com.gc.iotools.stream.is
Class InputStreamFromOutputStream<T>

java.lang.Object
  java.io.InputStream
      java.io.PipedInputStream
          com.gc.iotools.stream.is.InputStreamFromOutputStream<T>

Type Parameters:

T - Optional result returned by the function produce(OutputStream) after the data has been written. It can be obtained calling the getResult()

All Implemented Interfaces:

Closeable

Direct Known Subclasses:

ReadAheadInputStream

public abstract class InputStreamFromOutputStream<T>
extends PipedInputStream

This class allow to read the data written to an OutputStream from an InputStream.

To use this class you must subclass it and implement the abstract method produce(OutputStream). The data who is produced inside this function can be written to the sink OutputStream passed as a parameter. Later it can be read back from from the InputStreamFromOutputStream class (whose ancestor is java.io.InputStream ).

 final String dataId=//id of some data.
 final InputStreamFromOutputStream<String> isos
                          = new InputStreamFromOutputStream<String>() {
   @Override
   public String produce(final OutputStream dataSink) throws Exception {
      //call your application function who produces the data here
      //WARNING: we're in another thread here, so this method shouldn't
      //write any class field or make assumptions on the state of the class.
      return produceMydata(dataId,dataSink)
   }
 };
  try {
    //now you can read from the InputStream the data that was written to the
    //dataSink OutputStream
     byte[] read=IOUtils.toByteArray(isos);
     //Use data here
   } catch (final IOException e) {
     //Handle exception here
   } finally {
   isos.close();
 }
 //You can get the result of produceMyData after the stream has been closed.
 String resultOfProduction = isos.getResult();
 

This class encapsulates a pipe and a Thread, hiding the complexity of using them. It is possible to select different strategies for allocating the internal thread or even specify the ExecutorService for thread execution.

Since:

1.0

Author:

dvd.smnt

See Also:

ExecutionModel

Field Summary

Fields inherited from class java.io.PipedInputStream

buffer, in, out, PIPE_SIZE

Constructor Summary

InputStreamFromOutputStream()
It creates a InputStreamFromOutputStream with a THREAD_PER_INSTANCE thread strategy.

InputStreamFromOutputStream(boolean startImmediately, boolean joinOnClose, ExecutorService executor, int pipeBufferSize)

InputStreamFromOutputStream(boolean joinOnClose, ExecutionModel executionModel)
It creates a InputStreamFromOutputStream and let the user choose the thread allocation strategy he likes.

InputStreamFromOutputStream(boolean joinOnClose, ExecutorService executor)
It creates a InputStreamFromOutputStream and let the user specify the ExecutorService that will execute the produce(OutputStream) method.

InputStreamFromOutputStream(boolean joinOnClose, ExecutorService executor, int pipeBufferSize)
It creates a InputStreamFromOutputStream and let the user specify the ExecutorService that will execute the produce(OutputStream) method and the pipe buffer size.

InputStreamFromOutputStream(ExecutionModel executionModel)
It creates a InputStreamFromOutputStream and let the user choose the thread allocation strategy he likes.

InputStreamFromOutputStream(ExecutorService executor)
It creates a InputStreamFromOutputStream and let the user specify the ExecutorService that will execute the produce(OutputStream) method.

Method Summary

protected void	afterClose() This method is called just before the close() method completes, and after the eventual join with the internal thread.
void	close()
static String[]	getActiveThreadNames() This method can be used for debugging purposes to get a list of the currently active threads.
T	getResult() Returns the object that was previously returned by the produce(OutputStream) method.
protected abstract T	produce(OutputStream sink) This method must be implemented by the user of this class to produce the data that must be read from the external InputStream.
int	read()
int	read(byte[] b, int off, int len)
static void	setDefaultPipeSize(int defaultPipeSize) Set the size for the pipe circular buffer for the newly created InputStreamFromOutputStream.

Methods inherited from class java.io.PipedInputStream

available, connect, receive

Methods inherited from class java.io.InputStream

mark, markSupported, read, reset, skip

Methods inherited from class java.lang.Object

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

Constructor Detail

InputStreamFromOutputStream

public InputStreamFromOutputStream()

It creates a InputStreamFromOutputStream with a THREAD_PER_INSTANCE thread strategy.

