Batchers may be registered with a DbControl even if constructor throw an exception

[Nicklas Nordborg]

This issue is related to #765. What is happening there is that a batcher is created to try to delete raw data for an Affymetrix raw bioassay. Since it is not stored in database the creation of the batcher will fail:

java.lang.NullPointerException
	at net.sf.basedb.core.BasicBatcher.<init>(BasicBatcher.java:149)
	at net.sf.basedb.core.RawDataBatcher.<init>(RawDataBatcher.java:172)
	at net.sf.basedb.core.RawDataBatcher.getNew(RawDataBatcher.java:103)
	at net.sf.basedb.core.RawBioAssay.onBeforeCommit(RawBioAssay.java:296)
	at net.sf.basedb.core.DbControl.commit(DbControl.java:372)
	at net.sf.basedb.core.Trashcan.delete(Trashcan.java:229)

But, before the failure the following code has been executed:

AbstractBatcher(DbControl dc)
{
   ....
   dc.addBatcher(this);
}

Thus, the DbControl has a link to "half-constructed" object. Due to the NullPointerException the transaction is beeing rollbacked. The rollback code is calling close() on all registered batchers, which generates the exception we see in ticket #765:

java.lang.NullPointerException
	at net.sf.basedb.core.RawDataBatcher.onBeforeClose(RawDataBatcher.java:319)
	at net.sf.basedb.core.AbstractBatcher.close(AbstractBatcher.java:122)
	at net.sf.basedb.core.DbControl.rollback(DbControl.java:269)
	at net.sf.basedb.core.DbControl.close(DbControl.java:237)
	at net.sf.basedb.core.Trashcan.delete(Trashcan.java:233)

This exception happens because not all fields get initialized due to the first exception. The safest way to solve this is to not register a batcher with the DbControl until the object has been completely constructed. This requires that we move the call to dc.addBatcher(this) to some other (non-central) place.

[Nicklas Nordborg]

(In [3747]) Fixes #766: Batchers may be registered with a DbControl even if constructor throw an exception