使用ServLet编写简易登录Web界面

1.新建项目，选中JAVA或者JAVA Enterprise中的Web Application（每个人略有不同，总之在二者之一中找到Web Application即可）：

2.新建libs文件夹，导入如下两个包，右键Add as Library

其中mysql包是连接数据库的Jar包，可自行下载和自己数据库版本对应的包，jstl（ JSP Standard Tag Library jsp）简化我们写spring框架。
3.配置tomcat

在此处选择自己tomcat的安装路径

4.文件编码环节（实践课老师给的样例，如有雷同，纯属同门)`
model.user文件:

//User.java
public class User {
    private int id;
    private String name;
    private String password;
    private int age;



    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", password='" + password + '\'' +
                ", age=" + age +
                '}';
    }
}

Service.UserService文件:

//UserService
public class UserService {
    UserDao userDao = new UserDao();

    //查找用户
    public User SelectByName(String name){
        return userDao.selectByName(name);
    }
    //插入一个新用户
    public boolean Register(String name,String password,int age){
        return userDao.InsertUser(name,password,age);
    }
}

dao.UserDao文件:

//UserDao.java
public class UserDao {
    public User selectByName(String name){
        ResultSet rs = null;
        Connection connection = null;
        PreparedStatement pstmt = null;
        DBUtil dbUtil = new DBUtil();
        User user = new User();

        try {
            connection = dbUtil.getConnection();
            pstmt = connection.prepareStatement("select * from user where name=?");
            pstmt.setString(1,name);

            rs = pstmt.executeQuery();
            while(rs.next()){
                user.setId(rs.getInt(1));
                user.setName(rs.getString(2));
                user.setPassword(rs.getString(3));
                user.setAge(rs.getInt(4));
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            dbUtil.closeAll(rs,pstmt,connection);
        }
        return user;
    }

    public boolean InsertUser(String name,String password,int age){
        Connection connection = null;
        PreparedStatement pstmt = null;

        try {
            connection = DBUtil.getConnection();
            pstmt = connection.prepareStatement("insert into user(name,password,age) values (?,?,?)");
            pstmt.setString(1,name);
            pstmt.setString(2,password);
            pstmt.setInt(3,age);

            pstmt.execute();
            return true;
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return false;
    }
}

ServLet.LoginServLet文件：

//loginServLet.java
public class LoginServLet extends HttpServlet {
    UserService userService = new UserService();
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    	//如果点击的是登录按钮则获取数据
        String name = req.getParameter("name");
        String password = req.getParameter("password");
        System.out.println("name:"+name);
        User user = userService.SelectByName(name);
        System.out.println(user);
        //验证密码是否正确
        if (password.equals(user.getPassword())) {
            resp.getWriter().write("success");
            System.out.println("success");
        } else {
            resp.getWriter().write("fail");
            System.out.println("fail");
        }

    }
}

Utils.DBUtil文件:

//DBUtil.java
public class DBUtil {
    public static Connection connection = null;
    public static Connection getConnection() throws ClassNotFoundException, SQLException {
        if(connection==null) {
            Class.forName("com.mysql.cj.jdbc.Driver");
            Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/test?useSSL=false&autoReconnect=true&serverTimezone=GMT", "root", "hxh19981225");
            return connection;
        }else {
            return connection;
        }
    }

    public static void closeAll(ResultSet rs, Statement statement, Connection connection){
        if(rs!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(statement!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(connection!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

5.配置index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>servlet登录跳转</title>
  </head>
  <body>

  <h1>登录界面</h1>
  <form action="/login" method="post">
    name:<input name="name" type="text">
    password:<input name="password" type="password">
    <input type="submit" value="登录">
  </form>
  </body>
</html>

6.配置web.xml

<?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_4_0.xsd"
         version="4.0">
    <!--    登录界面-->
    <servlet>
        <servlet-name>login</servlet-name>
        <servlet-class>com.xs1701.servlet.LoginServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>login</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>
    <!--    注册界面-->
</web-app>