Mybatis 一對多延遲載入，並且子查詢中與主表欄位不對應 （19）

東北大亨發表於2021-10-20
MyBatis

Mybatis  一對多延遲載入，並且子查詢中與主表欄位不對應應用說明。

實現一對多關聯（懶載入），一個教研組對應多個教師，既：教師的教研編號與教研組的教研編號關聯，並且教師關聯教研組外來鍵與教研組編號不一致。

1、工程資源配置檔案

   1）、本應用實際應用到了（開啟延遲載入配置、關閉立即載入配置）；

   2） 、外關聯查詢語句對應xml檔案 :<mapper resource="com/mybatis03/mapper/teacherGroupToTeacherMapper.xml"/>

   3）、主查詢xml文件：<mapper resource="com/mybatis03/mapper/TeacherMapper.xml"/>

<?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">
<configuration>

    <settings>
        <!-- 開啟日誌，並制定使用的具體日誌,LOG4J 對應 log4j.properties的檔名 -->
        <setting name="logImpl" value="LOG4J"/>
        <!-- 開啟延遲載入 -->
        <setting name="lazyLoadingEnabled" value="true"/>
        <!-- g關閉立即載入 -->
        <setting name="aggressiveLazyLoading" value="false"/>
    </settings>
    <!-- 轉換器 -->
    <typeHandlers>
        <!-- 把java類的boolean型別轉換資料 int，資料庫int轉換為java類的boolean型別 -->
        <typeHandler handler="com.mybatis03.util.BooleanAndIntConverter" javaType="Boolean" jdbcType="INTEGER"/>
    </typeHandlers>
    <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/mybatis01"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <!-- 載入對映檔案 -->
        <mapper resource="com/mybatis03/mapper/personMapper.xml"/>
        <mapper resource="com/mybatis03/mapper/TeacherMapper.xml"/>
        <mapper resource="com/mybatis03/mapper/teacherCourseMapper.xml"/>
        <!-- 外關聯查詢語句對應xml檔案 -->
        <mapper resource="com/mybatis03/mapper/teacherGroupToTeacherMapper.xml"/>
    </mappers>
</configuration>

2、mapper檔案

2.1 教師.xml 檔案

<?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.mybatis03.mapper.TeacherMapper">
    <!-- 實現一對多關聯（懶載入），一個教研組對應多個教師，既：教師的教研編號與教研組的教研編號關聯  -->
    <select id="queryWithLazyGroupAndTeachers"  parameterType="int" resultMap="lazyGroupTeacherMap">
        SELECT g.*,g.groupID AS groupno FROM teachergroup g
        WHERE g.groupid =#{groupid}
    </select>
    <!--類和表對應關係 (一對多都用collection，一對一用 association) -->
    <resultMap id="lazyGroupTeacherMap" type="com.mybatis03.bean.TeacherGroup">
        <!-- 因為type主類是TeacherGroup，所以先配置 TeacherGroup類屬性對應關係 -->
        <id property="groupID" column="groupid" />
        <result property="groupName" column="groupname"/>
        <!-- 配置成員屬性教師 ,一對多；屬性型別：javaType,屬性元素型別 ofType-->
        <!--property 中的屬性為實體類中的屬性，column對應資料庫中的欄位 -->
        <collection property="teacherList" ofType="com.mybatis03.bean.Teacher"
         select="com.mybatis03.mapper.teacherGroupToTeacherMapper.queryGroupToTeacherByNO" column="groupno" >
        </collection>
    </resultMap>
</mapper>

說明：由於在關聯過程中，教研組編號與教師編號不一致，通過重新命名方式使。關聯欄位一致：

A、本應用實現懶載入使用原始SQL關聯查詢應為：SELECT g.*,t.* FROM teachergroup g  INNER JOIN teacher t  ON g.groupid = t.groupno  WHERE g.groupid =#{groupid}

B、應用懶載入實現說明解決欄位不一致參加紅色浪線；

 2.2 外關聯查詢教師資訊xml檔案

<?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">
<!--指定為介面的全類名-->
<mapper namespace="com.mybatis03.mapper.teacherGroupToTeacherMapper">
    <!-- 查詢教師，延遲載入應用此配置檔案 -->
    <!-- 查詢教師對應的課程 -->
    <select id="queryGroupToTeacherByNO" parameterType="int" resultType="com.mybatis03.bean.Teacher">
        SELECT * FROM teacher WHERE groupno = #{groupno}
    </select>
</mapper>

3、教師介面類

public interface TeacherMapper {
    /* 實現一對多關聯(延遲載入)，一個教研組對應多個教師，既：教師的教研編號與教研組的教研編號關聯  */
    TeacherGroup queryWithLazyGroupAndTeachers(int groupNo);
}

