MyBatis3_[tp-26-27]_映射文件_select_返回List_记录封装Map:返回单个元素的Map或者整体Map集合

笔记要点
出错分析与总结
工程组织

1.定义接口

public interface EmployeeMapper {

    //多条记录封装到一个map中: Map<Integer,Employee>,键是这条记录的主键,值时记录封装后的JavaBean

    @MapKey("id")  //告诉Mybatis 封装Map的时候,使用哪个属性作为map的key,当然要对应你的下一行的Integer

    public Map<Integer,Employee>  getEmpsByLastNameLikeRetMap( String lastName);

    //select 的返回值类型是Map ,返回一条记录的Map,key是列名,值就是对应的值;

    public Map<String,Object> getEmpsByIdReturnMap(Integer id);

    //select 的返回值类型是List

    public List<Employee> getEmpsByLastNameLike( String lastName);

    //多个参数处理,传入map

    public Employee getEmpByMap(Map<String,Object> map);

}

2.定义XML映射文件  EmployeeMapper.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.dao.EmployeeMapper"><!--namespace: 名称空间;id: 唯一标识; resultType:返回值类型; -->

    <!--public Map<Integer,Employee>  getEmpsByLastNameLikeRetMap( String lastName);

         如果返回的是一个集合,resultType要写Map中值 元素的类型:Employee

    -->

    <select id="getEmpsByLastNameLikeRetMap" resultType="com.bean.Employee" databaseId="mysql">

         select * from tbl_employee

        where last_name like #{lastName}

    </select>

    <!--public Map<String,Object> getEmpsByIdReturnMap(Integer id);

        记得更改,resultType="map"

    -->

    <select id="getEmpsByIdReturnMap" resultType="map" databaseId="mysql">

        select * from tbl_employee

        where id =#{id}

    </select>

    <!--public List<Employee> getEmpsByLastNameLike( String lastName);

        如果返回的是一个集合,resultType要写集合中元素的类型;

    -->

    <select id="getEmpsByLastNameLike" resultType="com.bean.Employee" databaseId="mysql">

        select * from tbl_employee

        where last_name like #{lastName}

    </select>

    <!--public Employee getEmpByMap(Map<String,Object> map);-->

    <select id="getEmpByMap" resultType="com.bean.Employee" databaseId="mysql">

        select * from ${table_name}

        where id = ${id} and last_name = #{lastName}

    </select>

3.编写测试代码

public class test_tp26 {

    public SqlSessionFactory getSqlSessionFactory() throws IOException {

        String resource = "mybatis-config.xml";

        InputStream inputStream=Resources.getResourceAsStream(resource);

        return new SqlSessionFactoryBuilder().build(inputStream);

    }

    @Test

    public void test06() throws Exception{

        //默认是不自动提交数据的,需要我们自己手动提交

        SqlSession openSession = getSqlSessionFactory().openSession();

        try {

            EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);

            //1.select 返回List列表

            List<Employee> like = mapper.getEmpsByLastNameLike("%e%");

            for(Employee e:like){

                System.out.println(e);

            }

            System.out.println("*********************");

            //2.select 记录封装Map,返回单条记录

            Map<String, Object> emps = mapper.getEmpsByIdReturnMap(1);

            System.out.println(emps);  //{gender=1, last_name=jerry, id=1, [email protected]}

            System.out.println("*********************");

            //3.select 记录封装Map,返回多组记录

            Map<Integer, Employee> emps1 = mapper.getEmpsByLastNameLikeRetMap("%e%");

            for(Map.Entry m: emps1.entrySet()){

                System.out.println(m);

            }

           //{gender=1, last_name=jerry, id=1, [email protected]}

            System.out.println("*********************");

            //最后手动提交

            openSession.commit();

        }finally {

            openSession.close();

        }

    }

}

测试结果

DEBUG 11-29 16:10:26,474 ==>  Preparing: select * from tbl_employee where last_name like ?   (BaseJdbcLogger.java:145)

DEBUG 11-29 16:10:26,493 ==> Parameters: %e%(String)  (BaseJdbcLogger.java:145)

DEBUG 11-29 16:10:26,505 <==      Total: 2  (BaseJdbcLogger.java:145)

Employee{id=1, lastname='jerry', email='[email protected]', gender='1'}

Employee{id=5, lastname='葫芦娃e', email='[email protected]', gender='1'}

*********************

DEBUG 11-29 16:10:26,506 ==>  Preparing: select * from tbl_employee where id =?   (BaseJdbcLogger.java:145)

DEBUG 11-29 16:10:26,506 ==> Parameters: 1(Integer)  (BaseJdbcLogger.java:145)

DEBUG 11-29 16:10:26,507 <==      Total: 1  (BaseJdbcLogger.java:145)

{gender=1, last_name=jerry, id=1, [email protected]}

*********************

DEBUG 11-29 16:10:26,508 ==>  Preparing: select * from tbl_employee where last_name like ?   (BaseJdbcLogger.java:145)

DEBUG 11-29 16:10:26,508 ==> Parameters: %e%(String)  (BaseJdbcLogger.java:145)

DEBUG 11-29 16:10:26,509 <==      Total: 2  (BaseJdbcLogger.java:145)

1=Employee{id=1, lastname='jerry', email='[email protected]', gender='1'}

5=Employee{id=5, lastname='葫芦娃e', email='[email protected]', gender='1'}

*********************