Communication link failure: java.io.IOException, underlying cause: Unexpected end of input stream ** BEGIN NESTED EXCEPTION ** java.io.IOException MESSAGE: Unexpected end of input stream STACKTRACE: java.io.IOException: Unexpected end of input stream at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:1096) at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:626) at com.mysql.jdbc.Connection.createNewIO(Connection.java:1562) at com.mysql.jdbc.Connection.(Connection.java:491) at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:346) at java.sql.DriverManager.getConnection(Unknown Source) at java.sql.DriverManager.getConnection(Unknown Source) at mypack.BookDB.getConnection(BookDB.java:20) at mypack.BookDB.getBooks(BookDB.java:79) at org.apache.jsp.catalog_jsp._jspService(catalog_jsp.java:144) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:133) at javax.servlet.http.HttpServlet.service(HttpServlet.java:856) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:311) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248) at javax.servlet.http.HttpServlet.service(HttpServlet.java:856) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:284) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:204) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256) at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:563) at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:245) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:199) at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:563) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:195) at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:164) at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:149) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:563) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:156) at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:563) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:972) at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:209) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:670) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:517) at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:575) at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:666) at java.lang.Thread.run(Unknown Source) ** END NESTED EXCEPTION ** 
连接数据库的时候出现以上问题,请问是什么原因?我用的是mysql,我觉得是数据库的问题,是不是有什么包没导入?谢谢了!