Bean后处理器

Bean后处理器是一种特殊的Bean,这种特殊的Bean并不对外提供服务,无需id属性,可以负责对容器中的其他Bean执行后处理

Bean后处理必须实现BeanPostProcessor接口,该接口包含以下两个方法

Object postProcessorBeforeInitialization(Object bean,String beanName) throws BeansException

Object postProcessorAfterInitialization(Object bean,String beanName) throws BeansException

public interface Person {
	public void sayHello();
}

public class Teacher implements Person{
	
	private Student student;
	private String username;
	@Override
	public void sayHello() {
		System.out.println("我是一个老师");
		student.sayHello();
	}
	
	@PostConstruct
	public void init(){
		System.out.println("教师类初始化");
	}
	
	@PreDestroy
	public void close(){
		System.out.println("教师类销毁之前调用的方法");
	}

	public String getUsername() {
		return username;
	}

	public void setUsername(String username) {
		this.username = username;
	}

	public Student getStudent() {
		return student;
	}

	public void setStudent(Student student) {
		this.student = student;
	}
}

public class Student implements Person{

	@Override
	public void sayHello() {
		System.out.println("我是一个学生");
		
	}

}

<bean id="student" class="com.Student"></bean>
	<bean id="teacher" class="com.Teacher">
		<property name="student" ref="student"></property>
		<property name="username">
			<value>moweng</value>
		</property>
	</bean>
	<bean id="beanPostProcessor" class="com.MyBean"></bean>

public static void main(String[] args) {
		ApplicationContext context=new ClassPathXmlApplicationContext("config/applicationContext.xml");
		Person teacher=(Teacher)context.getBean("teacher");
		teacher.sayHello();
	}

 小结:当采用BeanFactory作为spring容器时,必须手动注册BeanPostProcessor,.ApplicationContext可以自动检测容器中Bean后处理器,并自动注册

public static void main(String[] args) {
	
		ClassPathResource resource=new ClassPathResource("config/applicationContext.xml");
		XmlBeanFactory factory=new XmlBeanFactory(resource);
		MyBean beanProcessorBean=(MyBean)factory.getBean("beanPostProcessor");
		factory.addBeanPostProcessor(beanProcessorBean);
		Person teacher=(Teacher)factory.getBean("teacher");
		teacher.sayHello();
	}