java中基于jdbc的dbhelper辅助类写法

以下是一个基于 JDBC 的 DBHelper 辅助类的示例代码：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class DBHelper {
    private static final String DRIVER = "com.mysql.jdbc.Driver";
    private static final String URL = "jdbc:mysql://localhost:3306/database_name";
    private static final String USERNAME = "username";
    private static final String PASSWORD = "password";
    
    private Connection conn;
    private PreparedStatement ps;
    private ResultSet rs;
    
    public DBHelper() {
        try {
            Class.forName(DRIVER);
            conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    
    public ResultSet executeQuery(String sql, Object... params) throws SQLException {
        ps = conn.prepareStatement(sql);
        for (int i = 0; i < params.length; i++) {
            ps.setObject(i + 1, params[i]);
        }
        rs = ps.executeQuery();
        return rs;
    }
    
    public int executeUpdate(String sql, Object... params) throws SQLException {
        ps = conn.prepareStatement(sql);
        for (int i = 0; i < params.length; i++) {
            ps.setObject(i + 1, params[i]);
        }
        return ps.executeUpdate();
    }
    
    public void close() {
        try {
            if (rs != null) {
                rs.close();
            }
            if (ps != null) {
                ps.close();
            }
            if (conn != null) {
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

这个 DBHelper 类包含了连接数据库、执行查询和更新操作、关闭数据库连接等常用方法。使用时，只需实例化 DBHelper 类，然后调用其中的方法即可。例如：

DBHelper dbHelper = new DBHelper();
try {
    ResultSet rs = dbHelper.executeQuery("SELECT * FROM table_name WHERE column_name = ?", "value");
    while (rs.next()) {
        // 处理查询结果
    }
} catch (SQLException e) {
    e.printStackTrace();
} finally {
    dbHelper.close();
}