Java-中软-1 jdbc+servlet+tomcat

jdbc：
1、加载驱动

Class.forName("com.mysql.jdbc.Driver");

2、创建连接

public static Connection getConnection() throws ClassNotFoundException, SQLException {
        Class.forName("com.mysql.jdbc.Driver");
        Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/whlg","root","xyj123");
        return connection;
}

3、写sql语句

//findAll()
String sql = "select * from tb_user";
//deleteById(int id)
String sql = "delete from tb_user where id = ?";
//findUserByUsername(String username)
String sql = "select * from tb_user where username=?";

4、得到statement对象

PreparedStatement ps = connection.prepareStatement(sql);

5、执行sql语句得到结果集

//findAll()
ResultSet resultSet = ps.executeQuery();
//deleteById(int id)
ps.setInt(1,id);
ps.executeUpdate();
//findUserByUsername(String username)
ps.setString(1,username);
ResultSet resultSet = ps.executeQuery();

6、处理结果集

//findAll()
List<User> userList = new ArrayList<>();
while (resultSet.next()){
            User user=new User();
            int id = resultSet.getInt(1);
            String username = resultSet.getString(2);
            String password = resultSet.getString(3);
            user.setId(id);
            user.setUsername(username);
            user.setPassword(password);
            userList.add(user);
}
//findUserByUsername(String username)
User user=null;
while (resultSet.next()){
            user=new User();
            int id = resultSet.getInt(1);
            String username1 = resultSet.getString(2);
            String password = resultSet.getString(3);
            user.setId(id);
            user.setUsername(username1);
            user.setPassword(password);
}

7、关闭资源

public static void close(ResultSet resultSet, Statement statement,Connection connection) throws SQLException {
        if(resultSet!=null){
            resultSet.close();
        }
        if(statement!=null){
            statement.close();
        }
        if(connection!=null){
            connection.close();
        }
}

实体类：
alt+insert
1.属性
2.get set
3.tostring
4.构造方法

public class User {
    private int id;
    private String username;
    private String password;
    public User() {
    }
    public User(int id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = password;
    }
    public int getId() {
        return id;
    }
    public void setId(int 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 + '\'' +
                '}';
    }
}

软件：
jdk idea mysql sqlyog tomcat teamview
mysql闪退：ctrl+shift+esc打开任务管理器；启动mysql服务

util.DBUtil

public class DBUtil {
    public static Connection getConnection() throws ClassNotFoundException, SQLException {
        Class.forName("com.mysql.jdbc.Driver");
        Connection connection= DriverManager.getConnection("jdbc:mysql://localhost:3306/whlg", "root", "xyj123");
        return connection;
    }
    public static void close(ResultSet resultSet, Statement ps, Connection connection) throws SQLException {
        if(resultSet!=null){
            resultSet.close();
        }
        if(ps!=null){
            ps.close();
        }
        if(connection!=null){
            connection.close();
        }
    }
}

dao.UserDao：持久层对数据库的操作 crud

public class UserDao {
    public List<User> findAll() throws ClassNotFoundException, SQLException {
        Connection connection= DBUtil.getConnection();
        System.out.println("获得连接成功");
        String sql="select * from tb_user";
        PreparedStatement ps= connection.prepareStatement(sql);
        ResultSet resultSet = ps.executeQuery();
        List<User> userList=new ArrayList<>();
        while (resultSet.next()){
            User user=new User();
            int id = resultSet.getInt(1);
            String username = resultSet.getString(2);
            String password = resultSet.getString(3);
            user.setId(id);
            user.setUsername(username);
            user.setPassword(password);
            userList.add(user);
//            System.out.println(user);
//            System.out.println(id+"----"+username+"----"+password);
        }
        DBUtil.close(resultSet,ps,connection);
        return userList;
    }
    public void deleteById(int id) throws SQLException, ClassNotFoundException {
        Connection connection= DBUtil.getConnection();
        System.out.println("获得连接成功");
        String sql="delete from tb_user where id=?";
        PreparedStatement ps=connection.prepareStatement(sql);
        ps.setInt(1,id);
        ps.executeUpdate();
        DBUtil.close(null,ps,connection);
    }
    public User findUserByUsername(String username) throws SQLException, ClassNotFoundException {
        Connection connection= DBUtil.getConnection();
        System.out.println("获得连接成功");
        String sql="select * from tb_user where username=?";
        PreparedStatement ps= connection.prepareStatement(sql);
        ps.setString(1,username);
        ResultSet resultSet = ps.executeQuery();
        User user=null;
        while (resultSet.next()){
            user=new User();
            int id = resultSet.getInt(1);
            String username1 = resultSet.getString(2);
            String password = resultSet.getString(3);
            user.setId(id);
            user.setUsername(username1);
            user.setPassword(password);
        }
        DBUtil.close(resultSet,ps,connection);
        return user;
    }
}

service.UserService：业务层

public class UserService {
    public List<User> hello() {
        UserDao userDao=new UserDao();
        List<User> all=null;
        try{
            all=userDao.findAll();
        }catch (ClassNotFoundException e){
            e.printStackTrace();
        }catch (SQLException throwables){
            throwables.printStackTrace();
        }
        return all;
    }
    public boolean login(String username, String password) {
        UserDao userDao=new UserDao();
        User user = null;
        try {
            user = userDao.findUserByUsername(username);
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        if(user!=null&&user.getPassword().equals(password)){
            return true;
        }
        return false;
    }
    
}

servlet.UserServlet：控制层实现页面跳转

public class UserServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        UserService userService=new UserService();
        List<User> all=userService.hello();
        resp.getWriter().write(all.toString());
    }
}

servlet.LoginServlet：控制层实现页面跳转

public class LoginServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String username=req.getParameter("username");
        String password=req.getParameter("password");
        UserService userService=new UserService();
        boolean flag = userService.login(username, password);
        if(flag){
            resp.getWriter().write("ok");
        }else {
            resp.getWriter().write("failure");
        }
    }
}

web.xml

    <servlet>
         <servlet-name>hello</servlet-name>
         <servlet-class>com.summer.servlet.UserServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>hello</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>login</servlet-name>
        <servlet-class>com.summer.servlet.LoginServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>login</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>

index.jsp

<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
  <a href="/hello">查询所有用户</a>
  <form action="/login" method="post">
      name:<input name="username" type="text">
      password:<input name="password" type="password">
      <input type="submit" value="login">
  </form>>
  </body>
</html>

Tomcat
点击导航栏上面的run，选择Edit configurations，点击左上角的+，在下面找到Tomcat server，添加Tomcat下的local服务器。
默认选择Server，在上方的Name中填写名字，在Application server中找到自己电脑上安装的Tomcat。
选择Deployment，点击+，选择External source，将其添加上，之后选择OK，Tomcat就添加到了我们的项目之中。
点击运行按钮，项目在浏览器中打开。
在这里插入图片描述

查询所有用户：
hello
查询结果：

登录：
login
登录成功、失败：
failure

Java-中软-1 jdbc+servlet+tomcat

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