    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.File;
    020import java.io.FileNotFoundException;
    021import java.io.FileOutputStream;
    022import java.io.IOException;
    023import java.io.OutputStream;
    024import java.io.OutputStreamWriter;
    025import java.io.StringWriter;
    026import java.io.Writer;
    027import java.nio.charset.Charset;
    028import java.nio.charset.StandardCharsets;
    029import java.util.Locale;
    030import java.util.Objects;
    031import java.util.regex.Matcher;
    032
    033import org.apache.commons.io.Charsets;
    034import org.apache.commons.io.IOUtils;
    035import org.apache.commons.io.build.AbstractStreamBuilder;
    036import org.apache.commons.io.input.XmlStreamReader;
    037
    038/**
    039 * Character stream that handles all the necessary work to figure out the charset encoding of the XML document written to the stream.
    040 * <p>
    041 * To build an instance, use {@link Builder}.
    042 * </p>
    043 *
    044 * @see Builder
    045 * @see XmlStreamReader
    046 * @since 2.0
    047 */
    048public class XmlStreamWriter extends Writer {
    049
    050    // @formatter:off
    051    /**
    052     * Builds a new {@link XmlStreamWriter}.
    053     *
    054     * <p>
    055     * For example:
    056     * </p>
    057     * <pre>{@code
    058     * WriterOutputStream w = WriterOutputStream.builder()
    059     *   .setPath(path)
    060     *   .setCharset(StandardCharsets.UTF_8)
    061     *   .get();}
    062     * </pre>
    063     *
    064     * @see #get()
    065     * @since 2.12.0
    066     */
    067    // @formatter:off
    068    public static class Builder extends AbstractStreamBuilder<XmlStreamWriter, Builder> {
    069
    070        /**
    071         * Constructs a new builder of {@link XmlStreamWriter}.
    072         */
    073        public Builder() {
    074            setCharsetDefault(StandardCharsets.UTF_8);
    075            setCharset(StandardCharsets.UTF_8);
    076        }
    077
    078        /**
    079         * Builds a new {@link XmlStreamWriter}.
    080         * <p>
    081         * You must set an aspect that supports {@link #getOutputStream()} on this builder, otherwise, this method throws an exception.
    082         * </p>
    083         * <p>
    084         * This builder uses the following aspects:
    085         * </p>
    086         * <ul>
    087         * <li>{@link #getOutputStream()}</li>
    088         * <li>{@link #getCharset()}</li>
    089         * </ul>
    090         *
    091         * @return a new instance.
    092         * @throws IllegalStateException         if the {@code origin} is {@code null}.
    093         * @throws UnsupportedOperationException if the origin cannot be converted to an {@link OutputStream}.
    094         * @throws IOException                   if an I/O error occurs converting to an {@link OutputStream} using {@link #getOutputStream()}.
    095         * @see #getOutputStream()
    096         * @see #getUnchecked()
    097         */
    098        @Override
    099        public XmlStreamWriter get() throws IOException {
    100            return new XmlStreamWriter(getOutputStream(), getCharset());
    101        }
    102
    103    }
    104
    105    private static final int BUFFER_SIZE = IOUtils.DEFAULT_BUFFER_SIZE;
    106
    107    /**
    108     * Constructs a new {@link Builder}.
    109     *
    110     * @return a new {@link Builder}.
    111     * @since 2.12.0
    112     */
    113    public static Builder builder() {
    114        return new Builder();
    115    }
    116
    117    private final OutputStream out;
    118
    119    private final Charset defaultCharset;
    120
    121    private StringWriter prologWriter = new StringWriter(BUFFER_SIZE);
    122
    123    private Writer writer;
    124
    125    private Charset charset;
    126
    127    /**
    128     * Constructs a new XML stream writer for the specified file
    129     * with a default encoding of UTF-8.
    130     *
    131     * @param file The file to write to
    132     * @throws FileNotFoundException if there is an error creating or
    133     * opening the file
    134     * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
    135     */
    136    @Deprecated
    137    public XmlStreamWriter(final File file) throws FileNotFoundException {
    138        this(file, null);
    139    }
    140
    141    /**
    142     * Constructs a new XML stream writer for the specified file
    143     * with the specified default encoding.
    144     *
    145     * @param file The file to write to
    146     * @param defaultEncoding The default encoding if not encoding could be detected
    147     * @throws FileNotFoundException if there is an error creating or
    148     * opening the file
    149     * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
    150     */
    151    @Deprecated
    152    @SuppressWarnings("resource")
    153    public XmlStreamWriter(final File file, final String defaultEncoding) throws FileNotFoundException {
    154        this(new FileOutputStream(file), defaultEncoding);
    155    }
    156
    157    /**
    158     * Constructs a new XML stream writer for the specified output stream
    159     * with a default encoding of UTF-8.
