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From "Sebastian Nagel (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (NUTCH-797) URL not properly constructed when link target begins with a "?"
Date Sun, 27 Apr 2014 22:28:16 GMT

     [ https://issues.apache.org/jira/browse/NUTCH-797?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Sebastian Nagel updated NUTCH-797:
----------------------------------

    Attachment: NUTCH-797-2x-v2.patch

Simplified patch for 2.x, without changes to fixEmbeddedParams: it would break unit tests,
and should also fixed in parse-tika. Opened NUTCH-1767 to address links containing "params".

> URL not properly constructed when link target begins with a "?"
> ---------------------------------------------------------------
>
>                 Key: NUTCH-797
>                 URL: https://issues.apache.org/jira/browse/NUTCH-797
>             Project: Nutch
>          Issue Type: Bug
>          Components: parser
>    Affects Versions: 1.1, nutchgora
>         Environment: Win 7, Java(TM) SE Runtime Environment (build 1.6.0_16-b01)
> Also repro's on RHEL and java 1.4.2
>            Reporter: Robert Hohman
>            Assignee: Julien Nioche
>            Priority: Minor
>             Fix For: 1.9
>
>         Attachments: NUTCH-797-2x-v2.patch, NUTCH-797-2x.patch, NUTCH-797.patch, pureQueryUrl-2.patch,
pureQueryUrl.patch, test_nutch_797.html
>
>
> This is my first bug and patch on nutch, so apologies if I have not provided enough detail.
> In crawling the page at http://careers3.accenture.com/Careers/ASPX/Search.aspx?co=0&sk=0
there are links in the page that look like this:
> <a href="?co=0&sk=0&p=2&pi=1">2</a></td><td><a
href="?co=0&sk=0&p=3&pi=1">3</a>
> in org.apache.nutch.parse.tika.DOMContentUtils rev 916362 (trunk), as getOutlinks looks
for links, it comes across this link, and constucts a new url with a base URL class built
from "http://careers3.accenture.com/Careers/ASPX/Search.aspx?co=0&sk=0", and a target
of "?co=0&sk=0&p=2&pi=1"
> The URL class, per RFC 3986 at http://labs.apache.org/webarch/uri/rfc/rfc3986.html#relative-merge,
defines how to merge these two, and per the RFC, the URL class merges these to: http://careers3.accenture.com/Careers/ASPX/?co=0&sk=0&p=2&pi=1
> because the RFC explicitly states that the rightmost url segment (the Search.aspx in
this case) should be ripped off before combining.
> While this is compliant with the RFC, it means the URLs which are created for the next
round of fetching are incorrect.  Modern browsers seem to handle this case (I checked IE8
and Firefox 3.5), so I'm guessing this is an obscure exception or handling of what is a poorly
formed url on accenture's part.
> I have fixed this by modifying DOMContentUtils to look for the case where a ? begins
the target, and then pulling the rightmost component out of the base and inserting it into
the target before the ?, so the target in this example becomes:
> Search.aspx?co=0&sk=0&p=2&pi=1
> The URL class then properly constructs the new url as:
> http://careers3.accenture.com/Careers/ASPX/Search.aspx?co=0&sk=0&p=2&pi=1
> If it is agreed that this solution works, I believe the other html parsers in nutch would
need to be modified in a similar way.
> Can I get feedback on this proposed solution?  Specifically I'm worried about unforeseen
side effects.
> Much thanks
> Here is the patch info:
> Index: src/plugin/parse-tika/src/java/org/apache/nutch/parse/tika/DOMContentUtils.java
> ===================================================================
> --- src/plugin/parse-tika/src/java/org/apache/nutch/parse/tika/DOMContentUtils.java	(revision
916362)
> +++ src/plugin/parse-tika/src/java/org/apache/nutch/parse/tika/DOMContentUtils.java	(working
copy)
> @@ -299,6 +299,50 @@
>      return false;
>    }
>    
> +  private URL fixURL(URL base, String target) throws MalformedURLException
> +  {
> +	  // handle params that are embedded into the base url - move them to target
> +	  // so URL class constructs the new url class properly
> +	  if  (base.toString().indexOf(';') > 0)  
> +          return fixEmbeddedParams(base, target);
> +	  
> +	  // handle the case that there is a target that is a pure query.
> +	  // Strictly speaking this is a violation of RFC 2396 section 5.2.2 on how to assemble
> +	  // URLs but I've seen this in numerous places, for example at
> +	  // http://careers3.accenture.com/Careers/ASPX/Search.aspx?co=0&sk=0
> +	  // It has urls in the page of the form href="?co=0&sk=0&pg=1", and by default
> +	  // URL constructs the base+target combo as 
> +	  // http://careers3.accenture.com/Careers/ASPX/?co=0&sk=0&pg=1, incorrectly
> +	  // dropping the Search.aspx target
> +	  //
> +	  // Browsers handle these just fine, they must have an exception similar to this
> +	  if (target.startsWith("?"))
> +	  {
> +		  return fixPureQueryTargets(base, target);
> +	  }
> +	  
> +	  return new URL(base, target);
> +  }
> +  
> +  private URL fixPureQueryTargets(URL base, String target) throws MalformedURLException
> +  {
> +	if (!target.startsWith("?"))
> +		return new URL(base, target);
> +
> +	String basePath = base.getPath();
> +	String baseRightMost="";
> +	int baseRightMostIdx = basePath.lastIndexOf("/");
> +	if (baseRightMostIdx != -1)
> +	{
> +		baseRightMost = basePath.substring(baseRightMostIdx+1);
> +	}
> +	
> +	if (target.startsWith("?"))
> +		target = baseRightMost+target;
> +	
> +	return new URL(base, target);
> +  }
> +
>    /**
>     * Handles cases where the url param information is encoded into the base
>     * url as opposed to the target.
> @@ -400,8 +444,7 @@
>              if (target != null && !noFollow && !post)
>                try {
>                  
> -                URL url = (base.toString().indexOf(';') > 0) ? 
> -                  fixEmbeddedParams(base, target) :  new URL(base, target);
> +                URL url = fixURL(base, target);
>                  outlinks.add(new Outlink(url.toString(),
>                                           linkText.toString().trim()));
>                } catch (MalformedURLException e) {



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