目录结构同中的目录结构

这里需要再添加一张表：

CREATE TABLE `tbl_department` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `depart_name` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ;

一、select 返回

1.select 返回对象：

如中的单个参数和多个参数中的查询一样；这里不再多说了；

2.select 返回list

接口EmployeeMapper.java:

List getEmps(String param);

映射文件EmployeeMapper.xml;

• parameterType 可以不传
• resultType 如果返回的是一个集合，要写集合中元素的类型

<select id="getEmps"  resultType="entity.Employee">
        select ID AS id,LAST_NAME AS
        lastName,gender as gender,email as email from
        tbl_employee where LAST_NAME like #{e}
    select>

junit 测试类：

 1 @Test
 2     public void test06() {
 3         String resource = "mybatis-config.xml";
 4         SqlSession openSession = null;
 5         try {
 6             InputStream inputStream = Resources.getResourceAsStream(resource);
 7             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 8             // 获取openSession 不会自动提交数据
 9             openSession = sqlSessionFactory.openSession(true);
10             EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
11 
12             List employees = mapper.getEmps("%joy%");
13             System.out.println("测试 select 返回list：" + employees);
14 
15         } catch (Exception e) {
16             // TODO: handle exception
17         } finally {
18             if (openSession != null) {
19                 openSession.close();
20             }
21 
22         }
23     }

运行结果：

测试 select 返回list：[Employee [id=1, lastName=joy33333, email=joy52112225@iclound.com, gender=女], Employee [id=2, lastName=joy2x22222, email=joy52112225@iclound.com, gender=男], Employee [id=4, lastName=joy, email=joy521125@iclound.com, gender=女], Employee [id=5, lastName=joy, email=joy521125@iclound.com, gender=女], Employee [id=6, lastName=joy, email=joy521125@iclound.com, gender=女], Employee [id=7, lastName=joy, email=1602211057@qq.com, gender=女], Employee [id=8, lastName=joy, email=1602211058@qq.com, gender=女], Employee [id=25, lastName=joy1111, email=joy521125@icloud.com, gender=女], Employee [id=26, lastName=joy222, email=joy521125@icloud.com, gender=女]]

 

3.select 返回单条数据的map

接口EmployeeMapper.java:

• 返回一条记录的map，key就是列名，值就是对于的值

Employee getEmpByMap(Map map);

映射文件EmployeeMapper.xml;

<select id="getMapById"  resultType="map">
        select ID AS id,LAST_NAME AS
        lastName,gender as gender,email as email from
        tbl_employee where id = #{id}
    select>

junit 测试类：

 1 @Test
 2     public void test06() {
 3         String resource = "mybatis-config.xml";
 4         SqlSession openSession = null;
 5         try {
 6             InputStream inputStream = Resources.getResourceAsStream(resource);
 7             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 8             // 获取openSession 不会自动提交数据
 9             openSession = sqlSessionFactory.openSession(true);
10             EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
11             Map map = mapper.getMapById(1);
12             System.out.println("测试 select 返回单条数据的map：" + map);
13 
14         } catch (Exception e) {
15             // TODO: handle exception
16         } finally {
17             if (openSession != null) {
18                 openSession.close();
19             }
20 
21         }
22     }

运行结果：

测试 select 返回单条数据的map：{lastName=[B@202b0582, gender=女, id=1, email=joy52112225@iclound.com}

 

4.select 返回多条数据的map

接口EmployeeMapper.java:

• 多条记录封装一个map。Map ：键是id,value 是数据对象
• @MapKey 告诉mybatis 封装map的时候使用哪个属性作为主键

@MapKey("id")
    Map getMaps();

映射文件EmployeeMapper.xml：

 <select id="getMaps"  resultType="map">
        select ID AS id,LAST_NAME AS
        lastName,gender as gender,email as email from
        tbl_employee 
    select>

junit 测试类：

 1 @Test
 2     public void test06() {
 3         String resource = "mybatis-config.xml";
 4         SqlSession openSession = null;
 5         try {
 6             InputStream inputStream = Resources.getResourceAsStream(resource);
 7             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 8             // 获取openSession 不会自动提交数据
 9             openSession = sqlSessionFactory.openSession(true);
10             EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
11 
12             Map maps = mapper.getMaps();
13             System.out.println("测试 select 返回多条数据的map：" + maps);
14 
15         } catch (Exception e) {
16             // TODO: handle exception
17         } finally {
18             if (openSession != null) {
19                 openSession.close();
20             }
21 
22         }
23     }

