Cannot get Jedis connection; nested exception is java.lang.NullPointerException

前提：Redis服务器已经运行，且端口号，服务器地址都已经配置正常，但任然抛出无法获取连接异常

原来的代码如下：

[java]
view plain
copy

@Bean  
   public JedisConnectionFactory connectionFactory(){  
       JedisConnectionFactory jedisConnectionFactory = new JedisConnectionFactory();  
       jedisConnectionFactory.setUsePool(true);  
       jedisConnectionFactory.setPoolConfig(jedisPoolConfig());  
       jedisConnectionFactory.setHostName(environment.getProperty("redis.host"));  
       jedisConnectionFactory.setPort(Integer.parseInt(environment.getProperty("redis.port")));  
       return jedisConnectionFactory;  
   }  

其他配置都很正常，但是运行后会抛出空指针异常。

Request processing failed; nested exception is org.springframework.data.redis.RedisConnectionFailureException: Cannot get Jedis connection; nested exception is java.lang.NullPointerException

解决方法如下，在return前添加如下代码

[java]
view plain
copy

jedisConnectionFactory.afterPropertiesSet();  

看源码便知原因：看jedis如何获取到连接的：

[java]
view plain
copy

public JedisConnection getConnection() {  
        Jedis jedis = fetchJedisConnector();  
        JedisConnection connection = (usePool ? new JedisConnection(jedis, pool, dbIndex) : new JedisConnection(jedis,  
                null, dbIndex));  
        connection.setConvertPipelineAndTxResults(convertPipelineAndTxResults);  
        return postProcessConnection(connection);  
    }  

我们看fetchJedisConnector()方法：

[java]
view plain
copy

protected Jedis fetchJedisConnector() {  
        try {  
            if (usePool && pool != null) {  
                return pool.getResource();  
            }  
            Jedis jedis = new Jedis(getShardInfo());  
            // force initialization (see Jedis issue #82)  
            jedis.connect();  
            return jedis;  
        } catch (Exception ex) {  
            throw new RedisConnectionFailureException("Cannot get Jedis connection", ex);  
        }  
    }  

如果没用用pool的话，需要用到getShardInfo()方法，而这个方法就是返回一个JedisShardInfo shardInfo。那么这个JedisShardInfo shardInfo在什么时候初始化呢？查看后发现，哈哈在这：

[java]
view plain
copy

public void afterPropertiesSet() {  
        if (shardInfo == null) {  
            shardInfo = new JedisShardInfo(hostName, port);  
  
            if (StringUtils.hasLength(password)) {  
                shardInfo.setPassword(password);  
            }  
  
            if (timeout > 0) {  
                setTimeoutOn(shardInfo, timeout);  
            }  
        }  
  
        if (usePool) {  
            this.pool = createPool();  
        }  
    }  

这个方法将在所有的属性被初始化后调用。但是会在init前调用。是spring中InitializingBean接口的方法。spring-data-redis里面实现了它。在这里对shardIndo类进行了初始化。所以，我们只要在代码中添加：

[java]
view plain
copy

jedisConnectionFactory.afterPropertiesSet();  

这句就可以啦。再运行一次，连接成功！