JavaWeb增删改查的基本操作是什么

发布时间：2022-09-26 13:52:16 作者：iii
来源：亿速云阅读：198

这篇文章主要介绍了JavaWeb增删改查的基本操作是什么的相关知识，内容详细易懂，操作简单快捷，具有一定借鉴价值，相信大家阅读完这篇JavaWeb增删改查的基本操作是什么文章都会有所收获，下面我们一起来看看吧。

大致流程是：

首先访问到servlet层，在servlet层里调用StudentRepository的各个方法，然后展示到jsp页面中。所以浏览器访问路径是servlet层里StudentServlet中@WebServlet("/student")的路径(http://localhost:8080/student)

工具：idea，mysql数据库

1.首先看一下我的基本目录：

JavaWeb增删改查的基本操作是什么

数据库：

JavaWeb增删改查的基本操作是什么

2.各个层的代码：

Student.java

public class Student {    private Integer id;    private String name;    private Integer numsex;    private Integer age;    private String password;    
    public Integer getId() {        return id;
    }    public void setId(Integer id) {        this.id = id;
    }    public String getName() {        return name;
    }    public void setName(String name) {        this.name = name;
    }    public Integer getNumsex() {        return numsex;
    }    public void setNumsex(Integer numsex) {        this.numsex = numsex;
    }    public Integer getAge() {        return age;
    }    public void setAge(Integer age) {        this.age = age;
    }    public String getPassword() {        return password;
    }    public void setPassword(String password) {        this.password = password;
    }    public Student(Integer id, String name, Integer numsex, Integer age, String password) {        this.id = id;        this.name = name;        this.numsex = numsex;        this.age = age;        this.password = password;
    }    @Override
    public String toString() {        return "Student{" +                "id=" + id +                ", name='" + name + '\'' +                ", numsex=" + numsex +                ", age=" + age +                ", password='" + password + '\'' +                '}';
    }

StudentRepository：

import com.javaweb.entity.Student;import com.javaweb.util.JDBCTools;import java.sql.*;import java.util.ArrayList;import java.util.List;
public class StudentRepository {
    public List<Student> findAll(){
        List<Student> list=new ArrayList<>();
        Connection connection=null;
        PreparedStatement preparedStatement=null;
        ResultSet resultSet=null;        try {            //调用JDBCTools连接mysql数据库
            connection= JDBCTools.getConnection();            String sql="select * from student";//查询语句
            preparedStatement=connection.prepareStatement(sql);
            resultSet = preparedStatement.executeQuery();            while (resultSet.next()){                //从resultSet拿出每个属性数据
                Integer id=resultSet.getInt(1);                String name=resultSet.getString(2);
                Integer numsex=resultSet.getInt(3);
                Integer age=resultSet.getInt(4);                String password=resultSet.getString(5);                //这里可以理解为，resultSet拿出每个属性数据赋予student对象，形成一个有数据的student对象
                Student student = new Student(id, name, numsex, age, password);
                list.add(student);//可能多条数据，放到集合中
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {            //调用JDBCTools，关闭connection，preparedStatement，resultSet
            JDBCTools.release(connection,preparedStatement,resultSet);
        }        return list;
    }    //添加操作
    public void add(Integer id,String name,Integer numsex,
                     Integer age,String password){
        Connection connection=null;
        PreparedStatement preparedStatement=null;        try {
            connection= JDBCTools.getConnection();            String sql="insert into student(id,name,numsex,age,password) values (?,?,?,?,?)";
            preparedStatement=connection.prepareStatement(sql);            //这里注意第一个参数对应sql语句问号的序号，
            preparedStatement.setInt(1,id);//就是把id替代sql的第一个问号，id由前端传过来
            preparedStatement.setString(2,name);
            preparedStatement.setInt(3,numsex);
            preparedStatement.setInt(4,age);
            preparedStatement.setString(5,password);
            preparedStatement.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JDBCTools.release(connection,preparedStatement,null);
        }
    }    //删除操作
    public void deleteById(Integer id){
        Connection connection=null;
        PreparedStatement preparedStatement=null;    try {
        connection= JDBCTools.getConnection();        String sql="delete from student where id=?";
        preparedStatement=connection.prepareStatement(sql);
        preparedStatement.setInt(1,id);
        preparedStatement.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            JDBCTools.release(connection,preparedStatement,null);
        }
    }    //根据id查询
    public Student findById(Integer id){
        Connection connection=null;
        PreparedStatement preparedStatement=null;
        ResultSet resultSet=null;
        Student student=null;        try {
            connection= JDBCTools.getConnection();            String sql="select * from student where id=?";
            preparedStatement=connection.prepareStatement(sql);
            preparedStatement.setInt(1,id);
            resultSet = preparedStatement.executeQuery();            while (resultSet.next()){
                Integer id2=resultSet.getInt(1);                String name=resultSet.getString(2);
                Integer numsex=resultSet.getInt(3);
                Integer age=resultSet.getInt(4);                String password=resultSet.getString(5);
                student = new Student(id2, name, numsex, age, password);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            JDBCTools.release(connection,preparedStatement,resultSet);
        }        return student;
    }    //更新操作
    public void update(Integer id,String name,Integer numsex,
                       Integer age,String password){
        Connection connection=null;
        PreparedStatement preparedStatement=null;        try {
            connection= JDBCTools.getConnection();            String sql="update student set name=?,numsex=?,age=?,password=? where id=?";
            preparedStatement=connection.prepareStatement(sql);
            preparedStatement.setString(1,name);
            preparedStatement.setInt(2,numsex);
            preparedStatement.setInt(3,age);
            preparedStatement.setString(4,password);
            preparedStatement.setInt(5,id);
            preparedStatement.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JDBCTools.release(connection,preparedStatement,null);
        }
    }
}

