三种依赖注入的方式
1、注解
@Component
public class User {
@Autowired
private ApplicationContext applicationContext;
public void show() {
System.out.println("user:"+applicationContext.getClass());
}
}
2、实现ApplicationContextAware接口
@Component
public class Book implements ApplicationContextAware {
private ApplicationContext applicationcontext;
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
this.applicationcontext=applicationContext;
}
public void show() {
System.out.println("book:"+applicationcontext.getClass());
}
}
3、构造方法直接构造（局限性 1⃣️构造函数只能有一个，如果有多个必须要有无参构造此时spring 就会调用无参，不会调用 applicationcontext
2⃣️构造函数的参数，必须要在Spring 容器中有 ）
@Component
public class Bank {
private ApplicationContext applicationContext;
public Bank(ApplicationContext applicationContext) {
this.applicationContext=applicationContext;
}
public void show() {
System.out.println("Bank:"+applicationContext.getClass());
}
}
___________________________BeanPostProcesser___________________________
在bean依赖装配（设置完成后）完成触发
这里可以指定Bean做一些处理，比如返回该对象的代理对象
@Component
public class EchoBeanPostProcesser implements BeanPostProcessor {
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
System.out.println("≈≈≈≈≈≈≈≈≈>>>属性设置之后，init之前"+bean.getClass());
if(bean instanceof User)
return new LogUser();
return bean;
}
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
System.out.println("≈≈≈≈≈≈≈≈≈>>>属性设置之后，init之后"+bean.getClass());
return bean;
}
}