运行结果：

测试 select 返回多条数据的map：{1={lastName=[B@268f106e, gender=女, id=1, email=joy52112225@iclound.com}, 2={lastName=[B@6e9a5ed8, gender=男, id=2, email=joy52112225@iclound.com}, 4={lastName=[B@7e057f43, gender=女, id=4, email=joy521125@iclound.com}, 5={lastName=[B@6c284af, gender=女, id=5, email=joy521125@iclound.com}, 6={lastName=[B@5890e879, gender=女, id=6, email=joy521125@iclound.com}, 7={lastName=[B@6440112d, gender=女, id=7, email=1602211057@qq.com}, 8={lastName=[B@31ea9581, gender=女, id=8, email=1602211058@qq.com}, 9={lastName=[B@231f98ef, id=9, email=zhumama@166.com}, 10={lastName=[B@7c137fd5, id=10, email=zhubaba@166.com}, 11={lastName=[B@183ec003, id=11, email=zhumama@166.com}, 12={lastName=[B@7d9d0818, id=12, email=zhubaba@166.com}, 13={lastName=[B@221a3fa4, id=13, email=zhumama@166.com}, 14={lastName=[B@451001e5, id=14, email=zhubaba@166.com}, 15={lastName=[B@2b40ff9c, gender=男, id=15, email=678@qq.com}, 16={lastName=[B@3e08ff24, gender=男, id=16, email=678@qq.com}, 17={lastName=[B@4d1c005e, gender=男, id=17, email=678@qq.com}, 18={lastName=[B@8462f31, gender=男, id=18, email=678@qq.com}, 19={lastName=[B@24569dba, gender=男, id=19, email=678@qq.com}, 20={lastName=[B@5ddeb7cb, gender=男, id=20, email=678@qq.com}, 21={lastName=[B@70ed52de, gender=男, id=21, email=678@qq.com}, 22={lastName=[B@496bc455, gender=男, id=22, email=678@qq.com}, 23={lastName=[B@59402b8f, gender=男, id=23, email=678@qq.com}, 25={lastName=[B@7188af83, gender=女, id=25, email=joy521125@icloud.com}, 26={lastName=[B@6be968ce, gender=女, id=26, email=joy521125@icloud.com}}

 二、resultMap：自定义某个javabean的封装规则

实体类Employee.java添加的部门字段：

 1 package entity;
 2 
 3 public class Employee {
 4 
 5     private Integer id;
 6     private String lastName;
 7     private String email;
 8     private String gender;
 9     private Department dept;
10 
11     public Integer getId() {
12         return id;
13     }
14 
15     public void setId(Integer id) {
16         this.id = id;
17     }
18 
19     public String getLastName() {
20         return lastName;
21     }
22 
23     public void setLastName(String lastName) {
24         this.lastName = lastName;
25     }
26 
27     public String getEmail() {
28         return email;
29     }
30 
31     public void setEmail(String email) {
32         this.email = email;
33     }
34 
35     public String getGender() {
36         return gender;
37     }
38 
39     public void setGender(String gender) {
40         this.gender = gender;
41     }
42 
43     public Department getDept() {
44         return dept;
45     }
46 
47     public void setDept(Department dept) {
48         this.dept = dept;
49     }
50 
51     @Override
52     public String toString() {
53         return "Employee [id=" + id + ", lastName=" + lastName + ", email=" + email + ", gender=" + gender + ", dept="
54                 + dept + "]";
55     }
56 
57 }

