現象

使用get請求，incrment請求，返回結果一直為null

業務程式碼

org.springframework.transaction.support.TransactionTemplate

transactionTemplate.execute(t -> {
	...
	// 在事務裡進行了redis的操作，且需要獲取資料
    Long incr = redisTemplate.opsForValue().increment(key,1L);
});

輸出結果：incr為null。

原因

redis操作在事務之間的時候，全部返回null

原始碼解析

1. 執行redis操作的入口：

org.springframework.data.redis.core.RedisTemplate.class

public <T> T execute(RedisCallback<T> action, boolean exposeConnection, boolean pipeline) {
		Assert.isTrue(initialized, "template not initialized; call afterPropertiesSet() before using it");
		Assert.notNull(action, "Callback object must not be null");

		RedisConnectionFactory factory = getConnectionFactory();
		RedisConnection conn = null;
		try {
            // 如果配置支援事務，然後就會執行下面的方法，我的配置檔案是支援事務的
			if (enableTransactionSupport) {
				// only bind resources in case of potential transaction synchronization
				conn = RedisConnectionUtils.bindConnection(factory, enableTransactionSupport);
			} else {
				conn = RedisConnectionUtils.getConnection(factory);
			}

			boolean existingConnection = TransactionSynchronizationManager.hasResource(factory);

			RedisConnection connToUse = preProcessConnection(conn, existingConnection);

			boolean pipelineStatus = connToUse.isPipelined();
			if (pipeline && !pipelineStatus) {
				connToUse.openPipeline();
			}

			RedisConnection connToExpose = (exposeConnection ? connToUse : createRedisConnectionProxy(connToUse));
			T result = action.doInRedis(connToExpose);

			// close pipeline
			if (pipeline && !pipelineStatus) {
				connToUse.closePipeline();
			}

			// TODO: any other connection processing?
			return postProcessResult(result, connToUse, existingConnection);
		} finally {
			RedisConnectionUtils.releaseConnection(conn, factory);
		}
	}
 

2. RedisConnectionUtils.bindConnection

public static RedisConnection bindConnection(RedisConnectionFactory factory, boolean enableTranactionSupport) {
		return doGetConnection(factory, true, true, enableTranactionSupport);
	}
	
// 獲取connect連線
public static RedisConnection doGetConnection(RedisConnectionFactory factory, boolean allowCreate, boolean bind,
			boolean enableTransactionSupport) {

		Assert.notNull(factory, "No RedisConnectionFactory specified");
        
		RedisConnectionHolder connHolder = (RedisConnectionHolder) TransactionSynchronizationManager.getResource(factory);

		if (connHolder != null) {
			if (enableTransactionSupport) {
			    // 可能會進行註冊事務同步，主要設定redis事務開啟的地方就在這裡
				potentiallyRegisterTransactionSynchronisation(connHolder, factory);
			}
			return connHolder.getConnection();
		}

		if (!allowCreate) {
			throw new IllegalArgumentException("No connection found and allowCreate = false");
		}

		if (log.isDebugEnabled()) {
			log.debug("Opening RedisConnection");
		}

		RedisConnection conn = factory.getConnection();

		if (bind) {

			RedisConnection connectionToBind = conn;
			if (enableTransactionSupport && isActualNonReadonlyTransactionActive()) {
				connectionToBind = createConnectionProxy(conn, factory);
			}

			connHolder = new RedisConnectionHolder(connectionToBind);

			TransactionSynchronizationManager.bindResource(factory, connHolder);
			if (enableTransactionSupport) {
				potentiallyRegisterTransactionSynchronisation(connHolder, factory);
			}

			return connHolder.getConnection();
		}

		return conn;
	}	
	
// 可能會進行註冊事務同步
private static void potentiallyRegisterTransactionSynchronisation(RedisConnectionHolder connHolder,
			final RedisConnectionFactory factory) {
        // 如果當前事務已開啟
		if (isActualNonReadonlyTransactionActive()) {
            // 當前redis的事務同步還未開始
			if (!connHolder.isTransactionSyncronisationActive()) {
			    // 啟動redis事務
				connHolder.setTransactionSyncronisationActive(true);

				RedisConnection conn = connHolder.getConnection();
				// 主要有個操作是給redis的client的isInMulti設定為true
				conn.multi();

				TransactionSynchronizationManager.registerSynchronization(new RedisTransactionSynchronizer(connHolder, conn,
						factory));
			}
		}
	}
	
 

3. RedisTemplate

// 執行redis操作
T result = action.doInRedis(connToExpose);

4. JedisConnection

public byte[] get(byte[] key) {
		try {
			if (isPipelined()) {
				pipeline(new JedisResult(pipeline.get(key)));
				return null;
			}
			// 當事務開啟的時候，isQueueing的返回結果為true，所以get的操作會返回null
			if (isQueueing()) {
				transaction(new JedisResult(transaction.get(key)));
				return null;
			}

			return jedis.get(key);
		} catch (Exception ex) {
			throw convertJedisAccessException(ex);
		}
	}
	
public Long incr(byte[] key) {
		try {
			if (isPipelined()) {
				pipeline(new JedisResult(pipeline.incr(key)));
				return null;
			}
			// 當事務開啟的時候，isQueueing的返回結果為true，所以incr的操作會返回null
			if (isQueueing()) {
				transaction(new JedisResult(transaction.incr(key)));
				return null;
			}
			return jedis.incr(key);
		} catch (Exception ex) {
			throw convertJedisAccessException(ex);
		}
	}

總結

使用redis事務需謹慎，可以使用，但是在使用的過程中獲取資料都是獲取不到的