MyBatis多對多映射查詢 Day12 2018-11-30

7 <collection>一對多查詢

<collection>元素的解釋:

column 表示當前查詢數據庫表的列名DEPARTMENT_ID
property 表示返回類型PhoneUserIdAndDepartment屬性名department
javaType 表示該屬性對于的類型名稱，本例是一個ArrayList集合
select 表示執行的查詢語句，將查詢到的數據封裝到property所代表的類型對象當中
ofType 表示集合當中的類型

7.1 基本應用

7.1.1 java bean

同 6.1.1

7.1.2 映射文件

<mapper namespace="com.zhougl.web.dao.WebClassDao">
    <resultMap id="WebClassMap"
        type="com.zhougl.web.beans.WebClass">
        <id column="ID" jdbcType="DECIMAL" property="id" />
        <result column="CODE" jdbcType="VARCHAR" property="code" />
        <result column="NAME" jdbcType="VARCHAR" property="name" />
        <!-- 一對多 -->
        <collection property="students" column="id"
            javaType="ArrayList" ofType="com.zhougl.web.beans.Student"
            select="selectStudentByClassId"
            fetchType="lazy" />
    </resultMap>
    
    <select id="selectStudentByClassId" parameterType="int" resultType="com.zhougl.web.beans.Student">
    select * from STUDENT  where class_id = #{classId,jdbcType=DECIMAL}
  </select>
  <select id="selectClass" parameterType="int" resultMap="WebClassMap">
    select * from WEB_CLASS
  </select>

</mapper>

7.1.3 測試代碼

SqlSession session = SqlSessionFactoryUtil.getSession();
        List<WebClass> classes = session.selectList("com.zhougl.web.dao.WebClassDao.selectClass");
        classes.forEach(classe ->{
            System.out.println(classe);
            List<Student> students = classe.getStudents();
            students.forEach(student -> System.out.println(student));
        });
        session.commit();
        session.close();

結果

==>  Preparing: select * from WEB_CLASS 
==> Parameters: 
<==      Total: 2
==>  Preparing: select * from STUDENT where class_id = ? 
==> Parameters: 2(Integer)
<==      Total: 2
WebClass [id=2, code=C002, name=無限流戰斗班]
Student [id=2, name=王怡, sex=女, age=24]
Student [id=4, name=王多燕, sex=女, age=26]
==>  Preparing: select * from STUDENT where class_id = ? 
==> Parameters: 1(Integer)
<==      Total: 2
WebClass [id=1, code=C001, name=大亂斗指導班]
Student [id=1, name=王一倩, sex=女, age=22]
Student [id=3, name=王二贊, sex=男, age=28]

7.2 一對多映射

7.2.1 mybatis配置

mybatis-config.xml添加如下配置

<settings>
    <!-- 延遲加載的全局開關 -->
    <setting name="lazyLoadingEnabled" value="true"/>
    <!-- true 使帶有延遲加載的屬性對象立即加載 ，false-按需加載-->
    <setting name="aggressiveLazyLoading" value="false"/>
</settings>

7.2.2 java bean

同 6.1.1

7.2.3 mapper映射文件

WebClassMapper.xml

<mapper namespace="com.zhougl.web.dao.mapper.WebClassMapper">
    <resultMap id="WebClassMap"
        type="com.zhougl.web.beans.WebClass">
        <id column="ID" jdbcType="DECIMAL" property="id" />
        <result column="CODE" jdbcType="VARCHAR" property="code" />
        <result column="NAME" jdbcType="VARCHAR" property="name" />
        <!-- 一對多 -->
        <collection property="students" column="id"
            javaType="ArrayList" ofType="com.zhougl.web.beans.Student"
            select="com.zhougl.web.dao.mapper.StudentMapper.selectStudentByClassId"
            fetchType="lazy" >
            <id column="ID" jdbcType="DECIMAL" property="id" />
            <result column="NAME" jdbcType="VARCHAR" property="name" />
            <result column="SEX" jdbcType="VARCHAR" property="sex" />
            <result column="AGE" jdbcType="DECIMAL" property="age" />
        </collection>
    </resultMap>

    <sql id="Base_Column_List">
        ID, CODE, NAME
    </sql>
    <select id="selectWebClassById"
        parameterType="int" resultMap="WebClassMap">
        select
        <include refid="Base_Column_List" />
        from WEB_CLASS
        where ID = #{id,jdbcType=DECIMAL}
    </select>

