Datanucleus JDO检索新生成的主键 [英] Datanucleus JDO Retrieve newly generated primary key
本文介绍了Datanucleus JDO检索新生成的主键的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
$ b 编辑
我们使用注释,这里是主键:
@PrimaryKey
@Column(name =id_bla,allowsNull =false )
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY,extensions = {@Extension(vendorName =datanucleus,key =strategy-when-notnull,value =false)})
private Long idBla;
我不是那个做过映射的人,我还没有完全掌握这一点。 / p>
解决方案
对象的关键字应该在持久保存时自动设置:
MyObject obj = new MyObject();
Long id = obj.getId(); //错误!仍然是空的。
pm.makePersistent(obj);
id = obj.getId(); //正确。
I am using datanucleus and jdo in a GWT project. How can I retrieve the generated primary key after adding an element to the database with makePersistent()
Edit We use annotations, here is the primary key:
@PrimaryKey
@Column(name = "id_bla", allowsNull = "false")
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY, extensions = { @Extension(vendorName = "datanucleus", key = "strategy-when-notnull", value = "false") })
private Long idBla;
I am not the one who did the mapping and I don't get all of this yet.
解决方案
The object's key should be automatically set when it is persisted:
MyObject obj = new MyObject();
Long id = obj.getId(); // WRONG! Will still be null.
pm.makePersistent(obj);
id = obj.getId(); // Correct.
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