Redis事务异常：Caused by: io.lettuce.core.RedisCommandExecutionException: ERR EXEC without MULTI

2020-07-29 21:15:00.635  INFO 26920 --- [           main] io.lettuce.core.EpollProvider            : Starting without optional epoll library
2020-07-29 21:15:00.643  INFO 26920 --- [           main] io.lettuce.core.KqueueProvider           : Starting without optional kqueue library

org.springframework.data.redis.RedisSystemException: Error in execution; nested exception is io.lettuce.core.RedisCommandExecutionException: ERR EXEC without MULTI

    at org.springframework.data.redis.connection.lettuce.LettuceExceptionConverter.convert(LettuceExceptionConverter.java:54)
    at org.springframework.data.redis.connection.lettuce.LettuceExceptionConverter.convert(LettuceExceptionConverter.java:52)
    at org.springframework.data.redis.connection.lettuce.LettuceExceptionConverter.convert(LettuceExceptionConverter.java:41)
    at org.springframework.data.redis.PassThroughExceptionTranslationStrategy.translate(PassThroughExceptionTranslationStrategy.java:44)
    at org.springframework.data.redis.FallbackExceptionTranslationStrategy.translate(FallbackExceptionTranslationStrategy.java:42)
    at org.springframework.data.redis.connection.lettuce.LettuceConnection.convertLettuceAccessException(LettuceConnection.java:268)
    at org.springframework.data.redis.connection.lettuce.LettuceConnection.exec(LettuceConnection.java:653)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at org.springframework.data.redis.core.CloseSuppressingInvocationHandler.invoke(CloseSuppressingInvocationHandler.java:61)
    at com.sun.proxy.$Proxy83.exec(Unknown Source)
    at org.springframework.data.redis.core.RedisTemplate$$Lambda$515/1273684451.doInRedis(Unknown Source)
    at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:224)
    at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:184)
    at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:171)
    at org.springframework.data.redis.core.RedisTemplate.execRaw(RedisTemplate.java:696)
    at org.springframework.data.redis.core.RedisTemplate.exec(RedisTemplate.java:677)
    at com.xds.redis.manager.XdsRedisManagerApplicationTests.redisTransaction(XdsRedisManagerApplicationTests.java:60)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.springframework.test.context.junit4.statements.RunBeforeTestExecutionCallbacks.evaluate(RunBeforeTestExecutionCallbacks.java:74)
    at org.springframework.test.context.junit4.statements.RunAfterTestExecutionCallbacks.evaluate(RunAfterTestExecutionCallbacks.java:84)
    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:251)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: io.lettuce.core.RedisCommandExecutionException: ERR EXEC without MULTI
    at io.lettuce.core.ExceptionFactory.createExecutionException(ExceptionFactory.java:135)
    at io.lettuce.core.ExceptionFactory.createExecutionException(ExceptionFactory.java:108)
    at io.lettuce.core.protocol.AsyncCommand.completeResult(AsyncCommand.java:120)
    at io.lettuce.core.protocol.AsyncCommand.complete(AsyncCommand.java:111)
    at io.lettuce.core.protocol.CommandHandler.complete(CommandHandler.java:646)
    at io.lettuce.core.protocol.CommandHandler.decode(CommandHandler.java:604)
    at io.lettuce.core.protocol.CommandHandler.channelRead(CommandHandler.java:556)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
    at io.netty.channel.ChannelInboundHandlerAdapter.channelRead(ChannelInboundHandlerAdapter.java:86)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
    at io.netty.channel.ChannelInboundHandlerAdapter.channelRead(ChannelInboundHandlerAdapter.java:86)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
    at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1408)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
    at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:930)
    at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:163)
    at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:677)
    at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:612)
    at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:529)
    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:491)
    at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:905)
    at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
    at java.lang.Thread.run(Thread.java:745)

出现场景：使用RedisTemplate操作redis事务，如

redisTemplate.multi();
redisTemplate.opsForValue().set("username", "xds");
List<Object> exec = redisTemplate.exec();
System.out.println(JSONObject.toJSONString(exec));

上面报错的意思是我们在执行exec()方法之前没有先执行mutli()方法，所以抛了异常，解决办法是在代码前将enableTransactionSupport设置为true，如下

redisTemplate.setEnableTransactionSupport(true);
redisTemplate.multi();
redisTemplate.opsForValue().set("username", "xds");
List<Object> exec = redisTemplate.exec();
System.out.println(JSONObject.toJSONString(exec));

