hibernate 注解方式实现联合主键

联合主键的实现方式有三种

方式1.将联合主键的字段单独放在一个类中，该类需要实现java.io.Serializable接口并重写equals和hascode，再将该类注解为@Embeddable,最后在主类中(该类不包含联合主键类中的字段)保存该联合主键类的一个引用，并生成set和get方法，并将该引用注解为@Id

@Embeddable
public class DogPrimarykey implements Serializable {

	private static final long serialVersionUID = 2555027553374060423L;

	private String id;
	@Column(name="DOG_NAME")
	private String name;

	public String getId() {
		return id;
	}

	public void setId(String id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + ((id == null) ? 0 : id.hashCode());
		result = prime * result + ((name == null) ? 0 : name.hashCode());
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		DogPrimarykey other = (DogPrimarykey) obj;
		if (id == null) {
			if (other.id != null)
				return false;
		} else if (!id.equals(other.id))
			return false;
		if (name == null) {
			if (other.name != null)
				return false;
		} else if (!name.equals(other.name))
			return false;
		return true;
	}

}

@Entity(name = "DOG")
public class Dog {
	private static final long serialVersionUID = 7219216851705947642L;
	@Id
	private DogPrimarykey dogPrimarykey;

	@Column(name = "DOG_AGE", length = 2)
	private int age;

	public DogPrimarykey getDogPrimarykey() {
		return dogPrimarykey;
	}

	public void setDogPrimarykey(DogPrimarykey dogPrimarykey) {
		this.dogPrimarykey = dogPrimarykey;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		if (age > 100 || age < 1) {
			this.age = 1;
		} else {
			this.age = age;
		}
	}

	public void say() {
		// TODO Auto-generated method stub
		System.out.println("汪  汪  汪");
	}

	@Override
	public String toString() {
		return "Dog [dogPrimarykey=" + dogPrimarykey + ", age=" + age + "]";
	}

}

 方式2:将联合主键的字段单独放在一个类中，该类需要实现java.io.Serializable接口并重写equals和hascode，最后在主类中(该类不包含联合主键类中的字段)保存该联合主键类的一个引用，并生成set和get方法，并将该引用注解为@EmbeddedId

public class DogPrimarykey implements Serializable {

	private static final long serialVersionUID = 2555027553374060423L;

	private String id;
	@Column(name="DOG_NAME")
	private String name;

	public String getId() {
		return id;
	}

	public void setId(String id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + ((id == null) ? 0 : id.hashCode());
		result = prime * result + ((name == null) ? 0 : name.hashCode());
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		DogPrimarykey other = (DogPrimarykey) obj;
		if (id == null) {
			if (other.id != null)
				return false;
		} else if (!id.equals(other.id))
			return false;
		if (name == null) {
			if (other.name != null)
				return false;
		} else if (!name.equals(other.name))
			return false;
		return true;
	}
}

@Entity(name = "DOG")
public class Dog {
	private static final long serialVersionUID = 7219216851705947642L;
	@EmbeddedId
	private DogPrimarykey dogPrimarykey;

	@Column(name = "DOG_AGE", length = 2)
	private int age;

	public DogPrimarykey getDogPrimarykey() {
		return dogPrimarykey;
	}

	public void setDogPrimarykey(DogPrimarykey dogPrimarykey) {
		this.dogPrimarykey = dogPrimarykey;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		if (age > 100 || age < 1) {
			this.age = 1;
		} else {
			this.age = age;
		}
	}

	public void say() {
		// TODO Auto-generated method stub
		System.out.println("汪  汪  汪");
	}

	@Override
	public String toString() {
		return "Dog [dogPrimarykey=" + dogPrimarykey + ", age=" + age + "]";
	}

}

 方式3:将联合主键的字段单独放在一个类中，该类需要实现java.io.Serializable接口并要重写equals和hashcode.最后在主类中(该类包含联合主键类中的字段)将联合主键字段都注解为@Id,并在该类上方加上这样的注解：@IdClass(联合主键类.class)

public class DogPrimarykey implements Serializable {

	private static final long serialVersionUID = 2555027553374060423L;

	private String id;
	@Column(name="DOG_NAME")
	private String name;

	public String getId() {
		return id;
	}

	public void setId(String id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + ((id == null) ? 0 : id.hashCode());
		result = prime * result + ((name == null) ? 0 : name.hashCode());
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		DogPrimarykey other = (DogPrimarykey) obj;
		if (id == null) {
			if (other.id != null)
				return false;
		} else if (!id.equals(other.id))
			return false;
		if (name == null) {
			if (other.name != null)
				return false;
		} else if (!name.equals(other.name))
			return false;
		return true;
	}
}

@Entity(name = "DOG")
@IdClass(DogPrimarykey.class)
public class Dog {
	private static final long serialVersionUID = 7219216851705947642L;

	@Id
	private String id;
	@Id
	private String name;
	@Column(name = "DOG_AGE", length = 2)
	private int age;

	public String getId() {
		return id;
	}

	public void setId(String id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		if (age > 100 || age < 1) {
			this.age = 1;
		} else {
			this.age = age;
		}
	}

	public void say() {
		// TODO Auto-generated method stub
		System.out.println("汪  汪  汪");
	}

	@Override
	public String toString() {
		return "Dog [id=" + id + ", name=" + name + ", age=" + age + "]";
	}
}