The batch agent adds transaction points to a DRAgent. It is the super class for all batch agents. The following methods are defined:

• initialize

  The initialize (DRStorable, DRInputStream) method is called during startup to give the agent its configuration and optionally a stream, where the state is read from. The config argument is the agent configuration class, populated with the configuration saved in the user interface. The state argument is an input stream that, if not null, must be read in the same order as written in the writeState method.
  
  
• beginBatch

  This method is called at the beginning of a batch and it is fed the transaction id. Agents must prepare themselves to be fed with data at this point.
  
  
• endBatch

  This method is called when all data for the current batch has been processed by the workflow. Agents must be prepared for a commit of the current transaction at this point.
  
  
• writeState

  This method is invoked after endBatch and allows the agent to persist transaction specific information. In case of a crash during commit/rollback, the state will be used at startup to apply the correct logic for commit/rollback of the transaction.
  
  
• rollback

  Called if the current transaction should be rolled back, that is, removed. This method is only called after initialization in case of a previous crash.
  
  
• commit

  Called when the current transaction should be committed. The transaction is closed at this point and the produced data is considered safe.
  
  
• cancelBatch

  Invoked when a batch is being canceled. A Collection agent should route the incoming file to the error service. Other agents should make sure temporary data that has been persisted in interfaced systems is removed.
  
  
• getTransactionResources

  If the agent depends on resources that must take an active part of the workflow transaction in terms of prepare/rollback/commit, it must return a reference to these resources in this method. These resources must be defined in the initialize method. For example, return the DRECSBatchServiceExec if it is dependent on the transaction.

Transaction Order

An important feature of a mediation system is transaction safety. The system provides a two-phase commit transaction model, with the possibility to save a transaction state with the current transaction. The Collection agent controls a transaction, since it feeds the incoming batches.

The DTK defines a method that can be called to hint the Collection agent to close a transaction. This method is called hintEndBatch and is defined in DRBatchServerEnv. The collector may choose to ignore this call.

The following examples shows possible method invocation orders for Processor agents.