servlet

为什么需要Servlet

使用JSP技术如何编写服务器动态网页？

JSP工作原理

什么是Servlet

定义

Servlet 是一个 Java程序，是在服务器上运行以处理客户端请求并做出响应的程序

Servlet生命周期示例

Servlet的生命周期由Servlet容器(如：Tomcat)控制，主要有以下阶段：

实例化

Servlet 容器创建 Servlet 的实例

初始化

该容器调用 init() 方法

服务

如果请求 Servlet，则容器调用 service() 方法

销毁

销毁实例之前调用 destroy() 方法

Servlet生命周期

HelloServlet
// 导入必需的 java 库
import java.io.IOException;

import jakarta.servlet.ServletConfig;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

//扩展 HttpServlet 类
public class HelloServlet extends HttpServlet {
  private static final long serialVersionUID = 1L;

  public HelloServlet() {
    // 执行必需的初始化
  }

  public void init(ServletConfig config) throws ServletException {
  }

  public void destroy() {
  }

  protected void service(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    response.getWriter().append("Served at: ").append(request.getContextPath());
  }

  protected void doGet(HttpServletRequest request, HttpServletResponse response) 
      throws ServletException, IOException {
    response.getWriter().append("Served at: ").append(request.getContextPath());
  }

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

}

Servlet定义

创建Servlet分两步：

创建Servlet类
- 实现Servlet业务功能
URL映射
- 建立Servlet业务类与URL地址之间的映射关系

创建Servlet类

创建Servlet

HelloAnnotationServlet
@WebServlet("/HelloAnnotation") // 映射URL
public class HelloAnnotationServlet extends HttpServlet {
  protected void service(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    response.getWriter().append("Served at: ").append(request.getContextPath());
  }

  protected void doGet(HttpServletRequest request, HttpServletResponse response) 
      throws ServletException, IOException {
    response.getWriter().append("Served at: ").append(request.getContextPath());
  }

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

源代码

HelloAnnotationServlet
// 导入必需的 java 库
import java.io.IOException;

import jakarta.servlet.ServletConfig;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

//扩展 HttpServlet 类
@WebServlet("/HelloAnnotation") // 映射URL
public class HelloAnnotationServlet extends HttpServlet {
  private static final long serialVersionUID = 1L;

  public HelloAnnotationServlet() {
    // 执行必需的初始化
  }

  public void init(ServletConfig config) throws ServletException {
  }

  public void destroy() {
  }

  protected void service(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    response.getWriter().append("Served at: ").append(request.getContextPath());
  }

  protected void doGet(HttpServletRequest request, HttpServletResponse response) 
      throws ServletException, IOException {
    response.getWriter().append("Served at: ").append(request.getContextPath());
  }

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

}

URL映射

Servlet有两种映射方式：注解、web.xml

注解式web.xml式

HelloAnnotationServlet
@WebServlet("/HelloAnnotation") // 映射URL
public class HelloAnnotationServlet extends HttpServlet {
}

源代码

HelloAnnotationServlet
// 导入必需的 java 库
import java.io.IOException;

import jakarta.servlet.ServletConfig;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

//扩展 HttpServlet 类
@WebServlet("/HelloAnnotation") // 映射URL
public class HelloAnnotationServlet extends HttpServlet {
  private static final long serialVersionUID = 1L;

  public HelloAnnotationServlet() {
    // 执行必需的初始化
  }

  public void init(ServletConfig config) throws ServletException {
  }

  public void destroy() {
  }

  protected void service(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    response.getWriter().append("Served at: ").append(request.getContextPath());
  }

  protected void doGet(HttpServletRequest request, HttpServletResponse response) 
      throws ServletException, IOException {
    response.getWriter().append("Served at: ").append(request.getContextPath());
  }

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

}

WEB-INF/web.xml
<servlet>
  <servlet-name>HelloServlet</servlet-name>   <!-- Servlet名 -->
  <servlet-class>HelloServlet</servlet-class> <!-- 业务类 -->
</servlet>

<servlet-mapping>
  <servlet-name>HelloServlet</servlet-name> <!-- Servlet名 -->
  <url-pattern>/Hello</url-pattern>         <!-- 映射地址 -->
</servlet-mapping>

源代码

WEB-INF/web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns="http://xmlns.jcp.org/xml/ns/javaee"
  xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
  id="WebApp_ID" version="4.0">
  <display-name>HelloServlet</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>

