JPA / Hibernate - 实体名称似乎很重要。如果我重命名为“Bob”工作正常 [英] JPA/Hibernate - Entity name seems to be important. If I rename to "Bob" works fine
问题描述
$ b更新子行
$ b
我摆脱了几乎所有的代码并缩小了问题范围。我有三个非常简单的实体：
@Entity
public class Building {
@ Id
@GeneratedValue（strategy = GenerationType.AUTO）
private Long id;
public Building（）{
}
public Long getId（）{
return id;
}
public void setId（Long id）{
this.id = id;
$ / code> Other.java
@Entity
public class其他{
@Id
@GeneratedValue（strategy = GenerationType.AUTO）
私人长ID;
@ManyToOne
@JoinColumn（name =building_id）
私人建筑物;
$ b $ public其他（）{
}
public Long getId（）{
return id;
}
public void setId（Long id）{
this.id = id;
}
public Building getBuilding（）{
return building;
}
public void setBuilding（建筑学校）{
this.building = school;
$ / code $ / pre
$ b $ Event.java
@Entity
public class Event {
@Id
@GeneratedValue（strategy = GenerationType.AUTO）
私人长ID;
@ManyToOne
@JoinColumn（name =other_id）
private其他;
public long getId（）{
return id;
}
public void setId（long id）{
this.id = id;
}
public其他getOther（）{
return other;
}
public void setOther（other other）{
this.other = other;
$ b 这会失败并且违反外键约束：
$ b $> / p>
原因：com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException：无法添加或更新子行：外键约束失败（`blah`.`event`，CONSTRAINT`FK403827A76D0546B` FOREIGN KEY（`other_id`）REFERENCES`Other`（`id`））
at sun.reflect.NativeConstructorAccessorImpl.newInstance0（Native Method）
在sun.reflect.NativeConstructorAccessorImpl.newInstance（NativeConstructorAccessorImpl.java:39）
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance（DelegatingConstructorAccessorImpl.java:27）
现在这是真正的奇怪的部分！如果我做了一个eclipse重构并重命名其他实体鲍勃，它的工作原理非常好。如果我们在同一页面上，Event实体现在看起来像这样：
@Entity
public class Event {
@Id
@GeneratedValue（strategy = GenerationType.AUTO）
私人长ID;
@ManyToOne
@JoinColumn（name =bob_id）
私人Bob bob;
public long getId（）{
return id;
}
public void setId（long id）{
this.id = id;
}
public Bob getBob（）{
return bob;
}
public void setBob（Bob bob）{
this.bob = bob;
}
}
现在它工作得很好。有人可以解释一下像我这样的Hibernate新手吗？这真的让我难住。当我在服务层中将新事件持久化到数据库时失败：
@Transactional（propagation = Propagation.REQUIRED，rollbackFor = Exception.class）
public void addEvent（Event event）throws ErrorCodeException，Exception
{
//不知道如果我需要这样做，仍然失败，如果我删除它
event.setOther（otherDAO.getReferenceById（event.getOther（）的getId（））。）;
eventDAO.persist（event）;
}
还有一点评论。而不是将其他人重命名为Bob，我也可以将表名设置为小写：
@Entity
@Table ）
public class其他{
这也同样解决了这个问题。但我不能接受这些解决方案。我想知道它为什么失败。我做了一个技术决定，不使用Grails来避免这种魔力。
这里是SQL hibernate日志：
$ b $ （）
Hibernate：插入到Building值（）
Hibernate：插入到其他（building_id）值（？）
//插入抛出异常
Hibernate：插入Event（other_id）值（？）
2011-06-27 11:31:51 JDBCExceptionReporter [WARN] SQL错误：1452，SQLState ：23000
2011-06-27 11:31:51 JDBCExceptionReporter [错误]无法添加或更新子行：外键约束失败（`blah`.`event`，CONSTRAINT`FK403827A76D0546B` FOREIGN KEY（` other_id`）参考`其他`（`id`））
org.springframework.orm.jpa.JpaSystemException：org.hibernate.exception.ConstraintViolationException：无法插入：[com.blah.server.domain.Event] ;嵌套异常是javax.persistence.PersistenceException：org.hibernate.exception.ConstraintViolationException：无法插入：[com.blah.server.domain.Event]
解决方案更新：我在这里找到了解决方案：
似乎mysql，hibernate和mac os x的组合导致了这个问题。作为解决方案，请使用小写字母命名策略。
This one has had me stumped for several hours. It's related to my other question here:
JPA/hibernate - Cannot add or update a child row: a foreign key constraint fails - BUT record exists
I got rid of nearly all the code and narrowed down the problem. I have three very simple entities:
@Entity
public class Building {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private Long id;
public Building() {
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
}
Other.java
@Entity
public class Other {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private Long id;
@ManyToOne
@JoinColumn(name = "building_id")
private Building building;
public Other() {
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public Building getBuilding() {
return building;
}
public void setBuilding(Building school) {
this.building = school;
}
}
Event.java
@Entity
public class Event {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private long id;
@ManyToOne
@JoinColumn(name = "other_id")
private Other other;
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public Other getOther() {
return other;
}
public void setOther(Other other) {
this.other = other;
}
}
This will fail with a foreign key constraint violation:
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails (`blah`.`event`, CONSTRAINT `FK403827A76D0546B` FOREIGN KEY (`other_id`) REFERENCES `Other` (`id`))
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
NOW HERE'S THE REALLY BIZARRE PART!!!! If I do an eclipse refactor and rename the "Other" entity "Bob" it works perfectly fine. Just so we're on the same page, the Event entity will now look like this:
@Entity
public class Event {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private long id;
@ManyToOne
@JoinColumn(name = "bob_id")
private Bob bob;
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public Bob getBob() {
return bob;
}
public void setBob(Bob bob) {
this.bob = bob;
}
}
And now it works perfectly fine. Can someone please explain this to a Hibernate newbie like myself? This really has me stumped. It fails when I persist a new Event to the database in my service layer:
@Transactional(propagation=Propagation.REQUIRED, rollbackFor=Exception.class)
public void addEvent(Event event) throws ErrorCodeException, Exception
{
// not sure if I need to do this, still fails if I remove it
event.setOther(otherDAO.getReferenceById(event.getOther().getId()));
eventDAO.persist(event);
}
One further comment. Instead of renaming Other to Bob, I can also set the table name to lowercase:
@Entity
@Table(name = "other")
public class Other {
This ALSO fixes it. But I cannot accept these solutions. I want to know why it's failing. I made a technology decision not to use Grails to avoid this type of "magic".
Here's the SQL hibernate logs:
// Initial database inserts
Hibernate: insert into Building values ( )
Hibernate: insert into Other (building_id) values (?)
// Insert which throws exception
Hibernate: insert into Event (other_id) values (?)
2011-06-27 11:31:51 JDBCExceptionReporter [WARN] SQL Error: 1452, SQLState: 23000
2011-06-27 11:31:51 JDBCExceptionReporter [ERROR] Cannot add or update a child row: a foreign key constraint fails (`blah`.`event`, CONSTRAINT `FK403827A76D0546B` FOREIGN KEY (`other_id`) REFERENCES `Other` (`id`))
org.springframework.orm.jpa.JpaSystemException: org.hibernate.exception.ConstraintViolationException: could not insert: [com.blah.server.domain.Event]; nested exception is javax.persistence.PersistenceException: org.hibernate.exception.ConstraintViolationException: could not insert: [com.blah.server.domain.Event]
解决方案 UPDATE: I found the solution here:
It seems the combination of mysql, hibernate, and mac os x cause this problem. As a solution, use a lowercase naming strategy.
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