BasicDAO 设计模式

1.BasicDAO设计模式

在开发中需要用到多个表,BasicDAO设计模式可以对多个表进行管理，增加开发效率。

1.1 BasicDAO 设计模式图解

1.2 BasicDAO 设计模式的文件目录

实际开发中，这些目录会有很多。

2. BasicDAO设计模式小案例

2.1 项目需求

2.2 创建goods数据库

用到的SQL语句

CREATE DATABASE goods;

CREATE TABLE goods(
id INT PRIMARY KEY AUTO_INCREMENT,
	goods_name VARCHAR(10),
	price DOUBLE
)CHARSET=utf8;

SELECT *FROM goods;

DROP TABLE goods;

SELECT COUNT(*) FROM goods;

SELECT goods_name FROM goods

2.3 创建BasicDAO类

在dao目录下创建BasicDAO类,类型为泛型

package com.dz.dao.dao;

import com.dz.jdbc.utilis.JDBCUtils;
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;

public class BasicDAO<T> {
    private QueryRunner queryRunner = new QueryRunner();

    public int update(String sql, Object... parameters) {
        Connection connection = null;
        try {
            connection = JDBCUtils.connection();
            int update = queryRunner.update(connection, sql, parameters);
            return update;
        } catch (Exception e) {
            throw new RuntimeException(e);
        } finally {
            JDBCUtils.close(null, null, connection);
        }
    }

    public List<T> QueryMulti(String sql, Class<T> clazz, Object... parameters) {
        Connection connection = null;
        try {
            connection = JDBCUtils.connection();
            return queryRunner.query(connection, sql, new BeanListHandler<>(clazz), parameters);
        } catch (Exception e) {
            throw new RuntimeException(e);
        } finally {
            JDBCUtils.close(null, null, connection);
        }
    }

    public T single(String sql, Class<T> clazz, Object... parameters) {
        Connection connection = null;
        try {
            connection = JDBCUtils.connection();
            return queryRunner.query(connection, sql, new BeanHandler<T>(clazz), parameters);

        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            JDBCUtils.close(null, null, connection);
        }
    }

    public Object Scalar(String sql, Object... parameters) {
        Connection connection = null;
        try {
            connection = JDBCUtils.connection();
            return queryRunner.query(connection,sql, new ScalarHandler<T>(), parameters);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            JDBCUtils.close(null, null, connection);
        }
    }
}

2.4 创建Goods类

对应goods数据库的字段

package com.dz.dao.domain;

public class Goods {
    private Integer id;
    private String goods_name;
    private Double price;

    public Goods() {
    }

    public Goods(Integer id, String goods_name, Double price) {
        this.id = id;
        this.goods_name = goods_name;
        this.price = price;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getGoods_name() {
        return goods_name;
    }

    public void setGoods_name(String goods_name) {
        this.goods_name = goods_name;
    }

    public Double getPrice() {
        return price;
    }

    public void setPrice(Double price) {
        this.price = price;
    }

    @Override
    public String toString() {
        return "\nGoods{" +
                "id=" + id +
                ", goods_name='" + goods_name + '\'' +
                ", price=" + price +
                '}';
    }
}

2.5 创建GoodsDAO类

创建GoodsDAO类,并继承BasicDAO类，类型为Goods.

package com.dz.dao.dao;

import com.dz.dao.domain.Goods;

public class GoodsDAO extends BasicDAO<Goods> {
    //根据需求可以，增加特有的方法。
}

2.5 创建TestDAO测试类

完成对goods表的增删改查操作

package com.dz.dao.test;

import com.dz.dao.dao.GoodsDAO;
import com.dz.dao.domain.Goods;
import org.junit.Test;

import java.util.List;

public class TestDAO {
    @Test
    public void testGoods() {
        GoodsDAO goodsDAO = new GoodsDAO();
        String sql = "insert into goods value (null,?,?)";
        int affectedRow = goodsDAO.update(sql, "小米11", "2500.0");
        System.out.println(affectedRow > 0 ? "执行成功" : "执行没有影响数据库");
        String sql1 = "select * from goods";
        List<Goods> goods = goodsDAO.QueryMulti(sql1, Goods.class);
        for (Goods actor : goods) {
            System.out.print(actor);
        }
        System.out.println("查询单行记录");
        String sql2 = "select * from goods where id=?";
        Object single = goodsDAO.single(sql2, Goods.class, 1);
        System.out.print(single);
        System.out.println("查询单行单列");
        String sql3 = "select goods_name from goods where id=?";
        Object scalar = goodsDAO.Scalar(sql3,3);
        System.out.print(scalar);
    }
}