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     * Constructs 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     * Constructs 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    @SuppressWarnings("resource") // Fluent API.
081    @Override
082    public Writer append(final char c) throws IOException {
083        try {
084            beforeWrite(1);
085            super.append(c);
086            afterWrite(1);
087        } catch (final IOException e) {
088            handleIOException(e);
089        }
090        return this;
091    }
092
093    /**
094     * Invokes the delegates' {@code append(CharSequence)} methods.
095     *
096     * @param csq The character sequence to write
097     * @return this writer
098     * @throws IOException if an I/O error occurs.
099     */
100    @SuppressWarnings("resource") // Fluent API.
101    @Override
102    public Writer append(final CharSequence csq) throws IOException {
103        try {
104            final int len = IOUtils.length(csq);
105            beforeWrite(len);
106            super.append(csq);
107            afterWrite(len);
108        } catch (final IOException e) {
109            handleIOException(e);
110        }
111        return this;
112    }
113
114    /**
115     * Invokes the delegates' {@code append(CharSequence, int, int)} methods.
116     *
117     * @param csq   The character sequence to write
118     * @param start The index of the first character to write
119     * @param end   The index of the first character to write (exclusive)
120     * @return this writer
121     * @throws IOException if an I/O error occurs.
122     */
123    @SuppressWarnings("resource") // Fluent API.
124    @Override
125    public Writer append(final CharSequence csq, final int start, final int end) throws IOException {
126        try {
127            beforeWrite(end - start);
128            super.append(csq, start, end);
129            afterWrite(end - start);
130        } catch (final IOException e) {
131            handleIOException(e);
132        }
133        return this;
134    }
135
136    /**
137     * Invoked by the write methods before the call is proxied. The number of chars to be written (1 for the
138     * {@link #write(int)} method, buffer length for {@link #write(char[])}, etc.) is given as an argument.
139     * <p>
140     * Subclasses can override this method to add common pre-processing functionality without having to override all the
141     * write methods. The default implementation does nothing.
142     * </p>
143     *
144     * @param n number of chars to be written
145     * @throws IOException if the pre-processing fails
146     */
147    @SuppressWarnings("unused") // Possibly thrown from subclasses.
148    protected void beforeWrite(final int n) throws IOException {
149        // noop
150    }
151
152    /**
153     * Invokes the delegate's {@code close()} method.
154     *
155     * @throws IOException if an I/O error occurs.
156     */
157    @Override
158    public void close() throws IOException {
159        try {
160            super.close();
161        } catch (final IOException e) {
162            handleIOException(e);
163        }
164    }
165
166    /**
167     * Invokes the delegate's {@code flush()} method.
168     *
169     * @throws IOException if an I/O error occurs.
170     */
171    @Override
172    public void flush() throws IOException {
173        try {
174            super.flush();
175        } catch (final IOException e) {
176            handleIOException(e);
177        }
178    }
179
180    /**
181     * Handle any IOExceptions thrown.
182     * <p>
183     * This method provides a point to implement custom exception handling. The default behavior is to re-throw the
184     * exception.
185     * </p>
186     *
187     * @param e The IOException thrown
188     * @throws IOException if an I/O error occurs.
189     */
190    protected void handleIOException(final IOException e) throws IOException {
191        throw e;
192    }
193
194    /**
195     * Invokes the delegate's {@code write(char[])} method.
196     *
197     * @param cbuf the characters to write
198     * @throws IOException if an I/O error occurs.
199     */
200    @Override
201    public void write(final char[] cbuf) throws IOException {
202        try {
203            final int len = IOUtils.length(cbuf);
204            beforeWrite(len);
205            super.write(cbuf);
206            afterWrite(len);
207        } catch (final IOException e) {
208            handleIOException(e);
209        }
210    }
211
212    /**
213     * Invokes the delegate's {@code write(char[], int, int)} method.
214     *
215     * @param cbuf the characters to write
216     * @param off  The start offset
217     * @param len  The number of characters to write
218     * @throws IOException if an I/O error occurs.
219     */
220    @Override
221    public void write(final char[] cbuf, final int off, final int len) throws IOException {
222        try {
223            beforeWrite(len);
224            super.write(cbuf, off, len);
225            afterWrite(len);
226        } catch (final IOException e) {
227            handleIOException(e);
228        }
229    }
230
231    /**
232     * Invokes the delegate's {@code write(int)} method.
233     *
234     * @param c the character to write
235     * @throws IOException if an I/O error occurs.
236     */
237    @Override
238    public void write(final int c) throws IOException {
239        try {
240            beforeWrite(1);
241            super.write(c);
242            afterWrite(1);
243        } catch (final IOException e) {
244            handleIOException(e);
245        }
246    }
247
248    /**
249     * Invokes the delegate's {@code write(String)} method.
250     *
251     * @param str the string to write
252     * @throws IOException if an I/O error occurs.
253     */
254    @Override
255    public void write(final String str) throws IOException {
256        try {
257            final int len = IOUtils.length(str);
258            beforeWrite(len);
259            super.write(str);
260            afterWrite(len);
261        } catch (final IOException e) {
262            handleIOException(e);
263        }
264    }
265
266    /**
267     * Invokes the delegate's {@code write(String)} method.
268     *
269     * @param str the string to write
270     * @param off The start offset
271     * @param len The number of characters to write
272     * @throws IOException if an I/O error occurs.
273     */
274    @Override
275    public void write(final String str, final int off, final int len) throws IOException {
276        try {
277            beforeWrite(len);
278            super.write(str, off, len);
279            afterWrite(len);
280        } catch (final IOException e) {
281            handleIOException(e);
282        }
283    }
284
285}