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前言

  事情是这样的 今天在拉取了同事的代码做redis缓存设置的时候，发现即使已经设置了database, 但是存数据的时候还是用的默认0数据库。这引起了我的好奇，遂开始琢磨是什么情况造成的这种现象。

配置

上述仅为测试代码问题，为了便于维护可以这么写，

spring:
  redis:
    host: ${REDIS_HOST:localhost}
    port: ${REDIS_PORT:6379}
    password: ${REDIS_PASSWORD:}
    database: ${REDIS_DATABASE:0}

加载类

然后通过RedisConfiguration 加载

@ConfigurationProperties("spring.redis")
public class RedisConfiguration {
	private String host;
	private int port;
	private String password;
	private int database;

    // getters and setters...
}

问题

  上网找了一系列的文章都没解决，后来仔细观察研究发现是database多了个空格，正确的该是这样，没想到一个空格浪费了这么多时间

  信心满满的以为这就万事大吉了，结果一运行发现依然不可以，后又开始检查,最后发现是少了几个依赖

发现没有引入commons-pool2依赖，加上了依赖之后再运行发现已经切换了

commons-pool 对象池

  引入Commons Pool对象池，用于缓存Redis连接的原因是因为Lettuce本身是基于Netty的异步驱动，在异步访问时并不需要创建连接池，但基于Servlet模型的同步访问时，连接池是有必要的。目的是为了复用对象，以减少创建对象的开销，所以一定记得要加这个依赖。

/**

* Creates an instance that can be served by the pool and wrap it in a

* {@link PooledObject} to be managed by the pool.

*

* @return a {@code PooledObject} wrapping an instance that can be served by the pool

*

* @throws Exception if there is a problem creating a new instance,

*    this will be propagated to the code requesting an object.

*/

PooledObject makeObject()throws Exception;

/**

* Destroys an instance no longer needed by the pool.

* <p>* It is important for implementations of this method to be aware that there

* is no guarantee about what state <code>obj</code>will be in and the

* implementation should be prepared to handle unexpected errors.

* </p> * <p>* Also, an implementation must take in to consideration that instances lost

* to the garbage collector may never be destroyed.

* </p>*

* @param p a {@code PooledObject} wrapping the instance to be destroyed

*

* @throws Exception should be avoided as it may be swallowed by

*    the pool implementation.

*

* @see #validateObject

* @see ObjectPool#invalidateObject

*/

void destroyObject(PooledObject p)throws Exception;

/**

* Ensures that the instance is safe to be returned by the pool.

*

* @param p a {@code PooledObject} wrapping the instance to be validated

*

* @return <code>false</code> if <code>obj</code>is not valid and should

*        be dropped from the pool, <code>true</code>otherwise.

*/

boolean validateObject(PooledObject p);

/**

* Reinitializes an instance to be returned by the pool.

*

* @param p a {@code PooledObject} wrapping the instance to be activated

*

* @throws Exception if there is a problem activating <code>obj</code>,

*    this exception may be swallowed by the pool.

*

* @see #destroyObject

*/

void activateObject(PooledObject p)throws Exception;

/**

* Uninitializes an instance to be returned to the idle object pool.

*

* @param p a {@code PooledObject} wrapping the instance to be passivated

*

* @throws Exception if there is a problem passivating <code>obj</code>,

*    this exception may be swallowed by the pool.

*

* @see #destroyObject

*/

void passivateObject(PooledObject p)throws Exception;

注意：
  Jedis 和Lettuce 是Java 操作Redis 的客户端。
在Spring Boot 1.x 版本默认使用的是Jedis ，而在Spring Boot 2.x 版本默认使用的就是Lettuce。
所以如果你用的是1.x版本的话 需要把 RedisConnectionFactory factory 替换为LettuceConnectionFactory lettuceConnectionFactory

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