jsp mvc项目上的java空指针异常

Question

我收到此错误 The server encountered an unexpected condition that prevented it from fulfilling the request. java.lang.NullPointerException。我正在尝试将数据插入 mysql 数据库。我创建了一个动态 Web 项目，在 index.jsp 文件中我有表单。我也在关注 MVC 架构。

这是我得到的错误

CustomerController.java serverlet

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    //doGet(request, response);

    //Get the data
    String name = request.getParameter("name");
    String email = request.getParameter("email");
    String address = request.getParameter("address");
    String sex = request.getParameter("sex");
    String bday = request.getParameter("bday");
    String tel = request.getParameter("tele");
    String password= request.getParameter("password");

    //Setup an Employee object
    Customer customer = new Customer();
    customer.setName(name);
    customer.setEmail(email);
    customer.setAddress(address);
    customer.setSex(sex);
    customer.setBday(bday);
    customer.setTelephone(tel);
    customer.setPassword(password);

    //Setup am EmpAddQuery object
    CustomerAddQuery obj = new CustomerAddQuery();

    //Pass the Employee to EmpAddQuery to add to the database
    obj.addData(customer); //line 69

    //Pass execution control to the ReadServlet
    String url = "/index.jsp";

    RequestDispatcher dispatcher = request.getRequestDispatcher(url);
    dispatcher.forward(request, response);

}

我只复制了servelet的doPost方法

CustomerAddQuery.java

package dbhelpers;


import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.Statement;

import models.Customer;

public class CustomerAddQuery {
    DBConnection databaseCon = new DBConnection();

    public void addData(Customer customer)
    {

        String query = "insert into customers (`name`, `email`, `address`, 
     `sex`, `bday`, `telephone` , `password`) values (?,?,?,?,?,?,?)" ;
        try {
            Connection con = databaseCon.dbconnect();
            PreparedStatement pst = con.prepareStatement(query); //line 27
            pst.setString(1, customer.getName());
            pst.setString(2, customer.getEmail());
            pst.setString(3, customer.getAddress());
            pst.setString(4, customer.getSex());
            pst.setString(5, customer.getBday());
            pst.setString(6, customer.getTelephone());
            pst.setString(7, customer.getPassword());
            pst.execute();


        } catch (SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

}

DBConnect.java 文件

package dbhelpers;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class DBConnection {
   public static Connection dbconnect(){
        Connection con = null;
        try {

        Class.forName("com.mysql.jdbc.Driver");
        con = DriverManager.getConnection("jdbc:mysql://localhost/vehicle_rental_system", "root", "");


    }
    catch (ClassNotFoundException | SQLException e){
        System.out.println(e);
    }
       return con; 
   }
}

Answer 1

复制mysql jdbc驱动到Tomcat\lib目录解决