学生管理系统优化

1.解决乱码

　　使用过滤器实现所有资源的编码统一。

2.检查登录

　　使用过滤器实现校验是否登陆问题

3.优化JSP页面

　　通过EL表达式和JSTL替换之前的Java代码块和JSP表达式

获取 真实路径

request.getContextPath()+/login.jsp

目录结构如下

 

 实体类 Student

package com.itheima.bean;

public class Student {
    private String username;
    private int age;
    private int score;

    public Student() {
    }

    public Student(String username, int age, int score) {
        this.username = username;
        this.age = age;
        this.score = score;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public int getScore() {
        return score;
    }

    public void setScore(int score) {
        this.score = score;
    }

    @Override
    public String toString() {
        return "Student{" +
                "username='" + username + '\'' +
                ", age=" + age +
                ", score=" + score +
                '}';
    }
}

　　解决全局乱码问题过滤器

package com.itheima.filter;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/*
* 解决全局乱码问题
* */
@WebFilter("/*")
public class EncodingFilter implements Filter {
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        //1.将请求和响应对象转换为和http协议相关
        HttpServletRequest request= (HttpServletRequest) servletRequest;
        HttpServletResponse response= (HttpServletResponse) servletResponse;

        //2.设置编码格式
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");

        //放行
        filterChain.doFilter(request,response);

    }
}

　　限制必须登录 过滤器

package com.itheima.filter;


import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebFilter(value = {"/addStudent.jsp","/listStudentServlet"})
public class LoginFilter implements Filter {
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        //1.将请求和响应对象转换为和http协议相关
        HttpServletRequest request= (HttpServletRequest) servletRequest;
        HttpServletResponse response= (HttpServletResponse) servletResponse;

        //2.获取会话域对象中的数据
        Object username = request.getSession().getAttribute("username");

        //3.判断用户名
        if (username == null||"".equals(username)) {
            //重定向到登陆页面
            response.sendRedirect(request.getContextPath()+"/login.jsp");
            return;
        }

        //4.放行
        filterChain.doFilter(request,response);
    }
}

　　添加Servlet

package com.itheima.servlet;

import com.itheima.bean.Student;

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.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;

/*
*
*实现添加功能
* */
@WebServlet("/addStudentServlet")
public class AddStudentServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //1.获取表单中的数据
        String username=req.getParameter("username");
        String age=req.getParameter("age");
        String score = req.getParameter("score");
        //2.创建学生对象并赋值
        Student stu=new Student();
        stu.setUsername(username);
        stu.setAge(Integer.parseInt(age));
        stu.setScore(Integer.parseInt(score));

        //3.将学生对象的数据保存到d:\\stu.txt中
        BufferedWriter bw=new BufferedWriter(new FileWriter("d:\\stu.txt",true));
        bw.write(stu.getUsername()+","+stu.getAge()+","+stu.getScore());
        bw.newLine();
        bw.close();
        //通过定时刷新功能相应给浏览器
        //resp.setContentType("text/html;charset=UTF-8");
        resp.getWriter().write("添加成功。2秒后自动跳转到首页");
        resp.setHeader("Refresh","2;URL="+req.getContextPath()+"/index.jsp");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

　　查看功能的Servlet

package com.itheima.servlet;

import com.itheima.bean.Student;

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.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;

/**
 * 实现查看功能
 * */
@WebServlet("/listStudentServlet")
public class ListStudentServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.创建一个字符输入流对象，关联读取的文件
        BufferedReader br=new BufferedReader(new FileReader("d:\\stu.txt"));
        //2.创建集合对象，保存Student对象
        ArrayList<Student> list=new ArrayList<>();


        //3.循环读取文件中的数据，将数据封装到Student对象中，在把多个对象添加到集合中
        String line;
        while((line= br.readLine())!=null){
            //张三,23,90
            Student stu=new Student();
            String[] split = line.split(",");
            stu.setUsername(split[0]);
            stu.setAge(Integer.parseInt(split[1]));
            stu.setScore(Integer.parseInt(split[2]));
            list.add(stu);
        }
        //4.将集合对象存入到会话域中
        req.getSession().setAttribute("students",list);

        //重定向到学生列表页面
        resp.sendRedirect(req.getContextPath() +"/listStudent.jsp");


    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

　　学生登陆的Servlet

package com.itheima.servlet;

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;

@WebServlet("/loginStudentServlet")
public class LoginStudentServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取到用户名和密码
        String username = req.getParameter("username");
        String password = req.getParameter("password");

        //2.判断用户名
        if (username == null||"".equals(username)) {
            //2.1用户名为空，重定向到登陆页面
            resp.sendRedirect(req.getContextPath()+"/login.jsp");
            return;
        }


        //2.2用户名不为空，将用户名存入到会话域对象中
        req.getSession().setAttribute("username",username);
        //3.重定向到首页
        resp.sendRedirect(req.getContextPath()+"/index.jsp");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

　　添加学生页面addStudent.jsp

<%--
  Created by IntelliJ IDEA.
  User: 12270
  Date: 2021/3/18
  Time: 22:03
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>添加学生</title>
</head>
<body>
<form action="${pageContext.request.contextPath}/addStudentServlet" method="get" autocomplete="off">
    学生姓名：<input type="text" name="username"><br>
    学生年龄：<input type="number" name="age"><br>
    学生成绩：<input type="number" name="score"><br>
    <button type="submit">保存</button>
</form>
</body>
</html>

　　主页面index.jsp

<%--
  Created by IntelliJ IDEA.
  User: 12270
  Date: 2021/3/18
  Time: 21:39
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<html>
  <head>
    <title>学生管理系统首页</title>
  </head>
  <body>
 <%--
      获取会话域中的数据
      如果获取到了则显示添加和查看功能的超链接
      如果没获取到则显示登录功能额超链接
 --%>
    <c:if test="${sessionScope.username eq null}">
        <a href="${pageContext.request.contextPath}/login.jsp">请登录</a>
    </c:if>

    <c:if test="${sessionScope.username ne null}">
        <a href="${pageContext.request.contextPath}/addStudent.jsp">添加学生</a>
        <a href="${pageContext.request.contextPath}/listStudentServlet">查看学生</a>
    </c:if>
  </body>
</html>

　　展示学生页面listStudent.jsp

<%@ page import="java.util.ArrayList" %>
<%@ page import="com.itheima.bean.Student" %><%--
  Created by IntelliJ IDEA.
  User: 12270
  Date: 2021/3/18
  Time: 22:27
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<html>
<head>
    <title>查看学生</title>
</head>
<body>
    <table width="600px" border="1px">
        <tr>
            <th>姓名</th>
            <th>年龄</th>
            <th>成绩</th>

        </tr>
        <c:forEach items="${students}" var="s">
        <tr>
            <td>${s.username}</td>
            <td>${s.age}</td>
            <td>${s.score}</td>
        </tr>
        </c:forEach>
    </table>
</body>
</html>

　　登陆页面login.jsp

<%--
  Created by IntelliJ IDEA.
  User: 12270
  Date: 2021/3/18
  Time: 21:46
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>学生登陆</title>
</head>
<body>
    <form action="${pageContext.request.contextPath}/loginStudentServlet" method="get"autocomplete="off">
        姓名：<input type="text" name="username"><br>
        密码：<input type="password" name="password"><br>
        <button type="submit">登录</button>

    </form>
</body>
</html>