Spring-Bean的构造函数和Setter执行顺序以及InitializingBean

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经过试验得知，Spring注入Bean，实例化一个Bean的时候，顺序如下：

1. 这个class的构造函数被执行；

2.Setter被执行；

3.如果这个class实现了InitializingBean（即implements InitializingBean）则，接下来执行public void afterPropertiesSet() throws Exception() 中的内容。

实例，

当我不用InitializingBean 方法，而是直接在构造器中知己执行jedis = jedisPool.getResource(); 则因为此时程序只是执行到上面的第1步，这时候jedisPool==null，那这里肯定会报错。会导致RedisClient实例化失败，并且抛出NullPointerException

下面贴上错误的代码。注意这里对RedisClient进行了Spring的Setter注入。

package com.foundjet.flylib.redis;import java.util.ArrayList;import java.util.List;import redis.clients.jedis.Jedis;import redis.clients.jedis.JedisPool;import redis.clients.jedis.JedisPoolConfig;import redis.clients.jedis.ShardedJedis;import redis.clients.jedis.ShardedJedisPool;import redis.clients.jedis.JedisShardInfo;public class RedisClient {private Jedis jedis;//非切片额客户端连接      private JedisPool jedisPool;//非切片连接池      private ShardedJedis shardedJedis;//切片额客户端连接      private ShardedJedisPool shardedJedisPool;//切片连接池          private String password = "tea@fjdev";          public RedisClient()       {           initialPool();   //        initialShardedPool();           jedis = jedisPool.getResource();          jedis.auth(password);        jedis.select(10);//      shardedJedis = shardedJedisPool.getResource();           }          /**      * 初始化非切片池      */      private void initialPool()       {           // 池基本配置           JedisPoolConfig config = new JedisPoolConfig();   //        config.setMaxActive(20);         config.setMaxTotal(20);        config.setMaxIdle(5);           config.setMaxWaitMillis(1000L);           config.setTestOnBorrow(false);                     jedisPool = new JedisPool(config, "127.0.0.1", 6379);      }            /**       * 初始化切片池       */       private void initialShardedPool()       {           // 池基本配置           JedisPoolConfig config = new JedisPoolConfig();   //        config.setMaxActive(20);         config.setMaxTotal(20);        config.setMaxIdle(5);           config.setMaxWaitMillis(1000l);           config.setTestOnBorrow(false);           // slave链接           List<JedisShardInfo> shards = new ArrayList<JedisShardInfo>();           shards.add(new JedisShardInfo("127.0.0.1", 6379, "master"));                   // 构造池           shardedJedisPool = new ShardedJedisPool(config, shards);       }         public void show() {               keyOperate();           //        StringOperate();   //        ListOperate();   //        SetOperate();  //        SortedSetOperate();  //        HashOperate();           jedis.close();//        shardedJedis.close();    }           private void keyOperate() {    String k = "key3";    jedis.set(k, "ccc");    System.out.println("value of " + k + " is: "  + jedis.get(k));    }    public static void main(String[] args) {RedisClient client = new RedisClient();client.show();}}

修正后的代码见https://github.com/flylib/rediskit

RedisClient.java

片段如下

package net.flylib.rediskit;import org.springframework.beans.factory.InitializingBean;import redis.clients.jedis.Jedis;import redis.clients.jedis.JedisPool;import redis.clients.jedis.Protocol;public class RedisClient implements InitializingBean {private Jedis jedis;// 非切片额客户端连接private JedisPool jedisPool;// 非切片连接池public RedisClient() {//jedis = jedisPool.getResource();}@Override public void afterPropertiesSet() throws Exception {jedis = jedisPool.getResource();}public JedisPool getJedisPool() {return jedisPool;}public void setJedisPool(JedisPool jedisPool) {this.jedisPool = jedisPool;}public String set(final String key, String value) {jedis.get("");return jedis.set(key, value);}public String get(final String key) {return jedis.get(key);}}

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