StudentServlet：

import com.javaweb.entity.Student;import com.javaweb.repository.StudentRepository;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 java.io.IOException;import java.util.List;@WebServlet("/student")public class StudentServlet extends HttpServlet {    //调用StudentRepository中的增删改查方法
    private StudentRepository studentRepository=new StudentRepository();    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        //判断前端传来的标记，以此执行相对应的增删改查操作
        String method=req.getParameter("method");        if (method==null){
            method="findAll";
        }        switch (method){            case "findAll"://查询所有数据
                List<Student> list = studentRepository.findAll();//调用StudentRepository中的findAll()方法
                req.setAttribute("list",list);//存入request中
                req.getRequestDispatcher("index.jsp").forward(req,resp);//转发到index.jsp中
            case "delete"://删除操作
                String idStr=req.getParameter("id");
                Integer id=Integer.parseInt(idStr);
                studentRepository.deleteById(id);//根据id删除
                resp.sendRedirect("/student");                break;            case "findById":
                idStr=req.getParameter("id");
                id=Integer.parseInt(idStr);
                req.setAttribute("student",studentRepository.findById(id));
                req.getRequestDispatcher("update.jsp").forward(req,resp);                break;            case "add":
                req.getRequestDispatcher("add.jsp").forward(req,resp);
        }
    }    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("UTF-8");//防止中文乱码
        String method=req.getParameter("method");        switch (method){            case "add"://添加操作
                //获取前端传来的数据
                String idStr=req.getParameter("id");
                String name=req.getParameter("name");
                String numsexStr=req.getParameter("numsex");
                String ageStr=req.getParameter("age");
                String password=req.getParameter("password");
                Integer id=Integer.parseInt(idStr);//转化为整型
                Integer numsex=Integer.parseInt(numsexStr);
                Integer age=Integer.parseInt(ageStr);
                studentRepository.add(id,name,numsex,age,password);//调用add方法
                break;            case "update"://更新操作
                idStr=req.getParameter("id");
                name=req.getParameter("name");
                numsexStr=req.getParameter("numsex");
                ageStr=req.getParameter("age");
                password=req.getParameter("password");
                id=Integer.parseInt(idStr);
                numsex=Integer.parseInt(numsexStr);
                age=Integer.parseInt(ageStr);
                studentRepository.update(id, name, numsex, age, password);                break;
        }
        resp.sendRedirect("/student");//重定向到index.jsp页面
    }
}

JDBCTools：

import java.sql.*;public class JDBCTools {    private static Connection connection;    private static String url="jdbc:mysql://localhost:3306/he?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone = GMT";    private static String user="root";//用户名
    private static String pass="123z";//密码
    static {        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }    public static Connection getConnection(){        try {
            connection= DriverManager.getConnection(url,user,pass);
        } catch (SQLException e) {
            e.printStackTrace();
        }        return connection;
    }    public static void release(Connection connection, Statement statement, ResultSet resultSet){        try {            if (connection!=null) {
                connection.close();
            }            if (statement!=null){
                statement.close();
            }            if (resultSet!=null){
                resultSet.close();
            }
            } catch (SQLException e) {
                e.printStackTrace();
            }
    }
}

其中，web.xml创建之后不曾配置过，所以不贴代码了

add.jsp：

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>
    <title>Title</title></head><body><form action="/student" method="post">
    编号: <input type="text" name="id"/><br/>
    姓名：<input type="text" name="name"/><br/>
    性别：<input type="text" name="numsex"/><br/>
    年龄：<input type="text" name="age"/><br/>
    密码：<input type="password" name="password"/><br/>
    <input type="hidden" name="method" value="add"/>
    <input type="submit" value="提交"/></form></body></html>

index.jsp：

<%@ page contentType="text/html;charset=UTF-8" language="java" %><%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %><html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
      <h1>学生管理系统</h1>
        <div ><a href="/student?method=add">添加</a></div>
  <table>
    <tr>
      <th>编号</th>
      <th>姓名</th>
      <th>性别</th>
      <th>年龄</th>
      <th>密码</th>
      <th>操作</th>
    </tr>
    <c:forEach items="${list}" var="student">
      <tr>
        <td>${student.id}</td>
        <td>${student.name}</td>
        <td>${student.numsex}</td>
        <td>${student.age}</td>
        <td>${student.password}</td>
        <td>
          <a href="/student?method=delete&id=${student.id}">删除</a>
          <a href="/student?method=findById&id=${student.id}">修改</a>
        </td>
      </tr>
    </c:forEach>
  </table>
  </body></html>

update.jsp：

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>
    <title>Title</title></head><body><form action="/student" method="post">
    编号: <input type="text" name="id" value="${student.id}" readonly/><br/>
    姓名：<input type="text" name="name" value="${student.name}"/><br/>
    性别：<input type="text" name="numsex" value="${student.numsex}"/><br/>
    年龄：<input type="text" name="age" value="${student.age}"/><br/>
    密码：<input type="password" name="password" value="${student.password}"/><br/>
    <input type="hidden" name="method" value="update"/>
    <input type="submit" value="修改"/></form></body></html>