数据库连接池与com.mysql.jdbc.exceptions.jdbc4.CommunicationsException异常

刺骨的言语ヽ痛彻心扉 2022-06-17 08:26 76阅读 0赞

异常信息如下：

com.ibatis.common.jdbc.exception.NestedSQLException:   
    --- The error occurred in mit/datamodel/ibatis/person.xml.  
    --- The error occurred while executing query.  
    --- Check the select * from person where pID = ?.  
    --- Check the SQL Statement (preparation failed).  
    --- Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after connection closed.
    Connection was implicitly closed due to underlying exception/error:
    
    ** BEGIN NESTED EXCEPTION ** 
    
    com.mysql.jdbc.exceptions.jdbc4.CommunicationsException
    MESSAGE: Communications link failure
    
    Last packet sent to the server was 18912 ms ago.
    
    STACKTRACE:
    
    com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
    
    Last packet sent to the server was 18912 ms ago.
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
        at java.lang.reflect.Constructor.newInstance(Unknown Source)
        at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
        at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074)
        at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2873)
        at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2763)
        at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3299)
        at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1837)
        at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1961)
        at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2537)
        at com.mysql.jdbc.ConnectionImpl.rollbackNoChecks(ConnectionImpl.java:4668)
        at com.mysql.jdbc.ConnectionImpl.rollback(ConnectionImpl.java:4553)
        at com.ibatis.common.jdbc.SimpleDataSource.popConnection(SimpleDataSource.java:629)
        at com.ibatis.common.jdbc.SimpleDataSource.getConnection(SimpleDataSource.java:222)
        at com.ibatis.sqlmap.engine.transaction.jdbc.JdbcTransaction.init(JdbcTransaction.java:48)
        at com.ibatis.sqlmap.engine.transaction.jdbc.JdbcTransaction.getConnection(JdbcTransaction.java:89)
        at com.ibatis.sqlmap.engine.mapping.statement.GeneralStatement.executeQueryForObject(GeneralStatement.java:104)
        at com.ibatis.sqlmap.engine.impl.SqlMapExecutorDelegate.queryForObject(SqlMapExecutorDelegate.java:566)
        at com.ibatis.sqlmap.engine.impl.SqlMapExecutorDelegate.queryForObject(SqlMapExecutorDelegate.java:541)
        at com.ibatis.sqlmap.engine.impl.SqlMapSessionImpl.queryForObject(SqlMapSessionImpl.java:106)
        at com.ibatis.sqlmap.engine.impl.SqlMapClientImpl.queryForObject(SqlMapClientImpl.java:83)
        at mit.datamodel.dataaccess.CommonDAO.searchForObject(CommonDAO.java:142)
        at mit.datamodel.dataaccess.BasicDataAccess.queryObject(BasicDataAccess.java:46)
        at mit.datamodel.dataaccess.PersonAccess.queryPatientById(PersonAccess.java:93)
        at mit.business.service.PatientManagement.getPatientById(PatientManagement.java:335)
        at mit.servlet.PatientServiceInvocation.PatientQuery(PatientServiceInvocation.java:110)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at mit.business.service.BasicService.invokeService(BasicService.java:45)
        at mit.servlet.BaseServlet.dispatcher(BaseServlet.java:63)
        at mit.servlet.BaseServlet.doPost(BaseServlet.java:49)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:650)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:218)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:958)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:452)
        at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1087)
        at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
        at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
        at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
        at java.lang.Thread.run(Unknown Source)
    Caused by: java.net.SocketTimeoutException: Read timed out
        at java.net.SocketInputStream.socketRead0(Native Method)
        at java.net.SocketInputStream.read(Unknown Source)
        at java.net.SocketInputStream.read(Unknown Source)
        at com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:113)
        at com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:160)
        at com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:188)
        at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2329)
        at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2774)
        ... 50 more
    
