[Java] JSP - 用户登录Demo

Z时代
2024-01-10
分类：综合

java

实现一个很简单的例子，用户登录。

此Demo用到了过滤器、servlet、注解。

运行效果如图：

<%@ page language="java" contentType="text/html; charset=UTF-8" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
    // 如果用户名已经存在，说明已经登录，跳转到主页
    String username = (String) request.getSession().getAttribute("username");
    if (username != null && username.length() > 0) {
        response.sendRedirect("index.jsp");
        return;
    }
%>
<form action="<%=request.getContextPath()%>/servlet/LoginServlet" method="post">
用户：<input type="text" name="username" />
密码: <input type="password" name="password" />
昵称: <input type="text" name="nickname" />
<input type="submit" value="登录" /><br>
</form>
</body>
</html>

index.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8" %>
<%@ page import="java.util.*" %>
<%@ page import="java.text.*" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>欢迎访问我的主页</h1><hr>
你好，<font color="red">${nickname}</font> [<font color="blue">${username}</font>]<br>
今天是 <%= new SimpleDateFormat("yyyy年MM月dd日 HH:kk:ss").format(new Date()) %>.<br>
</body>
</html>

<%@ page language="java" contentType="text/html; charset=UTF-8" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
登录成功，欢迎你，${username}
</body>
</html>

<%@ page language="java" contentType="text/html; charset=UTF-8" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
登录失败，请重新输入用户名和密码。<br>
[<a href="login.jsp">返回登录</a>]
</body>
</html>

LoginFilter.java

package com.demo.servlet;
import java.io.IOException;
import java.util.HashMap;
import javax.servlet.DispatcherType;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.annotation.WebInitParam;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * 登录过滤器
 * @author Administrator
 */
@WebFilter(filterName="LoginFilter",
    urlPatterns={"/*"},
    initParams={
            @WebInitParam(name="NotFilterURI", value="/login.jsp;/login.fail.jsp;/LoginServlet")
    },
    dispatcherTypes={DispatcherType.REQUEST})
public class LoginFilter implements Filter {
    private HashMap<String, Integer> NotFilterMap;
    // 将URI中的最后一截取出来
    protected String getPageName(String v) {
        if (v == null || v.length() == 0) return v;
        int i = v.lastIndexOf("/");
        if (i < 1) 
            return v;
        else
            return v.substring(i);
    }
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        // 将不过滤的URI加载到哈希表中
        String noFilterURI = filterConfig.getInitParameter("NotFilterURI");
        if (noFilterURI != null && noFilterURI.length() > 0) {
            NotFilterMap = new HashMap<String, Integer>();
            String[] uris = noFilterURI.split(";");
            for (String uri : uris) 
                NotFilterMap.put(uri, 0);
        }
    }
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest) request;
        // 设置字符集，防止乱码
        req.setCharacterEncoding("utf-8");
        // 检测URI是否需要过滤。如果不过滤，则直接放行
        String reqPage = getPageName(req.getRequestURI());
        if (NotFilterMap != null && NotFilterMap.containsKey(reqPage)) {
            chain.doFilter(request, response);
            return;
        }
        String username = (String) ((HttpServletRequest) request).getSession().getAttribute("username");
        if (username == null || username.length() == 0)
            ((HttpServletResponse)response).sendRedirect("login.jsp");
        else
            chain.doFilter(request, response);
    }
}

LoginServlet.java

package com.demo.servlet;
import java.io.IOException;
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;
/**
 * 登录处理
 * @author Administrator
 */
@WebServlet(name="LoginServlet",urlPatterns={"/servlet/LoginServlet"})
public class LoginServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        System.out.println("LoginServlet.doPost...");
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        if ("admin".equals(username) && "admin".equals(password)) {
            HttpSession session = req.getSession();
            session.setAttribute("username", username);
            String nickname = req.getParameter("nickname");
            if (nickname == null || nickname.length() == 0)
                nickname = "匿名用户";
            session.setAttribute("nickname", nickname);
            resp.sendRedirect(req.getContextPath()+"/login.sucess.jsp");
        } else
            resp.sendRedirect(req.getContextPath()+"/login.fail.jsp");
    }
}