  <servlet>
    <servlet-name>HelloServlet</servlet-name>   <!-- Servlet名 -->
    <servlet-class>HelloServlet</servlet-class> <!-- 业务类 -->
  </servlet>

  <servlet-mapping>
    <servlet-name>HelloServlet</servlet-name> <!-- Servlet名 -->
    <url-pattern>/Hello</url-pattern>         <!-- 映射地址 -->
  </servlet-mapping>

</web-app>

Servlet与JSP关系

Servlet与JSP之间的关系

JSP在服务器上转译的文件

MyJsp.jspMyJsp.java

jsp_servlet_2.jsp
<%@ page contentType="text/html;charset=utf-8" %>
<html>

<head>
  <title>MyJsp</title>
</head>

<body>
  This is my JSP page. <br>
</body>

</html>

jsp_servlet_2.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

// 扩展 HttpServlet 类
public class HelloWorld extends HttpServlet {
  public void service(ServletRequest request,
      ServletResponse response)
      throws ServletException, IOException {
    PrintWriter out = response.getWriter();
    out.write("<html>\r\n");
    out.write("  <head>\r\n");
    out.write("    <title>MyJsp.jsp</title>\r\n");
    out.write("  </head>\r\n");
    out.write("  <body>\r\n");
    out.write(" This is my JSP page. <br>\r\n");
    out.write("  </body>\r\n");
    out.write("</html>\r\n");
  }
}

Servlet应用流程

前台页面的创建

FORM表单的编写

后台Servlet的创建

使用Eclipse的Servlet向导创建Servlet代码模板
根据表单提交方法，确定接收方法
接收请求数据、处理数据、返回响应页面

示例

login.jsp
<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8" %>
<!DOCTYPE html>
<html>

<head>
  <meta charset="utf-8">
  <title>登录</title>
</head>

<body>
  <form action="Login" method="Get" name="login">
    <input type="text" name="user_name" placeholder="用户名" />
    <input type="password" name="password" placeholder="密码" />
    <button type="submit">登录</button>
  </form>
</body>

</html>

LoginServlet
protected void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
  String user_name = request.getParameter("user_name");
  String password = request.getParameter("password");
  if ("xust".equals(user_name) && "666".equals(password)) {
    RequestDispatcher dispatcher = request.getRequestDispatcher("/success.jsp");
    dispatcher.forward(request, response);
  } else {
    response.sendRedirect("fail.jsp");
  }
}

源代码

LoginServlet
import java.io.IOException;
import jakarta.servlet.RequestDispatcher;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

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

  public LoginServlet() {
  }

  protected void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    String user_name = request.getParameter("user_name");
    String password = request.getParameter("password");
    if ("xust".equals(user_name) && "666".equals(password)) {
      RequestDispatcher dispatcher = request.getRequestDispatcher("/success.jsp");
      dispatcher.forward(request, response);
    } else {
      response.sendRedirect("fail.jsp");
    }
  }

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

}

CRUD操作

为了实现代码的可维护性、可扩展性和可测试性。分层架构将系统分解为不同的层次，每个层次都有明确的职责和功能。通常将应用程序分为四个层次结构：控制层、服务层、数据访问层和实体层。

下面是基于Servlet 的实现这些层级的详细介绍：

控制层：负责处理来自客户端的 HTTP 请求，并将请求路由到正确的服务方法中。在基于 Servlet 的架构中，通常使用一个名为 "Front Controller" 的 Servlet 来作为控制器，该 Servlet 负责管理请求和响应，以及进行必要的身份验证和授权。
服务层：负责执行业务逻辑，例如处理请求并生成相应的数据模型。在基于 Servlet 的架构中，通常将服务层实现为简单的 POJO（普通的Java 对象），它们可能会从数据库中读取数据并通过 Servlet 控制器发送响应。
数据访问层：负责提供与数据存储系统的交互，并负责将数据转换为可在服务层中使用的格式。在基于Servlet 的架构中，数据访问层通常使用称为 DAO（数据访问对象）的对象来隐藏底层数据源的复杂性和细节。
实体层：表示应用程序的业务实体和规则。在基于Servlet 的架构中，通常使用 POJO 来表示域对象，并将其与数据访问层和服务层结合使用。

