Hibernate的继承关系分类，annotation表示

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hibernate继承映射
以下测试是在mysql中进行的。

1、单表方式
Animal.java

Java代码

@Entity
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name="animalType")
@DiscriminatorValue("animal")
public class Animal {
private int id;
private String name;
@Id
@GeneratedValue
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;
}
}

Cat.java

Java代码

@Entity
@DiscriminatorValue("cat")
public class Cat extends Animal {
private String catName;
public String getCatName() {
return catName;
}
public void setCatName(String catName) {
this.catName = catName;
}
}

Dog.java

Java代码

@Entity
@DiscriminatorValue(value="dog")
public class Dog extends Animal{
private String dogName;
public String getDogName() {
return dogName;
}
public void setDogName(String dogName) {
this.dogName = dogName;
}
}

TestJunit.java

Java代码

@Test
public void testAnimal(){
Animal t = new Animal();
t.setName("animal");
session.saveOrUpdate(t);
}
@Test
public void testCat(){
Cat t = new Cat();
t.setName("cat");
t.setCatName("cat");
session.saveOrUpdate(t);
}
@Test
public void testDog(){
Dog t = new Dog();
t.setName("dog");
t.setDogName("dog");
session.saveOrUpdate(t);
}

对应生成的数据表是这样的
table---animal

id	name	animalType	catName	dogName
1	animal	animal	null	null
2	cat	cat	cat	null
3	dog	dog	null	dog

2、join方式
Animal.java

Java代码

@Entity
@Inheritance(strategy=InheritanceType.JOINED)
public class Animal {
private int id;
private String name;
@Id
@GeneratedValue
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;
}
}

Cat.java

Java代码

@Entity
@PrimaryKeyJoinColumn(name="catId")
public class Cat extends Animal {
private String catName;
public String getCatName() {
return catName;
}
public void setCatName(String catName) {
this.catName = catName;
}
}

Dog.java

Java代码

@Entity
@PrimaryKeyJoinColumn(name="dogId")
public class Dog extends Animal{
private String dogName;
public String getDogName() {
return dogName;
}
public void setDogName(String dogName) {
this.dogName = dogName;
}
}

TestJunit.java

Java代码

@Test
public void testAnimal(){
Animal t = new Animal();
t.setName("animal");
session.saveOrUpdate(t);
}
@Test
public void testCat(){
Cat t = new Cat();
t.setName("cat");
t.setCatName("cat");
session.saveOrUpdate(t);
}
@Test
public void testDog(){
Dog t = new Dog();
t.setName("dog");
t.setDogName("dog");
session.saveOrUpdate(t);
}

对应生成的数据表是这样的
table---Animal

id	name
1	animal
2	cat
3	dog

table---cat

catId	catName
2	cat

table---dog

dogId	dogName
3	dog

3、每个实体类对应一个数据表
以下的测试中，Anamal.java中的主键生成策略需要注解成@GeneratedValue(strategy=GenerationType.TABLE)，测试是在mysql数据库中进行的。
Animal.java

Java代码

@Entity
@Inheritance(strategy=InheritanceType.TABLE_PER_CLASS)
public class Animal {
private int id;
private String name;
@Id
@GeneratedValue(strategy=GenerationType.TABLE)
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;
}
}

Cat.java

Java代码

@Entity
@Inheritance(strategy=InheritanceType.TABLE_PER_CLASS)
public class Cat extends Animal {
private String catName;
public String getCatName() {
return catName;
}
public void setCatName(String catName) {
this.catName = catName;
}
}

Dog.java

Java代码

@Entity
@Inheritance(strategy=InheritanceType.TABLE_PER_CLASS)
public class Dog extends Animal{
private String dogName;
public String getDogName() {
return dogName;
}
public void setDogName(String dogName) {
this.dogName = dogName;
}
}

TestJunit.java

Java代码

@Test
public void testAnimal(){
Animal t = new Animal();
t.setName("animal");
session.saveOrUpdate(t);
}
@Test
public void testCat(){
Cat t = new Cat();
t.setName("cat");
t.setCatName("cat");
session.saveOrUpdate(t);
}
@Test
public void testDog(){
Dog t = new Dog();
t.setName("dog");
t.setDogName("dog");
session.saveOrUpdate(t);
}

对应生成的数据表是这样的
table---animal

id	name
1	animal

table---cat

id	name	catName
2	cat	cat

table---dog

id	name	dogName
3	dog	dog

来源：oschina

链接：https://my.oschina.net/u/133242/blog/174996

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