添加了部门的实体类：

 1 package entity;
 2 
 3 import java.util.List;
 4 
 5 public class Department {
 6 
 7     private Integer id;
 8     private String departmentName;
 9     private List empList;
10 
11     public Integer getId() {
12         return id;
13     }
14 
15     public void setId(Integer id) {
16         this.id = id;
17     }
18 
19     public String getDepartmentName() {
20         return departmentName;
21     }
22 
23     public void setDepartmentName(String departmentName) {
24         this.departmentName = departmentName;
25     }
26 
27     public List getEmpList() {
28         return empList;
29     }
30 
31     public void setEmpList(List empList) {
32         this.empList = empList;
33     }
34 
35     @Override
36     public String toString() {
37         return "Department [id=" + id + ", departmentName=" + departmentName + "]";
38     }
39 
40 }

1.自定义java bean 封装规则的实例：

接口文件EmployeeMapper.java：

Employee testResultType(Integer id);

映射文件EmployeeMapper.xml:

 1 
 2     <resultMap type="entity.Employee" id="MyEmp">
 3         
 4         <id column="id" property="id" />
 5         
 6         <result column="last_name" property="lastName" />
 7         <result column="email" property="email" />
 8         <result column="gender" property="gender" />
 9     resultMap>
10 
11     <select id="testResultType" resultMap="MyEmp">
12         select
13         t01.* from
14         tbl_employee t01 where id=#{id}
15     select>

Junit测试类：

 1 @Test
 2     public void test01() {
 3         String resource = "mybatis-config.xml";
 4         SqlSession openSession = null;
 5         try {
 6             InputStream inputStream = Resources.getResourceAsStream(resource);
 7             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 8             // 获取openSession 不会自动提交数据
 9             openSession = sqlSessionFactory.openSession(true);
10             EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
11 
12             Employee testResultType = mapper.testResultType(1);
13             System.out.println("测试 stestResultType：" + testResultType);
14         } catch (Exception e) {
15             // TODO: handle exception
16         } finally {
17             if (openSession != null) {
18                 openSession.close();
19             }
20 
21         }
22     }

运行结果：

测试 stestResultType：Employee [id=1, lastName=joy33333, email=joy52112225@iclound.com, gender=女, dept=null]

2.关联查询级联属性封装：

接口文件EmployeeMapper.java：

1 package dao;
2 
3 import entity.Employee;
4 
5 public interface EmployeeMapper {
6 
7     Employee testResultType(Integer id);
8 
9 }

映射文件EmployeeMapper.xml

• type:自定义的java类型 id:唯一ID，方便引用

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 DOCTYPE mapper
 3   PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 4   "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 5 <mapper namespace="dao.EmployeeMapper">
 6 
 7 
 8     
 9     <resultMap type="entity.Employee" id="MyEmp">
10         
11         <id column="id" property="id" />
12         
13         <result column="last_name" property="lastName" />
14         <result column="email" property="email" />
15         <result column="gender" property="gender" />
16         <result column="d_id" property="dept.id" />
17         <result column="depart_name" property="dept.departmentName" />
18     resultMap>
19 
20     <select id="testResultType" resultMap="MyEmp">
21         select
22         t01.*,t02.depart_name from
23         tbl_employee t01 left join tbl_department
24         t02 on t01.d_id = t02.id where t01.id =#{id}
25     select>
26 mapper>

junit测试类：

 1 @Test
 2     public void test01() {
 3         String resource = "mybatis-config.xml";
 4         SqlSession openSession = null;
 5         try {
 6             InputStream inputStream = Resources.getResourceAsStream(resource);
 7             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 8             // 获取openSession 不会自动提交数据
 9             openSession = sqlSessionFactory.openSession(true);
10             EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
11 
12             Employee testResultType = mapper.testResultType(1);
13             System.out.println("测试 stestResultType：" + testResultType);
14         } catch (Exception e) {
15             // TODO: handle exception
16         } finally {
17             if (openSession != null) {
18                 openSession.close();
19             }
20 
21         }
22     }

运行测试结果：

测试 stestResultType：Employee [id=1, lastName=joy33333, email=joy52112225@iclound.com, gender=女, dept=Department [id=1, departmentName=开发部]]

3.关联查询association级联属性封装：

接口文件EmployeeMapper.java：

Employee testResultType2(Integer id);

