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:

Closeable, AutoCloseable

Direct Known Subclasses:

AutoCloseInputStream, BOMInputStream, BoundedInputStream, CloseShieldInputStream, org.apache.commons.io.input.CountingInputStream, MarkShieldInputStream, ObservableInputStream, SwappedDataInputStream, TaggedInputStream, TeeInputStream

public abstract class ProxyInputStream
extends 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

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected static class	ProxyInputStream.AbstractBuilder<T,B extends AbstractStreamBuilder<T,B>> Abstracts builder properties for subclasses.

Field Summary

Fields inherited from class java.io.FilterInputStream

in

Constructor Summary

Constructors

Modifier	Constructor and Description
	ProxyInputStream(InputStream proxy) Constructs a new ProxyInputStream.
protected	ProxyInputStream(InputStream proxy, ProxyInputStream.AbstractBuilder<?,?> builder) Constructs a new ProxyInputStream.
protected	ProxyInputStream(ProxyInputStream.AbstractBuilder<?,?> builder) Constructs a new ProxyInputStream.

Method Summary

Modifier and Type	Method and Description
protected void	afterRead(int n) Called by the read methods after the proxied call has returned successfully.
int	available() Invokes the delegate's InputStream.available() method.
protected void	beforeRead(int n) Invoked by the read methods before the call is proxied.
(package private) void	checkOpen() Checks if this instance is closed and throws an IOException if so.
void	close() Invokes the delegate's InputStream.close() method.
protected void	handleIOException(IOException e) Handles any IOExceptions thrown; by default, throws the given exception.
(package private) boolean	isClosed() Tests whether this instance is closed.
void	mark(int readLimit) Invokes the delegate's InputStream.mark(int) method.
boolean	markSupported() Invokes the delegate's InputStream.markSupported() method.
int	read() Invokes the delegate's InputStream.read() method unless the stream is closed.
int	read(byte[] b) Invokes the delegate's InputStream.read(byte[]) method.
int	read(byte[] b, int off, int len) Invokes the delegate's InputStream.read(byte[], int, int) method.
void	reset() Invokes the delegate's InputStream.reset() method.
ProxyInputStream	setReference(InputStream in) Sets the underlying input stream.
long	skip(long n) Invokes the delegate's InputStream.skip(long) method.
InputStream	unwrap() Unwraps this instance by returning the underlying InputStream.

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 proxy.

ProxyInputStream

protected ProxyInputStream(InputStream proxy,
                           ProxyInputStream.AbstractBuilder<?,?> builder)

Constructs a new ProxyInputStream.

Parameters:

proxy - the InputStream to proxy.

builder - How to build an instance.

ProxyInputStream

protected ProxyInputStream(ProxyInputStream.AbstractBuilder<?,?> builder)
                    throws IOException

Constructs a new ProxyInputStream.

Parameters:

builder - How to build an instance.

Throws:

IOException - if an I/O error occurs.

Method Detail

afterRead

protected void afterRead(int n)
                  throws IOException

Called by the read methods after the proxied call has returned successfully. The argument is the number of bytes returned to the caller or EOF if the end of stream was reached.

The default delegates to the consumer given to ProxyInputStream.AbstractBuilder.setAfterRead(IOIntConsumer).

Alternatively, a subclasses can override this method to add post-processing functionality without having to override all the read methods.

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 EOF if the end of stream was reached.

Throws:

IOException - Thrown by a subclass or the consumer given to ProxyInputStream.AbstractBuilder.setAfterRead(IOIntConsumer).

available

public int available()
              throws IOException

Invokes the delegate's InputStream.available() method.

Overrides:

available in class FilterInputStream

Returns:

the number of available bytes, 0 if the stream is closed.

Throws:

IOException - if an I/O error occurs.

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 in a subclass.

checkOpen

void checkOpen()
        throws IOException

Checks if this instance is closed and throws an IOException if so.

Throws:

IOException - if this instance is closed.

close

public void close()
           throws IOException

Invokes the delegate's InputStream.close() method.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Overrides:

close in class FilterInputStream

Throws:

IOException - if an I/O error occurs.

handleIOException

protected void handleIOException(IOException e)
                          throws 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:

IOException - if an I/O error occurs.

isClosed

boolean isClosed()

Tests whether this instance is closed.

Returns:

whether this instance is closed.

mark

public void mark(int readLimit)

Invokes the delegate's InputStream.mark(int) method.

Overrides:

mark in class FilterInputStream

Parameters:

readLimit - read ahead limit.

markSupported

public boolean markSupported()

Invokes the delegate's InputStream.markSupported() method.

Overrides:

markSupported in class FilterInputStream

Returns:

true if this stream instance supports the mark and reset methods; false otherwise.

See Also:

mark(int), reset()

read

public int read()
         throws IOException

Invokes the delegate's InputStream.read() method unless the stream is closed.

Overrides:

read in class FilterInputStream

Returns:

the byte read or EOF if we reached the end of stream.

Throws:

IOException - if an I/O error occurs.

read

public int read(byte[] b)
         throws IOException

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

Overrides:

read in class FilterInputStream

Parameters:

b - the buffer to read the bytes into.

Returns:

the number of bytes read or EOF if we reached the end of stream.

Throws:

IOException -

• If the first byte cannot be read for any reason other than the end of the file,
• if the input stream has been closed, or
• if some other I/O error occurs.

read

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

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

Overrides:

read in class 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 EOF if we reached the end of stream.

Throws:

IOException -

• If the first byte cannot be read for any reason other than the end of the file,
• if the input stream has been closed, or
• if some other I/O error occurs.

reset

public void reset()
           throws IOException

Invokes the delegate's InputStream.reset() method.

Overrides:

reset in class FilterInputStream

Throws:

IOException - if this stream has not been marked or if the mark has been invalidated.

setReference

public ProxyInputStream setReference(InputStream in)

Sets the underlying input stream.

Parameters:

in - The input stream to set in FilterInputStream.in.

Returns:

this instance.

skip

public long skip(long n)
          throws IOException

Invokes the delegate's InputStream.skip(long) method.

Overrides:

skip in class FilterInputStream

Parameters:

n - the number of bytes to skip.

Returns:

the actual number of bytes skipped.

Throws:

IOException - if the stream does not support seek, or if some other I/O error occurs.

unwrap

public InputStream unwrap()

Unwraps this instance by returning the underlying InputStream.

Use with caution; useful to query the underlying InputStream.

Returns:

the underlying InputStream.