</mapper>

7.2.4 mapper接口

WebClassMapper.xml

public interface WebClassMapper {
  
    WebClass selectWebClassById(int i);
}

7.2.5 測試類

public class OneToManyTest {

    public static void main(String[] args) {
        SqlSession session = SqlSessionFactoryUtil.getSession();
        OneToManyTest test = new OneToManyTest();
        //測試一對多
        test.testOneToMany(session);
        
        //測試多對一
        //test.testManyToOne(session);
        session.commit();
        session.close();

    }
    //測試一對多，查詢班級（一）級聯查詢學生（多）
    public void testOneToMany(SqlSession session) {
        WebClassMapper mapper = session.getMapper(WebClassMapper.class);
        WebClass webClass = mapper.selectWebClassById(1);
        System.out.println(webClass.getId()+" "+webClass.getCode()+" "+webClass.getName());
        System.out.println(webClass.toString());
        List<Student> students = webClass.getStudents();
        for (Student student : students) {
            System.out.println(student.toString());
        }
    }

}

==>  Preparing: select ID, CODE, NAME from WEB_CLASS where ID = ? 
==> Parameters: 1(Integer)
<==      Total: 1
1 C001 大亂斗指導班
==>  Preparing: select ID as studentId, NAME as studentName, SEX, AGE, CLASS_ID from STUDENT where CLASS_ID = ? 
==> Parameters: 1(Integer)
<==      Total: 4
WebClass [id=1, code=C001, name=大亂斗指導班]
Student [id=1, name=王一倩, sex=女, age=22]
Student [id=2, name=王怡, sex=女, age=24]
Student [id=3, name=王二贊, sex=男, age=28]
Student [id=4, name=王多燕, sex=女, age=26]

7.3 多對一映射

7.3.1 java bean

同 6.1.1

7.3.2 mapper配置

StudentMapper.xml

<mapper namespace="com.zhougl.web.dao.mapper.StudentMapper">
  <resultMap id="StudentMap" type="com.zhougl.web.beans.Student">
    <id column="studentId" jdbcType="DECIMAL" property="id" />
    <result column="studentName" jdbcType="VARCHAR" property="name" />
    <result column="SEX" jdbcType="VARCHAR" property="sex" />
    <result column="AGE" jdbcType="DECIMAL" property="age" />
    <!-- 多對一 -->
    <association property="webClass" javaType="com.zhougl.web.beans.WebClass">
        <id column="ID" jdbcType="DECIMAL" property="id" />
        <result column="CODE" jdbcType="VARCHAR" property="code" />
        <result column="NAME" jdbcType="VARCHAR" property="name" />
    </association>
  </resultMap>
 
  <sql id="Base_Column_List">
    ID as studentId, NAME as studentName, SEX, AGE, CLASS_ID
  </sql>
  <sql id="student_List">
    ${student}.ID as studentId, ${student}.NAME as studentName, ${student}.SEX, ${student}.AGE, ${student}.CLASS_ID
  </sql>
  <sql id="Web_Class_Column_List">
        ${webClass}.ID , ${webClass}.CODE, ${webClass}.NAME 
  </sql>
 <!-- 多表連接 -->
 <!-- 查出來的列同名時需要使用別名區分 -->
  <select id="selectStudentById" parameterType="int" resultMap="StudentMap">
    select 
    <include refid="student_List" >
        <property name="student" value="s"/>
    </include>,
    <include refid="Web_Class_Column_List" >
        <property name="webClass" value="c"/>
    </include>
    from STUDENT s,WEB_CLASS c
    where s.class_id=c.id and s.ID = #{id,jdbcType=DECIMAL}
  </select>
  <select id="selectStudentByClassId" parameterType="int" resultMap="StudentMap">
    select 
    <include refid="Base_Column_List" />
    from STUDENT
    where CLASS_ID = #{classId,jdbcType=DECIMAL}
  </select>
 
</mapper>

7.3.3 mapper接口

StudentMapper.java

public interface StudentMapper {
   
    Student selectStudentById(int id);
    List<Student> selectStudentByClassId(int classId);

}

7.3.4 測試類

public class OneToManyTest {
    //測試多對一，查詢學生（多）級聯查詢班級（一）
    public void testManyToOne(SqlSession session) {
        StudentMapper studentMapper = session.getMapper(StudentMapper.class);
        Student student = studentMapper.selectStudentById(1);
        System.out.println(student);
        System.out.println(student.getWebClass().toString());
    }