映射文件EmployeeMapper.xml

• type:自定义的java类型 id:唯一ID，方便引用

 1 
 2     <resultMap type="entity.Employee" id="MyEmp2">
 3         
 4         <id column="id" property="id" />
 5         
 6         <result column="last_name" property="lastName" />
 7         <result column="email" property="email" />
 8         <result column="gender" property="gender" />
 9         
13         <association property="dept"
14             javaType="introduction.Department">
15             <result column="d_id" property="id" />
16             <result column="depart_name" property="departmentName" />
17         association>
18     resultMap>
19 
20     <select id="testResultType2" resultMap="MyEmp2">
21         select
22         t01.*,t02.depart_name from
23         tbl_employee t01 left join tbl_department
24         t02 on t01.d_id = t02.id where t01.id =#{id}
25     select>

junit测试类：

 1 @Test
 2     public void test02() {
 3         String resource = "mybatis-config.xml";
 4         SqlSession openSession = null;
 5         try {
 6             InputStream inputStream = Resources.getResourceAsStream(resource);
 7             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 8             // 获取openSession 不会自动提交数据
 9             openSession = sqlSessionFactory.openSession(true);
10             EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
11 
12             Employee testResultType = mapper.testResultType2(1);
13             System.out.println("测试 stestResultType：" + testResultType);
14         } catch (Exception e) {
15             // TODO: handle exception
16         } finally {
17             if (openSession != null) {
18                 openSession.close();
19             }
20 
21         }
22     }

运行结果：

测试 stestResultType：Employee [id=1, lastName=joy33333, email=joy52112225@iclound.com, gender=女, dept=Department [id=1, departmentName=开发部]]

 

4.关联查询association 分步查寻：

接口文件

EmployeeMapper.java：

Employee getEmpByIdStep(Integer id);

DepartmentMapper.java：

    Department getDepartmentById(Integer id);

映射文件EmployeeMapper.xml

• type:自定义的java类型 id:唯一ID，方便引用

 1 
 2     <resultMap type="entity.Employee" id="MyEmp3">
 3         
 4         <id column="id" property="id" />
 5         
 6         <result column="last_name" property="lastName" />
 7         <result column="email" property="email" />
 8         <result column="gender" property="gender" />
 9         
10         
15         <association property="dept" select="dao.DepartmentMapper.getDepartmentById" column="d_id">
16         association>
17     resultMap>
18     
19     <select id="getEmpByIdStep" resultMap="MyEmp3">
20         SELECT * FROM tbl_employee WHERE ID= #{id}
21     select>

DepartmentMapper.xml

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 DOCTYPE mapper
 3   PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 4   "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 5 <mapper namespace="dao.DepartmentMapper">
 6 
 7     <select id="getDepartmentById" resultType="entity.Department">
 8         SELECT id,depart_name as departmentName  FROM TBL_DEPARTMENT WHERE ID= #{id}
 9     select>
10 
11 mapper>

junit测试类：

 1 @Test
 2     public void test03() {
 3         String resource = "mybatis-config.xml";
 4         SqlSession openSession = null;
 5         try {
 6             InputStream inputStream = Resources.getResourceAsStream(resource);
 7             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 8             // 获取openSession 不会自动提交数据
 9             openSession = sqlSessionFactory.openSession(true);
10             EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
11 
12             Employee testResultType = mapper.getEmpByIdStep(1);
13             System.out.println("测试 分步：" + testResultType);
14         } catch (Exception e) {
15             // TODO: handle exception
16         } finally {
17             if (openSession != null) {
18                 openSession.close();
19             }
20 
21         }
22     }

运行结构：

测试 分步：Employee [id=1, lastName=joy33333, email=joy52112225@iclound.com, gender=女, dept=Department [id=1, departmentName=开发部]]

