JavaWeb快速入门八(后附源码)
优化
在test2的基础上做修改。
创建util包，在utils包中创建JdbcUtils.java工具类。为项目提供数据库连接和释放资源。内容如下：
JdbcUtils.java
package util;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class JdbcUtils {
//mysql数据库连接协议；mytest为数据库名称
private static String url = "jdbc:mysql://localhost:3306/mytest";
private static String user = "root";//mysql数据库用户名
private static String password = "root";//mysql的密码
private JdbcUtils() {
}
// 加载驱动类
static {
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e) {
throw new ExceptionInInitializerError(e);
}
}
// 得到连接
public static Connection getConnection() throws SQLException {
return DriverManager.getConnection(url, user, password);
}
// 释放资源
public static void free(ResultSet rs, Statement st, Connection conn) {
try {
if (rs != null) {
rs.close();
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if (st != null) {
st.close();
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if (conn != null) {
conn.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}
前面我们写了一个注册的例子，现在我们在前面基础上写一个登陆的类。创建LoginServlet.java，处理登陆操作。内容如下：
LoginServlet.java
package servlet;
import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import util.JdbcUtils;
public class LoginServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request,response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String registerName = request.getParameter("name");
String registerPassword = request.getParameter("password");
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try {
conn = JdbcUtils.getConnection();
String sql = "select name,password from user where name=? and password=?";
ps = conn.prepareStatement(sql);
ps.setString(1, registerName);
ps.setString(2, registerPassword);
rs = ps.executeQuery();
if(rs.next()){
String name = rs.getString(1);
String password = rs.getString(2);
System.out.println(name+password);
request.setAttribute("name", name);// 将从数据库获得名字和密码set到request对象里
request.setAttribute("password", password);
request.getRequestDispatcher("/login_success.jsp").forward(request,response);
}else{
request.getRequestDispatcher("/login_fail.jsp").forward(request,response);
}
} catch (SQLException e) {
e.printStackTrace();
}finally{
JdbcUtils.free(rs, ps, conn);
}
}
}
新建三个jsp页面——login.jsp 登陆页面；login_success.jsp登陆成功页面；login_fail.jsp登陆失败页面
login.jsp 内容如下：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
</head>
<body>
<form action="servlet/LoginServlet" method="post">
Plase write your name and password!<br/>
name:<input type="text" name="name"/><br/>
password:<input type="password" name="password"/>
<input type="submit" value="login"/>
</form>
</body>
</html>
login_success.jsp 内容如下：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<body>
<font color="red">login success!</font><br/>
<font color="blue">Your name is :</font><%=request.getAttribute("name") %><br/>
<font color="blue">Your password is :</font><%=request.getAttribute("password") %>
</body>
</html>
login_fail.jsp 内容如下：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<body>
<font color="red">login fail!</font><br/>
</body>
</html>
测试地址：http://localhost:8080/test2/login.jsp