    160     *
    161     * @param out The output stream
    162     * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
    163     */
    164    @Deprecated
    165    public XmlStreamWriter(final OutputStream out) {
    166        this(out, StandardCharsets.UTF_8);
    167    }
    168
    169    /**
    170     * Constructs a new XML stream writer for the specified output stream
    171     * with the specified default encoding.
    172     *
    173     * @param out The output stream
    174     * @param defaultEncoding The default encoding if not encoding could be detected
    175     */
    176    private XmlStreamWriter(final OutputStream out, final Charset defaultEncoding) {
    177        this.out = out;
    178        this.defaultCharset = Objects.requireNonNull(defaultEncoding);
    179    }
    180
    181    /**
    182     * Constructs a new XML stream writer for the specified output stream
    183     * with the specified default encoding.
    184     *
    185     * @param out The output stream
    186     * @param defaultEncoding The default encoding if not encoding could be detected
    187     * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
    188     */
    189    @Deprecated
    190    public XmlStreamWriter(final OutputStream out, final String defaultEncoding) {
    191        this(out, Charsets.toCharset(defaultEncoding, StandardCharsets.UTF_8));
    192    }
    193
    194    /**
    195     * Closes the underlying writer.
    196     *
    197     * @throws IOException if an error occurs closing the underlying writer
    198     */
    199    @Override
    200    public void close() throws IOException {
    201        if (writer == null) {
    202            charset = defaultCharset;
    203            writer = new OutputStreamWriter(out, charset);
    204            writer.write(prologWriter.toString());
    205        }
    206        writer.close();
    207    }
    208
    209    /**
    210     * Detects the encoding.
    211     *
    212     * @param cbuf the buffer to write the characters from
    213     * @param off The start offset
    214     * @param len The number of characters to write
    215     * @throws IOException if an error occurs detecting the encoding
    216     */
    217    private void detectEncoding(final char[] cbuf, final int off, final int len)
    218            throws IOException {
    219        int size = len;
    220        final StringBuffer xmlProlog = prologWriter.getBuffer();
    221        if (xmlProlog.length() + len > BUFFER_SIZE) {
    222            size = BUFFER_SIZE - xmlProlog.length();
    223        }
    224        prologWriter.write(cbuf, off, size);
    225
    226        // try to determine encoding
    227        if (xmlProlog.length() >= 5) {
    228            if (xmlProlog.substring(0, 5).equals("<?xml")) {
    229                // try to extract encoding from XML prolog
    230                final int xmlPrologEnd = xmlProlog.indexOf("?>");
    231                if (xmlPrologEnd > 0) {
    232                    // ok, full XML prolog written: let's extract encoding
    233                    final Matcher m = XmlStreamReader.ENCODING_PATTERN.matcher(xmlProlog.substring(0,
    234                            xmlPrologEnd));
    235                    if (m.find()) {
    236                        final String encName = m.group(1).toUpperCase(Locale.ROOT);
    237                        charset = Charset.forName(encName.substring(1, encName.length() - 1));
    238                    } else {
    239                        // no encoding found in XML prolog: using default
    240                        // encoding
    241                        charset = defaultCharset;
    242                    }
    243                } else if (xmlProlog.length() >= BUFFER_SIZE) {
    244                    // no encoding found in first characters: using default
    245                    // encoding
    246                    charset = defaultCharset;
    247                }
    248            } else {
    249                // no XML prolog: using default encoding
    250                charset = defaultCharset;
    251            }
    252            if (charset != null) {
    253                // encoding has been chosen: let's do it
    254                prologWriter = null;
    255                writer = new OutputStreamWriter(out, charset);
    256                writer.write(xmlProlog.toString());
    257                if (len > size) {
    258                    writer.write(cbuf, off + size, len - size);
    259                }
    260            }
    261        }
    262    }
    263
    264    /**
    265     * Flushes the underlying writer.
    266     *
    267     * @throws IOException if an error occurs flushing the underlying writer
    268     */
    269    @Override
    270    public void flush() throws IOException {
    271        if (writer != null) {
    272            writer.flush();
    273        }
    274    }
    275
    276    /**
    277     * Returns the default encoding.
    278     *
    279     * @return the default encoding
    280     */
    281    public String getDefaultEncoding() {
    282        return defaultCharset.name();
    283    }
    284
    285    /**
    286     * Returns the detected encoding.
    287     *
    288     * @return the detected encoding
    289     */
    290    public String getEncoding() {
    291        return charset.name();
    292    }
    293
    294    /**
    295     * Writes the characters to the underlying writer, detecting encoding.
    296     *
    297     * @param cbuf the buffer to write the characters from
    298     * @param off The start offset
    299     * @param len The number of characters to write
    300     * @throws IOException if an error occurs detecting the encoding
    301     */
    302    @Override
    303    public void write(final char[] cbuf, final int off, final int len) throws IOException {
    304        if (prologWriter != null) {
    305            detectEncoding(cbuf, off, len);
    306        } else {
    307            writer.write(cbuf, off, len);
    308        }
    309    }
    310}