nutch-1.7-二次开发-Content中增加编码

1 识别nutch-1.7的编码，完成

以前1.2是在 org.apache.nutch.parse.html.HtmlParser
               EncodingDetector detector = new EncodingDetector(conf);
               detector.autoDetectClues(content, true);
               detector.addClue(sniffCharacterEncoding(contentInOctets), "sniffed");
               String encoding = detector.guessEncoding(content,
                         defaultCharEncoding);

               metadata.set(Metadata.ORIGINAL_CHAR_ENCODING, encoding);
               metadata.set(Metadata.CHAR_ENCODING_FOR_CONVERSION, encoding);

              ------在这里讲识别出来的编码写进content的metadata中
               System.out.println("set charset in Content " + encoding);
               content.getMetadata().add("charset", encoding);

但是在1.7中却不行了。原因不详

目前的策略是，org.apache.nutch.protocol.http.api.HttpBase 
位置：src/plugin/lib-http/src/java下的org.apache.nutch.protocol.http.api包中
中进行修改。

做法是将HtmlParser中的代码搬过来。

               EncodingDetector detector = new EncodingDetector(conf);
               detector.autoDetectClues(c, true);
               detector
               .addClue(sniffCharacterEncoding(c.getContent()), "sniffed");
               String encoding = detector.guessEncoding(c, "windows-1252");

               System.out.println("set charset in Content " + encoding);
               c.getMetadata().add("charset", encoding);

同时将相关函数字段拷贝过来：

// NUTCH-1006 Meta equiv with single quotes not accepted
    private static Pattern metaPattern = Pattern.compile(
            "<meta\\s+([^>]*http-equiv=(\"|')?content-type(\"|')?[^>]*)>",
            Pattern.CASE_INSENSITIVE);
    private static Pattern charsetPattern = Pattern.compile(
            "charset=\\s*([a-z][_\\-0-9a-z]*)", Pattern.CASE_INSENSITIVE);

    // I used 1000 bytes at first, but found that some documents have
    // meta tag well past the first 1000 bytes.
    // (e.g. http://cn.promo.yahoo.com/customcare/music.html)
    private static final int CHUNK_SIZE = 2000;

    /**
     * Given a <code>byte[]</code> representing an html file of an
     * <em>unknown</em> encoding, read out 'charset' parameter in the meta tag
     * from the first <code>CHUNK_SIZE</code> bytes. If there's no meta tag for
     * Content-Type or no charset is specified, <code>null</code> is returned. <br />
     * FIXME: non-byte oriented character encodings (UTF-16, UTF-32) can't be
     * handled with this. We need to do something similar to what's done by
     * mozilla
     * (http://lxr.mozilla.org/seamonkey/source/parser/htmlparser/src/nsParser
     * .cpp#1993). See also http://www.w3.org/TR/REC-xml/#sec-guessing <br />
     *
     * @param content
     *            <code>byte[]</code> representation of an html file
     */

    private static String sniffCharacterEncoding(byte[] content) {
        int length = content.length < CHUNK_SIZE ? content.length : CHUNK_SIZE;

        // We don't care about non-ASCII parts so that it's sufficient
        // to just inflate each byte to a 16-bit value by padding.
        // For instance, the sequence {0x41, 0x82, 0xb7} will be turned into
        // {U+0041, U+0082, U+00B7}.
        String str = "";
        try {
            str = new String(content, 0, length, Charset.forName("ASCII")
                    .toString());
        } catch (UnsupportedEncodingException e) {
            // code should never come here, but just in case...
            return null;
        }

        Matcher metaMatcher = metaPattern.matcher(str);
        String encoding = null;
        if (metaMatcher.find()) {
            Matcher charsetMatcher = charsetPattern.matcher(metaMatcher
                    .group(1));
            if (charsetMatcher.find())
                encoding = new String(charsetMatcher.group(1));
        }

        return encoding;
    }

同时修改：SegmentReader的中的方法
public void reduce(Text key, Iterator<NutchWritable> values,
      OutputCollector<Text, Text> output, Reporter reporter)
          throws IOException {
    StringBuffer dump = new StringBuffer();

    dump.append("\nRecno:: ").append(recNo++).append("\n");
    dump.append("URL:: " + key.toString() + "\n");
    while (values.hasNext()) {
      Writable value = values.next().get(); // unwrap
      if (value instanceof CrawlDatum) {
        dump.append("\nCrawlDatum::\n").append(((CrawlDatum) value).toString());
      } else if (value instanceof Content) {
        Content ct = (Content)value;
        String charset = ct.getMetadata().get("charset");
        dump.append("\nContent::\n").append(ct.toString(charset));
      } else if (value instanceof ParseData) {
        dump.append("\nParseData::\n").append(((ParseData) value).toString());
      } else if (value instanceof ParseText) {
        dump.append("\nParseText::\n").append(((ParseText) value).toString());
      } else if (LOG.isWarnEnabled()) {
        LOG.warn("Unrecognized type: " + value.getClass());
      }
    }
    output.collect(key, new Text(dump.toString()));
  }