Hibernate学习7—Hibernate 映射继承

Posted 2020-09-30 有点懒惰的大青年

需求：学生有很多照片，分为生活照和工作照；

第一节：每个具体类对应一个表　　　　　　　　　　　　　　　　　　　　　　　　

Student.java:

package com.cy.model;

import java.util.Set;

public class Student {
    private int id;
    private String name;
    private Set<Image> images;
    
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Set<Image> getImages() {
        return images;
    }
    public void setImages(Set<Image> images) {
        this.images = images;
    }
    
    
    
}

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抽象类Image.java:

package com.cy.model;

public abstract class Image {
    private int id;
    private String imageName;
    private Student student;
    
    
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getImageName() {
        return imageName;
    }
    public void setImageName(String imageName) {
        this.imageName = imageName;
    }
    public Student getStudent() {
        return student;
    }
    public void setStudent(Student student) {
        this.student = student;
    }
    
    
}

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生活照LifeImage.java:

package com.cy.model;

public class LifeImage extends Image{

}

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工作照WorkImage.java:

package com.cy.model;

public class WorkImage extends Image{

}

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Student.hbm.xml:

<hibernate-mapping package="com.cy.model">

    <class name="Student" table="t_student">
        <id name="id" column="stuId">
            <generator class="native"></generator>
        </id>
        <property name="name" column="stuName"></property>
    </class>

</hibernate-mapping>

LifeImage.hbm.xml:

<hibernate-mapping package="com.cy.model">

    <class name="LifeImage" table="t_lifeImage">
        <id name="id" column="lifeImageId">
            <generator class="native"></generator>
        </id>
        <property name="imageName" column="imageName"></property>
        
        <many-to-one name="student" column="stuId" class="com.cy.model.Student"></many-to-one>
    </class>

</hibernate-mapping>

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WorkImage.hbm.xml:

<hibernate-mapping package="com.cy.model">

    <class name="WorkImage" table="t_workImage">
        <id name="id" column="workImageId">
            <generator class="native"></generator>
        </id>
        <property name="imageName" column="imageName"></property>
        
        <many-to-one name="student" column="stuId" class="com.cy.model.Student"></many-to-one>
    </class>

</hibernate-mapping>

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测试代码StudentTest.java:

    @Test
    public void testGetAllImages(){
        List<Image> imageList = new ArrayList<Image>();
        int stuId = 1;
        List<Image> lifeImageList = (List<Image>)session.createQuery("from LifeImage l where l.student.id = " + stuId).list();
        imageList.addAll(lifeImageList);
        List<Image> workImageList = (List<Image>)session.createQuery("from WorkImage w where w.student.id = " + stuId).list();
        imageList.addAll(workImageList);
        for(Image image: imageList){
            System.out.println(image.getImageName());
        }
        
    }

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三个表的关联关系：

t_lifeimage表结构：

t_lifeimage表数据：

t_workimage表数据：

 

 

第二节：根类对应一个表　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

 Student2.java:

package com.cy.model;

import java.util.Set;

public class Student2 {
    private int id;
    private String name;
    private Set<Image2> images;
    
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Set<Image2> getImages() {
        return images;
    }
    public void setImages(Set<Image2> images) {
        this.images = images;
    }
    
    
    
}

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Image2.java:

package com.cy.model;

public class Image2 {
    private int id;
    private String imageType;
    private String imageName;
    private Student2 student;
    
    
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getImageName() {
        return imageName;
    }
    public void setImageName(String imageName) {
        this.imageName = imageName;
    }
    public Student2 getStudent() {
        return student;
    }
    public void setStudent(Student2 student) {
        this.student = student;
    }
    public String getImageType() {
        return imageType;
    }
    public void setImageType(String imageType) {
        this.imageType = imageType;
    }
    
    
}

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LifeImage2.java:

package com.cy.model;

public class LifeImage2 extends Image2{

}

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WorkImage2.java:

package com.cy.model;

public class WorkImage2 extends Image2{

}

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Student2.hbm.xml:

<hibernate-mapping package="com.cy.model">

    <class name="Student2" table="t_student2">
        <id name="id" column="stuId">
            <generator class="native"></generator>
        </id>
        <property name="name" column="stuName"></property>
        
