最近在重新学习spring优秀的框架，顺便记录一下自己的总结，同时分享给大家。bean的生命周期指的是：bean创建–>初始化–>销毁 的过程，bean的生命周期由容器进行管理，我们可以自定义bean的初始化和销毁方法来满足我们的需求，当容器在bean进行到当前生命周期的时候，来调用自定义的初始化和销毁方法。今天主要讲解如何定义初始化和销毁的4中方法。
1，使用initMethod和destroyMethod
下面代码全部是通过配置类，而不是配置xml文件
Train.java
package cap5.bean;
public class Train {
public Train() {
// TODO Auto-generated constructor stub
super();
System.out.println("Train创建");
}
public void init() {
System.out.println("train init...");
}
public void destroy() {
System.out.println("train destroy");
}
}MainConfig.java
package cap5.config;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.FilterType;
import org.springframework.context.annotation.ComponentScan.Filter;
import cap5.bean.Bike;
import cap5.bean.Jeep;
import cap5.bean.TaolongBeanPostProcessor;
import cap5.bean.Train;
//@ComponentScan(value= {"cap5.bean"},includeFilters= {@Filter(type=FilterType.ASSIGNABLE_TYPE,classes=TaolongBeanPostProcessor.class)})
@Configuration
public class MainConfig {
@Bean(initMethod="init",destroyMethod="destroy")
public Train train() {
return new Train();
}
/*@Bean
public Bike bike() {
return new Bike();
}*/
/*@Bean
public Jeep jeep() {
return new Jeep();
}*/
}MainTest.java
package cap5.test;
import org.junit.Test;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import cap5.config.MainConfig;
public class MainTest {
@Test
public void test() {
AnnotationConfigApplicationContext app = new AnnotationConfigApplicationContext(MainConfig.class);
System.out.println("IOC 容器创建完成");
System.out.println("IOC 容易准备关闭");
/*String[] names = app.getBeanDefinitionNames();
for(String name:names) {
System.out.println("name="+name);
}*/
app.close();
}
}打印结果：
2，让bean实现InitializingBean和DisposableBean接口，然后分别实现afterPropertiesSet（）方法和destroy（）方法
afterPropertiesSet()：从名字上就能看出，这个其实不是bean真正的初始化方法，而是在bean构建完成，设置好了属性之后调用的方法—–作用相当于初始化方法
destroy()：当bean销毁时,会把单实例bean进行销毁
Bike.java
package cap5.bean;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
public class Bike implements InitializingBean,DisposableBean{
public Bike() {
// TODO Auto-generated constructor stub
super();
System.out.println("bike construct...");
}
public void destroy() throws Exception {
// TODO Auto-generated method stub
System.out.println("bike destroy");
}
public void afterPropertiesSet() throws Exception {
// TODO Auto-generated method stub
System.out.println("bike init...");
}
}MainConfig.java
package cap5.config;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.FilterType;
import org.springframework.context.annotation.ComponentScan.Filter;
import cap5.bean.Bike;
import cap5.bean.Jeep;
import cap5.bean.TaolongBeanPostProcessor;
import cap5.bean.Train;
//@ComponentScan(value= {"cap5.bean"},includeFilters= {@Filter(type=FilterType.ASSIGNABLE_TYPE,classes=TaolongBeanPostProcessor.class)})
@Configuration
public class MainConfig {
/*@Bean(initMethod="init",destroyMethod="destroy")
public Train train() {
return new Train();
}*/
@Bean
public Bike bike() {
return new Bike();
}
/*@Bean
public Jeep jeep() {
return new Jeep();
}*/
}MainTest.java和上面的一样，就不再贴上来了
测试结果：
3，使用JSR250规则定义的注解来实现，JSR250的详细了解可自行百度，主要使用如下两个注解
@PostConstruct：从名字上也能看出这个注解的意思，就是在bean构建完成之后调用—相当于初始化
@PreDestroy：从名字上也能看出是在beandestroy之前会执行的被注解的方法—相当于销毁
Jeep.java
package cap5.bean;
import javax.annotation.*;
public class Jeep {
public Jeep() {
// TODO Auto-generated constructor stub
super();
System.out.println("jeep construct...");
}
@PostConstruct
public void init() {
System.out.println("jeep init...");
}
@PreDestroy
public void destroy() {
System.out.println("jeep destroy...");