这种基于 Servlet 的架构模式主要优势是可扩展性高，可以快速部署和调试，以及具有良好的分离关注点的能力，使得不同的开发人员可以同时工作，从而提高生产率和代码质量。

优点：

易于维护：分层结构使得系统代码更具有可读性和可维护性，因为每个层都有清晰的职责和功能，易于定位和排除问题。

可扩展性：由于架构的松耦合性，每个层次的改变不会影响到其他层次，因此添加新功能或更改现有功能变得更容易实现。

可测试性：分离出的业务逻辑层可以进行单元测试，以便快速检测问题并改进代码。而且，数据访问层可以使用内存数据库或者Mock数据来进行单元测试，而不需要考虑外部存储的依赖性。

易于协作开发：分层结构可以使不同团队或不同开发者之间互相独立地开发代码，因为他们只需要知道接口而无需关注底层实现。

表结构实体数据访问对象DAO服务对象控制对象测试

demo/DaoTest/Student.sql
create table Student(
    no TEXT primary key,
    name TEXT not null,
    gender TEXT,
    age INTEGER,
    dept TEXT
);

xust.demo.stu.domain.Student
public class Student{      
  /**
   * 学号
   */
  private String no;
  public String getNo(){
    return no;
  }

  public void setNo(String newValue){
    no = newValue;
  }
}

源代码

xust.demo.stu.domain.Student
package xust.demo.stu.domain;

/**
 * Class Student
 * 学生表
 * @author XUST
 * @version 1.0, 2023-04-20
 */
public class Student{


    /**
     * 学号
     */
    private String no;
    public String getNo(){
        return no;
    }

    public void setNo(String newValue){
        no = newValue;
    }
    /**
     * 姓名
     */
    private String name;
    public String getName(){
        return name;
    }

    public void setName(String newValue){
        name = newValue;
    }
    /**
     * 性别
     */
    private String gender;
    public String getGender(){
        return gender;
    }

    public void setGender(String newValue){
        gender = newValue;
    }
    /**
     * 年龄
     */
    private Integer age;
    public Integer getAge(){
        return age;
    }

    public void setAge(Integer newValue){
        age = newValue;
    }
    /**
     * 所在系
     */
    private String dept;
    public String getDept(){
        return dept;
    }

    public void setDept(String newValue){
        dept = newValue;
    }

    @Override
    public String toString() {
    return "{" + "\"no\": " + "\"" + no + "\"" + ", " + "\"name\": " + "\"" + name + "\"" + ", " + "\"gender\": " + "\"" + gender + "\"" + ", " + "\"age\": " + age + ", " + "\"dept\": " + "\"" + dept + "\"" +  "}";
    }
}

xust.demo.stu.dao.StudentDao
package xust.demo.stu.dao;
import xust.demo.Result;
import xust.demo.stu.domain.Student;

public interface StudentDao {
  /**
   * 初始化表
   * @return
   */
  Result init();

  /**
   * 增
   * @param o
   * @return
   */
  Result create(Student o);

  /**
   * 删
   * @param id
   * @return
   */
  Result delete(String no);

  /**
   * 改
   * @param o
   * @return
   */
  Result update(Student o);

  /**
   * 查
   * @param no
   * @return
   */
  Result get(String no);

  /**
   * 查
   * @return
   */
  Result getAll();
}

源代码

xust.demo.stu.dao.StudentDaoImpl
package xust.demo.stu.dao;

import java.sql.*;
import java.util.ArrayList;

import xust.demo.ConnectionUtil;
import xust.demo.Result;
import xust.demo.stu.domain.Student;

public class StudentDaoImpl implements StudentDao{
  public Result init() {
    Result res = new Result(false);

    Connection con = null;
    Statement stmt = null;
    String sql = "create table Student(" +
      "no TEXT primary key," +
      "name TEXT not null," +
      "gender TEXT," +
      "age INTEGER," +
      "dept TEXT" +
      ");";

    con = ConnectionUtil.getConnection();
    if(con != null){
      try {
        stmt = con.createStatement();
        ResultSet rs = stmt.executeQuery(String.format("select count(*) from sqlite_master where type = 'table' and Upper(name) = '%s'", "Student".toUpperCase()));
        while(rs.next()){
          int count = rs.getInt(1);

          if(count == 0 && stmt.executeUpdate(sql) > 0){
            res.code = 0;
          }          
        }
      } catch (Exception e) {
        e.printStackTrace();
        res.message = e.getMessage();
      } finally {
        ConnectionUtil.closeStmt(stmt);
        ConnectionUtil.closeConnection(con);
      }      
    }

    return res;
  }

  /**
   * 对象填充到关系
   */
  private void toR(Student o, PreparedStatement stmt) throws Exception{
    if(o != null && stmt != null){
      String no = o.getNo();
      if(no != null){
        stmt.setString(1, no);       
      }
      String name = o.getName();
      if(name != null){
        stmt.setString(2, name);       
      }
      String gender = o.getGender();
      if(gender != null){
        stmt.setString(3, gender);       
      }
      Integer age = o.getAge();
      if(age != null){
        stmt.setInt(4, age);       
      }
      String dept = o.getDept();
      if(dept != null){
        stmt.setString(5, dept);       
      }
    }
  }

  /**
   * 关系填充到对象
   */
  private Student toO(ResultSet rs) throws Exception{
    Student res = null;

    if(rs != null){
      res = new Student();
      res.setNo(rs.getString("no"));
      res.setName(rs.getString("name"));
      res.setGender(rs.getString("gender"));
      res.setAge(rs.getInt("age"));
      res.setDept(rs.getString("dept"));
    }

    return res;
  }

  public Result create(Student o) {
    Result res = new Result(false);

    Connection con = null;
    PreparedStatement stmt = null;
    String sql = "insert into Student values (?, ?, ?, ?, ?)";
    con = ConnectionUtil.getConnection();
    if (o != null && con != null) {
      try {
        stmt = con.prepareStatement(sql);
        toR(o, stmt);
        if(stmt.executeUpdate() > 0){
          res.code = 0;
        }
      } catch (Exception e) {
        res.message = e.getMessage();
        e.printStackTrace();
      } finally {
        ConnectionUtil.closePstmt(stmt);
        ConnectionUtil.closeConnection(con);
      }
    }

    return res;
  }

  public Result delete(String no) {
    Result res = new Result(false);

    Connection con = null;
    PreparedStatement stmt = null;
    String sql = "delete from Student where no = ?;";
    con = ConnectionUtil.getConnection();
    if(con != null){
      try {

        stmt = con.prepareStatement(sql);
        stmt.setString(1, no);
        res.code = 0;
      } catch (Exception e) {
        res.message = e.getMessage();
        e.printStackTrace();
      } finally {
        ConnectionUtil.closePstmt(stmt);
        ConnectionUtil.closeConnection(con);
      }      
    }

    return res;
  }

  public Result update(Student o) {
    Result res = new Result(false);

    Connection con = null;
    PreparedStatement stmt = null;
    String sql = "update Student set No = ?, Name = ?, Gender = ?, Age = ?, Dept = ? where no = ?";
    con = ConnectionUtil.getConnection();
    if (o != null && con != null) {
      try {

        stmt = con.prepareStatement(sql);
        toR(o, stmt);
        stmt.setString(6, o.getNo());
        if(stmt.executeUpdate() > 0){
          res.code = 0;
        }
      } catch (Exception e) {
        e.printStackTrace();
        res.message = e.getMessage();
      } finally {
        ConnectionUtil.closePstmt(stmt);
        ConnectionUtil.closeConnection(con);
      }
    }

    return res;
  }

  public Result get(String no) {
    Result res = new Result(false);

    Connection con = null;
    PreparedStatement stmt = null;
    String sql = "select * from Student where no = ?";
    con = ConnectionUtil.getConnection();
    if(con != null){
      try {
        stmt = con.prepareStatement(sql);
        stmt.setString(1, no);
        ResultSet rs = stmt.executeQuery();
        Student last = null;
        while (rs.next()) {
          last = new Student();
          last.setNo(rs.getString("no"));
          last.setName(rs.getString("name"));
          last.setGender(rs.getString("gender"));
          last.setAge(rs.getInt("age"));
          last.setDept(rs.getString("dept"));
        }

        res.code = 0;
        res.data = last;
      } catch (Exception e) {
        res.message = e.getMessage();
        e.printStackTrace();
      } finally {
        ConnectionUtil.closePstmt(stmt);
        ConnectionUtil.closeConnection(con);
      }      
    }

    return res;
  }

  public Result getAll() {
    Result res = new Result(false);