4、實體類

4.1 教師實體類

public class Teacher {
    @Override
    public String toString() {
        return "Teacher{" +
                "teaNo=" + teaNo +
                ", courseNo=" + courseNo +
                ", teaName='" + teaName + '\'' +
                ", teacherCourse{" +

                "courseNo=" + teacherCourse.getCourseNo() +
                ", courseName=" + teacherCourse.getCourseName() +"}"+

                '}';
    }


    /* 教師編號 */
    private int teaNo;
    /* 課程編號 */
    private int courseNo;
    /* 教師名稱 */
    private String teaName;

    /* 教師課程類,課程作為老師屬性 */
    private TeacherCourse teacherCourse;

    /* 新增一個教研組編號，用於關聯教研組編號，實現多對一關聯*/
    private int  groupNo;

    /**
     *  <!--利用resultMap實現一對一 -->
     * @return
     */
    public TeacherCourse getTeacherCourse() {
        return teacherCourse;
    }

    public void setTeacherCourse(TeacherCourse teacherCourse) {
        this.teacherCourse = teacherCourse;
    }

    public int getGroupNo() {
        return groupNo;
    }

    public void setGroupNo(int groupNo) {
        this.groupNo = groupNo;
    }

    public int getCourseNo() {
        return courseNo;
    }

    public void setCourseNo(int courseNo) {
        this.courseNo = courseNo;
    }

    public int getTeaNo() {
        return teaNo;
    }

    public void setTeaNo(int teaNo) {
        this.teaNo = teaNo;
    }

    public String getTeaName() {
        return teaName;
    }

    public void setTeaName(String teaName) {
        this.teaName = teaName;
    }
}

4.2 教研組實體類

 1 public class TeacherGroup {
 2     @Override
 3     public String toString() {
 4 
 5         String str = "";
 6         for (int i = 0; i < teacherList.size(); i++) {
 7 
 8             str += "teaNo=" + teacherList.get(i).getTeaNo() + ",";
 9             str += "courseNo=" + teacherList.get(i).getCourseNo() + ",";
10             str += "teaName=" + teacherList.get(i).getTeaName() + ",";
11             str += "groupNo=" + teacherList.get(i).getGroupNo();
12             if (i < teacherList.size() - 1) {
13                 str += ",";
14             }
15 
16         }
17         return "TeacherGroup{" +
18                 "groupID=" + groupID +
19                 ", groupName='" + groupName + '\'' +
20                 ", teacherList{" +
21 //                "teaNo=" + teacherList.get(0).getTeaNo() + "," +
22 //                "courseNo=" + teacherList.get(0).getCourseNo() + "," +
23 //                "teaName=" + teacherList.get(0).getTeaName() + "," +
24 //                "groupNo=" + teacherList.get(0).getGroupNo() + "," +
25                     str+
26                 "}" +
27                 '}';
28     }
29 
30 
31     /* 教研組編號：漢語教研組 1，英語教研組2，日語教研組3，德語教研組 4 */
32     /* 教研組編號，用於關聯教師編號，實現多對一關聯*/
33     private int groupID;
34 
35     /* 教研組名稱，英語教研組，日語教研組還是德語教研組*/
36     private String groupName;
37 
38     /* 一個教研組對應多個教師,屬於一對多關係。關聯關係：教師的教研編號與教研組的教研編號關聯 */
39     private List<Teacher> teacherList;
40 
41     public List<Teacher> getTeacherList() {
42         return teacherList;
43     }
44 
45     public void setTeacherList(List<Teacher> teacherList) {
46         this.teacherList = teacherList;
47     }
48 
49     public int getGroupID() {
50         return groupID;
51     }
52 
53     public void setGroupID(int groupID) {
54         this.groupID = groupID;
55     }
56 
57     public String getGroupName() {
58         return groupName;
59     }
60 
61     public void setGroupName(String groupName) {
62         this.groupName = groupName;
63     }
64 }

5、測試類

 1     @Test
 2     public void queryWithLazyGroupAndTeachers() throws Exception {
 3         Reader reader = Resources.getResourceAsReader("mybatis-03.xml");
 4         SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
 5 
 6         SqlSession session = sessionFactory.openSession();
 7         int groupNo = 1;
 8         TeacherMapper personMapper = session.getMapper(TeacherMapper.class);
 9         TeacherGroup teacherGroup = personMapper.queryWithLazyGroupAndTeachers(groupNo);
10         System.out.println("教研組編號:"+teacherGroup.getGroupID()+",教研組名稱:"+teacherGroup.getGroupName());
11         List<Teacher> teacherList = teacherGroup.getTeacherList();
12         for (Teacher teacher : teacherList) {
13             System.out.println("教師編號:"+teacher.getTeaNo()+",教師名稱:"
14                     +teacher.getTeaName()+",教研組編號:"+teacher.getGroupNo());
15         }
16     }