5.分步查询的懒加载说明

接着上面的运行结果，查看控制台查询了两条SQL：

此时，如果Junit测试只查询单条一条SQL中的数据，那么该分步查询只执行一条SQL

 1 @Test
 2     public void test04() {
 3         String resource = "mybatis-config.xml";
 4         SqlSession openSession = null;
 5         try {
 6             InputStream inputStream = Resources.getResourceAsStream(resource);
 7             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 8             // 获取openSession 不会自动提交数据
 9             openSession = sqlSessionFactory.openSession(true);
10             EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
11 
12             Employee testResultType = mapper.getEmpByIdStep(1);
13             System.out.println("测试 分步 只查一条SQL：" + testResultType.getLastName());
14         } catch (Exception e) {
15             // TODO: handle exception
16         } finally {
17             if (openSession != null) {
18                 openSession.close();
19             }
20 
21         }
22     }

运行结果为：

测试 分步 只查一条SQL：joy33333

查看控制台日志：

6.关联查询 collection定义关联封装规则：

需求：查询部门下所有的员工；所有员工放入 list中；即 部门对象中 把部门信息放入对应的字段，把该部门下的员工放入list中；

接口文件DepartmentMapper.java：

    Department getDepartmentByIdPlus(Integer id);

映射文件DepartmentMapper.xml

• type:自定义的java类型 id:唯一ID，方便引用

 1 
 2 
 3     <resultMap type="entity.Department" id="MyDept">
 4         <id column="id" property="id" />
 5         <result column="depart_name" property="departmentName" />
 6         
 7         <collection property="empList"
 8             ofType="entity.Employee">
 9             <id column="eid" property="id" />
10             <result column="last_name" property="lastName" />
11             <result column="gender" property="gender" />
12             <result column="email" property="email" />
13         collection>
14 
15     resultMap>
16     <select id="getDepartmentByIdPlus" resultMap="MyDept">
17         SELECT
18         T01.id,
19         T01.depart_name,
20         T02.id eid,
21         T02.last_name,
22         T02.gender,
23         T02.email
24         FROM
25         TBL_DEPARTMENT t01
26         LEFT JOIN tbl_employee T02 ON T01.ID = T02.D_ID
27         WHERE
28         T01.ID = #{id}
29     select>

junit测试类：

 1 @Test
 2     public void test05() {
 3         String resource = "mybatis-config.xml";
 4         SqlSession openSession = null;
 5         try {
 6             InputStream inputStream = Resources.getResourceAsStream(resource);
 7             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 8             // 获取openSession 不会自动提交数据
 9             openSession = sqlSessionFactory.openSession(true);
10             DepartmentMapper mapper = openSession.getMapper(DepartmentMapper.class);
11 
12             Department testResultType = mapper.getDepartmentByIdPlus(1);
13             System.out.println("测试 bean中的列表查询：" + testResultType);// 显示 一个部门信息
14             System.out.println("测试 bean中的列表查询：" + testResultType.getEmpList());// 部门下的所有员工
15         } catch (Exception e) {
16             // TODO: handle exception
17         } finally {
18             if (openSession != null) {
19                 openSession.close();
20             }
21 
22         }
23     }

运行结果：

测试 bean中的列表查询：Department [id=1, departmentName=开发部]

测试 bean中的列表查询：[Employee [id=1, lastName=joy33333, email=joy52112225@iclound.com, gender=女, dept=null], Employee [id=5, lastName=joy, email=joy521125@iclound.com, gender=女, dept=null]]

7.关联查询 collection 分步查询：

同理可以实现懒加载，这里不赘述了；

接口文件EmployeeMapper.java：

    List getListByDid(Integer id);

接口文件DepartmentMapper.java：

Department getDepartmentByIdStep(Integer id);

映射文件EmployeeMapper.xml

• type:自定义的java类型 id:唯一ID，方便引用

<select id="getListByDid" resultType="entity.Employee">
SELECT * FROM tbl_employee WHERE D_ID= #{id}
select>

