工作中遇到的问题--Hibernate注解添加在一方和多方的区别

以Good和GoodStatus为例：

一、注解仅添加在一方：

@Entity
@Table(name = "GOOD")
@Where(clause="enabled=1") //Used for logical delete, disabled objects are always hidden
public class Good extends AMfgObject implements Serializable {

   /** serialVersionUID */
   private static final long serialVersionUID = -7656499731749432022L;

   @Id
   @GeneratedValue(strategy = GenerationType.AUTO)
   @Column(name = "GOOD_ID", nullable = false)
   private Long id;

   @OneToMany(fetch = FetchType.EAGER, cascade=CascadeType.ALL)
   private Set<GoodStatus> goodStatus;
   /**
   * Empty constructor
   */
   public Good(){}

   public Long getId() {
       return id;
   }

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

   public Set<GoodStatus> getGoodStatus() {
       return goodStatus;
   }

   public void setGoodStatus(Set<GoodStatus> goodStatus) {
       this.goodStatus = goodStatus;
   }

   /**
   * add GoodStatus directly
   * @param goodStatus
   */
   public void addGoodStatus(GoodStatus goodStatus){
       this.goodStatus.add(goodStatus);
       /*goodStatus.setGood(this);*/              //如果在多方也有注解则需添加这句，否则不能级联保存更新
   }
}

在多方不加一方的映射（即不加Good good;这个属性）

@Entity
@Table(name = "GOODSTATUS")
@Where(clause = "enabled=1")
public class GoodStatus extends AMfgObject implements Serializable {
   /**
   *
   */
   private static final long serialVersionUID = -1279190303132720639L;
   @Id
   @GeneratedValue(strategy = GenerationType.AUTO)
   @Column(name = "ID", nullable = false)
   private Long id;

   @Column(name = "VALUE")
   private String value;

   public GoodStatus() {
       super();
   }

   public String getValue() {
       return value;
   }

   public void setValue(String value) {
       this.value = value;
   }
   public Long getId() {
       return id;
   }

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

这种情况下生成的SQL语句是这样的：

CREATE TABLE good (
good_id bigint(20) NOT NULL auto_increment,
PRIMARY KEY (good_id)
) ;
-- create table goodstatus
CREATE TABLE goodstatus (
id bigint(20) NOT NULL AUTO_INCREMENT,
value varchar(255) COLLATE utf8_unicode_ci NOT NULL,
PRIMARY KEY (ID)
);
--good_good_status
CREATE TABLE good_good_status (
good_GOOD_ID bigint(20) NOT NULL,
good_status_id bigint(20) NOT NULL,
PRIMARY KEY (good_GOOD_ID,good_status_id),
KEY FK_GOOD_ID (good_GOOD_ID),
KEY FK_GOOD_STATUS_ID (good_status_id)
);

生成了三个表，类似于manytomany

二、注解仅添加在多的一方，则与双方都添加注解相同，仅生成两个表：

Good对应表不变，GoodStatus表

SQL语句对应如下：

-- create table goodstatus
CREATE TABLE goodstatus (
id bigint(20) NOT NULL AUTO_INCREMENT,
value varchar(255) COLLATE utf8_unicode_ci NOT NULL,

good_id bigint(20) DEFAULT NULL,
PRIMARY KEY (ID),

CONSTRAINT FK_GOOD_ID FOREIGN KEY (good_id) REFERENCES GOOD(ID)
);