測試結果

"C:\Program Files\Java\jdk1.8.0_25\bin\java" -ea -Didea.test.cyclic.buffer.size=1048576 "-javaagent:C:\Users\newsoft\AppData\Roaming\JetBrains\IntelliJ IDEA 2017.3.5\lib\idea_rt.jar=1031:C:\Users\newsoft\AppData\Roaming\JetBrains\IntelliJ IDEA 2017.3.5\bin" -Dfile.encoding=UTF-8 -classpath "C:\Users\newsoft\AppData\Roaming\JetBrains\IntelliJ IDEA 2017.3.5\lib\idea_rt.jar;C:\Users\newsoft\AppData\Roaming\JetBrains\IntelliJ IDEA 2017.3.5\plugins\junit\lib\junit-rt.jar;C:\Users\newsoft\AppData\Roaming\JetBrains\IntelliJ IDEA 2017.3.5\plugins\junit\lib\junit5-rt.jar;D:\download\lib\mavenTollTransfer\mic-repository\org\junit\platform\junit-platform-launcher\1.5.2\junit-platform-launcher-1.5.2.jar;D:\download\lib\mavenTollTransfer\mic-repository\org\apiguardian\apiguardian-api\1.1.0\apiguardian-api-1.1.0.jar;D:\download\lib\mavenTollTransfer\mic-repository\org\junit\platform\junit-platform-engine\1.5.2\junit-platform-engine-1.5.2.jar;D:\download\lib\mavenTollTransfer\mic-repository\org\opentest4j\opentest4j\1.2.0\opentest4j-1.2.0.jar;D:\download\lib\mavenTollTransfer\mic-repository\org\junit\platform\junit-platform-commons\1.5.2\junit-platform-commons-1.5.2.jar;D:\download\lib\mavenTollTransfer\mic-repository\org\junit\jupiter\junit-jupiter-engine\5.5.2\junit-jupiter-engine-5.5.2.jar;D:\download\lib\mavenTollTransfer\mic-repository\org\junit\jupiter\junit-jupiter-api\5.5.2\junit-jupiter-api-5.5.2.jar;D:\download\lib\mavenTollTransfer\mic-repository\org\junit\vintage\junit-vintage-engine\5.5.2\junit-vintage-engine-5.5.2.jar;D:\download\lib\mavenTollTransfer\mic-repository\junit\junit\4.12\junit-4.12.jar;D:\download\lib\mavenTollTransfer\mic-repository\org\hamcrest\hamcrest-core\1.3\hamcrest-core-1.3.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\rt.jar;D:\ideaworkspace\ProjectStudy\mybatis-02\target\classes;D:\download\lib\mavenTollTransfer\mic-repository\org\hamcrest\hamcrest-core\2.1\hamcrest-core-2.1.jar;D:\download\lib\mavenTollTransfer\mic-repository\org\hamcrest\hamcrest\2.1\hamcrest-2.1.jar;D:\download\lib\mavenTollTransfer\mic-repository\org\mybatis\mybatis\3.4.5\mybatis-3.4.5.jar;D:\download\lib\mavenTollTransfer\mic-repository\mysql\mysql-connector-java\5.1.44\mysql-connector-java-5.1.44.jar;D:\download\lib\mavenTollTransfer\mic-repository\log4j\log4j\1.2.17\log4j-1.2.17.jar;D:\download\lib\mavenTollTransfer\mic-repository\org\slf4j\slf4j-log4j12\1.7.12\slf4j-log4j12-1.7.12.jar;D:\download\lib\mavenTollTransfer\mic-repository\org\slf4j\slf4j-api\1.7.30\slf4j-api-1.7.30.jar;D:\download\lib\mavenTollTransfer\mic-repository\cglib\cglib\3.3.0\cglib-3.3.0.jar;D:\download\lib\mavenTollTransfer\mic-repository\org\ow2\asm\asm\7.1\asm-7.1.jar;D:\download\lib\mavenTollTransfer\mic-repository\net\logstash\logback\logstash-logback-encoder\5.3\logstash-logback-encoder-5.3.jar;D:\download\lib\mavenTollTransfer\mic-repository\com\fasterxml\jackson\core\jackson-databind\2.10.3\jackson-databind-2.10.3.jar;D:\download\lib\mavenTollTransfer\mic-repository\com\fasterxml\jackson\core\jackson-annotations\2.10.3\jackson-annotations-2.10.3.jar;D:\download\lib\mavenTollTransfer\mic-repository\com\fasterxml\jackson\core\jackson-core\2.10.3\jackson-core-2.10.3.jar" com.intellij.rt.execution.junit.JUnitStarter -ideVersion5 -junit5 com.mybatis03.test.testTeacher01,queryWithLazyGroupAndTeachers
