error: java.lang.ClassNotFoundException: com.mysql.jdbc.Driver?

Question

我正在尝试使用 servlet 和 jdbc 连接到 MySQL 数据库的简单登录身份验证。在 tomcat 服务器上执行后出现以下错误：

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1720)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1571)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at com.leader.prog.Validate.checkUser(Validate.java:13)
at com.leader.servlet.Login1.doPost(Login1.java:42)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:646)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2466)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2455)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Unknown Source)

我正在分享所有文件的内容：

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
  <servlet>
 <servlet-name>login</servlet-name>
    <servlet-class>com.leader.servlet.Login1</servlet-class>
  </servlet>
   <servlet-mapping>
<servlet-name>login</servlet-name>
<url-pattern>/login</url-pattern>
  </servlet-mapping>


   <servlet>
<servlet-name>welcome</servlet-name>
<servlet-class>com.leader.servlet.Welcome</servlet-class>
   </servlet>
  <servlet-mapping>
<servlet-name>welcome</servlet-name>
<url-pattern>/welcome</url-pattern>
  </servlet-mapping>


  <welcome-file-list>
<welcome-file>Home.html</welcome-file>
  </welcome-file-list>
</web-app>

Login1.java

package com.leader.servlet;


import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.leader.*;
import com.leader.prog.Validate;

@WebServlet("/Login1")
public class Login1 extends HttpServlet {
/**
 * @see HttpServlet#HttpServlet()
 */
public Login1() {
    super();
    // TODO Auto-generated constructor stub
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

}


      protected void doPost(HttpServletRequest request,
                        HttpServletResponse response)
                throws ServletException, IOException
      {
          response.setContentType("text/html;charset=UTF-8");
            PrintWriter out = response.getWriter();

            String user = request.getParameter("userName");
            String pass = request.getParameter("password");

            if(Validate.checkUser(user.toString(),pass.toString()))
            {
                RequestDispatcher rs = request.getRequestDispatcher("Welcome");
                rs.forward(request, response);
            }
            else
            {
               out.println("Username or Password incorrect");
               RequestDispatcher rs = request.getRequestDispatcher("Home.html");
               rs.include(request, response);
            }

        }  
      }

validate.java

package com.leader.prog;
import java.sql.*;

public class Validate
 {

 public static boolean checkUser(String user,String pass) 
 {
  boolean st =false;
  try{

 //loading driver 
     Class.forName("com.mysql.jdbc.Driver");

 //creating connection with the database 
     Connection con=DriverManager.getConnection
                    ("jdbc:mysql://localhost:3306/person","root","password");
     PreparedStatement ps =con.prepareStatement
                         ("select * from person where pid=? and password=?");
     ps.setString(1, user);
     ps.setString(2, pass);
     ResultSet rs =ps.executeQuery();
     st = rs.next();

  }catch(Exception e)
  {
      e.printStackTrace();
  }
     return st;                 
 }   
 }

请帮我解决这个问题。

Answer 1

检查 mysql 驱动程序是否在类路径中。如果您正在使用 IDE(eclipse)，请尝试将其添加到构建路径。

Answer 2

您应该在您的项目构建路径中添加 Mysql 连接器库

您可以从 http://dev.mysql.com/downloads/connector/j/5.0.html

或

http://www.java2s.com/Code/Jar/c/Downloadcommysqljdbc515jar.htm

error: java.lang.ClassNotFoundException: com.mysql.jdbc.Driver?

error: java.lang.ClassNotFoundException: com.mysql.jdbc.Driver?

java

servlets

jdbc