表与 domain

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表字段

domain属性
domain属性与表的字段要一一对应
提供相应的无参构造和getter和setter方法
(方法名一定要和表字段对应，比如表字段为id，那么方法为getId 和 setId)
DBUtils是通过反射将数据库的数据保存在对象中
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BasicDAO 与 XxxDAO

BasicDAO提供对数据库的增删改查方法，由DBUtils和Druid完成
灵活使用泛型，为所有DAO提供基本功能

package com.study.mhl.dao;

import com.study.mhl.utils.JDBCUtilsByDruid;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;

/**
 * @author 珀筱
 */
@SuppressWarnings({"all"})
public class BasicDAO<T> {
    private QueryRunner queryRunner = new QueryRunner();

    //开发通用DML语句
    public int update(String sql, Object... parameters) {
        Connection connection = null;
        try {
            connection = JDBCUtilsByDruid.getConnection();
            int rows = queryRunner.update(connection, sql, parameters);
            return rows;
        } catch (SQLException e) {
            throw new RuntimeException(e); //将编译异常转换成运行异常，抛出，方便调用
        } finally {
            JDBCUtilsByDruid.close(null, null, connection);
        }
    }

    //返回多个对象(即查询的结果是多行的)，针对任意表
    public List<T> queryMulti(String sql, Class<T> clazz, Object... parameters) {
        Connection connection = null;
        try {
            connection = JDBCUtilsByDruid.getConnection();
            return queryRunner.query(connection, sql, new BeanListHandler<T>(clazz), parameters);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            JDBCUtilsByDruid.close(null, null, connection);
        }
    }

    //返回单个对象
    public T querySingle(String sql, Class<T> clazz, Object... parameters) {
        Connection connection = null;
        try {
            connection = JDBCUtilsByDruid.getConnection();
            return queryRunner.query(connection, sql, new BeanHandler<T>(clazz), parameters);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            JDBCUtilsByDruid.close(null, null, connection);
        }
    }

    //返回单列单行
    public Object queryScalar(String sql, Object... parameters) {
        Connection connection = null;
        try {
            connection = JDBCUtilsByDruid.getConnection();
            return queryRunner.query(connection, sql, new ScalarHandler(), parameters);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            JDBCUtilsByDruid.close(null, null, connection);
        }
    }
}