ClassNotFoundException / mysql jdbc驱动程序[重复]

Question

我已经创建了一个登录和注册页面，但是当点击创建帐户按钮时，数据没有被存储到数据库中。它给出了一个例外，说

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver"

我已经在我的项目中添加了 mysql jar 文件。

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/loginandregister")
public class loginandregister extends HttpServlet {
    private static final long serialVersionUID = 1L;


    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String options=request.getParameter("button");
        System.out.println(options);
        PrintWriter pw=response.getWriter();


        if(options.equals("LOGIN")) {

                String username=request.getParameter("loginid");
                String password=request.getParameter("loginpassword");

            try {
                Class.forName("com.mysql.jdbc.Driver");
                Connection conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/loginclass","root","root");
                PreparedStatement login=conn.prepareStatement("select * from user_info where username=? and userpassword=?");
                login.setString(1, username);
                login.setString(2, password);

                ResultSet rs=login.executeQuery();
                    if(rs.next()) {

                        pw.println("Welcome");
                        pw.println("Welcome"+username);
                    }else {
                      pw.println("Error");
                    }
            }
            catch (Exception e) {
                e.printStackTrace();
            }
        }



        if(options.equals("CREATE ACCOUNT")) {

             try {

                    Class.forName("com.mysql.jdbc.Driver");
                    Connection conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/loginclass","root","root");


                    PreparedStatement register=conn.prepareStatement("insert into user_info values (?,?,?,?,?,?)");

                    String firstname=request.getParameter("fname");
                    String lastname=request.getParameter("lname");
                    String email=request.getParameter("email");
                    String phone=request.getParameter("phone");
                    String uname=request.getParameter("uname");
                    String pass=request.getParameter("password");

                    register.setString(1, firstname);
                    register.setString(2, lastname);
                    register.setString(3, email);
                    register.setString(4, phone);
                    register.setString(5, uname);
                    register.setString(6, pass);
                    register.executeUpdate();

                    }// try
                    catch (Exception e) {
                        e.printStackTrace();
                    }//catch

        }// if create acc.

    }// dopost
}//class

Answer 1

我认为您需要将jar 添加到您的tomcat 目录的lib 文件夹中。在那里添加jar 并重新启动服务器。

这可能对你有用。