        <set name="images">
            <key column="stuId"></key>
            <one-to-many class="com.cy.model.Image2"/>
        </set>
        
    </class>

</hibernate-mapping>

Image2.hbm.xml:

<hibernate-mapping package="com.cy.model">

    <class name="Image2" table="t_image2">
        <id name="id" column="imageId">
            <generator class="native"></generator>
        </id>

　　　　<!-- 用来区分是LifeImage2还是WorkImage2 -->
        <discriminator column="imageType" type="string"></discriminator> 
        <property name="imageName" column="imageName"></property>
        
        <many-to-one name="student" column="stuId" class="com.cy.model.Student2"></many-to-one>
        
        <subclass name="com.cy.model.LifeImage2" discriminator-value="life"></subclass>
        <subclass name="com.cy.model.WorkImage2" discriminator-value="work"></subclass>
    </class>

</hibernate-mapping>

hibernate.cfg.xml中只需加入两项映射配置就行了：

 <mapping resource="com/cy/model/Student2.hbm.xml"/>
 <mapping resource="com/cy/model/Image2.hbm.xml"/>

测试代码：

@Test
    public void testGetAllImages2(){
        Student2 s2 = (Student2) session.get(Student2.class, 1);
        Set<Image2> images = s2.getImages();
        Iterator<Image2> it = images.iterator();
        while(it.hasNext()){
            Image2 image = it.next();
            System.out.println(image.getImageName());
        }
    }

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生成的t_image2表结构：

 

 

第三节：每个类对应一个表　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

 Student3.java:

package com.cy.model;

import java.util.Set;

public class Student3 {
    private int id;
    private String name;
    private Set<Image3> images;
    
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Set<Image3> getImages() {
        return images;
    }
    public void setImages(Set<Image3> images) {
        this.images = images;
    }
    
    
    
}

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Image3.java:

package com.cy.model;

public class Image3 {
    private int id;
    private String imageName;
    private Student3 student;
    
    
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getImageName() {
        return imageName;
    }
    public void setImageName(String imageName) {
        this.imageName = imageName;
    }
    public Student3 getStudent() {
        return student;
    }
    public void setStudent(Student3 student) {
        this.student = student;
    }
    
    
}

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WorkImage3.java:

package com.cy.model;

public class WorkImage3 extends Image3{

}

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LifeImage3.java:

package com.cy.model;

public class LifeImage3 extends Image3{

}

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Student3.hbm.xml:

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.cy.model">

    <class name="Student3" table="t_student3">
        <id name="id" column="stuId">
            <generator class="native"></generator>
        </id>
        <property name="name" column="stuName"></property>
        
        <set name="images">
            <key column="stuId"></key>
            <one-to-many class="com.cy.model.Image3"/>
        </set>
        
    </class>

</hibernate-mapping>

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Image3.hbm.xml:

<hibernate-mapping package="com.cy.model">

    <class name="Image3" table="t_image3">
        <id name="id" column="imageId">
            <generator class="native"></generator>
        </id>
        <property name="imageName" column="imageName"></property>
        
        <many-to-one name="student" column="stuId" class="com.cy.model.Student3"></many-to-one>
        
        <joined-subclass name="com.cy.model.LifeImage3" table="t_lifeImage3">
            <key column="lifeImageId"></key>
        </joined-subclass>
        <joined-subclass name="com.cy.model.WorkImage3" table="t_workImage3">
            <key column="workImageId"></key>
        </joined-subclass>
    </class>

</hibernate-mapping>

hibernate.cfg.xml中加入如下映射关系：

 <mapping resource="com/cy/model/Student3.hbm.xml"/>
 <mapping resource="com/cy/model/Image3.hbm.xml"/>

测试代码：

@Test
    public void testGetAllImages3(){
        Student3 s3 = (Student3) session.get(Student3.class, 1);
        Set<Image3> images = s3.getImages();
        Iterator<Image3> it = images.iterator();
        while(it.hasNext()){
            Image3 image = it.next();
            System.out.println(image.getImageName());
        }
    }

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查看生成的表：

t_image3的表结构：