[lsjSso]2021-10-20 09:17:47,649-org.apache.ibatis.logging.LogFactory-0   [main]DEBUGorg.apache.ibatis.logging.LogFactory-Logging initialized using 'class org.apache.ibatis.logging.slf4j.Slf4jImpl' adapter.
[lsjSso]2021-10-20 09:17:47,753-org.apache.ibatis.logging.LogFactory-104 [main]DEBUGorg.apache.ibatis.logging.LogFactory-Logging initialized using 'class org.apache.ibatis.logging.log4j.Log4jImpl' adapter.
[lsjSso]2021-10-20 09:17:47,781-org.apache.ibatis.datasource.pooled.PooledDataSource-132 [main]DEBUGorg.apache.ibatis.datasource.pooled.PooledDataSource-PooledDataSource forcefully closed/removed all connections.
[lsjSso]2021-10-20 09:17:47,781-org.apache.ibatis.datasource.pooled.PooledDataSource-132 [main]DEBUGorg.apache.ibatis.datasource.pooled.PooledDataSource-PooledDataSource forcefully closed/removed all connections.
[lsjSso]2021-10-20 09:17:47,781-org.apache.ibatis.datasource.pooled.PooledDataSource-132 [main]DEBUGorg.apache.ibatis.datasource.pooled.PooledDataSource-PooledDataSource forcefully closed/removed all connections.
[lsjSso]2021-10-20 09:17:47,782-org.apache.ibatis.datasource.pooled.PooledDataSource-133 [main]DEBUGorg.apache.ibatis.datasource.pooled.PooledDataSource-PooledDataSource forcefully closed/removed all connections.
[lsjSso]2021-10-20 09:17:47,953-org.apache.ibatis.transaction.jdbc.JdbcTransaction-304 [main]DEBUGorg.apache.ibatis.transaction.jdbc.JdbcTransaction-Opening JDBC Connection
[lsjSso]2021-10-20 09:17:48,174-org.apache.ibatis.datasource.pooled.PooledDataSource-525 [main]DEBUGorg.apache.ibatis.datasource.pooled.PooledDataSource-Created connection 16503286.
[lsjSso]2021-10-20 09:17:48,174-org.apache.ibatis.transaction.jdbc.JdbcTransaction-525 [main]DEBUGorg.apache.ibatis.transaction.jdbc.JdbcTransaction-Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@fbd1f6]
[lsjSso]2021-10-20 09:17:48,177-com.mybatis03.mapper.TeacherMapper.queryWithLazyGroupAndTeachers-528 [main]DEBUGcom.mybatis03.mapper.TeacherMapper.queryWithLazyGroupAndTeachers-==>  Preparing: SELECT g.*,g.groupID AS groupno FROM teachergroup g WHERE g.groupid =? 
[lsjSso]2021-10-20 09:17:48,211-com.mybatis03.mapper.TeacherMapper.queryWithLazyGroupAndTeachers-562 [main]DEBUGcom.mybatis03.mapper.TeacherMapper.queryWithLazyGroupAndTeachers-==> Parameters: 1(Integer)
[lsjSso]2021-10-20 09:17:48,257-com.mybatis03.mapper.TeacherMapper.queryWithLazyGroupAndTeachers-608 [main]DEBUGcom.mybatis03.mapper.TeacherMapper.queryWithLazyGroupAndTeachers-<==      Total: 1
教研組編號:1,教研組名稱:chinese
[lsjSso]2021-10-20 09:17:48,258-com.mybatis03.mapper.teacherGroupToTeacherMapper.queryGroupToTeacherByNO-609 [main]DEBUGcom.mybatis03.mapper.teacherGroupToTeacherMapper.queryGroupToTeacherByNO-==>  Preparing: SELECT * FROM teacher WHERE groupno = ? 
[lsjSso]2021-10-20 09:17:48,258-com.mybatis03.mapper.teacherGroupToTeacherMapper.queryGroupToTeacherByNO-609 [main]DEBUGcom.mybatis03.mapper.teacherGroupToTeacherMapper.queryGroupToTeacherByNO-==> Parameters: 1(Integer)
[lsjSso]2021-10-20 09:17:48,261-com.mybatis03.mapper.teacherGroupToTeacherMapper.queryGroupToTeacherByNO-612 [main]DEBUGcom.mybatis03.mapper.teacherGroupToTeacherMapper.queryGroupToTeacherByNO-<==      Total: 2
教師編號:1001,教師名稱:sara,教研組編號:1
教師編號:1002,教師名稱:sakula,教研組編號:1

Process finished with exit code 0

說明：

 

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