联合主键

两个或多个字段组成的主键叫做联合主键

在面向对象描述

符合主键类的jpa的规范

1.必须提供public无参的构造函数

2.实现序列化接口（serializable）

3.必须重写hashCode()和equals()方法，用符合字段作为两个方法的参数

联合主键类代码

package other.test;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Embeddable;

@Embeddable
public class AirlinePK implements Serializable {
	@Column(length = 10)
	private String start;
	@Column(length = 10)
	private String end;

	public String getStart() {
		return start;
	}

	public void setStart(String start) {
		this.start = start;
	}

	public String getEnd() {
		return end;
	}

	public void setEnd(String end) {
		this.end = end;
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + ((end == null) ? 0 : end.hashCode());
		result = prime * result + ((start == null) ? 0 : start.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;
		AirlinePK other = (AirlinePK) obj;
		if (end == null) {
			if (other.end != null)
				return false;
		} else if (!end.equals(other.end))
			return false;
		if (start == null) {
			if (other.start != null)
				return false;
		} else if (!start.equals(other.start))
			return false;
		return true;
	}

}

实体类代码

package other.test;

import javax.persistence.Column;
import javax.persistence.EmbeddedId;
import javax.persistence.Entity;

@Entity
public class Airline {
	@EmbeddedId
	private AirlinePK id;
	@Column(length = 10)
	private String name;

	public AirlinePK getId() {
		return id;
	}

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

	public String getName() {
		return name;
	}

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

}

结果截图

级联操作

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