See Also:

ExecutionModel.THREAD_PER_INSTANCE

InputStreamFromOutputStream

public InputStreamFromOutputStream(boolean startImmediately,
                                   boolean joinOnClose,
                                   ExecutorService executor,
                                   int pipeBufferSize)

InputStreamFromOutputStream

public InputStreamFromOutputStream(boolean joinOnClose,
                                   ExecutionModel executionModel)

It creates a InputStreamFromOutputStream and let the user choose the thread allocation strategy he likes.

This class executes the produce method in a thread created internally.

Parameters:

executionModel - Defines how the internal thread is allocated.

joinOnClose - If true the close() method will also wait for the internal thread to finish.

Since:

1.2.2

See Also:

ExecutionModel

InputStreamFromOutputStream

public InputStreamFromOutputStream(boolean joinOnClose,
                                   ExecutorService executor)

It creates a InputStreamFromOutputStream and let the user specify the ExecutorService that will execute the produce(OutputStream) method.

Parameters:

executor - Defines the ExecutorService that will allocate the the internal thread.

joinOnClose - If true the close() method will also wait for the internal thread to finish.

Since:

1.2.2

See Also:

ExecutorService

InputStreamFromOutputStream

public InputStreamFromOutputStream(boolean joinOnClose,
                                   ExecutorService executor,
                                   int pipeBufferSize)

It creates a InputStreamFromOutputStream and let the user specify the ExecutorService that will execute the produce(OutputStream) method and the pipe buffer size.

Using this method the default size is ignored.

Parameters:

executor - Defines the ExecutorService that will allocate the the internal thread.

joinOnClose - If true the close() method will also wait for the internal thread to finish.

pipeBufferSize - The size of the pipe buffer to allocate.

Since:

1.2.6

See Also:

ExecutorService

InputStreamFromOutputStream

public InputStreamFromOutputStream(ExecutionModel executionModel)

It creates a InputStreamFromOutputStream and let the user choose the thread allocation strategy he likes.

This class executes the produce method in a thread created internally.

Parameters:

executionModel - Defines how the internal thread is allocated.

See Also:

ExecutionModel

InputStreamFromOutputStream

public InputStreamFromOutputStream(ExecutorService executor)

It creates a InputStreamFromOutputStream and let the user specify the ExecutorService that will execute the produce(OutputStream) method.

Parameters:

executor - Defines the ExecutorService that will allocate the the internal thread.

See Also:

ExecutorService

Method Detail

getActiveThreadNames

public static final String[] getActiveThreadNames()

This method can be used for debugging purposes to get a list of the currently active threads.

Returns:

Array containing names of the threads currently active.

setDefaultPipeSize

public static void setDefaultPipeSize(int defaultPipeSize)

Set the size for the pipe circular buffer for the newly created InputStreamFromOutputStream. Default is 4096 bytes.

Parameters:

defaultPipeSize - the default pipe buffer size in bytes.

Since:

1.2.2

afterClose

protected void afterClose()
                   throws IOException

This method is called just before the close() method completes, and after the eventual join with the internal thread.

It is an extension point designed for applications that need to perform some operation when the InputStream is closed.

Throws:

IOException - threw when the subclass wants to communicate an exception during close.

Since:

1.2.9

close

public final void close()
                 throws IOException

Specified by:

close in interface Closeable

Overrides:

close in class PipedInputStream

Throws:

IOException

getResult

public T getResult()
            throws Exception

Returns the object that was previously returned by the produce(OutputStream) method. It performs all the synchronization operations needed to read the result and waits for the internal thread to terminate.

This method must be called after the method close(), otherwise an IllegalStateException is thrown.

Returns:

Object that was returned by the produce(OutputStream) method.

Throws:

Exception - If the produce(OutputStream) method threw an java.lang.Exception this method will throw again the same exception.

IllegalStateException - If the close() method hasn't been called yet.

Since:

1.2.0

produce

protected abstract T produce(OutputStream sink)
                      throws Exception

This method must be implemented by the user of this class to produce the data that must be read from the external InputStream.

Special care must be paid passing arguments to this method or setting global fields because it is executed in another thread.

The right way to set a field variable is to return a value in the produceand retrieve it in the getResult().

Parameters:

sink - the implementing class should write its data to this stream.

Returns:

The implementing class can use this to return a result of data production. The result will be available through the method getResult().

Throws:

Exception - the exception eventually thrown by the implementing class is returned by the read() methods.

See Also:

getResult()

read

public final int read()
               throws IOException

Overrides:

read in class PipedInputStream

Throws:

IOException

read

public final int read(byte[] b,
                      int off,
                      int len)
               throws IOException

Overrides:

read in class PipedInputStream

Throws:

IOException