Java: String.replace(regex, string) to remove content from XML

Question

Lets say I have an XML in the form of a string. I wish to remove the content between two tags within the XML String, say . I have tried:

String newString = oldString.replaceFirst("\\<tagName>.*?\\<//tagName>",
                                                              "Content Removed");

but it does not work. Any pointers as to what am I doing wrong?

If you have anything other than the most simple, non-nested xml a regex isn't going to work. — Richard H, Jun 27 '11 at 14:32

score 10 · Accepted Answer · edited May 23 '17 at 10:27

10

OK, apart from the obvious answer (don't parse XML with regex), maybe we can fix this:

String newString = oldString.replaceFirst("(?s)<tagName[^>]*>.*?</tagName>",
                                          "Content Removed");

Explanation:

(?s)             # turn single-line mode on (otherwise '.' won't match '\n')
<tagName         # remove unnecessary (and perhaps erroneous) escapes
[^>]*            # allow optional attributes
>.*?</tagName>

Are you sure your matching the tag case correctly? Perhaps you also want to add the i flag to the pattern: (?si)

edited May 23 '17 at 10:27

Community

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answered Jun 27 '11 at 14:30

Sean Patrick Floyd

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In the end, simply using string.replaceFirst(".*", "Content Removed"); worked fine, I don't know why I was making it so complicated. Thanks for explaining the regex attributes in Java though, pretty helpful! – TookTheRook Jun 27 '11 at 15:43

score 0 · Answer 2 · answered Jun 27 '11 at 14:29

0

Probably the problem lies here:

<//tagName>

Try changing it to

<\/tagName>

answered Jun 27 '11 at 14:29

Pablo Fernandez

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In Java, ``will do nicely without any escapes. – Sean Patrick Floyd Jun 27 '11 at 14:36
@Pable yes, but that doesn't use a Java Regex engine, it's flex / flash – Sean Patrick Floyd Jun 27 '11 at 14:42
@Pable no, it works, it's just not necessary: "A backslash may be used prior to a non-alphabetic character regardless of whether that character is part of an unescaped construct." ( [source](http://download.oracle.com/javase/6/docs/api/java/util/regex/Pattern.html#bs) ) – Sean Patrick Floyd Jun 27 '11 at 14:53
All right so no harm done then. Thanks for the info (and BTW it's Pablo not Pable :) ) – Pablo Fernandez Jun 27 '11 at 14:59
@Pablo Grrr, the same typo twice. I knew it was Pablo all along, but somehow my fingers didn't agree. Sorry!!! – Sean Patrick Floyd Jun 27 '11 at 15:13

score 0 · Answer 3 · answered Jun 27 '11 at 14:40

XML is a grammar; regular expressions are not the best tools to work with grammars.

My advice would be working with a real parser to work with the DOM instead of doing matches

For example, if you have:

<xml>
 <items>
  <myItem>
     <tagtoRemove>something1</tagToRemove>
  </myItem>
  <myItem>
     <tagtoRemove>something2</tagToRemove>
  </myItem>
 </items>

A regex could try to match it (due to the greedy mechanism)

<xml>
 <items>
  <myItem>
     matchString
  </myItem>
 </items>

Also, some uses that some DTDs may allow (such as <tagToRemove/> or <tagToRemove attr="value">) make catching tags with regex more difficult.

Unless it is very clear to you that none of the above may occur (nor or in the future) I would go with a parser.

Java: String.replace(regex, string) to remove content from XML

3 Answers3