简单SQLHelper(java)

以下是一个简单的 SQLHelper 类，使用 Java 和 JDBC 进行数据库操作：

import java.sql.*;

public class SQLHelper {
   private Connection conn = null;
   private Statement stmt = null;
   private ResultSet rs = null;

   public SQLHelper(String url, String user, String password) throws SQLException {
      conn = DriverManager.getConnection(url, user, password);
      stmt = conn.createStatement();
   }

   public ResultSet executeQuery(String sql) throws SQLException {
      rs = stmt.executeQuery(sql);
      return rs;
   }

   public int executeUpdate(String sql) throws SQLException {
      return stmt.executeUpdate(sql);
   }

   public void close() throws SQLException {
      if (rs != null) rs.close();
      if (stmt != null) stmt.close();
      if (conn != null) conn.close();
   }
}

使用该类可以执行 SQL 查询和更新操作。例如，查询语句可以这样执行：

String url = "jdbc:mysql://localhost:3306/mydb";
String user = "root";
String password = "root";
SQLHelper sqlHelper = new SQLHelper(url, user, password);

String sql = "SELECT * FROM mytable";
ResultSet rs = sqlHelper.executeQuery(sql);

while (rs.next()) {
   int id = rs.getInt("id");
   String name = rs.getString("name");
   int age = rs.getInt("age");
   System.out.println("id=" + id + ", name=" + name + ", age=" + age);
}

sqlHelper.close();

更新语句可以这样执行：

String url = "jdbc:mysql://localhost:3306/mydb";
String user = "root";
String password = "root";
SQLHelper sqlHelper = new SQLHelper(url, user, password);

String sql = "UPDATE mytable SET name='Alice' WHERE id=1";
int rowsAffected = sqlHelper.executeUpdate(sql);
System.out.println(rowsAffected + " rows affected");

sqlHelper.close();

注意，这只是一个简单的 SQLHelper 类，实际应用中需要考虑更多的异常处理、连接池等问题。