（002）spring容器中bean初始化、销毁时执行的方法及其3种实现方式

spring容器中bean初始化或者销毁时会执行一些方法，有3种实现方式。

1、实现InitializingBean、DisposableBean接口，在bean的属性设置后和bean销毁时分别执行afterPropertiesSet和destroy方法

　　pom.xml文件

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.edu.spring</groupId>
    <artifactId>spring</artifactId>
    <version>1.0.0</version>

    <name>spring</name>
    <!-- FIXME change it to the project's website -->
    <url>http://www.example.com</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>
    
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.3.2.RELEASE</version>
        </dependency>
    </dependencies>

</project>

　　Cat.java

package com.edu.spring;

import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;

public class Cat implements InitializingBean,DisposableBean{

    @Override
    public void afterPropertiesSet() throws Exception {
        // TODO Auto-generated method stub
        System.out.println("-----------afterPropertiesSet--------------");
    }

    @Override
    public void destroy() throws Exception {
        // TODO Auto-generated method stub
        System.out.println("-----------destroy--------------");
    }

}

　　MyConfig.java

package com.edu.spring;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MyConfig {
    
    @Bean
    public Cat createCat(){
        return new Cat();
    }
}

　　App.java

package com.edu.spring;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;


public class App 
{
    public static void main( String[] args )
    {
        AnnotationConfigApplicationContext context=new AnnotationConfigApplicationContext(MyConfig.class);
        System.out.println(context.getBean(Cat.class));
        context.close();
    }
}

　　运行结果如下：

 2、在@Bean注解中用initMethod和destroyMethod两个属性指定实体类中的两个方法，这两个方法分别在bean初始化和销毁时候执行

　　Dog.java

package com.edu.spring;

public class Dog {

    public void init(){
        System.out.println("----------Dog init---------");
    }
    
    public void destroy(){
        System.out.println("----------Dog destroy---------");
    }
}

　　MyConfig.java

package com.edu.spring;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MyConfig {
    
    @Bean(initMethod="init",destroyMethod="destroy")
    public Dog createDog(){
        return new Dog();
    }
}

　　App.java

package com.edu.spring;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;


public class App 
{
    public static void main( String[] args )
    {
        AnnotationConfigApplicationContext context=new AnnotationConfigApplicationContext(MyConfig.class);
        System.out.println(context.getBean(Dog.class));
        context.close();
    }
}

　　运行结果如下：

 3、在实体类中方法上面分别添加@PostConstruct和@PreDestroy注解，分别指定初始化和销毁方法

　　Animal.java

package com.edu.spring;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;

public class Animal {

    @PostConstruct
    public void initial(){
        System.out.println("-------initial---------");
    }
    
    @PreDestroy
    public void close(){
        System.out.println("---------close---------");
    }
}

　　MyConfig.java

package com.edu.spring;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MyConfig {
    
    @Bean
    public Animal createAniaml(){
        return new Animal();
    }
}

　　App.java

package com.edu.spring;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;


public class App 
{
    public static void main( String[] args )
    {
        AnnotationConfigApplicationContext context=new AnnotationConfigApplicationContext(MyConfig.class);
        System.out.println(context.getBean(Animal.class));
        context.close();
    }
}

　　运行结果如下：