結果

==>  Preparing: select s.ID as studentId, s.NAME as studentName, s.SEX, s.AGE, s.CLASS_ID , c.ID , c.CODE, c.NAME from STUDENT s,WEB_CLASS c where s.class_id=c.id and s.ID = ? 
==> Parameters: 1(Integer)
<==      Total: 1
Student [id=1, name=王一倩, sex=女, age=22]
WebClass [id=1, code=C001, name=大亂斗指導班]

7.4 多對多映射

7.4.1 java bean

public class WebOrder {
    private BigDecimal id;
    private String code;
    private BigDecimal total;
    private BigDecimal userId;
    //訂單和用戶是多對一關系
    private WebUser user;
    //訂單和商品是多對多關系
    private List<WebArticle> articles;
}

public class WebUser {
    private BigDecimal id;
    private String username;
    private String loginname;
    private String password;
    private String phone;
    private String address;
    
    //用戶和訂單是一對多關系
    private List<WebOrder> orders;
}

public class WebArticle {
    private BigDecimal id;
    private String name;
    private BigDecimal price;
    private String remark;
}

7.4.2 mapper配置

WebOrderMapper.xml

<mapper namespace="com.zhougl.web.dao.mapper.WebOrderMapper">
  <resultMap id="BaseResultMap" type="com.zhougl.web.beans.WebOrder">
    <id column="oId" jdbcType="DECIMAL" property="id" />
    <result column="CODE" jdbcType="VARCHAR" property="code" />
    <result column="TOTAL" jdbcType="DECIMAL" property="total" />
    <!-- 多對一關聯 -->
    <association property="user" javaType="com.zhougl.web.beans.WebUser">
         <id column="ID" jdbcType="DECIMAL" property="id" />
        <result column="USERNAME" jdbcType="VARCHAR" property="username" />
        <result column="LOGINNAME" jdbcType="VARCHAR" property="loginname" />
        <result column="PASSWORD" jdbcType="VARCHAR" property="password" />
        <result column="PHONE" jdbcType="VARCHAR" property="phone" />
        <result column="ADDRESS" jdbcType="VARCHAR" property="address" />
    </association>
    <!-- 多對多關聯 -->
    <collection property="articles" javaType="ArrayList"
        column="oId" ofType="com.zhougl.web.beans.WebArticle"
        select="com.zhougl.web.dao.mapper.WebArticleMapper.selectArticleByOrderId"
        fetchType="lazy">
        <id column="ID" jdbcType="DECIMAL" property="id" />
        <result column="NAME" jdbcType="VARCHAR" property="name" />
        <result column="PRICE" jdbcType="DECIMAL" property="price" />
        <result column="REMARK" jdbcType="VARCHAR" property="remark" />
    </collection>
  </resultMap>
    <!-- 有同名列，需要使用別名 -->
  <select id="selectOrderById" parameterType="int" resultMap="BaseResultMap">
    select 
    o.ID as oId, o.CODE, o.TOTAL, u.*
    from WEB_ORDER o,WEB_USER u
    where o.user_id = u.id and o.ID = #{id,jdbcType=DECIMAL}
  </select>
  <select id="selectOrderByUserId" parameterType="int" resultType="com.zhougl.web.beans.WebOrder">
    select * from WEB_ORDER where user_id = #{userId,jdbcType=DECIMAL}
  </select>
</mapper>

<mapper namespace="com.zhougl.web.dao.mapper.WebUserMapper">
  <resultMap id="BaseResultMap" type="com.zhougl.web.beans.WebUser">
    <id column="ID" jdbcType="DECIMAL" property="id" />
    <result column="USERNAME" jdbcType="VARCHAR" property="username" />
    <result column="LOGINNAME" jdbcType="VARCHAR" property="loginname" />
    <result column="PASSWORD" jdbcType="VARCHAR" property="password" />
    <result column="PHONE" jdbcType="VARCHAR" property="phone" />
    <result column="ADDRESS" jdbcType="VARCHAR" property="address" />
    <!-- 一對多關聯 -->
    <collection property="orders" javaType="ArrayList" 
        ofType="com.zhougl.web.beans.WebOrder" 
        column="id" select="com.zhougl.web.dao.mapper.WebOrderMapper.selectOrderByUserId" 
        fetchType="lazy">
        <id column="ID" jdbcType="DECIMAL" property="id" />
        <result column="CODE" jdbcType="VARCHAR" property="code" />
        <result column="TOTAL" jdbcType="DECIMAL" property="total" />
    </collection>
  </resultMap>
 
