1.jsp實現登錄
思維過程：
1.index.jsp登錄界面
2.提交跳轉到a.jsp密碼匹配檢查
3.密碼正確就跳轉到登陸後界面
Index.jsp代碼：
<%--
Created by IntelliJ IDEA.
User: 張川
Date: 2020/4/30
Time: 14:10
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>form表單交互練習</title>
<style>
.btn-submit{
padding: 0 16px;
font-size: 16px;
color: #fff;
border: none;
border-radius: 4px;
white-space: nowrap;
background-color: #ca0c16;
cursor: pointer;
}
</style>
</head>
<body>
<form method="post" action="a.jsp" class="form-login">
請輸入姓名： <input type="text" name="username"><br>
請輸入密碼： <input type="text" name="password"><br>
<input class="btn-submit" type="submit" value="提交" >
</form>
<%-- action表示接收數據的頁面
method表示請求方法 因爲是修改數據 一般是post
name是後臺request.getParmter("uername")的參數
--%>
</body>
</html>
a.jsp代碼:
<%--
Created by IntelliJ IDEA.
User: 張川
Date: 2020/5/9
Time: 21:49
To change this template use File | Settings | File Templates.
--%>
<%@ page import="java.sql.*" contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>從index獲取數據</title>
</head>
<body>
<%
//獲取前端index的登錄數據
request.setCharacterEncoding("UTF-8");//編碼一定設置
String username=(String)request.getParameter("username");
String password=(String)request.getParameter("password");//取出login.jsp的值
/**
* 查詢獲得多條數據
* */
//1.將Driver驅動加載進jvm
Class.forName ("com.mysql.jdbc.Driver");
//數據庫鏈接地址 格式 jdbc:mysql:數據庫網址/數據庫名
String url="jdbc:mysql://localhost:3306/javaweb_learning";
String user="root";
String pwd="123456";
Connection cnn=null;
Statement st = null;
try {
//2.創建鏈接對象
cnn = (Connection) DriverManager.getConnection (url, user, pwd);
//3。創建sql語句
String sql = "select * from user where name=" + "'" + username + "'";//定義一個查詢語句
System.out.println (sql);
//創建鏈接管道
st = cnn.createStatement ();
//4.執行sql語句
ResultSet res=st.executeQuery(sql);//運行上面的語句
String password2 = null;
while (res.next ()){
password2=res.getString ("password");
}
System.out.println (password2);
if (password.equals (password2)) {
response.sendRedirect ("logined.jsp");
} else {
out.print ("<script language='javaScript'> alert('密碼錯誤');</script>");
response.setHeader ("refresh", "0;url=index.jsp");
}
}catch (Exception e){
}
%>
</body>
</html>
注意:密碼正確是跳轉頁面使用的是：
if (password.equals (password2)) {
response.sendRedirect ("logined.jsp");
}
2.密碼正確就返回logined.jsp
登陸後：
密碼錯誤的話：
