Servlet 案例（模拟登陆功能）
一.新建一个数据库
在数据库中存入一个数据
二.编写一个简单的用户登陆的界面
源代码：
<%--
Created by IntelliJ IDEA.
User: Administrator
Date: 2019/2/27
Time: 14:29
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>登陆</title>
<style type="text/css">
*{
padding: 0px;
margin: 0px;
}
.text{
width: 246px;
height: 34px;
border: none;
margin-top: 5px;
}
#box{
width: 400px;
height: 285px;
margin: 0px auto ;
background-color: aliceblue;
border: 1px solid #333;
text-align: center;
padding-top: 20px;
}
</style>
</head>
<body>
<div id="box">
<h1>Servlet案例</h1>
<form action="/untitled/log_in_verification" method="post">
<input type="text" name="user" class="text"/>
<input type="text" name="password" class="text"/>
<input type="submit" value="登陆" class="text"/>
</form>
</div>
</body>
</html>三.编写java代码，连接数据库（此处使用DBUtils），验证用户登陆。
3.1 编写连接池封装类用于连接数据库
（注意此处需要导入jar包，并且需要将c3p0-config.xml 配置文件，放在web项目的src目录下）
https://pan.baidu.com/s/1eev43QR5TAFKi_ZRqIn_PQ 提取码：ebcw（此处是jar包和xml配置文件）
package servlet;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.sql.DataSource;
import com.mchange.v2.c3p0.ComboPooledDataSource;
public class DataSourceUtils {
private static DataSource dataSource = new ComboPooledDataSource();
private static ThreadLocal<Connection> tl = new ThreadLocal<Connection>();
// 直接可以获取一个连接池
public static DataSource getDataSource() {
return dataSource;
}
// 获取连接对象
public static Connection getConnection() throws SQLException {
Connection con = tl.get();
if (con == null) {
con = dataSource.getConnection();
tl.set(con);
}
return con;
}
// 开启事务
public static void startTransaction() throws SQLException {
Connection con = getConnection();
if (con != null) {
con.setAutoCommit(false);
}
}
// 事务回滚
public static void rollback() throws SQLException {
Connection con = getConnection();
if (con != null) {
con.rollback();
}
}
// 提交并且 关闭资源及从ThreadLocall中释放
public static void commitAndRelease() throws SQLException {
Connection con = getConnection();
if (con != null) {
con.commit(); // 事务提交
con.close();// 关闭资源
tl.remove();// 从线程绑定中移除
}
}
// 关闭资源方法
public static void closeConnection() throws SQLException {
Connection con = getConnection();
if (con != null) {
con.close();
}
}
public static void closeStatement(Statement st) throws SQLException {
if (st != null) {
st.close();
}
}
public static void closeResultSet(ResultSet rs) throws SQLException {
if (rs != null) {
rs.close();
}
}
}
3.2 编写JavaBean类用于存储从数据库获取到的信息
package servlet;
public class User {
private String user;
private String password;
private String email;
public String getUser() {
return user;
}
public void setUser(String user) {
this.user = user;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
}
3.3 编写log_in_verification类用于，获取用户信息，并在数据库中进行验证，同时将结果响应在浏览器。
package servlet;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class log_in_verification extends HttpServlet {
public void doGet(HttpServletRequest req, HttpServletResponse resp){
this.doPost(req,resp);
}
public void doPost(HttpServletRequest req,HttpServletResponse resp){
//获取用户提交的用户名和密码
String name=req.getParameter("user");
String password=req.getParameter("password");
//从数据库中验证密码是否正确
QueryRunner runner=new QueryRunner(DataSourceUtils.getDataSource());
String sql="select * from user where username=? and password=?";
User user=null;
try{
user=runner.query(sql,new BeanHandler<User>(User.class),name,password);
if(user!=null){
user.setUser(name);
resp.getWriter().write("greet"+user.getUser());
}else{
resp.getWriter().write("login failure");
}
}catch (Exception e){
e.printStackTrace();
}
}
}四.展示效果
http://39.108.158.0:8080/mp4/123.mp4
目录
三.编写java代码，连接数据库（此处使用DBUtils），验证用户登陆。