IOC容器中Bean的生命周期方法
SpringIOC容器可以管理Bean的生命周期,Spring允许在Bean生命周期的特定点执行定制的任务
Spring IOC容器对Bean的生命周期进行管理的过程:
在Bean的声明里设置init-method和destory-method属性,为Bean指定初始化和销毁方法
// Car
public class Car {
public Car() {
System.out.println("car's constructor");
}
private String brand;
public void setBrand(String brand) {
this.brand = brand;
}
public void init() {
System.out.println("init...");
}
public void destroy() {
System.out.println("destroy...");
}
}
// xml
<bean id="car" class="com.sangyu.test03.Car" init-method="init" destroy-method="destroy">
<property name="brand" value="Audi"></property>
</bean>
// main
public class Main {
public static void main(String[] args) {
ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
Car car =(Car) ctx.getBean("car");
System.out.println(car);
ctx.close();
}
}
创建Bean后置处理器
Bean后置处理器允许在调用初始化方法前后对Bean进行额外的处理,并且是对IOC容器里的所有Bean实例逐一处理,并不是针对某一个Bean实例。最典型的应用是:检查Bean属性的正确性或根据特定的标准更改Bean的属性
// Car
public class Car {
public Car() {
System.out.println("car's constructor");
}
private String brand;
public void setBrand(String brand) {
this.brand = brand;
}
public void init() {
System.out.println("init...");
}
public void destroy() {
System.out.println("destroy...");
}
}
// XML
<bean id="car" class="com.sangyu.test03.Car" init-method="init" destroy-method="destroy">
<property name="brand" value="Audi"></property>
</bean>
<bean class="com.sangyu.test03.MyBeanPostProcessor"></bean>
// Main
public class Main {
public static void main(String[] args) {
ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
Car car =(Car) ctx.getBean("car");
System.out.println(car);
ctx.close();
}
}
// 实现BeanPostProcessor接口,并实现
// postProcessBeforeInitialization(Object bean, String beanName) :init-method之前被调用
// postProcessAfterInitialization(Object bean, String beanName) :init-method之后被调用
// bean:实例本身
// beanName:IOC容器配置的bean的名字
// 返回值:是实际上返回给用户的那个Bean,注意:可以在以上两个方法中修改返回的bean,甚至返回一个新的bean
public class MyBeanPostProcessor implements BeanPostProcessor {
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
System.out.println("postProcessBeforeInitialization :" + bean + ", " + beanName);
return bean;
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
System.out.println("postProcessAfterInitialization :" + bean + ", " + beanName);
return bean;
}
}
添加Bean后置处理器后Bean的生命周期