  <sql id="Base_Column_List">
    ID, USERNAME, LOGINNAME, PASSWORD, PHONE, ADDRESS
  </sql>
 
  <select id="selectUserById" parameterType="int" resultMap="BaseResultMap">
    select 
    <include refid="Base_Column_List" />
    from WEB_USER
    where ID = #{id,jdbcType=DECIMAL}
  </select>
  
</mapper>

<mapper namespace="com.zhougl.web.dao.mapper.WebArticleMapper">
  <resultMap id="BaseResultMap" type="com.zhougl.web.beans.WebArticle">
    <id column="ID" jdbcType="DECIMAL" property="id" />
    <result column="NAME" jdbcType="VARCHAR" property="name" />
    <result column="PRICE" jdbcType="DECIMAL" property="price" />
    <result column="REMARK" jdbcType="VARCHAR" property="remark" />
  </resultMap>
  
  <sql id="Base_Column_List">
    ID, NAME, PRICE, REMARK
  </sql>
  
  <select id="selectArticleByOrderId" parameterType="int" resultMap="BaseResultMap">
    select 
    <include refid="Base_Column_List" />
    from WEB_ARTICLE where id in(
        select article_id from WEB_ITEM where order_id =#{orderId,jdbcType=DECIMAL}
    )
  </select>
  
</mapper>

7.4.3 mapper接口

public interface WebOrderMapper {
    List<WebOrder> selectOrderByUserId(int userId);
    WebOrder selectOrderById(int id); 
}
public interface WebUserMapper {
    WebUser selectUserById(int id);
}

7.4.4 測試類


public class ManyToManyTest {

    public static void main(String[] args) {
        SqlSession session = SqlSessionFactoryUtil.getSession();
        ManyToManyTest test = new ManyToManyTest();
        //test.testOneToMany(session);
        test.testManyToMany(session);
        session.commit();
        session.close();
    }
    public void testOneToMany(SqlSession session) {
        WebUserMapper userMapper = session.getMapper(WebUserMapper.class);
        WebUser user = userMapper.selectUserById(1);
        System.out.println(user.getUsername()+" "+user.getLoginname()+" "+user.getPhone()+" "+user.getAddress());
        List<WebOrder> orders = user.getOrders();
        for (WebOrder webOrder : orders) {
            System.out.println(webOrder.toString());
        }
    }
    public void testManyToMany(SqlSession session) {
        WebOrderMapper orderMapper = session.getMapper(WebOrderMapper.class);
        WebOrder order = orderMapper.selectOrderById(1);
        System.out.println(order.getCode()+" "+order.getTotal());
        WebUser user = order.getUser();
        System.out.println(user.toString());
        List<WebArticle> articles = order.getArticles();
        for (WebArticle webArticle : articles) {
            System.out.println(webArticle.toString());
        }
    }
}

最后編輯于：2018.12.03 22:18:09

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MyBatis多對多映射查詢 Day12 2018-11-30

MyBatis多對多映射查詢 Day12 2018-11-30

7 <collection>一對多查詢

7.1 基本應用

7.1.1 java bean

7.1.2 映射文件

7.1.3 測試代碼

7.2 一對多映射

7.2.1 mybatis配置

7.2.2 java bean

7.2.3 mapper映射文件

7.2.4 mapper接口

7.2.5 測試類

7.3 多對一映射

7.3.1 java bean

7.3.3 mapper接口

7.3.4 測試類

7.4 多對多映射

7.4.1 java bean

7.4.2 mapper配置

7.4.3 mapper接口

7.4.4 測試類

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MyBatis多對多映射查詢 Day12 2018-11-30

7 <collection>一對多查詢

7.1 基本應用

7.1.1 java bean

7.1.2 映射文件

7.1.3 測試代碼

7.2 一對多映射

7.2.1 mybatis配置

7.2.2 java bean

7.2.3 mapper映射文件

7.2.4 mapper接口

7.2.5 測試類

7.3 多對一映射

7.3.1 java bean

7.3.3 mapper接口

7.3.4 測試類

7.4 多對多映射

7.4.1 java bean

7.4.2 mapper配置

7.4.3 mapper接口

7.4.4 測試類

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