【MyBatis】使用Mapper接口开发MyBatis项目

介绍

在实际开发中，不直接使用SqlSession的实例，而是使用Mapper接口，构建dao层。映射器是你创建的绑定映射语句的接口(interface)，映射器接口的实例可以从SqlSession中获得。

案例代码下载（注意实体类源代码里面GoodsType实体类和实体类的xml文件都是没有用到的）：本地下载

案例

1.创建实体类

Goods.java

package com.bean;

public class Goods {
    private Integer goodsId;
    private String goodsName;
    private Double goodsPrice;
    private Integer goodsNum;
    private Integer goodsType;

    public Goods() {
    }

    public Goods(Integer goodsId, String goodsName, Double goodsPrice,
                 Integer goodsNum, Integer goodsType) {
        super();
        this.goodsId = goodsId;
        this.goodsName = goodsName;
        this.goodsPrice = goodsPrice;
        this.goodsNum = goodsNum;
        this.goodsType = goodsType;
    }

    public Integer getGoodsId() {
        return goodsId;
    }

    public void setGoodsId(Integer goodsId) {
        this.goodsId = goodsId;
    }

    public String getGoodsName() {
        return goodsName;
    }

    public void setGoodsName(String goodsName) {
        this.goodsName = goodsName;
    }

    public Double getGoodsPrice() {
        return goodsPrice;
    }

    public void setGoodsPrice(Double goodsPrice) {
        this.goodsPrice = goodsPrice;
    }

    public Integer getGoodsNum() {
        return goodsNum;
    }

    public void setGoodsNum(Integer goodsNum) {
        this.goodsNum = goodsNum;
    }

    public Integer getGoodsType() {
        return goodsType;
    }

    public void setGoodsType(Integer goodsType) {
        this.goodsType = goodsType;
    }

    @Override
    public String toString() {
        return "Goods [goodsId=" + goodsId + ", goodsName=" + goodsName
                + ", goodsPrice=" + goodsPrice + ", goodsNum=" + goodsNum
                + ", goodsType=" + goodsType + "]";
    }
}

2.实体类对应的xml文件

Goods.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.bean.Goods">
<select id="findAll" resultMap="resultGoods">
select * from goods
</select>
<resultMap type="com.bean.Goods" id="resultGoods">
<id property="goodsId" column="goods_id" javaType="int" />
<result property="goodsName" column="goods_name" javaType="java.lang.String" />
<result property="goodsPrice" column="goods_price" javaType="java.lang.Double" />
<result property="goodsNum" column="goods_num" javaType="int" />
<result property="goodsType" column="goods_type" javaType="int" />
</resultMap>
</mapper>

3.在mybatis.xml注册Goods.xml

mybatis.xml

<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver" />
<property name="url" value="jdbc:mysql://127.0.0.1:3306/spring?useUnicode=true&amp;characterEncoding=utf8" />
<property name="username" value="root" />
<property name="password" value="123456" />
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="com/mapper/GoodsMapper.xml" />
</mappers>
</configuration>

4.编写Mapper接口

GoodsMapper.java

package com.mapper;

import java.util.List;

import com.bean.Goods;

public interface GoodsMapper {
    public List<Goods> findAll();
}

5.编写GoodsMapper接口的实现类

重点

GoodsMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.mapper.GoodsMapper">
<select id="findAll" resultMap="resultGoods">
select * from goods
</select>
<resultMap type="com.bean.Goods" id="resultGoods">
<id property="goodsId" column="goods_id" javaType="int" />
<result property="goodsName" column="goods_name" javaType="java.lang.String" />
<result property="goodsPrice" column="goods_price" javaType="double" />
<result property="goodsNum" column="goods_num" javaType="int" />
<result property="goodsType" column="goods_type" javaType="int" />
</resultMap>
</mapper>

6.测试代码

test.java

package com.test;

import java.io.IOException;
import java.io.Reader;
import java.util.List;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Before;
import org.junit.Test;

import com.bean.Goods;
import com.mapper.GoodsMapper;

public class test {

    private SqlSession sqlSession;

    public void test03() {
        try {
            GoodsMapper goodsMapper = this.sqlSession.getMapper(GoodsMapper.class);
            List<Goods> goodsList = goodsMapper.findAll();
            for (Goods goods : goodsList) {
                System.out.println(goods);
            }
        } catch(Exception e) {
            e.printStackTrace();
        } finally {
            this.sqlSession.close();
        }
    }

    @Test
    public void testF(){
        test03();
    }

    @Before
    public void before() {
        try {
            String resource = "mybatis.xml";
            Reader reader = Resources.getResourceAsReader(resource);
            SqlSessionFactory ssf = new SqlSessionFactoryBuilder().build(reader);
            this.sqlSession = ssf.openSession();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}