javaweb之servlet技术实现登录功能
一，需求分析
用户登录案例需求：
1.编写login.html登录页面
username & password 两个输入框
2.使用Druid数据库连接池技术,操作mysql，day14数据库中user表
3.使用JdbcTemplate技术封装JDBC
4.登录成功跳转展示：登录成功！用户名,欢迎您
5.登录失败跳转展示：登录失败，用户名或密码错误
二，技术实现
项目目录结构：
1，前端页面：
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<!-- 上述3个meta标签*必须*放在最前面，任何其他内容都*必须*跟随其后！ -->
<title>Login</title>
<!-- Bootstrap -->
<link href="css/bootstrap.min.css" rel="stylesheet">
</head>
<body>
<form class="form-horizontal" action="/login_project/login" method="post">
<div class="form-group">
<label for="inputEmail3" class="col-sm-2 control-label">用户名：</label>
<div class="col-sm-10">
<input type="text" class="form-control" name="username" id="inputEmail3" placeholder="请输入用户名">
</div>
</div>
<div class="form-group">
<label for="inputPassword3" class="col-sm-2 control-label">密码：</label>
<div class="col-sm-10">
<input type="password" class="form-control" name="password" id="inputPassword3" placeholder="请输入密码">
</div>
</div>
<div class="form-group">
<div class="col-sm-offset-2 col-sm-10">
<button type="submit" class="btn btn-default">登录</button>
</div>
</div>
</form>
<!-- jQuery (Bootstrap 的所有 JavaScript 插件都依赖 jQuery，所以必须放在前边) -->
<script src="js/jquery-3.2.1.min.js"></script>
<!-- 加载 Bootstrap 的所有 JavaScript 插件。你也可以根据需要只加载单个插件。 -->
<script src="js/bootstrap.min.js"></script>
</body>
</html>
2，servlet代码：
@WebServlet("/login")
public class login extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
/*
String username = request.getParameter("username");
String password = request.getParameter("password");
User user = new User();
user.setUsername(username);
user.setPassword(password);
*/
User user = new User();
Map<String, String[]> map = request.getParameterMap();
try {
BeanUtils.populate(user, map);
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
System.out.println(user);
//User{id=null, username='张三', password='123'}
//密码错误：User{id=null, username='张三峰', password='852'}
System.out.println("---------");
UserDao ud = new UserDao();
User user_login = ud.loginUser(user);
System.out.println(user_login);
//User{id=1, username='张三', password='123'}
//密码错误,null
if (user_login == null) {
response.setContentType("text/html;charset=utf-8");
response.getWriter().write("用户名或者密码错误，登录失败！");
} else {
response.setContentType("text/html;charset=utf-8");
response.getWriter().write(user_login.getUsername() + "你好，登录成功！");
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
3，User代码：
package domain;
public class User {
private Integer id;
private String username;
private String password;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
'}';
}
}
4，UserDao代码：
public class UserDao {
public User loginUser(User user){
try {
JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDatasource());
String sql = "select * from user where username= ? and password= ? ";
User user_login = template.queryForObject(sql,
new BeanPropertyRowMapper<>(User.class),
user.getUsername(),
user.getPassword());
return user_login;
}catch (Exception e){
e.printStackTrace();
return null;
}
}
}
5，JDBCUtils代码：
public class JDBCUtils {
private static DataSource ds;
static {
Properties pro = new Properties();
try {
pro.load(JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties"));
ds = DruidDataSourceFactory.createDataSource(pro);
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
public static Connection getConnection() throws SQLException {
return ds.getConnection();
}
public static void close(Statement sttm,Connection conn){
if (sttm != null){
try {
sttm.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (conn != null){
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
public static void close(ResultSet rs,Statement sttm, Connection conn){
if (rs != null){
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
close(sttm,conn);
}
public static DataSource getDatasource(){
return ds;
}
}
6，TestLogin代码：
public class TestLogin {
@Test
public void UserDao(){
UserDao userDao = new UserDao();
User user = new User();
user.setUsername("chs");
user.setPassword("321");
User user1 = userDao.loginUser(user);
System.out.println(user1);
}
}
三，需注意技术细节
1，login.html中form表单的action路径的写法：
/虚拟目录/Servlet的资源路径
2，BeanUtils工具类：
简化数据封装，用于封装JavaBean的
JavaBean：标准的Java类
要求：
1，类必须被public修饰
2， 必须提供空参的构造器
3，成员变量必须使用private修饰
4，提供公共setter和getter方法
功能：封装数据
3，概念：
成员变量：成员方法外的变量；
属性：setter和getter方法截取后的产物
例如：getUsername() --> Username–> username
4，BeanUtils方法：
setProperty()
getProperty()
populate(Object obj , Map map):将map集合的键值对信息，封装到对应的JavaBean对象中。
5，jar包必须写在web目录下的WEB-INF下的lib文件夹中。