Package org.apache.commons.io.input

Class ProxyInputStream

java.lang.Object

java.io.InputStream

java.io.FilterInputStream

org.apache.commons.io.input.ProxyInputStream

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

Direct Known Subclasses:

AutoCloseInputStream, BOMInputStream, BoundedInputStream, CloseShieldInputStream, CountingInputStream, MarkShieldInputStream, ObservableInputStream, SwappedDataInputStream, TaggedInputStream, TeeInputStream

public abstract class ProxyInputStream
extends java.io.FilterInputStream

A proxy stream which acts as a FilterInputStream, by passing all method calls on to the proxied stream, not changing which methods are 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).

In addition, this class allows you to:

• notify a subclass that n bytes are about to be read through beforeRead(int)
• notify a subclass that n bytes were read through afterRead(int)
• notify a subclass that an exception was caught through handleIOException(IOException)
• unwrap() itself

This class does not add any state (no additional instance variables).

Field Summary

Fields inherited from class java.io.FilterInputStream

in

Constructor Summary

Constructors

Constructor	Description
ProxyInputStream(java.io.InputStream proxy)	Constructs a new ProxyInputStream.

Method Summary

Modifier and Type	Method	Description
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(java.io.IOException e)	Handles any IOExceptions thrown; by default, throws the given exception.
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[] b)	Invokes the delegate's read(byte[]) method.
int	read(byte[] b, int off, int len)	Invokes the delegate's read(byte[], int, int) method.
void	reset()	Invokes the delegate's reset() method.
long	skip(long n)	Invokes the delegate's skip(long) method.
java.io.InputStream	unwrap()	Unwraps this instance by returning the underlying InputStream.

Methods inherited from class java.io.InputStream

nullInputStream, readAllBytes, readNBytes, readNBytes, transferTo

Methods inherited from class java.lang.Object

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

Constructor Detail

ProxyInputStream

public ProxyInputStream(java.io.InputStream proxy)

Constructs a new ProxyInputStream.

Parameters:

proxy - the InputStream to delegate to

Method Detail

afterRead

protected void afterRead(int n)
                  throws java.io.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:

java.io.IOException - if the post-processing fails in a subclass.

Since:

2.0

available

public int available()
              throws java.io.IOException

Invokes the delegate's available() method.

Overrides:

available in class java.io.FilterInputStream

Returns:

the number of available bytes

Throws:

java.io.IOException - if an I/O error occurs.

beforeRead

protected void beforeRead(int n)
                   throws java.io.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:

java.io.IOException - if the pre-processing fails in a subclass.

Since:

2.0

close

public void close()
           throws java.io.IOException

Invokes the delegate's close() method.

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in interface java.io.Closeable

Overrides:

close in class java.io.FilterInputStream

Throws:

java.io.IOException - if an I/O error occurs.

handleIOException

protected void handleIOException(java.io.IOException e)
                          throws java.io.IOException

Handles any IOExceptions thrown; by default, throws the given exception.

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

Parameters:

e - The IOException thrown

Throws:

java.io.IOException - if an I/O error occurs.

Since:

2.0

mark

public void mark(int readLimit)

Invokes the delegate's mark(int) method.

Overrides:

mark in class java.io.FilterInputStream

Parameters:

readLimit - read ahead limit

markSupported

public boolean markSupported()

Invokes the delegate's markSupported() method.

Overrides:

markSupported in class java.io.FilterInputStream

Returns:

true if mark is supported, otherwise false

read

public int read()
         throws java.io.IOException

Invokes the delegate's read() method.

Overrides:

read in class java.io.FilterInputStream

Returns:

the byte read or -1 if the end of stream

Throws:

java.io.IOException - if an I/O error occurs.

read

public int read(byte[] b)
         throws java.io.IOException

Invokes the delegate's read(byte[]) method.

Overrides:

read in class java.io.FilterInputStream

Parameters:

b - the buffer to read the bytes into

Returns:

the number of bytes read or EOF if the end of stream

Throws:

java.io.IOException - if an I/O error occurs.

read

public int read(byte[] b,
                int off,
                int len)
         throws java.io.IOException

Invokes the delegate's read(byte[], int, int) method.

Overrides:

read in class java.io.FilterInputStream

Parameters:

b - 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:

java.io.IOException - if an I/O error occurs.

reset

public void reset()
           throws java.io.IOException

Invokes the delegate's reset() method.

Overrides:

reset in class java.io.FilterInputStream

Throws:

java.io.IOException - if an I/O error occurs.

skip

public long skip(long n)
          throws java.io.IOException

Invokes the delegate's skip(long) method.

Overrides:

skip in class java.io.FilterInputStream

Parameters:

n - the number of bytes to skip

Returns:

the actual number of bytes skipped

Throws:

java.io.IOException - if an I/O error occurs.

unwrap

public java.io.InputStream unwrap()

Unwraps this instance by returning the underlying InputStream.

Use with caution; useful to query the underlying InputStream.

Returns:

the underlying InputStream.

Since:

2.16.0