映射文件DepartmentMapper.xml

 1 
 2 
 3     <resultMap type="entity.Department" id="MyDept2">
 4         <id column="id" property="id" />
 5         <result column="depart_name" property="departmentName" />
 6         
 7         <collection property="empList"
 8             ofType="entity.Employee"
 9             select="dao.EmployeeMapper.getListByDid" column="{id=id}">
10         collection>
11 
12     resultMap>
13     <select id="getDepartmentByIdStep" resultMap="MyDept2">
14         SELECT
15         T01.id,
16         T01.depart_name
17 
18         FROM
19         TBL_DEPARTMENT t01
20         WHERE
21         T01.ID = #{id}
22     select>

junit测试类：

 1 @Test
 2     public void test06() {
 3         String resource = "mybatis-config.xml";
 4         SqlSession openSession = null;
 5         try {
 6             InputStream inputStream = Resources.getResourceAsStream(resource);
 7             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 8             // 获取openSession 不会自动提交数据
 9             openSession = sqlSessionFactory.openSession(true);
10             DepartmentMapper mapper = openSession.getMapper(DepartmentMapper.class);
11 
12             Department testResultType = mapper.getDepartmentByIdStep(1);
13             System.out.println("测试 bean中的列表查询：" + testResultType.getDepartmentName());// 显示 一个部门信息
14         } catch (Exception e) {
15             // TODO: handle exception
16         } finally {
17             if (openSession != null) {
18                 openSession.close();
19             }
20 
21         }
22     }

运行结果：

测试 bean中的列表查询：开发部；

扩展内容：

多列值的传递； 将多列的值封装map传递 column={key1=column1,key2=column}; key为 目标xml中的占位符的名称；即 

SELECT * FROM tbl_employee WHERE D_ID= #{id}；id 其他属性： fetchType="lazy":表示延迟加载； 

按需加载 eager：表示立即  

select="dao.EmployeeMapper.getListByDid" column="{did=id}"> 

8.鉴别器：

说明：mybatis可以使用discriminator 判断某列的值，然后根据某列的值改变封装行为；

 

接口文件EmployeeMapper.java：

    Employee getEmpByIdStepDis(Integer id);

映射文件EmployeeMapper.xml

• type:自定义的java类型 id:唯一ID，方便引用

 1 <resultMap type="entity.Employee" id="MyEmpDis">
 2         <id column="id" property="id" />
 3         <result column="last_name" property="lastName" />
 4         <result column="email" property="email" />
 5         <result column="gender" property="gender" />
 6         <discriminator javaType="string" column="gender">
 7             <case value="女" resultType="entity.Employee">
 8                     <association property="dept" select="dao.DepartmentMapper.getDepartmentById" column="d_id">
 9                 association>
10             case>
11             <case value="男" resultType="entity.Employee">
12                     <id column="id" property="id"/>
13                     <result column="last_name" property="email" />
14                     <result column="email" property="lastName" />
15                     <result column="gender" property="gender" />
16             case>
17         discriminator>
24     resultMap>
25     
26     <select id="getEmpByIdStepDis" resultMap="MyEmpDis">
27         SELECT * FROM tbl_employee WHERE ID= #{id}
28     select>
29 mapper>

DepartmentMapper.xml:

1 <select id="getDepartmentById"
2         resultType="entity.Department">
3         SELECT id,depart_name as departmentName FROM TBL_DEPARTMENT WHERE ID= #{id}
4     select>

junit测试类：

 1 @Test
 2     public void test07() {
 3         String resource = "mybatis-config.xml";
 4         SqlSession openSession = null;
 5         try {
 6             InputStream inputStream = Resources.getResourceAsStream(resource);
 7             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 8             // 获取openSession 不会自动提交数据
 9             openSession = sqlSessionFactory.openSession(true);
10             EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
11 
12             Employee testResultType = mapper.getEmpByIdStepDis(2);
13             System.out.println("测试 bean中的列表查询：" + testResultType);
14         } catch (Exception e) {
15             // TODO: handle exception
16         } finally {
17             if (openSession != null) {
18                 openSession.close();
19             }
20 
21         }
22     }

运行结果：

测试 bean中的列表查询：

测试 bean中的列表查询：Employee [id=2, lastName=joy52112225@iclound.com, email=joy2x22222, gender=男, dept=null]

如果把数据中该条记录性别改为“女”：

测试 bean中的列表查询：

测试 bean中的列表查询：Employee [id=2, lastName=joy2x22222, email=joy52112225@iclound.com, gender=女, dept=Department [id=2, departmentName=测试部]]