Package org.apache.openjpa.lib.rop

Class MergedResultObjectProvider

java.lang.Object

org.apache.openjpa.lib.rop.MergedResultObjectProvider

All Implemented Interfaces:

ResultObjectProvider, Closeable

public class MergedResultObjectProvider
extends Object
implements ResultObjectProvider

A result object provider that merges multiple result object provider delegates. Support exists for maintaining ordering of the internally held results, provided that each of the individual results is itself ordered.

Author:

Abe White, Marc Prud'hommeaux

Constructor Summary

Constructors

Constructor	Description
MergedResultObjectProvider(ResultObjectProvider[] rops)	Constructor.
MergedResultObjectProvider(ResultObjectProvider[] rops, Comparator comp)	Constructor.

Method Summary

Modifier and Type	Method	Description
boolean	absolute(int pos)	Move to the given 0-based position.
void	close()	Free the resources associated with this provider.
protected Object	getOrderingValue(Object val, int idx, ResultObjectProvider rop)	Return the value to use for ordering on the given result value.
Object	getResultObject()	Instantiate the current result object.
void	handleCheckedException(Exception e)	Any checked exceptions that are thrown will be passed to this method.
boolean	next()	Advance the input to the next position.
void	open()	Open the result.
void	reset()	Reset this provider.
int	size()	Return the number of items in the input, or Integer.MAX_VALUE if the size in unknown.
boolean	supportsRandomAccess()	Return true if this provider supports random access.

Methods inherited from class java.lang.Object

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

Constructor Detail

MergedResultObjectProvider

public MergedResultObjectProvider(ResultObjectProvider[] rops)

Constructor. Provide delegates.

MergedResultObjectProvider

public MergedResultObjectProvider(ResultObjectProvider[] rops,
                                  Comparator comp)

Constructor. Provide delegates and optional comparator.

Method Detail

supportsRandomAccess

public boolean supportsRandomAccess()

Description copied from interface: ResultObjectProvider

Return true if this provider supports random access.

Specified by:

supportsRandomAccess in interface ResultObjectProvider

open

public void open()
          throws Exception

Description copied from interface: ResultObjectProvider

Open the result. This will be called before ResultObjectProvider.next(), ResultObjectProvider.absolute(int), or ResultObjectProvider.size().

Specified by:

open in interface ResultObjectProvider

Throws:

Exception

absolute

public boolean absolute(int pos)
                 throws Exception

Description copied from interface: ResultObjectProvider

Move to the given 0-based position. This method is only called for providers that support random access. Return true if there is data at this position; otherwise false. This may be invoked in place of ResultObjectProvider.next().

Specified by:

absolute in interface ResultObjectProvider

Throws:

Exception

size

public int size()
         throws Exception

Description copied from interface: ResultObjectProvider

Return the number of items in the input, or Integer.MAX_VALUE if the size in unknown.

Specified by:

size in interface ResultObjectProvider

Throws:

Exception

reset

public void reset()
           throws Exception

Description copied from interface: ResultObjectProvider

Reset this provider. This is an optional operation. If supported, it should move the position of the provider to before the first element. Non-random-access providers may be able to support this method by re-acquiring all resources as if the result were just opened.

Specified by:

reset in interface ResultObjectProvider

Throws:

Exception

close

public void close()
           throws Exception

Description copied from interface: ResultObjectProvider

Free the resources associated with this provider.

Specified by:

close in interface Closeable

Specified by:

close in interface ResultObjectProvider

Throws:

Exception

handleCheckedException

public void handleCheckedException(Exception e)

Description copied from interface: ResultObjectProvider

Any checked exceptions that are thrown will be passed to this method. The provider should re-throw the exception as an appropriate unchecked exception.

Specified by:

handleCheckedException in interface ResultObjectProvider

next

public boolean next()
             throws Exception

Description copied from interface: ResultObjectProvider

Advance the input to the next position. Return true if there is more data; otherwise false.

Specified by:

next in interface ResultObjectProvider

Throws:

Exception

getResultObject

public Object getResultObject()
                       throws Exception

Description copied from interface: ResultObjectProvider

Instantiate the current result object. This method will only be called after ResultObjectProvider.next() or ResultObjectProvider.absolute(int).

Specified by:

getResultObject in interface ResultObjectProvider

Throws:

Exception

getOrderingValue

protected Object getOrderingValue(Object val,
                                  int idx,
                                  ResultObjectProvider rop)

Return the value to use for ordering on the given result value. Returns the result value by default.

Parameters:

val - the result value

idx - the index of the result object provider in the array given on construction that produced the result value

rop - the result object provider that produced the result value