【Spring】- Bean的生命周期的init和destroy方法的三种方式
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2022-05-24 18:13:39
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概述
在Spring中,向容器中注入一个Bean的时候可能期望在Bean的创建或者Bean的销毁的时候“做一些事情”,Spring支持三种方式来让我们实现。
实现方法
准备
HelloPrinter类:
public class HelloPrinter {
public void print() {
System.out.println("hello");
}
public void init() {
System.out.println("init run...");
}
public void destroy() {
System.out.println("destroy run...");
}
}
期望在HelloPrinter被容器创建的时候执行init方法,销毁的时候执行destroy方法。Application类:
public class Application {
public static void main(String[] args) {
ConfigurableApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
HelloPrinter printer = (HelloPrinter) context.getBean("helloPrinter");
printer.print();
//shutdown容器
context.registerShutdownHook();
}
}
这里必须调用context.registerShutdownHook()方法去关闭容器(web应用中则不用)来达到容器销毁Bean的目的。1. xml配置指定
通过在xml配置文件依赖注入注入Bean的时候添加init-method和destroy-method属性来指定:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
<bean id="helloPrinter" class="io.spring.hello.HelloPrinter" init-method="init" destroy-method="destroy"/>
</beans>
容器在创建和销毁Bean的时候会去执行init-method和destroy-method中指定的方法
运行输出:
init run...
hello
七月 06, 2017 10:34:58 上午 org.springframework.context.support.ClassPathXmlApplicationContext doClose
信息: Closing org[email protected]2e817b38: startup date [Thu Jul 06 10:34:58 CST 2017]; root of context hierarchy
destroy run...
例:
<?xml version="1.0" encoding="UTF-8"?>
<beans default-init-method="init" default-destroy-method="destroy" xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
<bean id="helloPrinter" class="io.spring.hello.HelloPrinter" />
</beans>
运行输出:init run...
hello
七月 06, 2017 10:40:23 上午 org.springframework.context.support.ClassPathXmlApplicationContext doClose
信息: Closing org[email protected]2e817b38: startup date [Thu Jul 06 10:40:22 CST 2017]; root of context hierarchy
destroy run...
2. 实现InitializingBean接口和DisposableBean接口
InitializingBean和DisposableBean接口都只有一个方法
public interface InitializingBean {
void afterPropertiesSet() throws Exception;
}
public interface DisposableBean {
void destroy() throws Exception;
}
例:
HelloPrinter:
public class HelloPrinter implements InitializingBean, DisposableBean{
public void print() {
System.out.println("hello");
}
@Override
public void destroy() throws Exception {
System.out.println("InitializingBean init method run..");
}
@Override
public void afterPropertiesSet() throws Exception {
System.out.println("afterPropertiesSet run..");
}
}
xml配置如下:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
<bean id="helloPrinter" class="io.spring.hello.HelloPrinter" />
</beans>
只需要简单的注入即可。运行输出:
afterPropertiesSet run..
hello
七月 06, 2017 10:46:56 上午 org.springframework.context.support.ClassPathXmlApplicationContext doClose
信息: Closing org[email protected]2e817b38: startup date [Thu Jul 06 10:46:56 CST 2017]; root of context hierarchy
InitializingBean init method run..
3. 使用@PostConstruct和@PreDestroy注解
@PostConstruct和@PreDestroy注解效果基本等同于init-method和destroy-method。例:
HelloPrinter:
public class HelloPrinter {
public void print() {
System.out.println("hello");
}
@PostConstruct
public void init() {
System.out.println("init by annotation run...");
}
@PreDestroy
public void destroy() {
System.out.println("destroy by annotation run...");
}
}
xml配置支持注解方式:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
<!-- 注解支持 -->
<context:annotation-config />
<bean id="helloPrinter" class="io.spring.hello.HelloPrinter" />
</beans>
运行输出:init by annotation run...
hello
destroy by annotation run...
三种方式并存时候的顺序:
下面例子:
HelloPrinter:
public class HelloPrinter implements InitializingBean, DisposableBean {
public void print() {
System.out.println("hello");
}
public void initByXml() {
System.out.println("init by xml run...");
}
public void destroyByXml() {
System.out.println("detroy bry xml run...");
}
@PostConstruct
public void initByAnnotation() {
System.out.println("init by annotation run...");
}
@PreDestroy
public void destroyByAnnotation() {
System.out.println("destroy by annotation run...");
}
@Override
public void destroy() throws Exception {
System.out.println("destroy by DisposableBean");
}
@Override
public void afterPropertiesSet() throws Exception {
System.out.println("init by InitializingBean");
}
}
xml配置:<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
<!-- 注解支持 -->
<context:annotation-config />
<bean id="helloPrinter" class="io.spring.hello.HelloPrinter" init-method="initByXml" destroy-method="destroyByXml" />
</beans>
运行输出:
init by annotation run...
init by InitializingBean
init by xml run...
hello
七月 06, 2017 11:21:51 上午 org.springframework.context.support.ClassPathXmlApplicationContext doClose
信息: Closing org[email protected]2e817b38: startup date [Thu Jul 06 11:21:51 CST 2017]; root of context hierarchy
destroy by annotation run...
destroy by DisposableBean
detroy bry xml run...
顺序:
- @PostConstruct标记的方法
- InitializingBean中的afterPropertiesSet方法
- xml的init-method指定的方法
- Bean的行为。。。
- @PreDestroy标记的方法
- DisposableBean中的destroy方法
- xml的destroy-method指定的方法
注意:如果有多种方式指定同一个方法(例如xml配置和注解都指定的同一个方法)那么这个方法只会被运行一次。