[NUTCH-797] URL not properly constructed when link target begins with a "?"

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.1, nutchgora
• Fix Version/s: 2.3
• Component/s: parser

Environment

Win 7, Java(TM) SE Runtime Environment (build 1.6.0_16-b01)
Also repro's on RHEL and java 1.4.2

• Patch Info: Patch Available
• Assignee: Sebastian Nagel
• Reporter: Robert Hohman
• Created: 25/Feb/10 20:47
• Updated: 01/May/14 06:23
• Resolved: 28/Apr/14 21:10

Description

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) {

Issue Links

• incorporates: NUTCH-1115 Option to disable fixing of embedded params in DomContentUtils
• is duplicated by: NUTCH-952 fix outlink which started with '?' in html parser
• is duplicated by: NUTCH-566 Sun's URL class has bug in creation of relative query URLs
• is related to: NUTCH-952 fix outlink which started with '?' in html parser
• relates to: NUTCH-566 Sun's URL class has bug in creation of relative query URLs