文章目录
- 目录结构
- 处理类爆炸问题
- 功能测试
目录结构
将同一个业务的后端程序整合到一个类中，也是MVC 分层，的雏形
分类 整合
处理类爆炸问题
package com.yanyu;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 resources.DBUtil;import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;/*** @Author yanyu666_508200729@qq.com* @Date 2024/11/26 21:53* @description:解决类爆炸问题* 1.模拟 HttpServlet 的模板设计思想* 2.注解式开发* 3. 在原项目 stuid 基础 上开发，并修改号对应的 项目名字*/
@WebServlet({"/list","/modifyStuno","/modify","/delete","/add"})
public class StudentService extends HttpServlet {@Overrideprotected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//获取 servlet 对象的路径 /web2/list web2 项目名字， /listString servletPath = request.getServletPath();// /listif ("/list".equals(servletPath)) {
// 利用已知道的常量来调研方法，避开空引用异常
// 将 浏览器的请求对象带入doList(request, response);} else if ("/add".equals(servletPath)) {doAdd(request,response);// alt enter}else if ("/delete".equals(servletPath)){doDel(request,response);// 不要设置为 doDelete() 会与 HttpServlet 的 doDelete()} else if ("/modifyStuno".equals(servletPath)) {doModifyStuno(request,response);} else if ("/modify".equals(servletPath)) {doModify(request,response);}}private void doModify(HttpServletRequest request, HttpServletResponse response) throws IOException {request.setCharacterEncoding("utf-8");response.setCharacterEncoding("utf-8");response.setContentType("text/html");PrintWriter out = response.getWriter();String name = request.getParameter("name");String stuid = request.getParameter("stuid");String zhuanye = request.getParameter("zhuanye");Connection connection = null;Statement statement = null;ResultSet rs = null;try {connection = DBUtil.getConnection();connection.setAutoCommit(false);String sql = "update student set name = '"+name+"',zhuanye = '"+zhuanye+"' where stuid = '"+stuid+"'";statement = connection.createStatement();statement.executeUpdate(sql);connection.commit();} catch (SQLException e) {if (connection != null) {try {connection.close();} catch (SQLException ex) {throw new RuntimeException(ex);}}throw new RuntimeException(e);}finally {DBUtil.close(rs,statement,connection);}response.sendRedirect("/web2/list");}private void doModifyStuno(HttpServletRequest request, HttpServletResponse response) throws IOException {request.setCharacterEncoding("utf-8");response.setCharacterEncoding("utf-8");response.setContentType("text/html");PrintWriter out = response.getWriter();
// 获取待续该学生的学号String stuno = request.getParameter("stuno");Connection connection = null;Statement statement = null;ResultSet rs = null;try {connection = DBUtil.getConnection();connection.setAutoCommit(false);
// 获取 该学生的信息String sql = "select * from student where stuid = '" + stuno + "'";statement = connection.createStatement();rs = statement.executeQuery(sql);while (rs.next()) {String name = rs.getString("name");
// rs.getString("stuid");String zhuanye = rs.getString("zhuanye");out.print("<!DOCTYPE html>");out.print("<html lang='en'>");out.print("<head>");out.print(" <meta charset='UTF-8'>");out.print(" <meta name='viewport' content='width=device-width, initial-scale=1.0'>");out.print(" <title>Document</title>");out.print("</head>");out.print("<body>");out.print(" <h1>修改学生</h1>");
// 设置 修改后的学生信息out.print(" <form action='/web2/modify'>");out.print(" 原姓名："+name+"");out.print(" <br>");out.print(" 原学号："+stuno+"");out.print(" <br>");out.print(" 原专业："+zhuanye+"");out.print(" <br>");out.print(" 姓名：<input type='text' name='name'>");out.print(" <br>");
// 修改前后，学号是不变的，所以要把学号拼接到 学号输入框 ，并将输入框设置为 只读不可修改out.print(" 学号：<input type='text' name='stuid' value='"+stuno+"' readonly>");out.print(" <br>");out.print(" 专业：<input type='text' name='zhuanye' >");out.print(" <br><input type='submit' value='确认修改'>");out.print(" </form>");out.print("</body>");out.print("</html>");}connection.commit();} catch (SQLException e) {if (connection != null) {try {connection.rollback();} catch (SQLException ex) {throw new RuntimeException(ex);}}throw new RuntimeException(e);}finally {DBUtil.close(rs,statement,connection);}}private void doDel(HttpServletRequest request, HttpServletResponse response) throws IOException {request.setCharacterEncoding("utf-8");response.setCharacterEncoding("utf-8");response.setContentType("text/html");PrintWriter out = response.getWriter();
// 获取待续该学生的学号String delno = request.getParameter("delno");Connection connection = null;Statement statement = null;ResultSet rs = null;try {connection = DBUtil.getConnection();connection.setAutoCommit(false);String sql = "delete from student where stuid = '"+delno+"'";statement = connection.createStatement();statement.execute(sql);connection.commit();} catch (SQLException e) {if (connection != null) {try {connection.rollback();} catch (SQLException ex) {throw new RuntimeException(ex);}}throw new RuntimeException(e);}finally {DBUtil.close(rs,statement,connection);}response.sendRedirect("/web2/list");}private void doAdd(HttpServletRequest request, HttpServletResponse response) throws IOException {request.setCharacterEncoding("utf-8");response.setCharacterEncoding("utf-8");response.setContentType("text/html");PrintWriter out = response.getWriter();String name = request.getParameter("name");String stuid = request.getParameter("stuid");String zhuanye = request.getParameter("zhuanye");Connection connection = null;Statement statement = null;ResultSet rs = null;try {connection = DBUtil.getConnection();connection.setAutoCommit(false);String sql = "insert into student(name,stuid,zhuanye) values('"+name+"','"+stuid+"','"+zhuanye+"') ";statement = connection.createStatement();statement.execute(sql);connection.commit();} catch (SQLException e) {if (connection != null) {try {connection.rollback();} catch (SQLException ex) {throw new RuntimeException(ex);}}throw new RuntimeException(e);}finally {DBUtil.close(rs,statement,connection);}response.sendRedirect("/web2/list");}private void doList(HttpServletRequest request, HttpServletResponse response) throws IOException {
// 处理整个查询业务 IO异常交给tomcat 处理request.setCharacterEncoding("utf-8");response.setCharacterEncoding("utf-8");response.setContentType("text/html");PrintWriter out = response.getWriter();Connection connection = null;Statement statement = null;ResultSet rs = null;try {connection = DBUtil.getConnection();connection.setAutoCommit(false);String sql = "select * from student";statement = connection.createStatement();rs = statement.executeQuery(sql);out.print("<!DOCTYPE html>");out.print("<html lang='en'>");out.print("<head>");out.print(" <meta charset='UTF-8'>");out.print(" <meta name='viewport' content='width=device-width, initial-scale=1.0'>");out.print(" <title>Document</title>");out.print("</head>");out.print("<body>");out.print(" <h1>学生信息</h1>");out.print(" <table border='1px' width='600px'>");out.print(" <tr>");out.print(" <td>姓名</td>");out.print(" <td>学号</td>");out.print(" <td>专业</td>");out.print(" <td>操作</td>");out.print(" </tr>");while (rs.next()) {String name = rs.getString("name");String stuid = rs.getString("stuid");String zhuanye = rs.getString("zhuanye");out.print(" <tr></tr>");out.print(" <td>" + name + "</td>");out.print(" <td>" + stuid + "</td>");out.print(" <td>" + zhuanye + "</td>");out.print(" <td>");out.print(" <a href='./add.html'>新增</a>");
// 发送修改学生信息之前 ，查询学生原来的信息 根据 stuid 在修改前后不变的原则out.print(" <a href='/web2/modifyStuno?stuno=" + stuid + "'>修改</a>");
// 根据 stuid 去限制 where 进行学生的 删除操作out.print(" <a href='/web2/delete?delno=" + stuid + "'>删除</a>");out.print(" </td>");out.print(" </tr>");}out.print(" </table>");out.print("</body>");out.print("</html>");connection.commit();} catch (SQLException e) {if (connection != null) {try {connection.rollback();} catch (SQLException ex) {throw new RuntimeException(ex);}}throw new RuntimeException(e);} finally {DBUtil.close(rs, statement, connection);}}
}功能测试
其它功能正常