spring 初始化和销毁的三种方法

• spring 中初始化和销毁有三种办法

1、实现接口 DisposableBean ,initilzingBean
2、使用注解 @PostConstructor, @PreDestory
3、@Bean(initMethod = "",destroyMethod="")

package com.shanjiancaofu.ad.service.impl;

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

@Configuration
public class AppConfig {
       // initMethod  指定类的初始化方法, destroyMethod 指定类的销毁方法
    @Bean(initMethod = "init", destroyMethod = "destroyMethod")
    User user() {
        return new User();
    }
}

User 类

package com.shanjiancaofu.ad.service.impl;

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

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


class User implements InitializingBean, DisposableBean {
    public String userName;

    public User() {
        System.out.println("User constructor");
    }

    public void init() {
        this.userName = "initName";
        System.out.println(" user init. ....");
    }

    public void destroyMethod() {
        this.userName = "destroyName";
        System.out.println(" user destroy. ....");
    }

    @PreDestroy
    public void preDestroy() {
        System.out.println("@PreDestroy ...");
    }

    @PostConstruct
    public void postConstruct() {
        System.out.println(" @PostConstruct. ....");
    }

    @Override
    public String toString() {
        return "user:" + this.userName;
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        System.out.println("InitializingBean afterPropertiesSet");
    }

    @Override
    public void destroy() throws Exception {
        System.out.println("DisposableBean destroy");
    }
}

启动spring 应用 控制台输出:

User constructor
@PostConstruct. ....
InitializingBean afterPropertiesSet
user init. ....

关闭spring 应用 控制台输出:

@PreDestroy ...
DisposableBean destroy
user destroy. ....

•  获取spring 容器中的bean

@Service
@Lazy(false)
public class SpringContextHolder implements ApplicationContextAware, DisposableBean {
    private static ApplicationContext applicationContext = null;

    private static Logger logger = LoggerFactory.getLogger(SpringContextHolder.class);

    /**
     * 取得存储在静态变量中的ApplicationContext.
     */
    public static ApplicationContext getApplicationContext() {
        assertContextInjected();
        return applicationContext;
    }

    /**
     * 从静态变量applicationContext中取得Bean, 自动转型为所赋值对象的类型.
     */
    @SuppressWarnings("unchecked")
    public static <T> T getBean(String name) {
        assertContextInjected();
        return (T) applicationContext.getBean(name);
    }

    /**
     * 从静态变量applicationContext中取得Bean, 自动转型为所赋值对象的类型.
     */
    public static <T> T getBean(Class<T> requiredType) {
        assertContextInjected();
        return applicationContext.getBean(requiredType);
    }

    /**
     * 清除SpringContextHolder中的ApplicationContext为Null.
     */
    public static void clearHolder() {
        applicationContext = null;
    }

    /**
     * 实现ApplicationContextAware接口, 注入Context到静态变量中.
     */
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) {
        SpringContextHolder.applicationContext = applicationContext;
    }

    /**
     * 实现DisposableBean接口, 在Context关闭时清理静态变量.
     */
    @Override
    public void destroy() throws Exception {
        SpringContextHolder.clearHolder();
    }

    /**
     * 检查ApplicationContext不为空.
     */
    private static void assertContextInjected() {
        Validate.validState(applicationContext != null, "applicaitonContext属性未注入, 请在applicationContext.xml中定义SpringContextHolder.");
    }
}