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Servlet实现用户登录页面(通过数据库验证)

2017-11-10 21:09 846 查看
时间:2017年11月10日 21:08:51


最近学习了Servlet,为了巩固一下知识,用它来实现一个用户登录页面。

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实现原理:

1.用户通过login.html页面进行表单提交。

2.通过Servlet获取用户提交的表单,使用DBUtils技术获取数据库中的数据并进行校验

3.向页面输出校验结果

实现过程:

1.使用IDEA创建一个Web项目并配置好web.xml如下:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" version="3.1">
<servlet>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>com.liweijian.login.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/login</url-pattern>
</servlet-mapping>
</web-app>
<url-pattern>用于表单提交的虚拟地址




2. 创建继承于HttpServlet的类
LoginServlet 如下:

public class LoginServlet extends HttpServlet {
protected void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {
doGet(request,response);
}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws   ServletException, IOException {
}


3.导入DBUtils所需要的jar包并加入项目中

c3p0-0.9.1.2.jar
commons-dbutils-1.4.jar
mysql-connector-java-5.0.4-bin.jar

4.使用DBUtils工具类(此类需要自行提取封装)

package com.liweijian.utils;

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();
}
}

}


5. 配置c3p0-config.xml,此xml文件中定义了数据库的登录名和密码、数据库注册驱动以及需要连接的数据库名称

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
<default-config>
<property name="user">root</property>
<property name="password">qq352642663</property>
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl">jdbc:mysql:///web13</property>
</default-config>
</c3p0-config>

6.在doGet或者doPost方法中实现校验操作。

public class LoginServlet extends HttpServlet {
protected void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {
doGet(request,response);
}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws   ServletException, IOException {

//1.获得用户的用户名和密码
String username = request.getParameter("username");
String password = request.getParameter("password");
User user;

//2.从数据库判断用户名和密码
QueryRunner queryRunner = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "select * from User where username = ? and password = ?";
try {
user = queryRunner.query(sql, new BeanHandler<User>(User.class), username, password);

//3.输出验证结果
if (user!= null){
response.getWriter().write(user.toString());
}else {
response.getWriter().write("sorry, your username or password is wrong!");
}
} catch (SQLException e) {
e.printStackTrace();
}

}
}
 

在代码中使用query进行数据库操作时,需要创建与数据库字段所对应的实体类,即User,该类中包含相应的属性,且必须提供getter和setter

代码如下:

package com.liweijian.domain;

/**
* @Author:Liweijian
* @Description: 实体类 -- bean
* @Date:Create in 20:45 2017/11/10 0010
*/
public class User {

private int id;
private String username;
private String password;
private String emain;

public void setId(int id) {
this.id = id;
}

public void setUsername(String username) {
this.username = username;
}

public void setPassword(String password) {
this.password = password;
}

public void setEmain(String emain) {
this.emain = emain;
}

public int getId() {
return id;
}

public String getUsername() {
return username;
}

public String getPassword() {
return password;
}

public String getEmain() {
return emain;
}

@Override
public String toString() {
return getUsername() + "," + "welcome";
}
}


7. 页面代码如下:

<!DOCTYPE html>
<htmllang="en">
<head>
<meta charset="UTF-8">
<title>用户登录</title>
</head>
<body>
<form action="/login" method="post">
用户名:<input type="text" name="username">
密码:<input type="password" name="password">
<input type="submit" value="login">
</form>

</body>
</html>

8. 运行tomcat服务器后 打开页面网址如下:http://localhost:8080/login.html 

9. 当点击login按钮之后,如果数据库中存在该用户,则返回

否则向页面输出
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