InitializingBean、@PostConstruct、@Bean(initMethod = “init“)的作用和比较

需求背景：

1、项目启动时，加载缓存

2、项目启动时，开启对外服务端

InitializingBean是Spring提供的拓展性接口，InitializingBean接口为bean提供了属性初始化后的处理方法，它只有一个afterPropertiesSet方法，凡是继承该接口的类，在bean的属性初始化后都会执行该方法。

package com.pcf.spdemo.configuration;

import com.pcf.spdemo.common.httpserver.NettyServer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component
public class BeanInit implements InitializingBean {
    private static Logger log = LoggerFactory.getLogger(BeanInit.class);

    @Autowired
    private NettyServer nettyServer;

    @Override
    public void afterPropertiesSet() throws Exception {
        log.info("netty----------------------------------");
        init();
    }

    private void init() {
        
        new Thread(){
            @Override
            public void run() {
                nettyServer.start();
            }
        }.start();
        log.info("netty对外服务端已启动...");
    }
}

效果图：

@PostContruct是JDK自带的注解，用来修饰非静态void方法。spring初始化该bean后，会执行bean中的该方法。

示例代码：

package com.pcf.spdemo.configuration;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;

@Component
public class InitCache {
    private static Logger log = LoggerFactory.getLogger(InitCache.class);

    @PostConstruct
    public void init() {
        log.info("通过@PostConstruct注解，实现项目启动时加载缓存...");
    }
}

效果展示：

代码实现：

package com.pcf.spdemo.configuration;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Component;

@Component
public class InitCache {
    private static Logger log = LoggerFactory.getLogger(InitCache.class);

    @Bean(initMethod = "init")
    public void init() {
        log.info("通过配置@bean的init-method属性，实现项目启动时加载缓存...");
    }
}

效果展示：

bean初始化时实现。（没见用过，最好别用这种方式）

代码实例：

package com.pcf.spdemo.configuration;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

@Component
public class InitCache {
    private static Logger log = LoggerFactory.getLogger(InitCache.class);

    public InitCache() {
        init();
    }

    public void init() {
        log.info("通过放入bean构造方法，实现项目启动时加载缓存...");
    }
}

效果展示：

测试代码：

package com.pcf.spdemo.configuration;

import com.pcf.spdemo.common.httpserver.NettyServer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;

@Component
public class BeanInit implements InitializingBean {
    private static Logger log = LoggerFactory.getLogger(BeanInit.class);

    @Autowired
    private NettyServer nettyServer;

    public BeanInit() {
        init2();
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        log.info("netty----------------------------------");
        init();
    }

    private void init() {
        
        new Thread(){
            @Override
            public void run() {
                nettyServer.start();
            }
        }.start();
        log.info("netty对外服务端已启动...");
    }

    @PostConstruct
    public void init1() {
        log.info("通过@PostConstruct注解，实现项目启动时加载缓存...");
    }

    public void init2() {
        log.info("通过放入bean构造方法，实现项目启动时加载缓存...");
    }

    @Bean(initMethod = "init")
    public void init3() {
        log.info("通过配置@bean的init-method属性，实现项目启动时加载缓存...");
    }
}

测试结果展示：

由此可以看出：

优先级： 构造方法 > @PostContruct > afterPropertiesSet() > init-method