连接丢弃的Java应用程序处理
我的应用程序似乎一夜之间挂起，因为连接被丢弃（我认为这是问题。）我如何构建我的应用程序，以便它可以尝试卷起一个新的连接？
自从事件发生后我更新了我的应用程序使用的getConnection（）方法：
private Connection getConnection() { boolean failed = false; try{ failed = !connection.isValid(1000); }catch(SQLException ex){ System.out.println("WARNING: Connection not valid!"); } try{ failed = connection.isClosed(); }catch(SQLException ex){ System.out.println("WARNING: Connection is closed!"); } if(failed){ System.out.println("Renewing connection"); this.initializeConnection(); } return connection; } 这是输出：
** BEGIN NESTED EXCEPTION ** com.mysql.jdbc.exceptions.jdbc4.CommunicationsException MESSAGE: The last packet successfully received from the server was54521 seconds ago.The last packet sent successfully to the server was 54521 seconds ago, which is longer than the server configured value of 'wait_timeout'. You should consi der either expiring and/or testing connection validity before use in your applic ation, increasing the server configured values for client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem. STACKTRACE: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The last packet success fully received from the server was54521 seconds ago.The last packet sent success fully to the server was 54521 seconds ago, which is longer than the server conf igured value of 'wait_timeout'. You should consider either expiring and/or testi ng connection validity before use in your application, increasing the server con figured values for client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Sou rce) 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:1 074) at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3246) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1917) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2060) at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2536) at com.mysql.jdbc.ConnectionImpl.setCatalog(ConnectionImpl.java:4962) at com.mysql.jdbc.DatabaseMetaData.getCallStmtParameterTypes(DatabaseMet aData.java:1506) at com.mysql.jdbc.DatabaseMetaData.getProcedureOrFunctionColumns(Databas eMetaData.java:4120) at com.mysql.jdbc.DatabaseMetaData.getProcedureColumns(DatabaseMetaData. java:4057) at com.mysql.jdbc.CallableStatement.determineParameterTypes(CallableStat ement.java:809) at com.mysql.jdbc.CallableStatement.(CallableStatement.java:609) at com.mysql.jdbc.JDBC4CallableStatement.(JDBC4CallableStatement.j ava:46) at sun.reflect.GeneratedConstructorAccessor6.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Sou rce) at java.lang.reflect.Constructor.newInstance(Unknown Source) at com.mysql.jdbc.Util.handleNewInstance(Util.java:406) at com.mysql.jdbc.CallableStatement.getInstance(CallableStatement.java:5 05) at com.mysql.jdbc.ConnectionImpl.parseCallableStatement(ConnectionImpl.j ava:3881) at com.mysql.jdbc.ConnectionImpl.prepareCall(ConnectionImpl.java:3965) at com.mysql.jdbc.ConnectionImpl.prepareCall(ConnectionImpl.java:3939) at com.protocase.hmiclient.db.HMIDatabaseAdapter.getAvailableBatchesForW orkstation(HMIDatabaseAdapter.java:471) at com.protocase.hmiclient.views.WorkstationContainer.getBatches(Worksta tionContainer.java:74) at com.protocase.hmiclient.views.BatchList.(BatchList.java:55) at com.protocase.hmiclient.views.WorkstationContainer.goToBatchList(Work stationContainer.java:56) at com.protocase.hmiclient.views.forms.BatchListControlPanel.refreshButt onActionPerformed(BatchListControlPanel.java:118) at com.protocase.hmiclient.views.forms.BatchListControlPanel.access$200( BatchListControlPanel.java:16) at com.protocase.hmiclient.views.forms.BatchListControlPanel$3.actionPer formed(BatchListControlPanel.java:64) at javax.swing.AbstractButton.fireActionPerformed(Unknown Source) at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source) at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source) at javax.swing.DefaultButtonModel.setPressed(Unknown Source) at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Sour ce) at java.awt.Component.processMouseEvent(Unknown Source) at javax.swing.JComponent.processMouseEvent(Unknown Source) at java.awt.Component.processEvent(Unknown Source) at java.awt.Container.processEvent(Unknown Source) at java.awt.Component.dispatchEventImpl(Unknown Source) at java.awt.Container.dispatchEventImpl(Unknown Source) at java.awt.Component.dispatchEvent(Unknown Source) at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source) at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source) at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source) at java.awt.Container.dispatchEventImpl(Unknown Source) at java.awt.Window.dispatchEventImpl(Unknown Source) at java.awt.Component.dispatchEvent(Unknown Source) at java.awt.EventQueue.dispatchEventImpl(Unknown Source) at java.awt.EventQueue.access$000(Unknown Source) at java.awt.EventQueue$1.run(Unknown Source) at java.awt.EventQueue$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source) at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source) at java.awt.EventQueue$2.run(Unknown Source) at java.awt.EventQueue$2.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source) at java.awt.EventQueue.dispatchEvent(Unknown Source) at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.awt.EventDispatchThread.run(Unknown Source) Caused by: java.net.SocketException: Software caused connection abort: socket wr ite error at java.net.SocketOutputStream.socketWrite0(Native Method) at java.net.SocketOutputStream.socketWrite(Unknown Source) at java.net.SocketOutputStream.write(Unknown Source) at java.io.BufferedOutputStream.flushBuffer(Unknown Source) at java.io.BufferedOutputStream.flush(Unknown Source) at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3227) ... 61 more ** END NESTED EXCEPTION **
此exception表明您在应用程序启动期间仅打开一次连接，并在应用程序的生命周期内保持永久打开状态。 这是不好的。 DB迟早会收回连接，因为它已经打开太久了。 您应该在打开它并在其上执行查询时，在同一个try块的finally块中正确关闭连接。
例如
public Entity find(Long id) throws SQLException { Connection connection = null; // ... try { connection = database.getConnection(); // ... } finally { // ... if (connection != null) try { connection.close(); } catch (SQLException logOrIgnore) {} } return entity; }
如果您对此有性能问题（这是非常合理的，因为连接是最昂贵的任务），那么您应该使用连接池。 它还透明地处理这种“连接丢失”问题。 例如， BoneCP 。 请注意，在连接池的情况下，您仍应按照上面的JDBC代码习惯用法关闭finally块中的连接。 它将使它们可以重复使用。