Java tutorial
/* * 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.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.OutputStream; import java.io.OutputStreamWriter; import java.io.Writer; import java.nio.charset.Charset; import java.nio.charset.CharsetEncoder; import org.apache.commons.io.FileUtils; import org.apache.commons.io.IOUtils; /** * Writer of files that allows the encoding to be set. * <p> * This class provides a simple alternative to <code>FileWriter</code> * that allows an encoding to be set. Unfortunately, it cannot subclass * <code>FileWriter</code>. * <p> * By default, the file will be overwritten, but this may be changed to append. * <p> * The encoding must be specified using either the name of the {@link Charset}, * the {@link Charset}, or a {@link CharsetEncoder}. If the default encoding * is required then use the {@link java.io.FileWriter} directly, rather than * this implementation. * <p> * * * @since Commons IO 1.4 * @version $Id: FileWriterWithEncoding.java 611634 2008-01-13 20:35:00Z niallp $ */ public class FileWriterWithEncoding extends Writer { // Cannot extend ProxyWriter, as requires writer to be // known when super() is called /** The writer to decorate. */ private final Writer out; /** * Constructs a FileWriterWithEncoding with a file encoding. * * @param filename the name of the file to write to, not null * @param encoding the encoding to use, not null * @throws NullPointerException if the file name or encoding is null * @throws IOException in case of an I/O error */ public FileWriterWithEncoding(String filename, String encoding) throws IOException { this(new File(filename), encoding, false); } /** * Constructs a FileWriterWithEncoding with a file encoding. * * @param filename the name of the file to write to, not null * @param encoding the encoding to use, not null * @param append true if content should be appended, false to overwrite * @throws NullPointerException if the file name or encoding is null * @throws IOException in case of an I/O error */ public FileWriterWithEncoding(String filename, String encoding, boolean append) throws IOException { this(new File(filename), encoding, append); } /** * Constructs a FileWriterWithEncoding with a file encoding. * * @param filename the name of the file to write to, not null * @param encoding the encoding to use, not null * @throws NullPointerException if the file name or encoding is null * @throws IOException in case of an I/O error */ public FileWriterWithEncoding(String filename, Charset encoding) throws IOException { this(new File(filename), encoding, false); } /** * Constructs a FileWriterWithEncoding with a file encoding. * * @param filename the name of the file to write to, not null * @param encoding the encoding to use, not null * @param append true if content should be appended, false to overwrite * @throws NullPointerException if the file name or encoding is null * @throws IOException in case of an I/O error */ public FileWriterWithEncoding(String filename, Charset encoding, boolean append) throws IOException { this(new File(filename), encoding, append); } /** * Constructs a FileWriterWithEncoding with a file encoding. * * @param filename the name of the file to write to, not null * @param encoding the encoding to use, not null * @throws NullPointerException if the file name or encoding is null * @throws IOException in case of an I/O error */ public FileWriterWithEncoding(String filename, CharsetEncoder encoding) throws IOException { this(new File(filename), encoding, false); } /** * Constructs a FileWriterWithEncoding with a file encoding. * * @param filename the name of the file to write to, not null * @param encoding the encoding to use, not null * @param append true if content should be appended, false to overwrite * @throws NullPointerException if the file name or encoding is null * @throws IOException in case of an I/O error */ public FileWriterWithEncoding(String filename, CharsetEncoder encoding, boolean append) throws IOException { this(new File(filename), encoding, append); } /** * Constructs a FileWriterWithEncoding with a file encoding. * * @param file the file to write to, not null * @param encoding the encoding to use, not null * @throws NullPointerException if the file or encoding is null * @throws IOException in case of an I/O error */ public FileWriterWithEncoding(File file, String encoding) throws IOException { this(file, encoding, false); } /** * Constructs a FileWriterWithEncoding with a file encoding. * * @param file the file to write to, not null * @param encoding the encoding to use, not null * @param append true if content should be appended, false to overwrite * @throws NullPointerException if the file or encoding is null * @throws IOException in case of an I/O error */ public FileWriterWithEncoding(File file, String encoding, boolean append) throws IOException { super(); this.out = initWriter(file, encoding, append); } /** * Constructs a FileWriterWithEncoding with a file encoding. * * @param file the file to write to, not null * @param encoding the encoding to use, not null * @throws NullPointerException if the file or encoding is null * @throws IOException in case of an I/O error */ public FileWriterWithEncoding(File file, Charset encoding) throws IOException { this(file, encoding, false); } /** * Constructs a FileWriterWithEncoding with a file encoding. * * @param file the file to write to, not null * @param encoding the encoding to use, not null * @param append true if content should be appended, false to overwrite * @throws NullPointerException if the file or encoding is null * @throws IOException in case of an I/O error */ public FileWriterWithEncoding(File file, Charset encoding, boolean append) throws IOException { super(); this.out = initWriter(file, encoding, append); } /** * Constructs a FileWriterWithEncoding with a file encoding. * * @param file the file to write to, not null * @param encoding the encoding to use, not null * @throws NullPointerException if the file or encoding is null * @throws IOException in case of an I/O error */ public FileWriterWithEncoding(File file, CharsetEncoder encoding) throws IOException { this(file, encoding, false); } /** * Constructs a FileWriterWithEncoding with a file encoding. * * @param file the file to write to, not null * @param encoding the encoding to use, not null * @param append true if content should be appended, false to overwrite * @throws NullPointerException if the file or encoding is null * @throws IOException in case of an I/O error */ public FileWriterWithEncoding(File file, CharsetEncoder encoding, boolean append) throws IOException { super(); this.out = initWriter(file, encoding, append); } //----------------------------------------------------------------------- /** * Initialise the wrapped file writer. * Ensure that a cleanup occurs if the writer creation fails. * * @param file the file to be accessed * @param encoding the encoding to use - may be Charset, CharsetEncoder or String * @param append true to append * @return the initialised writer * @throws NullPointerException if the file or encoding is null * @throws IOException if an error occurs */ private static Writer initWriter(File file, Object encoding, boolean append) throws IOException { if (file == null) { throw new NullPointerException("File is missing"); } if (encoding == null) { throw new NullPointerException("Encoding is missing"); } boolean fileExistedAlready = file.exists(); OutputStream stream = null; Writer writer = null; try { stream = new FileOutputStream(file, append); if (encoding instanceof Charset) { writer = new OutputStreamWriter(stream, (Charset) encoding); } else if (encoding instanceof CharsetEncoder) { writer = new OutputStreamWriter(stream, (CharsetEncoder) encoding); } else { writer = new OutputStreamWriter(stream, (String) encoding); } } catch (IOException ex) { IOUtils.closeQuietly(writer); IOUtils.closeQuietly(stream); if (fileExistedAlready == false) { FileUtils.deleteQuietly(file); } throw ex; } catch (RuntimeException ex) { IOUtils.closeQuietly(writer); IOUtils.closeQuietly(stream); if (fileExistedAlready == false) { FileUtils.deleteQuietly(file); } throw ex; } return writer; } //----------------------------------------------------------------------- /** * Write a character. * @param idx the character to write * @throws IOException if an I/O error occurs */ public void write(int idx) throws IOException { out.write(idx); } /** * Write the characters from an array. * @param chr the characters to write * @throws IOException if an I/O error occurs */ public void write(char[] chr) throws IOException { out.write(chr); } /** * Write the specified characters from an array. * @param chr the characters to write * @param st The start offset * @param end The number of characters to write * @throws IOException if an I/O error occurs */ public void write(char[] chr, int st, int end) throws IOException { out.write(chr, st, end); } /** * Write the characters from a string. * @param str the string to write * @throws IOException if an I/O error occurs */ public void write(String str) throws IOException { out.write(str); } /** * Write the specified characters from a string. * @param str the string to write * @param st The start offset * @param end The number of characters to write * @throws IOException if an I/O error occurs */ public void write(String str, int st, int end) throws IOException { out.write(str, st, end); } /** * Flush the stream. * @throws IOException if an I/O error occurs */ public void flush() throws IOException { out.flush(); } /** * Close the stream. * @throws IOException if an I/O error occurs */ public void close() throws IOException { out.close(); } }