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## org.modeshape.graph.request
Class CompositeRequestChannel

    java.lang.Object
      org.modeshape.graph.request.CompositeRequestChannel

    public class CompositeRequestChannel

extends Object

A channel for Request objects that can be submitted to a consumer (typically a `RequestProcessor` or `RepositoryConnection`) while allowing the channel owner to continue adding more Request objects into the channel.

The owner of this channel is responsible for starting the processing using one of the two `start(...)` methods, adding `CompositeRequestChannel.ChannelCompositeRequest`s via `add(...)` methods, `closing` the channel when there are no more requests to be added, and finally `awaiting` until all of the submitted requests have been processed. Note that the owner can optionally pre-fill the channel with Request objects before calling `start(...)`.

The consumer will be handed a `CompositeRequestChannel.ChannelCompositeRequest`, and should use the `CompositeRequestChannel.ChannelCompositeRequest.iterator()` method to obtain an Iterator<Request>. The `Iterator.hasNext()` method will block until there is another Request available in the channel, or until the channel is closed (at which point `Iterator.hasNext()` will return false. (Notice that the `Iterator.next()` method will also block if it is not preceeded by a `Iterator.hasNext()`, but will throw a `NoSuchElementException` when there are no more Request objects and the channel is closed.)

Because the CompositeRequest's iterator will block, the consumer will block while processing the request. Therefore, this channel submits the CompositeRequest to the consumer asynchronously, via an `ExecutorService` supplied in one of the two `start` `methods`.

Nested Class Summary
`protected class` | `CompositeRequestChannel.ChannelCompositeRequest`
`protected static class` | `CompositeRequestChannel.LastRequest` A psuedo Request that is used by the `CompositeRequestChannel` to insert into a request queue so that the queue's iterator knows when there are no more requests to process.

Field Summary
`protected LinkedList<Request>` | `allRequests` The list of all requests that are or have been processed as part of this channel
`protected AtomicBoolean` | `closed` Flag that defines whether the channel has processed all requests
`protected CompositeRequest` | `composite` The CompositeRequest that is submitted to the underlying processor
`protected Throwable` | `compositeError`
`protected Future<String>` | `future` The Future that is submitted to the ExecutorService to do the processing, which is used to `await()` until the processing is completed or `cancel` the work
`protected String` | `sourceName`

Constructor Summary
`CompositeRequestChannel(String sourceName)` Create a new channel with the supplied channel name.
`CompositeRequestChannel(String sourceName, boolean keepRequests)` Create a new channel with the supplied channel name.

Method Summary
`void` | `add(Request request)` Add the request to this channel for asynchronous processing.
`CountDownLatch` | `add(Request request, CountDownLatch latch)` Add the request to this channel for asynchronous processing, and supply a `count-down latch` that should be `decremented` when this request is completed.
`void` | `addAndAwait(Request request)` Add the request to this channel for processing, but wait to return until the request has been processed.
`List<Request>` | `allRequests()` Get all the requests that were submitted to this queue.
`void` | `await()` Await until this channel has completed.
`void` | `cancel(boolean mayInterruptIfRunning)` Cancel this forked channel, stopping work as soon as possible.
`void` | `close()` Mark this source as having no more requests to process.
`protected Iterator<Request>` | `createIterator()` Utility method to create an iterator over the requests in this channel.
`boolean` | `isClosed()` Return whether this channel has been `closed`.
`boolean` | `isComplete()` Return whether this channel has completed all of its work.
`boolean` | `isStarted()` Return whether this channel has been `started` .
`String` | `sourceName()` Get the name of the source that this channel uses.
`void` | `start(ExecutorService executor, ExecutionContext context, RepositoryConnectionFactory connectionFactory)` Begins processing any requests that have been `added` to this channel.
`void` | `start(ExecutorService executor, RequestProcessor processor, boolean closeProcessorWhenCompleted)` Begins processing any requests that have been `added` to this channel.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### sourceName

    protected final String sourceName

### allRequests

    protected final LinkedList<Request> allRequests

  The list of all requests that are or have been processed as part of this channel

### composite

    protected final CompositeRequest composite

  The CompositeRequest that is submitted to the underlying processor

### future

    protected Future<String> future

  The Future that is submitted to the ExecutorService to do the processing, which is used to `await()` until the processing is completed or `cancel` the work

### closed

    protected final AtomicBoolean closed

  Flag that defines whether the channel has processed all requests

### compositeError

    protected Throwable compositeError

Constructor Detail

### CompositeRequestChannel

    public CompositeRequestChannel(String sourceName)

  Create a new channel with the supplied channel name.

