org.apache.commons.io.input
Class ProxyInputStream

java.lang.Object
  extended by java.io.InputStream
      extended by java.io.FilterInputStream
          extended by org.apache.commons.io.input.ProxyInputStream
All Implemented Interfaces:
Closeable
Direct Known Subclasses:
AutoCloseInputStream, BOMInputStream, CloseShieldInputStream, CountingInputStream, SwappedDataInputStream, TaggedInputStream, TeeInputStream

public abstract class ProxyInputStream
extends FilterInputStream

A Proxy stream which acts as expected, that is it passes the method calls on to the proxied stream and doesn't change which methods are being called.

It is an alternative base class to FilterInputStream to increase reusability, because FilterInputStream changes the methods being called, such as read(byte[]) to read(byte[], int, int).

See the protected methods for ways in which a subclass can easily decorate a stream with custom pre-, post- or error processing functionality.

Version:
$Id: ProxyInputStream.java 1304052 2012-03-22 20:55:29Z ggregory $

Field Summary
 
Fields inherited from class java.io.FilterInputStream
in
 
Constructor Summary
ProxyInputStream(InputStream proxy)
          Constructs a new ProxyInputStream.
 
Method Summary
protected  void afterRead(int n)
          Invoked by the read methods after the proxied call has returned successfully.
 int available()
          Invokes the delegate's available() method.
protected  void beforeRead(int n)
          Invoked by the read methods before the call is proxied.
 void close()
          Invokes the delegate's close() method.
protected  void handleIOException(IOException e)
          Handle any IOExceptions thrown.
 void mark(int readlimit)
          Invokes the delegate's mark(int) method.
 boolean markSupported()
          Invokes the delegate's markSupported() method.
 int read()
          Invokes the delegate's read() method.
 int read(byte[] bts)
          Invokes the delegate's read(byte[]) method.
 int read(byte[] bts, int off, int len)
          Invokes the delegate's read(byte[], int, int) method.
 void reset()
          Invokes the delegate's reset() method.
 long skip(long ln)
          Invokes the delegate's skip(long) method.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

ProxyInputStream

public ProxyInputStream(InputStream proxy)
Constructs a new ProxyInputStream.

Parameters:
proxy - the InputStream to delegate to
Method Detail

read

public int read()
         throws IOException
Invokes the delegate's read() method.

Overrides:
read in class FilterInputStream
Returns:
the byte read or -1 if the end of stream
Throws:
IOException - if an I/O error occurs

read

public int read(byte[] bts)
         throws IOException
Invokes the delegate's read(byte[]) method.

Overrides:
read in class FilterInputStream
Parameters:
bts - the buffer to read the bytes into
Returns:
the number of bytes read or -1 if the end of stream
Throws:
IOException - if an I/O error occurs

read

public int read(byte[] bts,
                int off,
                int len)
         throws IOException
Invokes the delegate's read(byte[], int, int) method.

Overrides:
read in class FilterInputStream
Parameters:
bts - the buffer to read the bytes into
off - The start offset
len - The number of bytes to read
Returns:
the number of bytes read or -1 if the end of stream
Throws:
IOException - if an I/O error occurs

skip

public long skip(long ln)
          throws IOException
Invokes the delegate's skip(long) method.

Overrides:
skip in class FilterInputStream
Parameters:
ln - the number of bytes to skip
Returns:
the actual number of bytes skipped
Throws:
IOException - if an I/O error occurs

available

public int available()
              throws IOException
Invokes the delegate's available() method.

Overrides:
available in class FilterInputStream
Returns:
the number of available bytes
Throws:
IOException - if an I/O error occurs

close

public void close()
           throws IOException
Invokes the delegate's close() method.

Specified by:
close in interface Closeable
Overrides:
close in class FilterInputStream
Throws:
IOException - if an I/O error occurs

mark

public void mark(int readlimit)
Invokes the delegate's mark(int) method.

Overrides:
mark in class FilterInputStream
Parameters:
readlimit - read ahead limit

reset

public void reset()
           throws IOException
Invokes the delegate's reset() method.

Overrides:
reset in class FilterInputStream
Throws:
IOException - if an I/O error occurs

markSupported

public boolean markSupported()
Invokes the delegate's markSupported() method.

Overrides:
markSupported in class FilterInputStream
Returns:
true if mark is supported, otherwise false

beforeRead

protected void beforeRead(int n)
                   throws IOException
Invoked by the read methods before the call is proxied. The number of bytes that the caller wanted to read (1 for the read() method, buffer length for read(byte[]), etc.) is given as an argument.

Subclasses can override this method to add common pre-processing functionality without having to override all the read methods. The default implementation does nothing.

Note this method is not called from skip(long) or reset(). You need to explicitly override those methods if you want to add pre-processing steps also to them.

Parameters:
n - number of bytes that the caller asked to be read
Throws:
IOException - if the pre-processing fails
Since:
2.0

afterRead

protected void afterRead(int n)
                  throws IOException
Invoked by the read methods after the proxied call has returned successfully. The number of bytes returned to the caller (or -1 if the end of stream was reached) is given as an argument.

Subclasses can override this method to add common post-processing functionality without having to override all the read methods. The default implementation does nothing.

Note this method is not called from skip(long) or reset(). You need to explicitly override those methods if you want to add post-processing steps also to them.

Parameters:
n - number of bytes read, or -1 if the end of stream was reached
Throws:
IOException - if the post-processing fails
Since:
2.0

handleIOException

protected void handleIOException(IOException e)
                          throws IOException
Handle any IOExceptions thrown.

This method provides a point to implement custom exception handling. The default behaviour is to re-throw the exception.

Parameters:
e - The IOException thrown
Throws:
IOException - if an I/O error occurs
Since:
2.0


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