Java 使用基本一对多映射获取错误
我通过遵循hibernate文档创建了一个简单的示例 我已经创建了Java 使用基本一对多映射获取错误,java,hibernate,Java,Hibernate,我通过遵循hibernate文档创建了一个简单的示例 我已经创建了个人实体和地址实体,如下所示: Person.java public class Person { private int id; private Set<Address> addresses = new HashSet<Address>(); // Setters & Getters public void addAddress(Address address)
个人
实体和地址
实体,如下所示:
Person.java
public class Person {
private int id;
private Set<Address> addresses = new HashSet<Address>();
// Setters & Getters
public void addAddress(Address address) {
this.addresses.add(address);
}
}
public class Address {
private int id;
// Setters & Getters
}
映射文件:
<hibernate-mapping>
<class name="Person">
<id name="id" column="personId">
<generator class="native" />
</id>
<set name="addresses">
<key column="personId" not-null="true" />
<one-to-many class="Address" />
</set>
</class>
<class name="Address">
<id name="id" column="addressId">
<generator class="native" />
</id>
</class>
</hibernate-mapping>
执行此程序会给出一个异常,因为:notnull属性引用一个null或暂时值:Address.\u Person.addressesBackref
完整堆栈跟踪:
org.hibernate.PropertyValueException: not-null property references a null or transient value : Address._Person.addressesBackref
at org.hibernate.engine.internal.Nullability.checkNullability(Nullability.java:106)
at org.hibernate.action.internal.AbstractEntityInsertAction.nullifyTransientReferencesIfNotAlready(AbstractEntityInsertAction.java:132)
at org.hibernate.action.internal.AbstractEntityInsertAction.makeEntityManaged(AbstractEntityInsertAction.java:141)
at org.hibernate.engine.spi.ActionQueue.addResolvedEntityInsertAction(ActionQueue.java:201)
at org.hibernate.engine.spi.ActionQueue.addInsertAction(ActionQueue.java:179)
at org.hibernate.engine.spi.ActionQueue.addAction(ActionQueue.java:166)
at org.hibernate.event.internal.AbstractSaveEventListener.addInsertAction(AbstractSaveEventListener.java:332)
at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:288)
at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:194)
at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:137)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:209)
at org.hibernate.event.internal.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:55)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:194)
at org.hibernate.event.internal.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:49)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:90)
at org.hibernate.internal.SessionImpl.fireSave(SessionImpl.java:715)
at org.hibernate.internal.SessionImpl.save(SessionImpl.java:707)
at org.hibernate.internal.SessionImpl.save(SessionImpl.java:702)
您能帮我解决这个问题吗。例外情况清楚地解释了您添加到
个人的地址。地址为空或暂时(未保存)。在将地址添加到Person.addresses之前,您可以尝试保存地址
您需要提交事务。请尝试以下代码
Session session = getSession();
Transaction tx;
try {
tx = session.beginTransaction();
//do some work
Person p = new Person();
Address a = new Address();
session.save(a);
p.addAddress(a);
session.save(p);
tx.commit();
}
catch (Exception e) {
if (tx!=null) tx.rollback();
throw e;
}
finally {
session.close();
}
在数据库级别,您的地址
表有一个外键,名为personId
,带有Person
表。另外,根据hibernate映射文件,外键具有notnull
约束
根据您的代码,您首先尝试保存地址
实体(进入地址
表),然后保存人员
实体。因此,当hiberate试图保存地址
实体时,它必须插入列personId
,因为它有非空
约束,因为Person
表中没有记录,所以hibernate将异常作为地址抛出
因此,要解决这个问题:
解决方案1:
首先保存人员
,然后尝试像这样保存地址
实体:
Person p = new Person();
Address a = new Address();
p.addAddress(a);
session.save(p);
session.save(a);
解决方案2
只需删除外键上的not null
约束-personId
这里清楚地表明您正在为声明为not null属性的属性设置null值
您正在直接设置没有任何值的对象。因此person id设置为null。但您将其配置为not null。请检查一次。此外,异常情况不同,显示的是地址。_person.addressesBackref
,不清楚地址BackRef
来自何处。
Person p = new Person();
Address a = new Address();
p.addAddress(a);
session.save(p);
session.save(a);