idea的那些坑(1)

原文地址 http://blog.csdn.net/woaixiaozhe/article/details/7326915
确认包已经被导入web工程目录，但是任然运行错误——Java.lang.ClassNotFoundException: com.MySQL.jdbc.Driver。找不到
com.mysql.jdbc.Driver这个驱动。

报错信息如下：

HTTP Status 500 - Servlet execution threw an exceptiontype Exception reportmessage Servlet execution threw an exceptiondescription The server encountered an internal error that prevented it from fulfilling this request.exceptionjavax.servlet.ServletException: Servlet execution threw an exception    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)root causejava.lang.NoClassDefFoundError: com/mysql/jdbc/Driver    com.wh.serveletDemo1.SearchServlet.getConnection(SearchServlet.java:29)    com.wh.serveletDemo1.SearchServlet.CheckLogin(SearchServlet.java:43)    com.wh.serveletDemo1.SearchServlet.doPost(SearchServlet.java:80)    javax.servlet.http.HttpServlet.service(HttpServlet.java:650)    javax.servlet.http.HttpServlet.service(HttpServlet.java:731)    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)root causejava.lang.ClassNotFoundException: com.mysql.jdbc.Driver    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1858)    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1701)    com.wh.serveletDemo1.SearchServlet.getConnection(SearchServlet.java:29)    com.wh.serveletDemo1.SearchServlet.CheckLogin(SearchServlet.java:43)    com.wh.serveletDemo1.SearchServlet.doPost(SearchServlet.java:80)    javax.servlet.http.HttpServlet.service(HttpServlet.java:650)    javax.servlet.http.HttpServlet.service(HttpServlet.java:731)    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)note The full stack trace of the root cause is available in the Apache Tomcat/7.0.69 logs.

    原来是tomcat找不到MYSQL JAR包的问题。后来又把mysql-connector-java-5.1.7-bin.jar导入到tomcat的lib目录下面就ok了，嘿……    在java项目中，只需要引入mysql-connector-java-5.1.7-bin.jar就可以运行java项目。    在web项目中，当Class.forName("om.mysql.jdbc.Driver");时myeclipse是不会去查找字符串，不会去查找驱动的。所以只需要把

mysql-connector-java-5.1.7-bin.jar拷贝到tomcat下lib目录就可以了。

    补充：1.如果web项目中有可运行的java，而且也用到了com.mysql.jdbc.Driver(即mysql)，先运行下java，再运行web 不会出现这个问题，因为运行java时已经向项目导入了驱动；          2.MyEclipse9.0(其他版本的应该类似)的tomcat在MyEclipse安装路径的：MyEclipse\Common\plugins\com.genuitec.eclipse.easie.tomcat.myeclipse_9.0.0.me201012172208\tomcat