  Parameters:
    `sourceName` - the name of the repository source used to execute this channel's `requests`; may not be null or empty

### CompositeRequestChannel

    public CompositeRequestChannel(String sourceName,
                                   boolean keepRequests)

  Create a new channel with the supplied channel name.

  Parameters:
    `sourceName` - the name of the repository source used to execute this channel's `requests`; may not be null or empty
    `keepRequests` - true if this channel should keep all of the requests that it processes, or false otherwise

Method Detail

### createIterator

    protected Iterator<Request> createIterator()

  Utility method to create an iterator over the requests in this channel. This really should be called once

  Returns:
    the iterator over the channels

### start

    public void start(ExecutorService executor,
                      ExecutionContext context,
                      RepositoryConnectionFactory connectionFactory)

  Begins processing any requests that have been `added` to this channel. Processing is done by submitting the channel to the supplied executor.

  Parameters:
    `executor` - the executor that is to do the work; may not be null
    `context` - the execution context in which the work is to be performed; may not be null
    `connectionFactory` - the connection factory that should be used to create connections; may not be null
  Throws:
    `IllegalStateException` - if this channel has already been started

### start

    public void start(ExecutorService executor,
                      RequestProcessor processor,
                      boolean closeProcessorWhenCompleted)

  Begins processing any requests that have been `added` to this channel. Processing is done by submitting the channel to the supplied executor.

  Parameters:
    `executor` - the executor that is to do the work; may not be null
    `processor` - the request processor that will be used to execute the requests; may not be null
    `closeProcessorWhenCompleted` - true if this method should call `RequestProcessor.close()` when the channel is completed, or false if the caller is responsible for doing this
  Throws:
    `IllegalStateException` - if this channel has already been started

### add

    public void add(Request request)

  Add the request to this channel for asynchronous processing.

  Parameters:
    `request` - the request to be submitted; may not be null
  Throws:
    `IllegalStateException` - if this channel has already been `closed`

### add

    public CountDownLatch add(Request request,
                              CountDownLatch latch)

  Add the request to this channel for asynchronous processing, and supply a `count-down latch` that should be `decremented` when this request is completed.

  Parameters:
    `request` - the request to be submitted; may not be null
    `latch` - the count-down latch that should be decremented when `request` has been completed; may not be null
  Returns:
    the same latch that was supplied, for method chaining purposes; never null
  Throws:
    `IllegalStateException` - if this channel has already been `closed`

### addAndAwait

    public void addAndAwait(Request request)
                     throws InterruptedException

  Add the request to this channel for processing, but wait to return until the request has been processed.

  Parameters:
    `request` - the request to be submitted; may not be null
  Throws:
    `InterruptedException` - if the current thread is interrupted while waiting

### close

    public void close()

  Mark this source as having no more requests to process.

### isClosed

    public boolean isClosed()

  Return whether this channel has been `closed`.

  Returns:
    true if the channel was marked as done, or false otherwise

### cancel

    public void cancel(boolean mayInterruptIfRunning)

  Cancel this forked channel, stopping work as soon as possible. If the channel has not yet been started, this method

  Parameters:
    `mayInterruptIfRunning` - true if the channel is still being worked on, and the thread on which its being worked on may be interrupted, or false if the channel should be allowed to finish if it is already in work.

### isStarted

    public boolean isStarted()

  Return whether this channel has been `started` .

  Returns:
    true if this channel was started, or false otherwise

### isComplete

    public boolean isComplete()

  Return whether this channel has completed all of its work.

  Returns:
    true if the channel was started and is complete, or false otherwise

### await

    public void await()
               throws ExecutionException,
                      InterruptedException,
                      CancellationException

  Await until this channel has completed.

  Throws:
    `CancellationException` - if the channel was cancelled
    `ExecutionException` - if the channel execution threw an exception
    `InterruptedException` - if the current thread is interrupted while waiting

### allRequests

    public List<Request> allRequests()

  Get all the requests that were submitted to this queue. The resulting list is the actual list that is appended when requests are added, and may change until the channel is `closed`.

  Returns:
    all of the requests that were submitted to this channel; never null

### sourceName

    public String sourceName()

  Get the name of the source that this channel uses.

  Returns:
    the source name; never null

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