PartitionReducer

All Known Implementing Classes:

AbstractPartitionReducer
```
public interface PartitionReducer
```
PartitionReducer provides unit of work demarcation across partitions. It is not a JTA transaction; no resources are enlisted. Rather, it provides transactional flow semantics to facilitate finalizing merge or compensation logic.

Nested Class Summary

Nested Classes
Modifier and Type Interface and Description

static class PartitionReducer.PartitionStatus
An enum used in afterPartitionedStepCompletion(PartitionStatus).

Nested Classes
Modifier and Type	Interface and Description
`static class`	`PartitionReducer.PartitionStatus` An enum used in `afterPartitionedStepCompletion(PartitionStatus)`.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method and Description
`void`	`afterPartitionedStepCompletion(PartitionReducer.PartitionStatus status)` The afterPartitionedStepCompletion method receives control at the end of a partition processing.
`void`	`beforePartitionedStepCompletion()` The beforePartitionedStepCompletion method receives control at the end of partitioned step processing.
`void`	`beginPartitionedStep()` The beginPartitionedStep method receives control at the start of partition processing.
`void`	`rollbackPartitionedStep()` The rollbackPartitionedStep method receives control if the runtime is rolling back a partitioned step.

- Method Detail
  - beginPartitionedStep
```
void beginPartitionedStep()
                   throws java.lang.Exception
```
    The beginPartitionedStep method receives control at the start of partition processing. It receives control before the PartitionMapper is invoked and before any partitions are started.
    
    Throws:
    
    java.lang.Exception - is thrown if an error occurs.
  - beforePartitionedStepCompletion
```
void beforePartitionedStepCompletion()
                              throws java.lang.Exception
```
    The beforePartitionedStepCompletion method receives control at the end of partitioned step processing. It receives control after all partitions have completed. It does not receive control if the PartitionReducer is rolling back.
    
    Throws:
    
    java.lang.Exception - is thrown if an error occurs.
  - rollbackPartitionedStep
```
void rollbackPartitionedStep()
                      throws java.lang.Exception
```
    The rollbackPartitionedStep method receives control if the runtime is rolling back a partitioned step. Any partition threads still running are allowed to complete before this method is invoked. This method receives control if any of the following conditions are true:
    1. One or more partitions end with a Batch Status of STOPPED or FAILED.
    2. Any of the following partitioned step callbacks throw an exception:
      PartitionMapper
      PartitionReducer
      PartitionCollector
      PartitionAnalyzer
    3. A job with partitioned steps is restarted.
    Throws:
    
    java.lang.Exception - is thrown if an error occurs.
  - afterPartitionedStepCompletion
```
void afterPartitionedStepCompletion(PartitionReducer.PartitionStatus status)
                             throws java.lang.Exception
```
    The afterPartitionedStepCompletion method receives control at the end of a partition processing. It receives a status value that identifies the outcome of the partition processing. The status string value is either "COMMIT" or "ROLLBACK".
    
    Parameters:
    
    status - specifies the outcome of the partitioned step. Values are "COMMIT" or "ROLLBACK".
    
    Throws:
    
    java.lang.Exception - is thrown if an error occurs.

Interface PartitionReducer

Nested Class Summary

Method Summary

Method Detail

beginPartitionedStep

beforePartitionedStepCompletion

rollbackPartitionedStep

afterPartitionedStepCompletion