Mybatis3.1-[tp_36-37]-_映射文件_select_resultMap关联查询__分步查询传递多列值&fetchType_discriminator鉴别器

_分步查询传递多列值&fetchType_discriminator鉴别器

笔记要点
出错分析与总结

Department.java  bean

public class Department {
    private Integer id;
    private String departmentName;
    private List<Employee> emps;

}

DepartmentMapper.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.DepartmentMapper">
    <!--public Department getDeptById(Integer id);-->
    <select id="getDeptById" resultType="com.bean.Department">
        select id,dept_name departmentName from tbl_dept
        where id=#{id}
    </select>
<!--==========================================================================================-->
    <!--
    public class Department {
    private Integer id;
    private String departmentName;
    private List<Employee> emps;
    }
    JavaBean中:   did  dept_name   ||   eid  last_name   email          gender
 -->
    <!--public Department getDeptByIdPlus(Integer id);-->
    <!--进行collection的联合查询/ 分步查询和延迟查询 -->
    <resultMap id="MyDept" type="com.bean.Department">
        <id column="did" property="id"/>
        <result column="dept_name" property="departmentName"/>

        <!--
        collection 用于定义关联集合类型的属性的封装规则!
            ofType用于指定集合中的类型;-->
        <collection property="emps" ofType="com.bean.Employee">
            <id column="eid" property="id"/>
            <result column="last_name" property="lastName"/>
            <result column="email" property="email"/>
            <result column="gender" property="gender"/>
        </collection>

    </resultMap>
    <select id="getDeptByIdPlus" resultMap="MyDept">
         SELECT d.id did,d.dept_name dept_name,e.id eid,e.last_name last_name,e.email email,gender
        FROM tbl_dept d LEFT JOIN tbl_employee e ON d.id=e.d_id
        WHERE d.id=#{id};

    </select>
    <!--========================================-->

    <!--Department中有属性: private List<Employee> emps;
    public Department getDeptByIdStep(Integer id);  //执行Collection 的分步查询-->

    <resultMap id="MyDeptStep" type="com.bean.Department">
        <id column="id" property="id"/>
        <result column="detp_name" property="departmentName"/>
        <collection property="emps" select="com.dao.EmployeeMapperPlus.getEmpsByDeptId"
            column="{deptId=id}" fetchType="lazy">
        </collection>
    </resultMap>

    <select id="getDeptByIdStep" resultMap="MyDeptStep">
       select id,dept_name departmentName from tbl_dept
        where id=#{id}
    </select>
    <!--=======================================-->
    <!--扩展,将多列的值传递过去,封装成map进行传递!
        column="{key1=列1,key2=列2}"
        fetchType="lazy" ,标识使用延迟加载;
        -lazy: 延迟;
        -eager:立即;
    -->

</mapper>

测试

public class test_tp36 {
    public SqlSessionFactory getSqlSessionFactory() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream=Resources.getResourceAsStream(resource);
        return new SqlSessionFactoryBuilder().build(inputStream);
    }
    @Test
    public void test08() throws Exception {
        SqlSession openSession = getSqlSessionFactory().openSession();
        try {
            EmployeeMapperPlus mapper = openSession.getMapper(EmployeeMapperPlus.class);
            System.out.println("---tp_37-使用鉴别器-");
            Employee emp = mapper.getEmpByIdStep(1);  //测试为女生 ,gender=0
            System.out.println(emp);

            emp = mapper.getEmpByIdStep(4);  //测试为男生,gender=1
             System.out.println(emp);

            openSession.commit();//默认是不自动提交数据的,需要我们自己手动提交
        } finally {
            openSession.close();
        }
    }
}

测试结果:

---tp_37-使用鉴别器-
DEBUG 12-04 13:10:50,471 ==>  Preparing: select id,last_name,gender,email,d_id from tbl_employee where id = ?   (BaseJdbcLogger.java:145)
DEBUG 12-04 13:10:50,488 ==> Parameters: 1(Integer)  (BaseJdbcLogger.java:145)
DEBUG 12-04 13:10:50,498 <==      Total: 1  (BaseJdbcLogger.java:145)
Employee{id=1, lastName='jerry', email='jerry', gender='1', dept=null}
DEBUG 12-04 13:10:50,499 ==>  Preparing: select id,last_name,gender,email,d_id from tbl_employee where id = ?   (BaseJdbcLogger.java:145)
DEBUG 12-04 13:10:50,499 ==> Parameters: 4(Integer)  (BaseJdbcLogger.java:145)
DEBUG 12-04 13:10:50,558 <==      Total: 1  (BaseJdbcLogger.java:145)
DEBUG 12-04 13:10:50,558 ==>  Preparing: select id,dept_name departmentName from tbl_dept where id=?   (BaseJdbcLogger.java:145)
DEBUG 12-04 13:10:50,558 ==> Parameters: 2(Integer)  (BaseJdbcLogger.java:145)
DEBUG 12-04 13:10:50,561 <==      Total: 1  (BaseJdbcLogger.java:145)
Employee{id=4, lastName='葫芦娃', email='葫芦娃@163.com', gender='0', dept=Department{id=2, departmentName='测试部'}}