Question

我想创建一个与数据库连接的注册表单。我有一个问题，因为填写表格后我得到了异常

java.lang.NullPointerException Database.Person.getName（Person.java:18） Database.Register.doPost（Register.java:25）

我一直在寻找答案，但只有简单的解决方案（我的意思是一堂课中的所有内容）。有我的代码

Person.java

package Database;


import javax.servlet.http.HttpServletRequest;

public class Person {
    private String name;
    private String surname;
    private String email;
    private String employer;
    private String getKnow;
    private String hobbies;

    HttpServletRequest request;


    public String getName() {
        return request.getParameter("name");
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSurname() {
        return request.getParameter("surname");
    }

    public void setSurname(String surname) {
        this.surname = surname;
    }

    public String getEmail() {
         return request.getParameter("email");
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getEmployer() {
        return request.getParameter("pracodawca");  }

    public void setEmployer(String employer) {
        this.employer = employer;
    }

    public String getGetKnow() {
        return request.getParameter("getKnow"); }

    public void setGetKnow(String getKnow) {
        this.getKnow = getKnow;
    }

    public String getHobbies() {
        return request.getParameter("hobbies"); }

    public void setHobbies(String hobbies) {
        this.hobbies = hobbies;
    }

Register.java

package Database;

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 java.sql.Statement;

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(urlPatterns = "/Register")
public class Register extends HttpServlet {
public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
    response.setContentType("text/html");
    PrintWriter out = response.getWriter();

    Person person = new Person();
    String name = person.getName();
    String surname = person.getSurname();
    String email = person.getEmail();
    String nameC = person.getEmployer();
    String getKnow = person.getGetKnow();
    String hobbies = person.getHobbies();


        try {
            Class.forName("org.postgresql.Driver");
            Connection connection = DriverManager.getConnection(
                    "jdbc:postgresql://localhost:5432/formularz", "postgres",
                    "qwerty");
            PreparedStatement ps = connection.prepareStatement(
                    "INSERT INTO zgloszenia(name,surname, email,pracodawca, getknow, hobbies) values(?,?,?,?,?,?)");
            ps.setString(1, name);
            ps.setString(2, surname);
            ps.setString(3, email);
            ps.setString(4, nameC);
            ps.setString(5, getKnow);
            ps.setString(6, hobbies);

            int i = ps.executeUpdate();
            if (i > 0) {
                out.print("Registered successfully...");
                connection.close();
            }


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

    }

Answer 1

你有：

 HttpServletRequest request;


    public String getName() {
        return request.getParameter("name");
    }

您希望请求的 not-null 值来自哪里？

Answer 2

person的request属性为null。你应该在使用它之前设置它。 person.request = request;或更好地使用Person构造函数来设置请求属性。

Servlet表单和获取参数

2 个答案: