com.hammurapi.common

Class Joiner<T,C,R>

java.lang.Object

com.hammurapi.common.Joiner<T,C,R>

Type Parameters:

T - Join element type.

C - Context type passed from addInput to join.

R - Return type passed from join to to addInput.

Direct Known Subclasses:

LocalJoiner

public abstract class Joiner<T,C,R>
extends Object

Helper class to join data from several inputs.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Joiner.CollectionAdapter<T> Adapter for collections.
static interface	Joiner.Collector<T> Collector of objects to join.
static class	Joiner.InputConsumer Interface to consume inputs in join() method.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Joiner(Joiner.Collector<T>[] inputCollectors, Class<T> inputType, boolean outerJoin) Creates joiner.

Method Summary

Methods

Modifier and Type	Method and Description
List<R>	addInput(int index, T input, C context) Adds input.
void	addPredicate(Predicate<T,C> predicate) Adds join predicate.
protected abstract void	endJoin() This method is invoked after join is finished.
protected boolean	isValidInput(int index, T input) This method is invoked for all inputs before joining.
protected abstract R	join(T[] inputs, C context, Joiner.InputConsumer consumer, int activator) This method is invoked for every combination of valid inputs.
protected void	join(T[] inputs, int currentIndex, int inputIndex, C context, Joiner.InputConsumer consumer, Map<C,Map<Extractor<T,? super Boolean,C>,? super Boolean>> cache, List<R> resultCollector) This method can be overridden to implement concurrent joining, i.e.
protected boolean	partialJoin(T[] inputs, C context, Joiner.InputConsumer consumer, int index, int activator) This method is invoked to validate already joined inputs.
void	reset() Clears join collections.
protected abstract void	startJoin() Start join is invoked before join.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Joiner

protected Joiner(Joiner.Collector<T>[] inputCollectors,
      Class<T> inputType,
      boolean outerJoin)

Creates joiner.

Parameters:

inputCollectors - Input collectors.

inputType - Input type is required because of erasure of generics and T is needed at runtime.

outerJoin - If true, each input addition triggers invocation of join, even if other input collectors don't have any data.

Method Detail

addPredicate

public void addPredicate(Predicate<T,C> predicate)

Adds join predicate.

Parameters:

predicate -

startJoin

protected abstract void startJoin()

Start join is invoked before join. Typically this method shall obtain a lock on input collectors.

endJoin

protected abstract void endJoin()

This method is invoked after join is finished. Typically this method shall release the lock on input collectors.

addInput

public List<R> addInput(int index,
               T input,
               C context)
                 throws Exception

Adds input. Input is joined with other accumulated inputs.

Parameters:

index - Input index.

input - Input.

Throws:

Exception

join

protected void join(T[] inputs,
        int currentIndex,
        int inputIndex,
        C context,
        Joiner.InputConsumer consumer,
        Map<C,Map<Extractor<T,? super Boolean,C>,? super Boolean>> cache,
        List<R> resultCollector)
             throws Exception

This method can be overridden to implement concurrent joining, i.e. at particular indices the sub-method wraps call to the super-method into a task executed in a separate thread.

Parameters:

inputs -

currentIndex -

inputIndex -

context -

consumer -

cache -

resultCollector -

Throws:

Exception

join

protected abstract R join(T[] inputs,
     C context,
     Joiner.InputConsumer consumer,
     int activator)
                   throws Exception

This method is invoked for every combination of valid inputs.

Parameters:

inputs - Inputs

context - Join context passed from addInput

consumer - callback interface to consume inputs.

activator - Index of join activator.

Returns:

Join result.

Throws:

Exception

isValidInput

protected boolean isValidInput(int index,
                   T input)

This method is invoked for all inputs before joining. It is useful for situation when inputs in internal collections may become invalid over the course of life of joiner.

Parameters:

index -

input -

Returns:

partialJoin

protected boolean partialJoin(T[] inputs,
                  C context,
                  Joiner.InputConsumer consumer,
                  int index,
                  int activator)
                       throws Exception

This method is invoked to validate already joined inputs. If this method returns false, further joining is abandoned.

Parameters:

inputs - Inputs array.

index - Index of last already joined input.

consumer - Callback interface to consume inputs.

Returns:

Throws:

Exception

reset

public void reset()

Clears join collections.