我正在弄一个用Servlet做的登陆功能，其中mysql数据库连接程序出现ClassNotFoundException，这个程序之前就写过的了，没看出有什么问题，下面贴出代码和异常语句，希望大家能找出问题，先谢了。
package com.vv.databaseConnection;
import java.sql.Connection;
import java.sql.DriverManager;
public class DatabaseConnection {
private static final String DBDRIVER = "com.mysql.jdbc.Driver" ;
private static final String DBURL = "jdbc:mysql://localhost:3306/vv";
private static final String DBUSER = "root" ;
private static final String DBPASS = "456" ;
private Connection conn = null ;
public DatabaseConnection() throws Exception{
try{
Class.forName(DBDRIVER);
conn=DriverManager.getConnection(DBURL, DBUSER, DBPASS);
}
catch(Exception e){
e.printStackTrace();
}
}
public Connection getConnection(){
return this.conn;
}
public void close(){
try{
if(this.conn != null){
this.conn.close();
}
}
catch(Exception e){
e.printStackTrace();
}
}
}
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1680)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1526)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:190)
at com.vv.databaseConnection.DatabaseConnection.<init>(DatabaseConnection.java:14)
at com.vv.controler.LoginCLServlet.doGet(LoginCLServlet.java:46)
at com.vv.controler.LoginCLServlet.doPost(LoginCLServlet.java:85)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:643)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:723)
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.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:861)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:606)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:744)
java.lang.NullPointerException
at com.vv.controler.LoginCLServlet.doGet(LoginCLServlet.java:48)
at com.vv.controler.LoginCLServlet.doPost(LoginCLServlet.java:85)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:643)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:723)
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.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:861)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:606)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:744)
------解决思路----------------------
拷贝一份mysql的jar包放在tomcat的lib目录下
------解决思路----------------------
这是jar包问题
建的如果是web工程，就把这个jar包拷贝到工程的lib目录下，如果是java工程，请右键build path--add active 那个选项并找到你的文件，点击打开即可！
右键项目属性看下