这个是怎么回事啊？大家帮忙 看下 Communications link failure due to underlying exception:

Question

由于需求每秒都要和数据库交互，开始的时候还很正常，几分钟后就出现了下面的错com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: 
** BEGIN NESTED EXCEPTION ** 
java.net.SocketException
MESSAGE: java.net.BindException: Address already in use: connectSTACKTRACE:java.net.SocketException: java.net.BindException: Address already in use: connect
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:151)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:280)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:1774)
at com.mysql.jdbc.Connection.<init>(Connection.java:437)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:268)
at java.sql.DriverManager.getConnection(Unknown Source) at org.directwebremoting.impl.ExecuteAjaxFilter.doFilter(ExecuteAjaxFilter.java:34)
at org.directwebremoting.impl.DefaultRemoter$1.doFilter(DefaultRemoter.java:428)
at org.directwebremoting.impl.DefaultRemoter.execute(DefaultRemoter.java:431)
at org.directwebremoting.impl.DefaultRemoter.execute(DefaultRemoter.java:283)
at org.directwebremoting.servlet.PlainCallHandler.handle.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Unknown Source)
** END NESTED EXCEPTION **
at com.mysql.jdbc.Connection.createNewIO(Connection.java:1839)
at com.mysql.jdbc.Connection.<init>(Connection.java:437)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:268)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at database.DataBaseConnector.getConnection((Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.directwebremoting.impl.ExecuteAjaxFilter.doFilter(ExecuteAjaxFilter.java:34)
at org.directwebremoting.impl.DefaultRemoter$1.doFilter(DefaultRemoter.java:428)
at org.directwebremoting.impl.DefaultRemoter.(ApplicationFilterChain.java:290)
at org.apache.catalina.core.(CoyoteAdapter.java:286)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Unknown Source)
警告: DbConnectionManager.getConnection() 获得数据库链接失败.链接类型:
com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.net.SocketException
MESSAGE: java.net.BindException: Address already in use: connectSTACKTRACE:java.net.SocketException: java.net.BindException: Address already in use: connect
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:151)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:280)
at com.mysql.jdbc.Connection.createNewIO((DataBaseConnector.java:36)
at database.DataBaseConnector.executeQuery(DataBaseConnector.java:54)
at database.SelectData.tempinfo(SelectData.java:26)
at com.test.dwr.servlet.Ttt.alarm(Ttt.java:38)
at sun.reflect.GeneratedMethodAccessor19.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.directwebremoting.impl..java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core..service(CoyoteAdapter.java:286)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Unknown Source)
** END NESTED EXCEPTION **
at com.mysql.jdbc.Connection.createNewIO(Connection.java:1839)
at com.mysql.jdbc.Connection.<init>(Connection.java:437)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:268)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.$1.doFilter(DefaultRemoter.java:428)
at org.directwebremoting.impl.DefaultRemoter.execute(DefaultRemoter.java:431)
at org.directwebremoting.impl.DefaultRemoter.execute(DefaultRemoter.java:283)
at org.directwebremoting.servlet.PlainCallHandler.handle(PlainCallHandler.java:52)
at org.directwebremoting.servlet.UrlProcessor.handle(UrlProcessor.java:101)
at org.directwebremoting.servlet.DwrServlet.doPost(DwrServlet.java:146)
at javax.servlet.http.HttpServlet.service(invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Unknown Source)
警告: DbConnectionManager.getConnection() 获得数据库链接失败.链接类型:

Answer 1

看你的代码应该是，在每次跟数据库交互时，新建一个connection。以你程序中每秒create一个connection来看，这样做的潜在风险就是：可能同一时间（网络延时导致两个create请求同时到达服务器端）有多个create connection的请求达到mysql服务器端，从而出现上面的错误可以使用数据库连接池来避免此问题。