idea Java 完成对用户表 的增删改查 用户表字段 ID username password 详细过程

好的，我可以帮你解决这个问题。

首先，我们需要创建一个用户类，其中包含 ID、username 和 password 字段，并定义相应的 getter 和 setter 方法。

public class User {
    private int ID;
    private String username;
    private String 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;
    }
}

接下来，我们需要创建一个用户 DAO 类，它负责处理对用户表的增删改查操作。这里我们使用 JDBC 技术来访问数据库。

import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class UserDao {
    private String jdbcUrl;
    private String username;
    private String password;
    private Connection connection;

    public UserDao(String jdbcUrl, String username, String password) {
        this.jdbcUrl = jdbcUrl;
        this.username = username;
        this.password = password;
    }

    public void connect() throws SQLException {
        connection = DriverManager.getConnection(jdbcUrl, username, password);
    }

    public void disconnect() throws SQLException {
        if (connection != null && !connection.isClosed()) {
            connection.close();
        }
    }

    public void addUser(User user) throws SQLException {
        String sql = "INSERT INTO users (username, password) VALUES (?, ?)";
        PreparedStatement statement = connection.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS);
        statement.setString(1, user.getUsername());
        statement.setString(2, user.getPassword());
        int affectedRows = statement.executeUpdate();
        if (affectedRows == 0) {
            throw new SQLException("Creating user failed, no rows affected.");
        }
        try (ResultSet generatedKeys = statement.getGeneratedKeys()) {
            if (generatedKeys.next()) {
                user.setID(generatedKeys.getInt(1));
            } else {
                throw new SQLException("Creating user failed, no ID obtained.");
            }
        }
    }

    public void updateUser(User user) throws SQLException {
        String sql = "UPDATE users SET username=?, password=? WHERE ID=?";
        PreparedStatement statement = connection.prepareStatement(sql);
        statement.setString(1, user.getUsername());
        statement.setString(2, user.getPassword());
        statement.setInt(3, user.getID());
        statement.executeUpdate();
    }

    public void deleteUser(int ID) throws SQLException {
        String sql = "DELETE FROM users WHERE ID=?";
        PreparedStatement statement = connection.prepareStatement(sql);
        statement.setInt(1, ID);
        statement.executeUpdate();
    }

    public User getUserByID(int ID) throws SQLException {
        String sql = "SELECT username, password FROM users WHERE ID=?";
        PreparedStatement statement = connection.prepareStatement(sql);
        statement.setInt(1, ID);
        ResultSet resultSet = statement.executeQuery();
        if (resultSet.next()) {
            User user = new User();
            user.setID(ID);
            user.setUsername(resultSet.getString("username"));
            user.setPassword(resultSet.getString("password"));
            return user;
        } else {
            return null;
        }
    }

    public List<User> getAllUsers() throws SQLException {
        List<User> userList = new ArrayList<>();
        String sql = "SELECT ID, username, password FROM users";
        Statement statement = connection.createStatement();
        ResultSet resultSet = statement.executeQuery(sql);
        while (resultSet.next()) {
            User user = new User();
            user.setID(resultSet.getInt("ID"));
            user.setUsername(resultSet.getString("username"));
            user.setPassword(resultSet.getString("password"));
            userList.add(user);
        }
        return userList;
    }
}

以上就是用户 DAO 类的详细实现过程。通过调用 addUser、updateUser、deleteUser、getUserByID 和 getAllUsers 方法，我们可以完成对用户表的增删改查操作。其中，connect 和 disconnect 方法用于连接和断开数据库连接。

同时，我们还需要在数据库中创建一个名为 users 的表，该表包含 ID、username 和 password 字段。可以使用以下 SQL 语句来创建该表：

CREATE TABLE users (
  ID INT PRIMARY KEY AUTO_INCREMENT,
  username VARCHAR(50) NOT NULL,
  password VARCHAR(50) NOT NULL
);

以上就是使用 Java 和 JDBC 完成对用户表的增删改查的详细过程。