    Connection con = null;
    PreparedStatement stmt = null;
    String sql = "select * from Student";
    con = ConnectionUtil.getConnection();
    if(con != null){
      try {
        stmt = con.prepareStatement(sql);
        ResultSet rs = stmt.executeQuery();
        ArrayList<Student> data = new ArrayList<Student>();
        while (rs.next()) {
          Student last = toO(rs);
          data.add(last);
        }

        res.code = 0;
        res.data = data;
      } catch (Exception e) {
        res.message = e.getMessage();
        e.printStackTrace();
      } finally {
        ConnectionUtil.closePstmt(stmt);
        ConnectionUtil.closeConnection(con);
      }      
    }

    return res;
  }
}

xust.demo.stu.service.StudentService
package xust.demo.stu.service;

import jakarta.servlet.http.HttpServletRequest;
import xust.demo.Result;
import xust.demo.stu.domain.Student;

public interface StudentService {
  Student toO(HttpServletRequest request);

  /**
   * 增
   * @param o
   * @return
   */
  Result create(Student o);

  /**
   * 删
   * @param id
   * @return
   */
  Result delete(String no);

  /**
   * 改
   * @param o
   * @return
   */
  Result update(Student o);

  /**
   * 查
   * @param no
   * @return
   */
  Result get(String no);

  /**
   * 查
   * @return
   */
  Result getAll();
}

源代码

xust.demo.stu.service.StudentServiceImpl
package xust.demo.stu.service;

import jakarta.servlet.http.HttpServletRequest;
import xust.demo.Result;
import xust.demo.stu.dao.StudentDao;
import xust.demo.stu.dao.StudentDaoImpl;
import xust.demo.stu.domain.Student;

public class StudentServiceImpl implements StudentService{
  private StudentDao _StudentDao;

  public StudentServiceImpl(){
    _StudentDao = new StudentDaoImpl();
    _StudentDao.init();
  }

  /**
   * 参数填充到对象
   */
  public Student toO(HttpServletRequest request){
    Student res = null;

    if(request != null){
      res = new Student();
      String p = null;
      p = request.getParameter("no");
      if(p != null){
        res.setNo(request.getParameter("no"));
      }
      p = request.getParameter("name");
      if(p != null){
        res.setName(request.getParameter("name"));
      }
      p = request.getParameter("gender");
      if(p != null){
        res.setGender(request.getParameter("gender"));
      }
      p = request.getParameter("age");
      if(p != null){
        res.setAge(Integer.parseInt(request.getParameter("age")));
      }
      p = request.getParameter("dept");
      if(p != null){
        res.setDept(request.getParameter("dept"));
      }
    }

    return res;
  }

  public Result create(Student o) {
    Result res = new Result(false);

    if(_StudentDao != null && o != null){
      res = _StudentDao.create(o);
    }

    return res;
  }

  public Result delete(String no) {
    Result res = new Result(false);

    if(_StudentDao != null){
      res = _StudentDao.delete(no);
    }

    return res;
  }

  public Result update(Student o) {
    Result res = new Result(false);

    if(_StudentDao != null && o != null){
      res = _StudentDao.update(o);
    }

    return res;
  }

  public Result get(String no) {
    Result res = new Result(false);

    if(_StudentDao != null){
      res = _StudentDao.get(no);
    }

    return res;
  }

  public Result getAll() {
    Result res = new Result(false);

    if(_StudentDao != null){
      res = _StudentDao.getAll();
    }

    return res;
  }
}

xust.demo.stu.action.StudentGetServlet.java
@WebServlet("/demo/Student/Get")
public class StudentGetServlet extends HttpServlet {
  private StudentService _StudentService = new StudentServiceImpl();

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

    Result res = _StudentService.get(request.getParameter("no"));
    response.setCharacterEncoding("utf-8");
    response.setContentType("application/json");
    response.getWriter().append(String.format("{\"code\":%d, \"message\":\"%s\", \"data\":%s}", res.code, res.message, res.data));
  }

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

源代码-Add

xust.demo.stu.action.StudentAddServlet
package xust.demo.stu.action;

import java.io.IOException;
import jakarta.servlet.ServletConfig;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import xust.demo.Result;
import xust.demo.stu.domain.Student;
import xust.demo.stu.service.StudentService;
import xust.demo.stu.service.StudentServiceImpl;

