运行nutch报错：unzipBestEffort returned null

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报错信息：fetch of http://szs.mof.gov.cn/zhengwuxinxi/zhengcefabu/201402/t20140224_1046354.html failed with: java.io.IOException: unzipBestEffort returned null

 

完整的报错信息为：

 

2014-03-12 16:48:38,031 ERROR http.Http - Failed to get protocol output
java.io.IOException: unzipBestEffort returned null
at org.apache.nutch.protocol.http.api.HttpBase.processGzipEncoded(HttpBase.java:317)
at org.apache.nutch.protocol.http.HttpResponse.(HttpResponse.java:164)
at org.apache.nutch.protocol.http.Http.getResponse(Http.java:64)
at org.apache.nutch.protocol.http.api.HttpBase.getProtocolOutput(HttpBase.java:140)
at org.apache.nutch.fetcher.Fetcher$FetcherThread.run(Fetcher.java:703)
2014-03-12 16:48:38,031 INFO  fetcher.Fetcher - fetch of http://szs.mof.gov.cn/zhengwuxinxi/zhengcefabu/201402/t20140224_1046354.html failed with: java.io.IOException: unzipBestEffort returned null
2014-03-12 16:48:38,031 INFO  fetcher.Fetcher - -finishing thread FetcherThread, activeThreads=0

 

由此可知抛出异常的代码位于src/plugin/lib-http/src/java/org/apache/nutch/protocol/http/api/HttpBase.java（lib-http插件）类的processGzipEncoded方法的317行：

 

byte[] content;
if (getMaxContent() >= 0) {
  content = GZIPUtils.unzipBestEffort(compressed, getMaxContent());
} else {
  content = GZIPUtils.unzipBestEffort(compressed);
}

if (content == null)
  throw new IOException("unzipBestEffort returned null");  

 

nutch1.7\src\plugin\protocol-http\src\java\org\apache\nutch\protocol\http\HttpResponse.java（protocol-http插件）的164行调用了processGzipEncoded方法： 

 

readPlainContent(in);

String contentEncoding = getHeader(Response.CONTENT_ENCODING);
if ("gzip".equals(contentEncoding) || "x-gzip".equals(contentEncoding)) {
	content = http.processGzipEncoded(content, url);
} else if ("deflate".equals(contentEncoding)) {
	content = http.processDeflateEncoded(content, url);
} else {
	if (Http.LOG.isTraceEnabled()) {
		Http.LOG.trace("fetched " + content.length + " bytes from " + url);
	}
}

 

 

通过Firefox的Firebug工具可查看该URL的响应头为Content-Encoding：gzip，Transfer-Encoding：chunked。

 

解决方法如下：

 

1、修改文件nutch1.7\src\java\org\apache\nutch\metadata\HttpHeaders.java，增加一个field：

 

public final static String TRANSFER_ENCODING = "Transfer-Encoding";

 
2、修改文件nutch1.7\src\plugin\protocol-http\src\java\org\apache\nutch\protocol\http\HttpResponse.java，替换第160行代码readPlainContent(in);为如下代码

 

String transferEncoding = getHeader(Response.TRANSFER_ENCODING); 
if(transferEncoding != null && "chunked".equalsIgnoreCase(transferEncoding.trim())){    	  
  readChunkedContent(in, line);  
}else{
  readPlainContent(in);  
}

 

3、http内容长度限制不能使用负值，只能使用一个大整数：

 

	http.content.limit
	655360000

 
4、因为修改了核心代码和插件代码，所以需要重新编译打包发布，执行nutch1.7\build.xml的默认target：runtime  

 

cd nutch1.7
ant

 

提交BUG：

1、https://issues.apache.org/jira/browse/NUTCH-1736

2、https://github.com/apache/nutch/pull/3