登陸頁面jsp+servlet
阿新 • • 發佈：2018-12-29
雖然登陸介面很簡單，但是自己老是忘記，所以寫下，以後看的時候能夠比較清楚的理解。
1.寫jsp頁面
<%@ 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="${pageContext.request.contextPath}/LoginServlet" method="post" class="" role="form"> username<input type="username" name="username" class="" id="username" placeholder="請輸入使用者名稱..."> password<input type="password" name="password" class="" id="password" placeholder="請輸入密碼..."> <span style="color:red">${msg }</span> <input type="submit"> </form> </body> </html>
說明：（1）action後面跟著的就是這個頁面要驗證的servlet類的位置
（2）name=“username” name=“password”相當於一個標識在servlet中就是通過name值來對資料進行操作的
（3）${msg }表示獲取內建物件中賦值給msg變數的值
2.寫對應的servlet，這裡的servlet的名字與login.jsp中action後面跟著的名字必須一致。
package demo.web.servlet; import java.io.IOException; import java.io.PrintWriter; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class LoginServlet extends HttpServlet { static final String driverClassName = "com.mysql.jdbc.Driver"; static final String url = "jdbc:mysql://localhost:3306/test?characterEncoding=utf-8"; static final String mysqlUsername = "root"; static final String mysqlPassword = "slzslz"; public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("utf-8"); response.setContentType("text/html;charset=utf-8"); Connection conn = null; PreparedStatement pstmt = null; ResultSet rs = null; try { Class.forName(driverClassName); conn = DriverManager.getConnection(url, mysqlUsername, mysqlPassword); String username = request.getParameter("username"); String password = request.getParameter("password"); String sql = "SELECT * FROM sign WHERE username=? and password=?"; pstmt = conn.prepareStatement(sql); pstmt.setString(1, username); pstmt.setString(2, password); rs = pstmt.executeQuery(); System.out.println(username +", " + password); if(rs.next()) { request.setAttribute("username", rs.getString("username")); request.getSession().setAttribute("user_name", username); /*System.out.println(rs.getString("username"));*/ request.setAttribute("msg", "成功登陸！"); request.getRequestDispatcher("/success.jsp").forward(request, response); } else { request.setAttribute("msg", "使用者名稱或密碼不正確！"); request.getRequestDispatcher("/login.jsp").forward(request, response); } } catch(Exception e) { throw new RuntimeException(e); } finally { try { if(conn != null) conn.close(); if(pstmt != null) pstmt.close(); if(conn != null) conn.close(); } catch(Exception e) { throw new RuntimeException(e); } } } }
說明：（1）首先獲取資料庫的連線
（2）request.setAttribute("msg", "成功登陸！")；意思就是把成功登陸這句話當作一個變數賦值給內建物件msg，這個內建物件可以通過jsp頁面直接呼叫。
（3）在（2）的程式碼後面必須跟上request.getRequestDispatcher("/success.jsp").forward(request, response);表明我們所設定的內建物件值傳給哪個jsp頁面。
3.成功登陸跳轉頁面success.jsp
<%@ 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>
${msg }
</body>
</html>4.配置檔案web.xml
<servlet>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>demo.web.servlet.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/LoginServlet</url-pattern>
</servlet-mapping>說明：（1）切記這裡的<url-pattern>的值必須要與login.jsp頁面的action後面跟的值的地址一致，否則一直會有報錯的。
（2）<servlet-class>後面跟的是包名+類名
5.頁面效果展示
使用者名稱或者密碼錯誤，會提示使用者名稱或者密碼錯誤
正確登陸會跳轉到success.jsp
Tips:這裡只需要一個架包 mysql-connector-java-5.1.7-bin.jar即可。