org.apache.commons.io.output.ProxyOutputStream Maven / Gradle / Ivy
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.io.output;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;
/**
* 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 FilterOutputStream
* to increase reusability.
*
* See the protected methods for ways in which a subclass can easily decorate
* a stream with custom pre-, post- or error processing functionality.
*
*/
public class ProxyOutputStream extends FilterOutputStream {
/**
* Constructs a new ProxyOutputStream.
*
* @param proxy the OutputStream to delegate to
*/
public ProxyOutputStream(final OutputStream proxy) {
super(proxy);
// the proxy is stored in a protected superclass variable named 'out'
}
/**
* Invokes the delegate's write(int) method.
* @param idx the byte to write
* @throws IOException if an I/O error occurs
*/
@Override
public void write(final int idx) throws IOException {
try {
beforeWrite(1);
out.write(idx);
afterWrite(1);
} catch (final IOException e) {
handleIOException(e);
}
}
/**
* Invokes the delegate's write(byte[]) method.
* @param bts the bytes to write
* @throws IOException if an I/O error occurs
*/
@Override
public void write(final byte[] bts) throws IOException {
try {
final int len = bts != null ? bts.length : 0;
beforeWrite(len);
out.write(bts);
afterWrite(len);
} catch (final IOException e) {
handleIOException(e);
}
}
/**
* Invokes the delegate's write(byte[]) method.
* @param bts the bytes to write
* @param st The start offset
* @param end The number of bytes to write
* @throws IOException if an I/O error occurs
*/
@Override
public void write(final byte[] bts, final int st, final int end) throws IOException {
try {
beforeWrite(end);
out.write(bts, st, end);
afterWrite(end);
} catch (final IOException e) {
handleIOException(e);
}
}
/**
* Invokes the delegate's flush() method.
* @throws IOException if an I/O error occurs
*/
@Override
public void flush() throws IOException {
try {
out.flush();
} catch (final IOException e) {
handleIOException(e);
}
}
/**
* Invokes the delegate's close() method.
* @throws IOException if an I/O error occurs
*/
@Override
public void close() throws IOException {
try {
out.close();
} catch (final IOException e) {
handleIOException(e);
}
}
/**
* Invoked by the write methods before the call is proxied. The number
* of bytes to be written (1 for the {@link #write(int)} method, buffer
* length for {@link #write(byte[])}, etc.) is given as an argument.
*
* Subclasses can override this method to add common pre-processing
* functionality without having to override all the write methods.
* The default implementation does nothing.
*
* @since 2.0
* @param n number of bytes to be written
* @throws IOException if the pre-processing fails
*/
protected void beforeWrite(final int n) throws IOException {
}
/**
* Invoked by the write methods after the proxied call has returned
* successfully. The number of bytes written (1 for the
* {@link #write(int)} method, buffer length for {@link #write(byte[])},
* etc.) is given as an argument.
*
* Subclasses can override this method to add common post-processing
* functionality without having to override all the write methods.
* The default implementation does nothing.
*
* @since 2.0
* @param n number of bytes written
* @throws IOException if the post-processing fails
*/
protected void afterWrite(final int n) 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.
* @param e The IOException thrown
* @throws IOException if an I/O error occurs
* @since 2.0
*/
protected void handleIOException(final IOException e) throws IOException {
throw e;
}
}