001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.io.output;
018
019import java.io.FilterWriter;
020import java.io.IOException;
021import java.io.Writer;
022import java.util.Collection;
023
024import org.apache.commons.io.IOUtils;
025
026/**
027 * A Proxy stream collection which acts as expected, that is it passes the method calls on to the proxied streams and
028 * doesn't change which methods are being called. It is an alternative base class to {@link FilterWriter} and
029 * {@link FilterCollectionWriter} to increase reusability, because FilterWriter changes the methods being called, such
030 * as {@code write(char[])} to {@code write(char[], int, int)} and {@code write(String)} to
031 * {@code write(String, int, int)}. This is in contrast to {@link ProxyWriter} which is backed by a single
032 * {@link Writer}.
033 *
034 * @since 2.7
035 */
036public class ProxyCollectionWriter extends FilterCollectionWriter {
037
038    /**
039     * Creates a new proxy collection writer.
040     *
041     * @param writers Writers object to provide the underlying targets.
042     */
043    public ProxyCollectionWriter(final Collection<Writer> writers) {
044        super(writers);
045    }
046
047    /**
048     * Creates a new proxy collection writer.
049     *
050     * @param writers Writers to provide the underlying targets.
051     */
052    public ProxyCollectionWriter(final Writer... writers) {
053        super(writers);
054    }
055
056    /**
057     * Invoked by the write methods after the proxied call has returned successfully. The number of chars written (1 for
058     * the {@link #write(int)} method, buffer length for {@link #write(char[])}, etc.) is given as an argument.
059     * <p>
060     * Subclasses can override this method to add common post-processing functionality without having to override all
061     * the write methods. The default implementation does nothing.
062     * </p>
063     *
064     * @param n number of chars written
065     * @throws IOException if the post-processing fails
066     */
067    @SuppressWarnings("unused") // Possibly thrown from subclasses.
068    protected void afterWrite(final int n) throws IOException {
069        // noop
070    }
071
072    /**
073     * Invokes the delegates' {@code append(char)} methods.
074     *
075     * @param c The character to write
076     * @return this writer
077     * @throws IOException if an I/O error occurs.
078     * @since 2.0
079     */
080    @Override
081    public Writer append(final char c) throws IOException {
082        try {
083            beforeWrite(1);
084            super.append(c);
085            afterWrite(1);
086        } catch (final IOException e) {
087            handleIOException(e);
088        }
089        return this;
090    }
091
092    /**
093     * Invokes the delegates' {@code append(CharSequence)} methods.
094     *
095     * @param csq The character sequence to write
096     * @return this writer
097     * @throws IOException if an I/O error occurs.
098     */
099    @Override
100    public Writer append(final CharSequence csq) throws IOException {
101        try {
102            final int len = IOUtils.length(csq);
103            beforeWrite(len);
104            super.append(csq);
105            afterWrite(len);
106        } catch (final IOException e) {
107            handleIOException(e);
108        }
109        return this;
110    }
111
112    /**
113     * Invokes the delegates' {@code append(CharSequence, int, int)} methods.
114     *
115     * @param csq   The character sequence to write
116     * @param start The index of the first character to write
117     * @param end   The index of the first character to write (exclusive)
118     * @return this writer
119     * @throws IOException if an I/O error occurs.
120     */
121    @Override
122    public Writer append(final CharSequence csq, final int start, final int end) throws IOException {
123        try {
124            beforeWrite(end - start);
125            super.append(csq, start, end);
126            afterWrite(end - start);
127        } catch (final IOException e) {
128            handleIOException(e);
129        }
130        return this;
131    }
132
133    /**
134     * Invoked by the write methods before the call is proxied. The number of chars to be written (1 for the
135     * {@link #write(int)} method, buffer length for {@link #write(char[])}, etc.) is given as an argument.
136     * <p>
137     * Subclasses can override this method to add common pre-processing functionality without having to override all the
138     * write methods. The default implementation does nothing.
139     * </p>
140     *
141     * @param n number of chars to be written
142     * @throws IOException if the pre-processing fails
143     */
144    @SuppressWarnings("unused") // Possibly thrown from subclasses.
145    protected void beforeWrite(final int n) throws IOException {
146        // noop
147    }
148
149    /**
150     * Invokes the delegate's {@code close()} method.
151     *
152     * @throws IOException if an I/O error occurs.
153     */
154    @Override
155    public void close() throws IOException {
156        try {
157            super.close();
158        } catch (final IOException e) {
159            handleIOException(e);
160        }
161    }
162
163    /**
164     * Invokes the delegate's {@code flush()} method.
165     *
166     * @throws IOException if an I/O error occurs.
167     */
168    @Override
169    public void flush() throws IOException {
170        try {
171            super.flush();
172        } catch (final IOException e) {
173            handleIOException(e);
174        }
175    }
176
177    /**
178     * Handle any IOExceptions thrown.
179     * <p>
180     * This method provides a point to implement custom exception handling. The default behavior is to re-throw the
181     * exception.
182     * </p>
183     *
184     * @param e The IOException thrown
185     * @throws IOException if an I/O error occurs.
186     */
187    protected void handleIOException(final IOException e) throws IOException {
188        throw e;
189    }
190
191    /**
192     * Invokes the delegate's {@code write(char[])} method.
193     *
194     * @param cbuf the characters to write
195     * @throws IOException if an I/O error occurs.
196     */
197    @Override
198    public void write(final char[] cbuf) throws IOException {
199        try {
200            final int len = IOUtils.length(cbuf);
201            beforeWrite(len);
202            super.write(cbuf);
203            afterWrite(len);
204        } catch (final IOException e) {
205            handleIOException(e);
206        }
207    }
208
209    /**
210     * Invokes the delegate's {@code write(char[], int, int)} method.
211     *
212     * @param cbuf the characters to write
213     * @param off  The start offset
214     * @param len  The number of characters to write
215     * @throws IOException if an I/O error occurs.
216     */
217    @Override
218    public void write(final char[] cbuf, final int off, final int len) throws IOException {
219        try {
220            beforeWrite(len);
221            super.write(cbuf, off, len);
222            afterWrite(len);
223        } catch (final IOException e) {
224            handleIOException(e);
225        }
226    }
227
228    /**
229     * Invokes the delegate's {@code write(int)} method.
230     *
231     * @param c the character to write
232     * @throws IOException if an I/O error occurs.
233     */
234    @Override
235    public void write(final int c) throws IOException {
236        try {
237            beforeWrite(1);
238            super.write(c);
239            afterWrite(1);
240        } catch (final IOException e) {
241            handleIOException(e);
242        }
243    }
244
245    /**
246     * Invokes the delegate's {@code write(String)} method.
247     *
248     * @param str the string to write
249     * @throws IOException if an I/O error occurs.
250     */
251    @Override
252    public void write(final String str) throws IOException {
253        try {
254            final int len = IOUtils.length(str);
255            beforeWrite(len);
256            super.write(str);
257            afterWrite(len);
258        } catch (final IOException e) {
259            handleIOException(e);
260        }
261    }
262
263    /**
264     * Invokes the delegate's {@code write(String)} method.
265     *
266     * @param str the string to write
267     * @param off The start offset
268     * @param len The number of characters to write
269     * @throws IOException if an I/O error occurs.
270     */
271    @Override
272    public void write(final String str, final int off, final int len) throws IOException {
273        try {
274            beforeWrite(len);
275            super.write(str, off, len);
276            afterWrite(len);
277        } catch (final IOException e) {
278            handleIOException(e);
279        }
280    }
281
282}