jlibs.core.io

Class PumpedReader

java.lang.Object

java.io.Reader

java.io.PipedReader

jlibs.core.io.PumpedReader

All Implemented Interfaces:

Closeable, AutoCloseable, Readable, Runnable

public abstract class PumpedReader
extends PipedReader
implements Runnable

This class simplifies usage of PipedReader and PipedWriter

Using PipedReader and PipedWriter looks cumbersome.

 PipedReader pipedReader = new PipedReader();
 final PipedWriter pipedWriter = new PipedWriter(pipedReader);
 final IOException ioEx[] = { null };
 new Thread(){
     @Override
     public void run(){
         try{
             writeDataTo(pipedWriter);
             pipedWriter.close();
         }catch(IOException ex){
             ioEx[0] = ex;
         }
     }
 }.start();
 readDataFrom(pipedReader);
 pipedReader.close();
 if(ioEx[0]!=null)
     throw new RuntimeException("something gone wrong", ioEx[0]);
 

The same can be achieved using PumpedReader as follows:

 PumpedReader reader = new PumpedReader(){
     @Override
     protected void pump(PipedWriter writer) throws Exception{
         writeDataTo(writer);
     }
 }.start(); // start() will spawn new thread
 readDataFrom(reader);
 reader.close(); // any exceptions occurred in pump(...) are thrown by close()
 

PumpedReader is an abstract class with following abstract method:

 protected abstract void pump(PipedWriter writer) throws Exception;
 

This method implementation should write data into writer which is passed as argument and close it.
Any exception thrown by pump(...) are wrapped in IOException and rethrown by PumpedReader.close().

PumpedReader implements Runnable which is supposed to be run in thread.
You can use PumpedReader.start() method to start thread or spawn thread implicitly.
start() method returns self reference.

 public PumpedReader start();
 

The advantage of PumpedReader over PipedReader/PipedWriter/Thread is:

• it doesn't clutter the exising flow of code
• exception handling is better

Author:

Santhosh Kumar T

See Also:

PumpedInputStream

Field Summary

Fields inherited from class java.io.Reader

lock

Constructor Summary

Constructors

Constructor and Description
PumpedReader()

Method Summary

Modifier and Type	Method and Description
void	close() Closes this stream and releases any system resources associated with the stream.
protected abstract void	pump(PipedWriter writer) Subclasse implementation should write data into writer.
void	run()
PumpedReader	start() Starts a thread with this instance as runnable.

Methods inherited from class java.io.PipedReader

connect, read, read, ready

Methods inherited from class java.io.Reader

mark, markSupported, read, read, reset, skip

Methods inherited from class java.lang.Object

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

Constructor Detail

PumpedReader

public PumpedReader()

Method Detail

run

public void run()

Specified by:

run in interface Runnable

start

public PumpedReader start()

Starts a thread with this instance as runnable.

Returns:

self reference

close

public void close()
           throws IOException

Closes this stream and releases any system resources associated with the stream.

Any exception thrown by pump(java.io.PipedWriter) are cached and rethrown by this method

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Overrides:

close in class PipedReader

Throws:

IOException - if an I/O error occurs.

pump

protected abstract void pump(PipedWriter writer)
                      throws Exception

Subclasse implementation should write data into writer.

Parameters:

writer - writer into which data should be written

Throws:

Exception