Redis 批量操作

如果频繁地使用Redis，比如在 for循环中调用 redis，有时可能会报错： Could not get a resource from the pool。

这是因为 Redis的连接数是有限的，打开了Redis的连接，用完记得要关闭，如果连接数不够了就会报错。

Redis 批量操作，可以使用 RedisTemplate 的 execute()方法。

RedisTemplate 源码

• org.springframework.data.redis.core.RedisOperations

• org.springframework.data.redis.core.RedisTemplate

RedisTemplate 的 execute()方法

org.springframework.data.redis.core.RedisTemplate#execute(org.springframework.data.redis.core.SessionCallback)

execute() 方法，可以在一次连接中进行多个命令操作。执行完会自动关闭连接。

	/*** Executes a Redis session. Allows multiple operations to be executed in the same session enabling 'transactional'* capabilities through {@link #multi()} and {@link #watch(Collection)} operations.** @param <T> return type* @param session session callback. Must not be {@literal null}.* @return result object returned by the action or <tt>null</tt>*/@Overridepublic <T> T execute(SessionCallback<T> session) {Assert.isTrue(initialized, "template not initialized; call afterPropertiesSet() before using it");Assert.notNull(session, "Callback object must not be null");RedisConnectionFactory factory = getRequiredConnectionFactory();// 打开连接RedisConnectionUtils.bindConnection(factory, enableTransactionSupport);try {return session.execute(this);} finally {//执行完会自动关闭连接RedisConnectionUtils.unbindConnection(factory);}}

execute()的SessionCallback参数和RedisCallback参数

SessionCallback 比 RedisCallck 更好些，优先使用 SessionCallback 。

使用SessionCallback , 还可以配合multi() 和 watch() 进行事务操作。

/*** Executes the given action within a Redis connection. Application exceptions thrown by the action object get* propagated to the caller (can only be unchecked) whenever possible. Redis exceptions are transformed into* appropriate DAO ones. Allows for returning a result object, that is a domain object or a collection of domain* objects. Performs automatic serialization/deserialization for the given objects to and from binary data suitable* for the Redis storage. Note: Callback code is not supposed to handle transactions itself! Use an appropriate* transaction manager. Generally, callback code must not touch any Connection lifecycle methods, like close, to let* the template do its work.** @param <T> return type* @param action callback object that specifies the Redis action. Must not be {@literal null}.* @return a result object returned by the action or <tt>null</tt>*/
@Nullable
<T> T execute(RedisCallback<T> action);/*** Executes a Redis session. Allows multiple operations to be executed in the same session enabling 'transactional'* capabilities through {@link #multi()} and {@link #watch(Collection)} operations.** @param <T> return type* @param session session callback. Must not be {@literal null}.* @return result object returned by the action or <tt>null</tt>*/
@Nullable
<T> T execute(SessionCallback<T> session);

execute() 使用示例：

    @Autowiredprivate StringRedisTemplate stringRedisTemplate;public void testExecute() {String userId = "userId";stringRedisTemplate.opsForValue().set(userId+"123", "lin");stringRedisTemplate.opsForValue().set(userId+"456", "wu");stringRedisTemplate.opsForValue().set(userId+"789", "chen");Map<String, String> map = new HashMap<>();stringRedisTemplate.execute(new SessionCallback<String>() {@Overridepublic <K, V> String execute(@NonNull RedisOperations<K, V> redisOperations) throws DataAccessException {List<String> list = Arrays.asList("123", "456", "789");for (String id : list) {String key = userId + id;String value = (String) redisOperations.opsForValue().get(key);map.put(key, value);}return null;}});map.forEach((k, v) -> System.out.println(k + ",val:" + v));}