[記錄]JPA雙向關聯一對多

參考資料JPA雙向關聯多對一映射

-- Table: works_base

-- DROP TABLE works_base;

CREATE TABLE works_base
(
  authorid integer,//fk
  id integer,//pk
  name character varying(80)
)
WITH (
  OIDS=FALSE
);
ALTER TABLE works_base
  OWNER TO jincheng;

-- Table: author_base

-- DROP TABLE author_base;

CREATE TABLE author_base
(
  id integer,//pk 
  name character varying(80),
  mail character varying(80)
)
WITH (
  OIDS=FALSE
);
ALTER TABLE author_base
  OWNER TO jincheng;

下面是entity的寫法，使用註釋

package com.jincheng.ssh.model;

import java.io.Serializable;
import java.lang.Integer;
import java.lang.String;
import javax.persistence.*;
import static javax.persistence.FetchType.EAGER;
import static javax.persistence.FetchType.LAZY;

/**
 * Entity implementation class for Entity: WorksBase
 *
 */
@Entity
@Table(name="works_base")
public class WorksBase implements Serializable {

	   
	@Id
	@Column(name="id")
	private Integer id;
	@Column(name="name")
	private String name;
	@ManyToOne(cascade=CascadeType.ALL)
	@JoinColumn(name="authorid")
	private AuthorBase authorBase;//使用authorBase代替了authorid
	private static final long serialVersionUID = 1L;

	public WorksBase() {
		super();
	}   
	public Integer getId() {
		return this.id;
	}

	public void setId(Integer id) {
		this.id = id;
	}   
	public String getName() {
		return this.name;
	}

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

package com.jincheng.ssh.model;

import java.io.Serializable;
import java.lang.Integer;
import java.lang.String;
import java.util.Set;

import javax.persistence.*;


/**
 * Entity implementation class for Entity: AuthorBase
 *
 */
@Entity
@Table(name="author_base")
public class AuthorBase implements Serializable {

	@Id
	@Column(name="id")
	private Integer id;
	@Column(name="name")
	private String name;
	@Column(name="mail")
	private String mail;
	@OneToMany(mappedBy="authorBase")
	private Set<WorksBase> worksBases;
	private static final long serialVersionUID = 1L;

	public AuthorBase() {
		super();
	}   
	public Integer getId() {
		return this.id;
	}

	public void setId(Integer id) {
		this.id = id;
	}   
	public String getName() {
		return this.name;
	}

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

	public void setMail(String mail) {
		this.mail = mail;
	}
   
}

代碼中紅色標記部分：一個mappedBy和JoinColumn, 就是告訴JPA實現者，worksBases是通過WorksBase裏的authorBase映射得到，每次查找worksBases是通過WorksBase裏的authorBase聯接