本篇文章给大家带来的内容是关于redis的事务操作的命令与执行操作（代码），有一定的参考价值，有需要的朋友可以参考一下，希望对你有所帮助。
序
本文主要研究一下redis的事务操作
命令
multi与exec
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命令行
127.0.0.1:6379> multi OK 127.0.0.1:6379> incr total QUEUED 127.0.0.1:6379> incr len QUEUED 127.0.0.1:6379> exec 1) (integer) 2 2) (integer) 2 127.0.0.1:6379> get total "2" 127.0.0.1:6379> get len "2"
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lettuce实例
@Test public void testMultiExec(){ RedisClient client = RedisClient.create("redis://192.168.99.100:6379/0"); StatefulRedisConnection<String, String> connection = client.connect(); RedisCommands<String, String> syncCommands = connection.sync(); syncCommands.set("hello","1"); syncCommands.set("world","2"); syncCommands.multi(); syncCommands.incr("hello"); syncCommands.incr("world"); //DefaultTransactionResult[wasRolledBack=false,result=[1, 2, 1, 3, 1]] TransactionResult transactionResult = syncCommands.exec(); System.out.println(transactionResult); System.out.println(syncCommands.get("hello")); System.out.println(syncCommands.get("world")); }
部分执行
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命令行
127.0.0.1:6379> multi OK 127.0.0.1:6379> set a hello QUEUED 127.0.0.1:6379> set b world QUEUED 127.0.0.1:6379> incr a QUEUED 127.0.0.1:6379> set c part QUEUED 127.0.0.1:6379> exec 1) OK 2) OK 3) (error) ERR value is not an integer or out of range 4) OK 127.0.0.1:6379> get a "hello" 127.0.0.1:6379> get b "world" 127.0.0.1:6379> get c "part"
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lettuce实例
@Test public void testMultiExecError(){ RedisClient client = RedisClient.create("redis://192.168.99.100:6379/0"); StatefulRedisConnection<String, String> connection = client.connect(); RedisCommands<String, String> syncCommands = connection.sync(); syncCommands.multi(); syncCommands.set("a","hello"); syncCommands.set("b","world"); syncCommands.incr("a"); syncCommands.set("c","part"); //DefaultTransactionResult[wasRolledBack=false,result=[OK, OK, io.lettuce.core.RedisCommandExecutionException: ERR value is not an integer or out of range, OK, 1]] TransactionResult transactionResult = syncCommands.exec(); System.out.println(transactionResult); System.out.println(syncCommands.get("a")); System.out.println(syncCommands.get("b")); System.out.println(syncCommands.get("c")); }
multi与discard
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命令行
127.0.0.1:6379> set sum 1 OK 127.0.0.1:6379> multi OK 127.0.0.1:6379> incr sum QUEUED 127.0.0.1:6379> discard OK 127.0.0.1:6379> get sum "1"
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lettuce实例
@Test public void testMultiDiscard(){ RedisClient client = RedisClient.create("redis://192.168.99.100:6379/0"); StatefulRedisConnection<String, String> connection = client.connect(); RedisCommands<String, String> syncCommands = connection.sync(); syncCommands.incr("key1"); syncCommands.multi(); syncCommands.incr("key1"); //需要有multi才可以执行discard，成功返回OK String result = syncCommands.discard(); System.out.println(result); System.out.println(syncCommands.get("key1")); }
check and set
@Test public void testWatch(){ RedisClient client = RedisClient.create("redis://192.168.99.100:6379/0"); StatefulRedisConnection<String, String> connection = client.connect(); RedisCommands<String, String> syncCommands = connection.sync(); String key = "key"; syncCommands.watch(key); //another connection StatefulRedisConnection<String, String> conn2 = client.connect(); RedisCommands<String, String> syncCommands2 = conn2.sync(); syncCommands2.set(key, "a"); syncCommands.multi(); syncCommands.append(key, "b"); //DefaultTransactionResult [wasRolledBack=true, responses=0] TransactionResult transactionResult = syncCommands.exec(); System.out.println(transactionResult); System.out.println(syncCommands.get(key)); }
小结
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reids提供multi exec/discard指令，类似open commit/rollback transaction，不过exec遇到类型操作等错误时不会滚，该成功执行的命令还是成功执行，该失败的还是失败
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multi exec保证的是，只要exec命令有执行成功，则事务中一系列的命令都能执行，如果exec因为网络等问题，server端没有接收到，则事务中的一系列命令都不会被执行
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discard需要在有调用multi的前提下才能使用，该命令会清空事务队列等待执行的命令
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redis提供watch指令，可以配合multi exec来使用，可以实现类似数据库的乐观锁的机制，一旦watch的key被其他client有更新，则整个exec操作失败
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