MyBatis_Study_004(动态代理)

源码:https://github.com/carryLess/mbtsstd-004

0.readme

基于前几篇:dao的实现类基本煤气到什么作用
        仅仅是通过SQLSession的相应API定位到mapper映射文件中指定id的sql语句,
        所以此刻,我们将实现类去掉,直接定位到映射文件的sql语句,
        这种对Dao的实现方式称为动态代理

此方式下需要注意:
    1.映射文件mapper标签中的namespace属性为Dao的全限定类名
    2.Dao接口中的方法名称要与mapper映射文件中sql标签的id一致
    3.dao对象的获取通过SqlSession.getMapper(dao.class);
    4.sqlSession.commit();注意添加
    5.动态代理下系统只会调用selectOne()或者selectList()方法,不支持返回Map的方法

1.主配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<!-- (以上)文件头在解压的文件夹中mybatis-3.4.4.pdf文件中搜索mybatis-3-config.dtd即可得到 -->
<configuration>

    <!-- 指定属性配置文件 -->
    <properties resource="jdbc.properties" />
    <!--
        配置类的别名,我建议使用package这种写法
        这样写会将该包中所有类的简单类名配置为别名,简单方便
        ,还有别的写法,自行google
     -->
    <typeAliases>
        <package name="model" />
    </typeAliases>
    <!-- 配置MyBatis运行环境 -->
    <environments default="development">
        <environment id="development">
            <!-- 使用JDBC事务管理 -->
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
    <!-- 注册映射文件 -->
    <mappers>
        <mapper resource="dao/mapper.xml"/>
        <!--
            实际开发中可能有多个映射文件,而其中sql标签的id相同时候,执行过程就会报错
            我们可以根据mapper映射文件中的namespace属性来区分,调用时候用如下方式
            namespace.id
        -->
        <!--
            <mapper resource="dao/mapper2.xml"/>
        -->
    </mappers>

</configuration>

2.映射文件

<?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="dao.IStudentDao">
    <insert id="insertStudentByList">
        insert into SStudent(sname,sage,score) values
        <!-- 这里面的collection必须写成list -->
        <foreach collection="list" separator="," item="stu">
            (#{stu.name},#{stu.age},#{stu.score})
        </foreach>
    </insert>

    <!-- 使用别名 -->
    <select id="selectById1" resultType="SStudent">
        select sid id,sname name,sage age,score from sstudent where sid = #{xxx}
    </select>

    <!-- 使用resultMap -->
    <select id="selectById2" resultMap="sStudentMapper">
        select sid,sname,sage,score from sstudent where sid = #{xxx}
    </select>

    <!--
        type:要映射的实体类
        id:resultMap标签的id,用于select标签中resultMap属性
    -->
    <resultMap id="sStudentMapper" type="SStudent">
        <id column="sid" property="id" />
        <result column="sname" property="name" />
        <result column="sage" property="age" />
    </resultMap>

    <!-- 通过map接收多个参数 -->
    <select id="selectByMap" resultMap="sStudentMapper">
        select * from sstudent where sname like '%' #{nameCon} '%' and sage > #{ageCon}
    </select>

    <select id="selectByCons" resultMap="sStudentMapper">
        select * from sstudent where sname like '%' #{name} '%' and sage > #{age}
    </select>

</mapper>

3.dao接口

package dao;

import model.SStudent;
import org.apache.ibatis.annotations.Param;

import java.util.List;
import java.util.Map;

/**
 * Created by carryLess on 2017/11/29.
 */
public interface IStudentDao {

    /**
     * 插入集合
     * @param studentList
     */
    void insertStudentByList(List<SStudent> studentList);

    /**
     * 根据id查询1
     * @param id
     * @return
     */
    SStudent selectById1(int id);

    /**
     * 根据id查询2
     * @param id
     * @return
     */
    SStudent selectById2(int id);

    /**
     * 根据map查询  map中key为:nameCon和ageCon
     * @param conMap
     * @return
     */
    List<SStudent> selectByMap(Map<String,Object> conMap);

    /**
     * 多参数查询,其中@Param中的value是字段名称
     * @param name
     * @param age
     * @return
     */
    List<SStudent> selectByCons(@Param("name") String name, @Param("age") int age);
}

4.test

package test;

import dao.IStudentDao;
import model.SStudent;
import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import utils.MyBatisUtils;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Created by carryLess on 2017/11/29.
 */
public class MyTest {
    private SqlSession sqlSession;
    private IStudentDao dao;

    @Before
    public void initDao(){
        sqlSession = MyBatisUtils.getSqlSession();
        dao = sqlSession.getMapper(IStudentDao.class);
    }

    @After
    public void over(){
        if(sqlSession != null){
            sqlSession.close();
        }
    }

    @Test
    public void testInsertList(){
        List<SStudent> sStudentList = new ArrayList<SStudent>();
        for(int i = 20;i<22;i++){
            SStudent sStudent = new SStudent();
            sStudent.setSname("ls-"+i);
            sStudent.setSage(25+i);
            sStudent.setScore(90);
            sStudentList.add(sStudent);
        }
        dao.insertStudentByList(sStudentList);
        sqlSession.commit();
    }

    @Test
    public void testSelectById(){
        SStudent sStudent = dao.selectById2(18);
        System.out.println(sStudent);
    }

    @Test
    public void testSelectByMap(){
        Map<String,Object> conMap = new HashMap<String,Object>();
        conMap.put("nameCon","s");
        conMap.put("ageCon",44);
        List<SStudent> sStudentList = dao.selectByMap(conMap);
        System.out.println(sStudentList);
    }

    @Test
    public void testSelectByCons(){
        List<SStudent> sStudentList = dao.selectByCons("s", 44);
        System.out.println(sStudentList);
    }

}