java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1714)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1559)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:190)
at com.dong.util.DBUtil.openConnection(DBUtil.java:31)
at com.dong.main.update.getMenuList(update.java:29)
at com.dong.servlet.UpdateMenuServlet.doGet(UpdateMenuServlet.java:38)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1002)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:585)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1813)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:744)
四月 25, 2014 8:45:47 上午 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet [UpdateMenuServlet] in context with path [/Stdu_course] threw exception
java.lang.NullPointerException
at com.dong.main.update.getMenuList(update.java:39)
at com.dong.servlet.UpdateMenuServlet.doGet(UpdateMenuServlet.java:38)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1002)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:585)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1813)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:744)
以下是部署到tomcat后，打开连接出现的问题
------解决方案--------------------
mysql 的 jdbc 驱动没加进来
------解决方案--------------------
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
找不到mysql驱动，你把mysql的jar包拷贝到工程下的WEB-INF下的lib就行了。
------解决方案--------------------
mysql的jar包拷贝到工程里。
------解决方案--------------------
你是不是拷重复了？删了重新拷，拷到web中lib
------解决方案--------------------
ctrl+shift+r，看看能不能看见你的jar包，能看见就是导进来了，看不见就是没有
------解决方案--------------------
myeclipse最好办了，它的部署是直接复制到tomat/webapps下，只看看你应用的lib下是否有mysql的驱动
------解决方案--------------------
java.lang.NullPointerException
at com.dong.main.update.getMenuList(update.java:39)
空指针了，
update.java:39
看看这里怎么写的
------解决方案--------------------
是不是有jar包冲突啊
------解决方案--------------------
mysql的jar包拷贝到工程里。
------解决方案--------------------
导入jar包后 tomcat内项目是否重新部署过了