开发中遇到这个异常：
NestedThrowablesStackTrace:
Attempt was made to manually set the id component of a Key primary key.
If you want to control the value of the primary key, set the name
component instead.
org.datanucleus.exceptions.NucleusUserException: Attempt was made to
manually set the id component of a Key primary key. If you want to
control the value of the primary key, set the name component instead.
原来的修改代码是这样些的：
public void attachDirty(UrlTarget instance) {
PersistenceManager pm = null;
try {
pm = PMF.get().getPersistenceManager();
UrlTarget ut = (UrlTarget) pm.getObjectById(UrlTarget.class, instance.getId());
ut.setName(instance.getName());
ut.setRemark(instance.getRemark());
ut.setUrl(instance.getUrl());
pm.makePersistent(ut);
} catch(Exception ex){
ex.printStackTrace();
}finally {
if(pm != null)pm.close();
}
}
public UrlTarget findById(Long id) {
PersistenceManager pm = PMF.get().getPersistenceManager();
try{
return (UrlTarget) pm.getObjectById(UrlTarget.class, id);
}catch(Exception ex){
ex.printStackTrace();
}finally {
pm.close();
}
return null;
}
在利用findById方法得到对象后修改，但是findById中pm已经关闭，这就是错误的原因了