mysql无法执行某些语句，并自动断开服务连接问题

存在了2天小问题终于解决

出现场景：

1. hibernate执行update语句的时候，出现这个错误，save和query没有任何问题;

2.  执行activity的processEngine.getTaskService().complete(taskId)方法时，抛出这个异常.

错误提示：

org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet successfully received from the server was 2,743 milliseconds ago.  The last packet sent successfully to the server was 2,743 milliseconds ago.
### The error may exist in org/activiti/db/mapping/entity/HistoricActivityInstance.xml
### The error may involve org.activiti.engine.impl.persistence.entity.HistoricActivityInstanceEntity.selectHistoricActivityInstancesByQueryCriteria-Inline
### The error occurred while setting parameters
### SQL: select RES.*            from ACT_HI_ACTINST RES      WHERE  RES.EXECUTION_ID_ = ?                              and RES.ACT_ID_ = ?                                            and RES.END_TIME_ is null           order by RES.ID_ asc      LIMIT ? OFFSET ?
### Cause: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet successfully received from the server was 2,743 milliseconds ago.  The last packet sent successfully to the server was 2,743 milliseconds ago.
	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:23)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:107)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:98)
	at org.activiti.engine.impl.db.DbSqlSession.selectListWithRawParameter(DbSqlSession.java:284)
	at org.activiti.engine.impl.db.DbSqlSession.selectList(DbSqlSession.java:275)
	at org.activiti.engine.impl.db.DbSqlSession.selectList(DbSqlSession.java:265)
	at org.activiti.engine.impl.persistence.entity.HistoricActivityInstanceEntityManager.findHistoricActivityInstancesByQueryCriteria(HistoricActivityInstanceEntityManager.java:56)
	at org.activiti.engine.impl.HistoricActivityInstanceQueryImpl.executeList(HistoricActivityInstanceQueryImpl.java:64)
	at org.activiti.engine.impl.AbstractQuery.listPage(AbstractQuery.java:126)
	at org.activiti.engine.impl.history.HistoryManager.findActivityInstance(HistoryManager.java:240)
	at org.activiti.engine.impl.history.HistoryManager.recordActivityEnd(HistoryManager.java:187)
	at org.activiti.engine.impl.history.handler.ActivityInstanceEndHandler.notify(ActivityInstanceEndHandler.java:28)
	at org.activiti.engine.impl.pvm.runtime.AbstractEventAtomicOperation.execute(AbstractEventAtomicOperation.java:42)
	at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:87)
	at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:532)
	at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:527)
	at org.activiti.engine.impl.persistence.entity.ExecutionEntity.take(ExecutionEntity.java:367)
	at org.activiti.engine.impl.bpmn.behavior.BpmnActivityBehavior.performOutgoingBehavior(BpmnActivityBehavior.java:105)
	at org.activiti.engine.impl.bpmn.behavior.BpmnActivityBehavior.performDefaultOutgoingBehavior(BpmnActivityBehavior.java:54)
	at org.activiti.engine.impl.bpmn.behavior.FlowNodeActivityBehavior.leave(FlowNodeActivityBehavior.java:44)
	at org.activiti.engine.impl.bpmn.behavior.AbstractBpmnActivityBehavior.leave(AbstractBpmnActivityBehavior.java:47)
	at org.activiti.engine.impl.bpmn.behavior.UserTaskActivityBehavior.signal(UserTaskActivityBehavior.java:96)
	at org.activiti.engine.impl.persistence.entity.ExecutionEntity.signal(ExecutionEntity.java:350)
	at org.activiti.engine.impl.persistence.entity.TaskEntity.complete(TaskEntity.java:160)
	at org.activiti.engine.impl.cmd.CompleteTaskCmd.execute(CompleteTaskCmd.java:39)
	at org.activiti.engine.impl.cmd.CompleteTaskCmd.execute(CompleteTaskCmd.java:24)
	at org.activiti.engine.impl.cmd.NeedsActiveTaskCmd.execute(NeedsActiveTaskCmd.java:61)
	at org.activiti.engine.impl.interceptor.CommandExecutorImpl.execute(CommandExecutorImpl.java:24)
	at org.activiti.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:61)
	at org.activiti.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:31)
	at org.activiti.engine.impl.TaskServiceImpl.complete(TaskServiceImpl.java:163)
	at com.whir.a_hellworld.HelloWorld.compeleteMyPersonalTask(HelloWorld.java:84)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:606)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
	at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
	at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet successfully received from the server was 2,743 milliseconds ago.  The last packet sent successfully to the server was 2,743 milliseconds ago.
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
	at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
	at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1121)
	at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3670)
	at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3559)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4110)
	at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2570)
	at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2731)
	at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2815)
	at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2155)
	at com.mysql.jdbc.PreparedStatement.execute(PreparedStatement.java:1379)
	at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:56)
	at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:70)
	at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:57)
	at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:259)
	at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:132)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:105)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:81)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:104)
	... 53 more
Caused by: java.net.SocketException: Connection reset
	at java.net.SocketInputStream.read(SocketInputStream.java:196)
	at java.net.SocketInputStream.read(SocketInputStream.java:122)
	at com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:114)
	at com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:161)
	at com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:189)
	at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:3116)
	at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3570)
	... 68 more

本人的解决方案：

更换mysql版本......

若此方法行不通

其它解决方法：请自行百度