@WebServlet("/demo/Student/Add")
public class StudentAddServlet extends HttpServlet {
  private StudentService _StudentService = new StudentServiceImpl();

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

    Student o = _StudentService.toO(request);
    Result res = _StudentService.create(o);
    response.setCharacterEncoding("utf-8");
    response.setContentType("application/json");
    response.getWriter().append(String.format("{\"code\":%d, \"message\":\"%s\"}", res.code, res.message));
  }

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

源代码-Delete

xust.demo.stu.action.StudentDeleteServlet
package xust.demo.stu.action;

import java.io.IOException;
import jakarta.servlet.ServletConfig;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import xust.demo.Result;
import xust.demo.stu.domain.Student;
import xust.demo.stu.service.StudentService;
import xust.demo.stu.service.StudentServiceImpl;

@WebServlet("/demo/Student/Delete")
public class StudentDeleteServlet extends HttpServlet {
  private StudentService _StudentService = new StudentServiceImpl();

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

    Result res = _StudentService.delete(request.getParameter("no"));
    response.setCharacterEncoding("utf-8");
    response.setContentType("application/json");
    response.getWriter().append(String.format("{\"code\":%d, \"message\":\"%s\"}", res.code, res.message));
  }

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

源代码-Update

xust.demo.stu.action.StudentUpdateServlet
package xust.demo.stu.action;

import java.io.IOException;
import jakarta.servlet.ServletConfig;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import xust.demo.Result;
import xust.demo.stu.domain.Student;
import xust.demo.stu.service.StudentService;
import xust.demo.stu.service.StudentServiceImpl;

@WebServlet("/demo/Student/Update") // 映射URL
public class StudentUpdateServlet extends HttpServlet {
  private StudentService _StudentService = new StudentServiceImpl();

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

    Student o = _StudentService.toO(request);
    Result res = _StudentService.update(o);
    response.setCharacterEncoding("utf-8");
    response.setContentType("application/json");
    response.getWriter().append(String.format("{\"code\":%d, \"message\":\"%s\"}", res.code, res.message));
  }

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

源代码-Get

xust.demo.stu.action.StudentGetServlet
package xust.demo.stu.action;

import java.io.IOException;
import jakarta.servlet.ServletConfig;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import xust.demo.Result;
import xust.demo.stu.domain.Student;
import xust.demo.stu.service.StudentService;
import xust.demo.stu.service.StudentServiceImpl;

@WebServlet("/demo/Student/Get")
public class StudentGetServlet extends HttpServlet {
  private StudentService _StudentService = new StudentServiceImpl();

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

    Result res = _StudentService.get(request.getParameter("no"));
    response.setCharacterEncoding("utf-8");
    response.setContentType("application/json");
    response.getWriter().append(String.format("{\"code\":%d, \"message\":\"%s\", \"data\":%s}", res.code, res.message, res.data));
  }

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

demo/DaoTest/StudentServletTest.txt
HTTP/1.1 200 
Content-Type: application/json;charset=utf-8
Content-Length: 103
Date: Sun, 23 Apr 2023 04:42:37 GMT
Connection: close

{
  "code": 0,
  "message": "null",
  "data": {
    "no": "X5",
    "name": "X5",
    "gender": "X5",
    "age": 2,
    "dept": "X2"
  }
}

demo/DaoTest/StudentServletTest.http
### 查
POST http://localhost:8080/{{app}}/demo/Student/Get HTTP/1.1
Content-Type: application/x-www-form-urlencoded

no=X2

源代码

demo/DaoTest/StudentServletTest.http
@app = DaoTest

### 增
POST http://localhost:8080/{{app}}/demo/Student/Add HTTP/1.1
Content-Type: application/x-www-form-urlencoded

id=1
&no=X2
&name=X2
&gender=X2
&age=2
&dept=X2

### 删
POST http://localhost:8080/{{app}}/demo/Student/Delete HTTP/1.1
Content-Type: application/x-www-form-urlencoded

no=X1

### 改
POST http://localhost:8080/{{app}}/demo/Student/Update HTTP/1.1
Content-Type: application/x-www-form-urlencoded

id=1
&no=X2
&name=X2
&gender=X2
&age=2
&dept=X2

### 查
POST http://localhost:8080/{{app}}/demo/Student/Get HTTP/1.1
Content-Type: application/x-www-form-urlencoded

no=X2