    
    ** END NESTED EXCEPTION **
    
    
    at com.ibatis.sqlmap.engine.mapping.statement.GeneralStatement.executeQueryWithCallback(GeneralStatement.java:185)
    at com.ibatis.sqlmap.engine.mapping.statement.GeneralStatement.executeQueryForObject(GeneralStatement.java:104)
    at com.ibatis.sqlmap.engine.impl.SqlMapExecutorDelegate.queryForObject(SqlMapExecutorDelegate.java:566)
    at com.ibatis.sqlmap.engine.impl.SqlMapExecutorDelegate.queryForObject(SqlMapExecutorDelegate.java:541)
    at com.ibatis.sqlmap.engine.impl.SqlMapSessionImpl.queryForObject(SqlMapSessionImpl.java:106)
    at com.ibatis.sqlmap.engine.impl.SqlMapClientImpl.queryForObject(SqlMapClientImpl.java:83)
    at mit.datamodel.dataaccess.CommonDAO.searchForObject(CommonDAO.java:142)
    at mit.datamodel.dataaccess.BasicDataAccess.queryObject(BasicDataAccess.java:46)
    at mit.datamodel.dataaccess.PersonAccess.queryPatientById(PersonAccess.java:93)
    at mit.business.service.PatientManagement.getPatientById(PatientManagement.java:335)
    at mit.servlet.PatientServiceInvocation.PatientQuery(PatientServiceInvocation.java:110)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at mit.business.service.BasicService.invokeService(BasicService.java:45)
    at mit.servlet.BaseServlet.dispatcher(BaseServlet.java:63)
    at mit.servlet.BaseServlet.doPost(BaseServlet.java:49)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:650)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:218)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:958)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:452)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1087)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Unknown Source)
    Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after connection closed.
    Connection was implicitly closed due to underlying exception/error:
    
    
    ** BEGIN NESTED EXCEPTION ** 
    
    com.mysql.jdbc.exceptions.jdbc4.CommunicationsException
    MESSAGE: Communications link failure
    
    Last packet sent to the server was 18912 ms ago.
    
    STACKTRACE:
    
    com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
    
    Last packet sent to the server was 18912 ms ago.
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
        at java.lang.reflect.Constructor.newInstance(Unknown Source)
        at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
        at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074)
        at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2873)
        at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2763)
        at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3299)
        at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1837)
        at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1961)
        at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2537)
        at com.mysql.jdbc.ConnectionImpl.rollbackNoChecks(ConnectionImpl.java:4668)
        at com.mysql.jdbc.ConnectionImpl.rollback(ConnectionImpl.java:4553)
        at com.ibatis.common.jdbc.SimpleDataSource.popConnection(SimpleDataSource.java:629)
        at com.ibatis.common.jdbc.SimpleDataSource.getConnection(SimpleDataSource.java:222)
        at com.ibatis.sqlmap.engine.transaction.jdbc.JdbcTransaction.init(JdbcTransaction.java:48)
        at com.ibatis.sqlmap.engine.transaction.jdbc.JdbcTransaction.getConnection(JdbcTransaction.java:89)
        at com.ibatis.sqlmap.engine.mapping.statement.GeneralStatement.executeQueryForObject(GeneralStatement.java:104)
        at com.ibatis.sqlmap.engine.impl.SqlMapExecutorDelegate.queryForObject(SqlMapExecutorDelegate.java:566)
        at com.ibatis.sqlmap.engine.impl.SqlMapExecutorDelegate.queryForObject(SqlMapExecutorDelegate.java:541)
        at com.ibatis.sqlmap.engine.impl.SqlMapSessionImpl.queryForObject(SqlMapSessionImpl.java:106)
        at com.ibatis.sqlmap.engine.impl.SqlMapClientImpl.queryForObject(SqlMapClientImpl.java:83)
        at mit.datamodel.dataaccess.CommonDAO.searchForObject(CommonDAO.java:142)
        at mit.datamodel.dataaccess.BasicDataAccess.queryObject(BasicDataAccess.java:46)
        at mit.datamodel.dataaccess.PersonAccess.queryPatientById(PersonAccess.java:93)
        at mit.business.service.PatientManagement.getPatientById(PatientManagement.java:335)
        at mit.servlet.PatientServiceInvocation.PatientQuery(PatientServiceInvocation.java:110)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at mit.business.service.BasicService.invokeService(BasicService.java:45)
        at mit.servlet.BaseServlet.dispatcher(BaseServlet.java:63)
        at mit.servlet.BaseServlet.doPost(BaseServlet.java:49)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:650)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:218)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:958)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:452)
        at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1087)
        at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
        at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
        at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
        at java.lang.Thread.run(Unknown Source)
    Caused by: java.net.SocketTimeoutException: Read timed out
        at java.net.SocketInputStream.socketRead0(Native Method)
        at java.net.SocketInputStream.read(Unknown Source)
        at java.net.SocketInputStream.read(Unknown Source)
        at com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:113)
        at com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:160)
        at com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:188)
        at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2329)
        at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2774)
        ... 50 more
    
