uk.org.ogsadai.activity
Class CallThroughPipe

java.lang.Object
  |
  +--uk.org.ogsadai.activity.CallThroughPipe

All Implemented Interfaces:

BlockReader, BlockWriter, Pipe

class CallThroughPipe

extends java.lang.Object

implements Pipe

This is a simple unsynchronized Pipe with a variable length internal buffer. It contains an Activity and when the consumer reads data from the pipe, this activity is processed incrementally to generate the data that will be returned. In other words, reading data from the pipe effectively drives the processing of the activity.

Author:

The OGSA-DAI Project Team

COPYRIGHT_NOTICE

private static final java.lang.String COPYRIGHT_NOTICE

Copyright statement.

See Also:

Constant Field Values

mActivity

private final Activity mActivity

The activity that outputs data into this pipe when processed.

mBuffer

private final java.util.List mBuffer

Stores the blocks of data put into the pipe by the activity.

mClosed

private boolean mClosed

Indicates whether or not the pipe has been closed.

CallThroughPipe

public CallThroughPipe(Activity activity)

Constructs a CallThroughPipe that will pull data from the specified source Activity. When another activity attempts to read data from the pipe, the source activity is processed enough to generate the data.

Parameters:

activity - Source Activity

hasNext

public boolean hasNext()

Description copied from interface: BlockReader

Indicates whether or not there are any more blocks of data to be read from the block reader.

Specified by:

hasNext in interface BlockReader

Returns:

true if there are more blocks to be read or false otherwise

next

public java.lang.Object next()

Description copied from interface: BlockReader

Gets the next block of data contained in the block reader.

Specified by:

next in interface BlockReader

Returns:

an Object

put

public void put(java.lang.Object block)

Description copied from interface: BlockWriter

Writes the specified block of output data.

Specified by:

put in interface BlockWriter

Parameters:

block - the Object block to write

process

private void process()

Processes the handler until its activity has generated some output. Note that this may be more than one block. If the activity finishes and there is no more data, then the internal mHasNext flag is set to false.

If a Throwable should inadvertently occur during the activity's process method, catch it, wrap it in an ActivityExecutionException and instruct the activity to save a reference using its setError method.

close

public void close()

Description copied from interface: BlockWriter

Closes the block writer to indicate that there are no more blocks are to be written. After close has been called, the put method should no longer be used.

Specified by:

close in interface BlockWriter

isOpen

public boolean isOpen()

Description copied from interface: BlockWriter

Indicates whether or not the block writer is open for writing via the put method. After the close method has been invoked this method should return false.

Specified by:

isOpen in interface BlockWriter

Returns:

A boolean value indicating whether this block writer is open for writing