第三十四章——java web的注册登录和留言板的制作

首先，搭建登录页面并且可以链接注册页面

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="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>
<form action="operation.jsp" method="post">
    <input type="hidden" name="paramType" value="log" />
    <table align="center">
        <tr>
            <td>用户名: </td><td><input type="text" name="username" /></td>
        </tr>
        <tr>
            <td>密码: </td><td><input type="password" name="password" /></td>
        </tr>
        <tr>
            <td colspan="2">
                <input type="submit" value="登录" />&nbsp;
                <a href="register.jsp">前往注册</a>
            </td>
        </tr>
    </table>
</form>
</body>
</html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="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>
<form action="operation.jsp" method="post">
    <input type="hidden" name="paramType" value="log" />
    <table align="center">
        <tr>
            <td>用户名: </td><td><input type="text" name="username" /></td>
        </tr>
        <tr>
            <td>密码: </td><td><input type="password" name="password" /></td>
        </tr>
        <tr>
            <td colspan="2">
                <input type="submit" value="登录" />&nbsp;
                <a href="register.jsp">前往注册</a>
            </td>
        </tr>
    </table>
</form>
</body>
</html>

同样的原理，搭建注册页面并且可以链接到登录页面，不同的是在里边加一个隐藏域用于后台分别登录和注册

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="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>
<form action="operation.jsp" method="post">
    <input type="hidden" name="paramType" value="reg" />
    <table align="center">
        <tr>
            <td>用户名: </td><td><input type="text" name="username" /></td>
        </tr>
        <tr>
            <td>密码: </td><td><input type="password" name="password" /></td>
        </tr>
        <tr>
            <td>确认密码: </td><td><input type="password" name="password1" /></td>
        </tr>
        <tr>
            <td colspan="2">
                <input type="submit" value="注册" />&nbsp;
                <a href="login.jsp">登录</a>
            </td>
        </tr>
    </table>
</form>
</body>
</html>

然后是后台页面，分别处理登录和注册的信息

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%
    request.setCharacterEncoding("utf-8");
    String s = request.getParameter("paramType");
    if(s.equals("log")) {
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        if(username!=null&&username.trim().length() > 0) {
            Object obj = application.getAttribute(username);
            if(obj==null) {
                response.sendRedirect("message.jsp?code=4");
            } else {
                String userinfo = (String)obj;
                if(password.equals(userinfo.split(",")[1])) {
                    session.setAttribute("currentUser", username);
                    response.sendRedirect("index.jsp");
                } else {
                    response.sendRedirect("message.jsp?code=5");
                }
            }
        }
        
    } else if(s.equals("reg")) {
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        String password1 = request.getParameter("password1");

        Object obj = application.getAttribute(username);
        
        if(obj==null) {
            if(password.equals(password1)) {
                application.setAttribute(username, username+","+password);
                response.sendRedirect("message.jsp?code=3");
            } else {
                response.sendRedirect("message.jsp?code=2");
            }
        } else {
            response.sendRedirect("message.jsp?code=1");
        }
    } else {
        response.sendRedirect("message.jsp?code=6");
    }
%>

插入一个信息页面

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="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">
<meta http-equiv="refresh" content="5; url='login.jsp'">
<title>Insert title here</title>
</head>
<body>
    <%
    String code = request.getParameter("code");
    if(code.equals("1")) {
        out.print("<span style='color:red;'><h1>该用户已经存在 !</h1></span>");
    }
    if(code.equals("2")) {
        out.print("<span style='color:red;'><h1>输入的两次不一致 !</h1></span>");
    }
    if(code.equals("3")) {
        out.print("<span style='color:green;'><h1>注册成功 !</h1></span>");
    }
    if(code.equals("4")) {
        out.print("<span style='color:red;'><h1>用户不存在 !</h1></span>");
    }
    if(code.equals("5")) {
        out.print("<span style='color:red;'><h1>密码错误 !</h1></span>");
    }
    if(code.equals("6")) {
        out.print("<span style='color:red;'><h1>非法访问 !</h1></span>");
    }
    out.print("<a href='login.jsp'>点击登录</a>");
    %>
</body>
</html>

最后就是留言板主页

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<%
String username = (String)session.getAttribute("currentUser");
if(username==null) {
    response.sendRedirect("login.jsp");
}
%>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>

<%
request.setCharacterEncoding("utf-8");
String mess = request.getParameter("k");
Date date = new Date();
SimpleDateFormat sdf= new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String s = sdf.format(date);
String a = (String)session.getAttribute("Current");
ArrayList list = (ArrayList)application.getAttribute("liuyan");
list.add(s+" "+a+"发表一条评论:<br>"+mess);
application.setAttribute("liuyan", list);
response.sendRedirect("message.jsp");
%>

</body>
</html>
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原文地址：https://www.cnblogs.com/yuanlaihenkuang/p/7109535.html