}
}MainConfig.java
package cap5.config;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.FilterType;
import org.springframework.context.annotation.ComponentScan.Filter;
import cap5.bean.Bike;
import cap5.bean.Jeep;
import cap5.bean.TaolongBeanPostProcessor;
import cap5.bean.Train;
//@ComponentScan(value= {"cap5.bean"},includeFilters= {@Filter(type=FilterType.ASSIGNABLE_TYPE,classes=TaolongBeanPostProcessor.class)})
@Configuration
public class MainConfig {
/*@Bean(initMethod="init",destroyMethod="destroy")
public Train train() {
return new Train();
}*/
/*@Bean
public Bike bike() {
return new Bike();
}*/
@Bean
public Jeep jeep() {
return new Jeep();
}
}MainTest.java和上面一样，不重新贴了
运行结果：
4，第四种方法是使用后置处理器，在bean初始化前后时会调用实现了BeanPostProcessor接口并重写两个方法，分别是：postProcessBeforeInitialization()和postProcessAfterInitialization()方法
TaolongBeanPostProcessor.java
package cap5.bean;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.stereotype.Component;
@Component
public class TaolongBeanPostProcessor implements BeanPostProcessor {
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
// TODO Auto-generated method stub
System.out.println("bean-----"+beanName+" init start...");
return bean;
}
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
// TODO Auto-generated method stub
System.out.println("bean------"+beanName+" init end...");
return bean;
}
}Plane.java
package cap5.bean;
public class Plane {
public Plane() {
// TODO Auto-generated constructor stub
System.out.println("plane construct...");
}
}MainConfig.java
package cap5.config;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.FilterType;
import org.springframework.context.annotation.ComponentScan.Filter;
import cap5.bean.Bike;
import cap5.bean.Jeep;
import cap5.bean.Plane;
import cap5.bean.TaolongBeanPostProcessor;
import cap5.bean.Train;
//@ComponentScan(value= {"cap5.bean"},includeFilters= {@Filter(type=FilterType.ASSIGNABLE_TYPE,classes=TaolongBeanPostProcessor.class)})
@Configuration
public class MainConfig {
/*@Bean(initMethod="init",destroyMethod="destroy")
public Train train() {
return new Train();
}*/
/*@Bean
public Bike bike() {
return new Bike();
}*/
/*@Bean
public Jeep jeep() {
return new Jeep();
}*/
@Bean
public Plane plane() {
return new Plane();
}
@Bean
public TaolongBeanPostProcessor taolongBeanPostProcessor() {
return new TaolongBeanPostProcessor();
}
}测试效果：
上面都是默认情况下的单例的bean模式，加入在多个bean的情况下呢？容器如何管理bean的生命周期呢？
（1）当bean是多实例的模式下，bean不会在IOC容器创建的时候，去实例化bean，而是在真正使用该bean的时候实例化，这一点可以进行简单的测试一下，当增加@scope（”protorype“）时，就是多实例创建bean了
（2）当容器关闭的时候，多实例的情况下怎么处理，会不会将多个实例同时销毁呢？
我们来简单的测试一下：
MainConfig.java部分代码
@Scope("prototype")
@Bean
public Bike bike() {
return new Bike();
}MianTest.java
package cap5.test;
import org.junit.Test;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import cap5.bean.Bike;
import cap5.config.MainConfig;
public class MainTest {
@Test
public void test() {
AnnotationConfigApplicationContext app = new AnnotationConfigApplicationContext(MainConfig.class);
System.out.println("IOC 容器创建完成");
Bike bike1 = (Bike)app.getBean(Bike.class);
Bike bike2 = (Bike)app.getBean(Bike.class);
System.out.println(bike1==bike2);
System.out.println("IOC 容易准备关闭");
/*String[] names = app.getBeanDefinitionNames();
for(String name:names) {
System.out.println("name="+name);
}*/
app.close();
}
}运行结果：
这个结果证实了一下问题
1，多实例的时候bean不会随着IOC容器的构建而创建，而是在使用的时候创建的getBean()
2,多实例的时候，当容器进行关闭的时候，bean实例不会调用destroy方法，说明容器不控制多实例的销毁
3，多实例的情况下，返回的bean的对象时不一样的，返回为false
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