在执行redisTemplate.multi()、redisTemplate.opsForValue.set("username","xds)、redisTemplate.exec()方法时，最终会调用RedisTemplate.execute(org.springframework.data.redis.core.RedisCallback<T>, boolean, boolean)方法，如下

@Nullable
    public <T> T execute(RedisCallback<T> action, boolean exposeConnection, boolean pipeline) {
        Assert.isTrue(this.initialized, "template not initialized; call afterPropertiesSet() before using it");
        Assert.notNull(action, "Callback object must not be null");
        RedisConnectionFactory factory = this.getRequiredConnectionFactory();
        RedisConnection conn = null;

        Object var11;
        try {
            //enableTransactionSupport标识是否开启事务支持，默认为false
            if (this.enableTransactionSupport) {
                //enableTransactionSupport为true，为当前连接池开启事务，将当前RedisConnectionFactory放入事务管理器
                //从事务管理器中获取RedisConnection对象，保证接下来的每一个操作使用的都是同一个RedisConnection对象
                conn = RedisConnectionUtils.bindConnection(factory, this.enableTransactionSupport);
            } else {
                //enableTransactionSupport为false，当前连接池未开启事务，每次操作都是连接池中重新获取的没有无事务的RRedisConnection对象
                //所以在执行List<Object> exec = redisTemplate.exec();时候就会抛出上面的异常
                conn = RedisConnectionUtils.getConnection(factory);
            }

            boolean existingConnection = TransactionSynchronizationManager.hasResource(factory);
            RedisConnection connToUse = this.preProcessConnection(conn, existingConnection);
            boolean pipelineStatus = connToUse.isPipelined();
            if (pipeline && !pipelineStatus) {
                connToUse.openPipeline();
            }

            RedisConnection connToExpose = exposeConnection ? connToUse : this.createRedisConnectionProxy(connToUse);
            T result = action.doInRedis(connToExpose);
            if (pipeline && !pipelineStatus) {
                connToUse.closePipeline();
            }

            var11 = this.postProcessResult(result, connToUse, existingConnection);
        } finally {
            RedisConnectionUtils.releaseConnection(conn, factory);
        }

        return var11;
    }

对于RedisConnection对象的获取，上面源码中根据是否开启事务支持分了两个方法去获取，但最终这两个方法都会调用到同一个方法去执行，唯一不同的是传递的参数值不一样

/**
* 1.enableTransactionSupport=true;bind=true;
* 2.enableTransactionSupport=false;bind=false;
*/
public static RedisConnection doGetConnection(RedisConnectionFactory factory, boolean allowCreate, boolean bind, boolean enableTransactionSupport) {
        Assert.notNull(factory, "No RedisConnectionFactory specified");
        //从事务管理器TransactionSynchronizationManager获取连接池对象RedisConnectionHolder
        RedisConnectionUtils.RedisConnectionHolder connHolder = (RedisConnectionUtils.RedisConnectionHolder)TransactionSynchronizationManager.getResource(factory);
        if (connHolder != null) {
            if (enableTransactionSupport) {
                potentiallyRegisterTransactionSynchronisation(connHolder, factory);
            }
            //返回事务管理器中的RedisConnection对象
            return connHolder.getConnection();
        } else if (!allowCreate) {
            throw new IllegalArgumentException("No connection found and allowCreate = false");
        } else {
            if (log.isDebugEnabled()) {
                log.debug("Opening RedisConnection");
            }
            //获取使用当前连接池中RedisConnection对象
            RedisConnection conn = factory.getConnection();
            if (bind) {
                 //如果bind为ture，新建一个RedisConnection对象
                RedisConnection connectionToBind = conn;
                if (enableTransactionSupport && isActualNonReadonlyTransactionActive()) {
                    connectionToBind = createConnectionProxy(conn, factory);
                }
                //新建RedisConnectionHolder对象
                connHolder = new RedisConnectionUtils.RedisConnectionHolder(connectionToBind);
                //将RedisConnectionHolder对象放入事务管理器中
                TransactionSynchronizationManager.bindResource(factory, connHolder);
                if (enableTransactionSupport) {
                    potentiallyRegisterTransactionSynchronisation(connHolder, factory);
                }

                return connHolder.getConnection();
            } else {
                 //bind为false，返回重新从连接池中获取的RedisConnection
                return conn;
            }
        }
    }

如果是开启了事务支持，redisTemplate.multi()执行后调用doGetConnection(...)方法，会首次将RedisConnection对象加入到事务管理器中，后面的方法每次调用doGetConnection(...)方法，都会基于事务管理器中的RedisConnection对象进行操作。