org.apache.openjpa.lib.rop
Class MergedResultObjectProvider

java.lang.Object
  extended by org.apache.openjpa.lib.rop.MergedResultObjectProvider
All Implemented Interfaces:
ResultObjectProvider, Closeable
Direct Known Subclasses:
OrderingMergedResultObjectProvider

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
MergedResultObjectProvider(ResultObjectProvider[] rops)
          Constructor.
MergedResultObjectProvider(ResultObjectProvider[] rops, Comparator comp)
          Constructor.
 
Method Summary
 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 ResultObjectProvider
Specified by:
close in interface Closeable
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


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