    
    ** END NESTED EXCEPTION **
    
    
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
    at com.mysql.jdbc.Util.getInstance(Util.java:381)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:985)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:957)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:927)
    at com.mysql.jdbc.ConnectionImpl.checkClosed(ConnectionImpl.java:1113)
    at com.mysql.jdbc.ConnectionImpl.prepareStatement(ConnectionImpl.java:4038)
    at com.mysql.jdbc.ConnectionImpl.prepareStatement(ConnectionImpl.java:4004)
    at sun.reflect.GeneratedMethodAccessor32.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at com.ibatis.common.jdbc.SimpleDataSource$SimplePooledConnection.invoke(SimpleDataSource.java:958)
    at com.sun.proxy.$Proxy4.prepareStatement(Unknown Source)
    at sun.reflect.GeneratedMethodAccessor32.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at com.ibatis.common.jdbc.logging.ConnectionLogProxy.invoke(ConnectionLogProxy.java:53)
    at com.sun.proxy.$Proxy4.prepareStatement(Unknown Source)
    at com.ibatis.sqlmap.engine.execution.SqlExecutor.prepareStatement(SqlExecutor.java:494)
    at com.ibatis.sqlmap.engine.execution.SqlExecutor.executeQuery(SqlExecutor.java:176)
    at com.ibatis.sqlmap.engine.mapping.statement.GeneralStatement.sqlExecuteQuery(GeneralStatement.java:205)
    at com.ibatis.sqlmap.engine.mapping.statement.GeneralStatement.executeQueryWithCallback(GeneralStatement.java:173)
    ... 39 more

com.ibatis.common.jdbc.exception.NestedSQLException是iBATIS实现的嵌套异常，继承自SQLException。从业务逻辑Service层方法调用开始，沿着异常堆栈跳着跟踪下：

at mit.business.service.PatientManagement.getPatientById(PatientManagement.java:335)
    at mit.datamodel.dataaccess.CommonDAO.searchForObject(CommonDAO.java:142)
    at com.ibatis.sqlmap.engine.impl.SqlMapClientImpl.queryForObject(SqlMapClientImpl.java:83)
    at com.ibatis.sqlmap.engine.transaction.jdbc.JdbcTransaction.getConnection(JdbcTransaction.java:89)
    at com.ibatis.common.jdbc.SimpleDataSource.popConnection(SimpleDataSource.java:629)
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2537)
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1837)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3299)
      at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2873)
        at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2329)
        at com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:160)
        at java.net.SocketInputStream.read(Unknown Source)
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074)

所以最根本的原因是由于数据库连接关闭所以抛出java.net.SocketTimeoutException: Read timed out，调用返回到checkErrorPacket方法，方法中抛出SQLError.createCommunicationsException创建CommunicationsException异常。因为DataSource类型配置的”SIMPLE”，所以获取数据库连接调用SimpleDataSource类的popConnection方法，从连接池空闲链表获取，问题还是出在连接池的使用上。MySQL服务”wait\_timeout”默认值是28800s，即意味着如果一个数据库连接的空闲时间超过8个小时，MySQL将自动断开连接，而连接池中并没有校验此连接的有效性而依然持有此连接，当下一次使用此连接时，就会出现`com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure`。  
  所以解决办法是对症下药，对连接进行有效性监测，更改iBATIS配置文件如下。这个系统使用的人员有限，并发量很小，连接池中最大连接数为5，最大空闲连接数为3就够用了，减少资源浪费。在数据库连接池回收连接时，如果空闲连接数大于等于3则将真正调用`conn.getRealConnection().close();`关闭此连接，否则使用`SimplePooledConnection`重新封装连接放入空闲链表中，供下个数据库请求线程申请。

延长MySQL wait\_timeout变量值可有可无，考虑工作人员放假等时间，设置为2星期，重启MySQL服务时需要重新设置。也可写在配置MySQL配置文件中，但是需要重启MySQL服务，生产环境不现实。  
![这里写图片描述][SouthEast]

[SouthEast]: /images/20220617/483e6a5546cb4fabac276fdb6dfb5042.png