connection close

Question

connection.close()执行完多长时间才会关闭connection
我在做数据追加的时候报异常com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failureThe last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The driver was unable to create a connection due to an inability to establish the client portion of a socket.This is usually caused by a limit on the number of sockets imposed by the operating system. This limit is usually configurable. For Unix-based platforms, see the manual page for the 'ulimit' command. Kernel or system reconfiguration may also be required.

Answer 1

connection.close()执行完多长时间才会关闭connection不会关闭，要等你把这个 connection 对象销毁之后才关闭。

Answer 2

难道光看异常看不出来吗？下面是全部的异常
严重: null
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failureThe last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
        at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
        at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074)
        at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2214)
        at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:781)
        at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
        at sun.reflect.GeneratedConstructorAccessor9.newInstance(Unknown Source)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
        at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
        at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:352)
        at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:284)
        at java.sql.DriverManager.getConnection(DriverManager.java:582)
        at java.sql.DriverManager.getConnection(DriverManager.java:185)
        at upgradedb.DBUtil.connect(DBUtil.java:27)
        at upgradedb.MysqlDB.getAltTables(MysqlDB.java:74)
        at upgradedb.XmlParse.parseAll(XmlParse.java:53)
        at upgradedb.UpgradeDBView$UpgradedbTask.doInBackground(UpgradeDBView.java:454)
        at org.jdesktop.swingworker.SwingWorker$1.call(Unknown Source)
        at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
        at java.util.concurrent.FutureTask.run(FutureTask.java:138)
        at org.jdesktop.swingworker.SwingWorker.run(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:885)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:907)
        at java.lang.Thread.run(Thread.java:619)
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The driver was unable to create a connection due to an inability to establish the client portion of a socket.This is usually caused by a limit on the number of sockets imposed by the operating system. This limit is usually configurable. For Unix-based platforms, see the manual page for the 'ulimit' command. Kernel or system reconfiguration may also be required.For Windows-based platforms, see Microsoft Knowledge Base Article 196271 (Q196271).
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
        at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
        at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074)
        at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:343)
        at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2137)
        ... 21 more
Caused by: java.net.BindException: Address already in use: connect
        at java.net.PlainSocketImpl.socketConnect(Native Method)
        at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
        at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
        at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
        at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
        at java.net.Socket.connect(Socket.java:519)
        at java.net.Socket.connect(Socket.java:469)
        at java.net.Socket.<init>(Socket.java:366)
        at java.net.Socket.<init>(Socket.java:209)
        at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:253)
        at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:292)
        ... 22 more
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after connection closed.
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
        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:984)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:926)
        at com.mysql.jdbc.ConnectionImpl.throwConnectionClosedException(ConnectionImpl.java:1160)
        at com.mysql.jdbc.ConnectionImpl.checkClosed(ConnectionImpl.java:1147)
        at com.mysql.jdbc.ConnectionImpl.prepareStatement(ConnectionImpl.java:4224)
        at com.mysql.jdbc.ConnectionImpl.prepareStatement(ConnectionImpl.java:4190)
        at upgradedb.MysqlDB.getAltTables(MysqlDB.java:78)
        at upgradedb.XmlParse.parseAll(XmlParse.java:53)
        at upgradedb.UpgradeDBView$UpgradedbTask.doInBackground(UpgradeDBView.java:454)
        at org.jdesktop.swingworker.SwingWorker$1.call(Unknown Source)
        at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
        at java.util.concurrent.FutureTask.run(FutureTask.java:138)
        at org.jdesktop.swingworker.SwingWorker.run(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:885)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:907)
        at java.lang.Thread.run(Thread.java:619)
2009-12-25 11:11:42 upgradedb.DBUtil connect