basedao代码

BaseDao 是一个基础的 DAO（Data Access Object）类，通常用于操作数据库。这里是一个示例代码：

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

public abstract class BaseDao<T> {
    protected Connection connection;

    public BaseDao(Connection connection) {
        this.connection = connection;
    }

    protected abstract T build(ResultSet resultSet) throws SQLException;

    protected abstract String getTableName();

    public T findById(int id) throws SQLException {
        String selectSql = "SELECT * FROM " + getTableName() + " WHERE id = ?";
        PreparedStatement preparedStatement = connection.prepareStatement(selectSql);
        preparedStatement.setInt(1, id);
        ResultSet resultSet = preparedStatement.executeQuery();
        if (resultSet.next()) {
            return build(resultSet);
        }
        return null;
    }

    public void deleteById(int id) throws SQLException {
        String deleteSql = "DELETE FROM " + getTableName() + " WHERE id = ?";
        PreparedStatement preparedStatement = connection.prepareStatement(deleteSql);
        preparedStatement.setInt(1, id);
        preparedStatement.executeUpdate();
    }

    public void save(T object) throws SQLException {
        String insertSql = "INSERT INTO " + getTableName() + " VALUES (?, ?, ?)";
        PreparedStatement preparedStatement = connection.prepareStatement(insertSql);
        // set values to preparedStatement
        preparedStatement.executeUpdate();
    }

    public void update(T object) throws SQLException {
        String updateSql = "UPDATE " + getTableName() + " SET column1 = ?, column2 = ? WHERE id = ?";
        PreparedStatement preparedStatement = connection.prepareStatement(updateSql);
        // set values to preparedStatement
        preparedStatement.executeUpdate();
    }
}

这个类中提供了一些基本的 CRUD（Create，Read，Update，Delete）方法，可以用于操作数据库表中的数据。具体的实现需要子类来完成，因为不同的数据表可能有不同的字段和数据类型。通常情况下，我们会为每个数据表定义一个 DAO 类，继承 BaseDao 类，然后在子类中实现 build() 和 getTableName() 方法。这样就可以使用这个 DAO 类来操作数据库表了。