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The Apache Commons IO library contains utility classes, stream implementations, file filters,
file comparators, endian transformation classes, and much more.
/*
* 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.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.StringWriter;
import java.io.Writer;
import java.util.Locale;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.commons.io.IOUtils;
import org.apache.commons.io.input.XmlStreamReader;
/**
* Character stream that handles all the necessary Voodoo to figure out the
* charset encoding of the XML document written to the stream.
*
* @see XmlStreamReader
* @since 2.0
*/
public class XmlStreamWriter extends Writer {
private static final int BUFFER_SIZE = IOUtils.DEFAULT_BUFFER_SIZE;
private final OutputStream out;
private final String defaultEncoding;
private StringWriter xmlPrologWriter = new StringWriter(BUFFER_SIZE);
private Writer writer;
private String encoding;
/**
* Constructs a new XML stream writer for the specified output stream
* with a default encoding of UTF-8.
*
* @param out The output stream
*/
public XmlStreamWriter(final OutputStream out) {
this(out, null);
}
/**
* Constructs a new XML stream writer for the specified output stream
* with the specified default encoding.
*
* @param out The output stream
* @param defaultEncoding The default encoding if not encoding could be detected
*/
public XmlStreamWriter(final OutputStream out, final String defaultEncoding) {
this.out = out;
this.defaultEncoding = defaultEncoding != null ? defaultEncoding : "UTF-8";
}
/**
* Constructs a new XML stream writer for the specified file
* with a default encoding of UTF-8.
*
* @param file The file to write to
* @throws FileNotFoundException if there is an error creating or
* opening the file
*/
public XmlStreamWriter(final File file) throws FileNotFoundException {
this(file, null);
}
/**
* Constructs a new XML stream writer for the specified file
* with the specified default encoding.
*
* @param file The file to write to
* @param defaultEncoding The default encoding if not encoding could be detected
* @throws FileNotFoundException if there is an error creating or
* opening the file
*/
@SuppressWarnings("resource")
public XmlStreamWriter(final File file, final String defaultEncoding) throws FileNotFoundException {
this(new FileOutputStream(file), defaultEncoding);
}
/**
* Returns the detected encoding.
*
* @return the detected encoding
*/
public String getEncoding() {
return encoding;
}
/**
* Returns the default encoding.
*
* @return the default encoding
*/
public String getDefaultEncoding() {
return defaultEncoding;
}
/**
* Closes the underlying writer.
*
* @throws IOException if an error occurs closing the underlying writer
*/
@Override
public void close() throws IOException {
if (writer == null) {
encoding = defaultEncoding;
writer = new OutputStreamWriter(out, encoding);
writer.write(xmlPrologWriter.toString());
}
writer.close();
}
/**
* Flushes the underlying writer.
*
* @throws IOException if an error occurs flushing the underlying writer
*/
@Override
public void flush() throws IOException {
if (writer != null) {
writer.flush();
}
}
/**
* Detects the encoding.
*
* @param cbuf the buffer to write the characters from
* @param off The start offset
* @param len The number of characters to write
* @throws IOException if an error occurs detecting the encoding
*/
private void detectEncoding(final char[] cbuf, final int off, final int len)
throws IOException {
int size = len;
final StringBuffer xmlProlog = xmlPrologWriter.getBuffer();
if (xmlProlog.length() + len > BUFFER_SIZE) {
size = BUFFER_SIZE - xmlProlog.length();
}
xmlPrologWriter.write(cbuf, off, size);
// try to determine encoding
if (xmlProlog.length() >= 5) {
if (xmlProlog.substring(0, 5).equals("");
if (xmlPrologEnd > 0) {
// ok, full XML prolog written: let's extract encoding
final Matcher m = ENCODING_PATTERN.matcher(xmlProlog.substring(0,
xmlPrologEnd));
if (m.find()) {
encoding = m.group(1).toUpperCase(Locale.ROOT);
encoding = encoding.substring(1, encoding.length() - 1);
} else {
// no encoding found in XML prolog: using default
// encoding
encoding = defaultEncoding;
}
} else if (xmlProlog.length() >= BUFFER_SIZE) {
// no encoding found in first characters: using default
// encoding
encoding = defaultEncoding;
}
} else {
// no XML prolog: using default encoding
encoding = defaultEncoding;
}
if (encoding != null) {
// encoding has been chosen: let's do it
xmlPrologWriter = null;
writer = new OutputStreamWriter(out, encoding);
writer.write(xmlProlog.toString());
if (len > size) {
writer.write(cbuf, off + size, len - size);
}
}
}
}
/**
* Writes the characters to the underlying writer, detecting encoding.
*
* @param cbuf the buffer to write the characters from
* @param off The start offset
* @param len The number of characters to write
* @throws IOException if an error occurs detecting the encoding
*/
@Override
public void write(final char[] cbuf, final int off, final int len) throws IOException {
if (xmlPrologWriter != null) {
detectEncoding(cbuf, off, len);
} else {
writer.write(cbuf, off, len);
}
}
static final Pattern ENCODING_PATTERN = XmlStreamReader.ENCODING_PATTERN;
}