBeanPostProcessor implements BeanPostProcessor { @Override public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { System.out.println("--------------postProcessBeforeInitialization-------------" + "bean" + bean.getClass()); return bean; } @Override public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { System.out.println("--------------postProcessBeforeInitialization-------------" + "bean" + bean.getClass()); return bean; } }
2）示例
User类
@Component public class User { private ApplicationContext applicationContext; @Autowired public void setApplicationContext(ApplicationContext applicationContext) { this.applicationContext = applicationContext; } public void init() { System.out.println("User init"); } public void show() { System.out.println("User:" + applicationContext.getClass()); } }
UserConfig类
@Configuration public class MyConfig { @Bean(initMethod = "init") public User createUser() { return new User(); } }
调用
System.out.println(context.getBean("user"));
查看日志
User Set属性
--------------postProcessBeforeInitialization-------------beanclass com.lhx.spring.kuozhan.User
User init
--------------postProcessAfterInitialization-------------beanclass com.lhx.spring.kuozhan.User
3）自行实现ApplicationContextAware，这里起名为SpringContextAware,逻辑参考ApplicationContextAwareProcessor
public interface SpringContextAware { public void setApplicationContext(ApplicationContext applicationContext); }
编写ContextBeanPostProcessor
package com.lhx.spring.kuozhan; import org.springframework.beans.BeansException; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.config.BeanPostProcessor; import org.springframework.context.ApplicationContext; import org.springframework.stereotype.Component; @Component public class ContextBeanPostProcessor implements BeanPostProcessor { @Autowired private ApplicationContext applicationContext; @Override public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { if (bean instanceof SpringContextAware) { SpringContextAware sca = (SpringContextAware) bean; sca.setApplicationContext(applicationContext); } return bean; } @Override public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { // TODO Auto-generated method stub return bean; } }
实际类使用
package com.lhx.spring.kuozhan; import org.springframework.context.ApplicationContext; import org.springframework.stereotype.Component; @Component public class Dog implements SpringContextAware { private ApplicationContext applicationContext; public void setApplicationContext(ApplicationContext applicationContext) { this.applicationContext = applicationContext; } public void show() { System.out.println("Dog:" + applicationContext.getClass()); } }
使用：
context.getBean(Dog.class).show();
4）查看ApplicationContextAware内部实现：
AnnotationConfigApplicationContext→GenericApplicationContext→AbstractApplicationContext
找打refresh方法，prepareBeanFactory，
// Configure the bean factory with context callbacks.
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
ApplicationContextAwareProcessor内部
class ApplicationContextAwareProcessor implements BeanPostProcessor
方法三、Spring 4.3 新特性，构造方法直接添加，有局限性，与构造方法直接相关
@Component public class Bank { private ApplicationContext applicationContext; //spring 4.3 提供,与构造方法调用有关 public Bank(ApplicationContext applicationContext) { this.applicationContext=applicationContext; } public void show() { System.out.println("book:"+applicationContext.getClass()); } }
二、容器扩展
2.1、BeanFactoryPostProcessor
在beanFactory之后，BeanFactoryPostProcessor容器初始化之后，只初始化一次，先于所有容器以及BeanPostProcessor
void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException;
示例代码扩展2
源码：
AnnotationConfigApplicationContext→GenericApplicationContext→AbstractApplicationContext
找打refresh方法
public void refresh() throws BeansException, IllegalStateException { synchronized (this.startupShutdownMonitor) { // Prepare this context for refreshing. prepareRefresh(); // Tell the subclass to refresh the internal bean factory. ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); // Prepare the bean factory for use in this context. prepareBeanFactory(beanFactory); try { // Allows post-processing of the bean factory in context subclasses. postProcessBeanFactory(beanFactory); // Invoke factory processors registered as beans in the context. invokeBeanFactoryPostProcessors(beanFactory); // Register bean processors that intercept bean creation. registerBeanPostProcessors(beanFactory); // Initialize message source for this context. initMessageSource(); // Initialize event multicaster for this context. initApplicationEventMulticaster(); // Initialize other special beans in specific context subclasses. onRefresh(); // Check for listener beans and register them. registerListeners(); // Instantiate all remaining (non-lazy-init) singletons. finishBeanFactoryInitialization(beanFactory); // Last step: publish corresponding event. finishRefresh(); } catch (BeansException ex) { if (logger.isWarnEnabled()) { logger.warn("Exception encountered during context initialization - " + "cancelling refresh attempt: " + ex); } // Destroy already created singletons to avoid dangling resources. destroyBeans(); // Reset ‘active‘ flag. cancelRefresh(ex); // Propagate exception to caller. throw ex; } finally { // Reset common introspection caches in Spring‘s core, since we // might not ever need metadata for singleton beans anymore... resetCommonCaches(); } } }
2.2、BeanDefinitionRegistryPostProcessor
BeanFactoryPostProcessor的子类BeanDefinitionRegistryPostProcessor
void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException;
注册一个Bean到Spring容器中，类似标注了@Componment
示例
新建一个Person类
public class Person { private String name; public String getName() { return name; } public void setName(String name) { this.name = name; } @Override public String toString() { return "Person [name=" + name + "]"; } }
MyBeanDefinitionRegistryPostProcessor实现
package com.lhx.spring.kuozhan2; import org.springframework.beans.BeansException; import org.springframework.beans.factory.config.ConfigurableListableBeanFactory; import org.springframework.beans.factory.support.BeanDefinitionBuilder; import org.springframework.beans.factory.support.BeanDefinitionRegistry; import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor; import org.springframework.stereotype.Component; @Component public class MyBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor { @Override public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException { // TODO Auto-generated method stub } @Override public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException { for (int i = 0; i < 10; i++) { BeanDefinitionBuilder rootBeanDefinition = BeanDefinitionBuilder.rootBeanDefinition(Person.class); rootBeanDefinition.addPropertyValue("name", "admin" + i); registry.registerBeanDefinition("person" + i, rootBeanDefinition.getBeanDefinition()); } } }
使用
public static void main(String[] args) { AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext("com.lhx.spring.kuozhan2"); System.out.println(context.getBean("person1")); context.getBeansOfType(Person.class).values().forEach(System.out::println); context.close(); }
当然在使用
AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext("com.lhx.spring.kuozhan2");
使用context也可以注入
context.registerBeanDefinition(beanName, beanDefinition);
beanDefinition定义可以使用：BeanDefinitionBuilder rootBeanDefinition = BeanDefinitionBuilder.rootBeanDefinition(Person.class);
