Question

这个让我难倒几个小时。这与我的另一个问题有关：

JPA/hibernate - Cannot add or update a child row: a foreign key constraint fails - BUT record exists

我摆脱了几乎所有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;
    }
}

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;
    }
}

这将因外键约束违规而失败：

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)

现在这是真正的BIZARRE PART !!!!如果我做一个eclipse重构并重命名“其他”实体“Bob”，它的工作完全正常。就这样我们在同一页面上，Event实体现在看起来像这样：

@Entity
public class Event {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    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;
    }
}

现在它完美无缺。有人可以向像我这样的Hibernate新手解释这个吗？这真让我难过。当我将新事件持久保存到服务层中的数据库时，它会失败：

@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);
}

进一步评论。我也可以将表名设置为小写：

，而不是将其他名称重命名为Bob

@Entity
@Table(name = "other")
public class Other {

此ALSO修复了它。但我无法接受这些解决方案。我想知道它失败的原因。我决定不使用Grails来避免这种“魔法”。

这是SQL hibernate日志：

// 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]

Answer 1

更新：我在这里找到了解决方案：

http://developmentality.wordpress.com/2011/05/23/hibernate-mysql-mac-foreign-key-nightmares-a-painless-solution-to-a-painful-problem/

似乎mysql，hibernate和mac os x的组合导致了这个问题。作为解决方案，请使用小写命名策略。

JPA / Hibernate - 实体名称似乎很重要。如果我重命名为“鲍勃”工作正常

1 个答案: