Java Web程序设计第9章课后第5题

编写一个应用，用户登录成功之后到达欢迎界面。为了防止某些用户直接访问欢迎页面，用过滤器来实现session的检查。

解析

先写login.jsp和status.jsp，把基本框架搭好，status.jsp的内容很简单，就两行
login.jsp


    账号：

    密码：

status.jsp

登录成功

退出登录

然后把验证逻辑给写了，注意一下我在这里仅仅只判断了用户名和密码是否为空，若不为空则提交表单。真正的匹配判断我放在了ValidationServlet

function validate() {
    let account = loginForm.account.value
    let pwd = loginForm.pwd.value

    if (account == "" || pwd == "") {
        alert("用户名、密码不能为空")
    } else {
        loginForm.submit()
    }
}

把ValidationServlet给写了

@WebServlet(name = "validationServlet", urlPatterns = {"/validationServlet"})
public class ValidationServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 处理响应乱码
        response.setContentType("text/html;charset=utf-8");

        // 处理请求乱码
        request.setCharacterEncoding("utf-8");

        String account = request.getParameter("account");
        String pwd = request.getParameter("pwd");

        if (account != null && pwd != null){
            if (account.equals("tom") && pwd.equals("123")){  // 在这里判断
                HttpSession session = request.getSession();
                session.setAttribute("account", account);  // 通过了验证，就要把用户名存在session中，方便后面做过滤
                response.sendRedirect("chapter9/9_5/status.jsp");  // 重定向到status.jsp
            }
            else {
                response.sendRedirect("chapter9/9_5/login.jsp");  // 验证失败，回到login.jsp
            }
        }
    }

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

最后写LoginFilter，我根据url的后缀来确定是否要启用过滤器。如果之前已经登录成功，那么说明session内一定存有account，可根据这个判断是否要访问欢迎界面

@WebFilter(filterName = "LoginFilter", urlPatterns = {"*.jsp"})
public class LoginFilter implements Filter {
    public void init(FilterConfig config) throws ServletException {
    }

    public void destroy() {
    }

    @Override
    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        HttpServletRequest request = (HttpServletRequest) req;  // 强制把参数req转换为HttpServletRequest类型，不然无法使用getSession
        HttpServletResponse response = (HttpServletResponse) resp;  // 同理
        HttpSession session = request.getSession();
        String requestURL = request.getRequestURI().toString();  // 获取url
        String account = (String) session.getAttribute("account");
        if (account == null && requestURL.contains("9_5/status.jsp")) {
            response.sendRedirect("login.jsp");
        }
        chain.doFilter(request, response);
    }
}

此外，还可以写一个LogOutServlet，记得让status.jsp的超链接给链接上

@WebServlet(name = "LogOutServlet", urlPatterns = {"/logOutServlet"})
public class LogOutServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 处理响应乱码
        response.setContentType("text/html;charset=utf-8");

        // 处理请求乱码
        request.setCharacterEncoding("utf-8");

        HttpSession session = request.getSession();
        session.invalidate();  // 清空session，即清除了登录状态
        response.sendRedirect("chapter9/9_5/login.jsp");
    }

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

代码

<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    登录
    



    账号：

    密码：

status.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    登录状态


登录成功

退出登录

validation.js

function validate() {
    let account = loginForm.account.value
    let pwd = loginForm.pwd.value

    if (account == "" || pwd == "") {
        alert("用户名、密码不能为空")
    } else {
        loginForm.submit()
    }
}

ValidationServlet.java

package chapter9.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 javax.servlet.http.HttpSession;
import java.io.IOException;

@WebServlet(name = "validationServlet", urlPatterns = {"/validationServlet"})
public class ValidationServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 处理响应乱码
        response.setContentType("text/html;charset=utf-8");

        // 处理请求乱码
        request.setCharacterEncoding("utf-8");

        String account = request.getParameter("account");
        String pwd = request.getParameter("pwd");

        if (account != null && pwd != null){
            if (account.equals("tom") && pwd.equals("123")){
                HttpSession session = request.getSession();
                session.setAttribute("account", account);
                response.sendRedirect("chapter9/9_5/status.jsp");
            }
            else {
                response.sendRedirect("chapter9/9_5/login.jsp");
            }
        }
    }

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

LoginFilter.java

package chapter9.filter;

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

@WebFilter(filterName = "LoginFilter", urlPatterns = {"*.jsp"})
public class LoginFilter implements Filter {
    public void init(FilterConfig config) throws ServletException {
    }

    public void destroy() {
    }

    @Override
    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) resp;
        HttpSession session = request.getSession();
        String requestURL = request.getRequestURI().toString();
        String account = (String) session.getAttribute("account");
        if (account == null && requestURL.contains("9_5/status.jsp")) {
            response.sendRedirect("login.jsp");
        }
        chain.doFilter(request, response);
    }
}

LogOutServlet.java

package chapter9.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 javax.servlet.http.HttpSession;
import java.io.IOException;

@WebServlet(name = "LogOutServlet", urlPatterns = {"/logOutServlet"})
public class LogOutServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 处理响应乱码
        response.setContentType("text/html;charset=utf-8");

        // 处理请求乱码
        request.setCharacterEncoding("utf-8");

        HttpSession session = request.getSession();
        session.invalidate();
        response.sendRedirect("chapter9/9_5/login.jsp");
    }

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

Java Web程序设计第9章课后第5题

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