ProxyCollectionWriter.java
/*
* 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.FilterWriter;
import java.io.IOException;
import java.io.Writer;
import java.util.Collection;
import org.apache.commons.io.IOUtils;
/**
* A Proxy stream collection which acts as expected, that is it passes the method calls on to the proxied streams and
* doesn't change which methods are being called. It is an alternative base class to {@link FilterWriter} and
* {@link FilterCollectionWriter} to increase reusability, because FilterWriter changes the methods being called, such
* as {@code write(char[])} to {@code write(char[], int, int)} and {@code write(String)} to
* {@code write(String, int, int)}. This is in contrast to {@link ProxyWriter} which is backed by a single
* {@link Writer}.
*
* @since 2.7
*/
public class ProxyCollectionWriter extends FilterCollectionWriter {
/**
* Constructs a new proxy collection writer.
*
* @param writers Writers object to provide the underlying targets.
*/
public ProxyCollectionWriter(final Collection<Writer> writers) {
super(writers);
}
/**
* Constructs a new proxy collection writer.
*
* @param writers Writers to provide the underlying targets.
*/
public ProxyCollectionWriter(final Writer... writers) {
super(writers);
}
/**
* Invoked by the write methods after the proxied call has returned successfully. The number of chars written (1 for
* the {@link #write(int)} method, buffer length for {@link #write(char[])}, etc.) is given as an argument.
* <p>
* Subclasses can override this method to add common post-processing functionality without having to override all
* the write methods. The default implementation does nothing.
* </p>
*
* @param n number of chars written
* @throws IOException if the post-processing fails
*/
@SuppressWarnings("unused") // Possibly thrown from subclasses.
protected void afterWrite(final int n) throws IOException {
// noop
}
/**
* Invokes the delegates' {@code append(char)} methods.
*
* @param c The character to write
* @return this writer
* @throws IOException if an I/O error occurs.
* @since 2.0
*/
@Override
public Writer append(final char c) throws IOException {
try {
beforeWrite(1);
super.append(c);
afterWrite(1);
} catch (final IOException e) {
handleIOException(e);
}
return this;
}
/**
* Invokes the delegates' {@code append(CharSequence)} methods.
*
* @param csq The character sequence to write
* @return this writer
* @throws IOException if an I/O error occurs.
*/
@Override
public Writer append(final CharSequence csq) throws IOException {
try {
final int len = IOUtils.length(csq);
beforeWrite(len);
super.append(csq);
afterWrite(len);
} catch (final IOException e) {
handleIOException(e);
}
return this;
}
/**
* Invokes the delegates' {@code append(CharSequence, int, int)} methods.
*
* @param csq The character sequence to write
* @param start The index of the first character to write
* @param end The index of the first character to write (exclusive)
* @return this writer
* @throws IOException if an I/O error occurs.
*/
@Override
public Writer append(final CharSequence csq, final int start, final int end) throws IOException {
try {
beforeWrite(end - start);
super.append(csq, start, end);
afterWrite(end - start);
} catch (final IOException e) {
handleIOException(e);
}
return this;
}
/**
* Invoked by the write methods before the call is proxied. The number of chars to be written (1 for the
* {@link #write(int)} method, buffer length for {@link #write(char[])}, etc.) is given as an argument.
* <p>
* Subclasses can override this method to add common pre-processing functionality without having to override all the
* write methods. The default implementation does nothing.
* </p>
*
* @param n number of chars to be written
* @throws IOException if the pre-processing fails
*/
@SuppressWarnings("unused") // Possibly thrown from subclasses.
protected void beforeWrite(final int n) throws IOException {
// noop
}
/**
* Invokes the delegate's {@code close()} method.
*
* @throws IOException if an I/O error occurs.
*/
@Override
public void close() throws IOException {
try {
super.close();
} catch (final IOException e) {
handleIOException(e);
}
}
/**
* Invokes the delegate's {@code flush()} method.
*
* @throws IOException if an I/O error occurs.
*/
@Override
public void flush() throws IOException {
try {
super.flush();
} catch (final IOException e) {
handleIOException(e);
}
}
/**
* Handle any IOExceptions thrown.
* <p>
* This method provides a point to implement custom exception handling. The default behavior is to re-throw the
* exception.
* </p>
*
* @param e The IOException thrown
* @throws IOException if an I/O error occurs.
*/
protected void handleIOException(final IOException e) throws IOException {
throw e;
}
/**
* Invokes the delegate's {@code write(char[])} method.
*
* @param cbuf the characters to write
* @throws IOException if an I/O error occurs.
*/
@Override
public void write(final char[] cbuf) throws IOException {
try {
final int len = IOUtils.length(cbuf);
beforeWrite(len);
super.write(cbuf);
afterWrite(len);
} catch (final IOException e) {
handleIOException(e);
}
}
/**
* Invokes the delegate's {@code write(char[], int, int)} method.
*
* @param cbuf the characters to write
* @param off The start offset
* @param len The number of characters to write
* @throws IOException if an I/O error occurs.
*/
@Override
public void write(final char[] cbuf, final int off, final int len) throws IOException {
try {
beforeWrite(len);
super.write(cbuf, off, len);
afterWrite(len);
} catch (final IOException e) {
handleIOException(e);
}
}
/**
* Invokes the delegate's {@code write(int)} method.
*
* @param c the character to write
* @throws IOException if an I/O error occurs.
*/
@Override
public void write(final int c) throws IOException {
try {
beforeWrite(1);
super.write(c);
afterWrite(1);
} catch (final IOException e) {
handleIOException(e);
}
}
/**
* Invokes the delegate's {@code write(String)} method.
*
* @param str the string to write
* @throws IOException if an I/O error occurs.
*/
@Override
public void write(final String str) throws IOException {
try {
final int len = IOUtils.length(str);
beforeWrite(len);
super.write(str);
afterWrite(len);
} catch (final IOException e) {
handleIOException(e);
}
}
/**
* Invokes the delegate's {@code write(String)} method.
*
* @param str the string to write
* @param off The start offset
* @param len The number of characters to write
* @throws IOException if an I/O error occurs.
*/
@Override
public void write(final String str, final int off, final int len) throws IOException {
try {
beforeWrite(len);
super.write(str, off, len);
afterWrite(len);
} catch (final IOException e) {
handleIOException(e);
}
}
}