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POpreserve formatting when updating xml file with groovy
 

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    <p>I have a large number of XML files that contain URLs. I'm writing a groovy utility to find each URL and replace it with an updated version.</p> <p>Given example.xml:</p> <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt; &lt;page&gt; &lt;content&gt; &lt;section&gt; &lt;link&gt; &lt;url&gt;/some/old/url&lt;/url&gt; &lt;/link&gt; &lt;link&gt; &lt;url&gt;/some/old/url&lt;/url&gt; &lt;/link&gt; &lt;/section&gt; &lt;section&gt; &lt;link&gt; &lt;url&gt; /a/different/old/url?with=specialChars&amp;amp;escaped=true &lt;/url&gt; &lt;/link&gt; &lt;/section&gt; &lt;/content&gt; &lt;/page&gt; </code></pre> <p>Once the script has run, example.xml should contain:</p> <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt; &lt;page&gt; &lt;content&gt; &lt;section&gt; &lt;link&gt; &lt;url&gt;/a/new/and/improved/url&lt;/url&gt; &lt;/link&gt; &lt;link&gt; &lt;url&gt;/a/new/and/improved/url&lt;/url&gt; &lt;/link&gt; &lt;/section&gt; &lt;section&gt; &lt;link&gt; &lt;url&gt; /a/different/new/and/improved/url?with=specialChars&amp;amp;stillEscaped=true &lt;/url&gt; &lt;/link&gt; &lt;/section&gt; &lt;/content&gt; &lt;/page&gt; </code></pre> <p>This is easy to do using groovy's excellent xml support, except that I want to <strong>change the URLs and nothing else</strong> about the file.</p> <p>By that I mean:</p> <ul> <li>whitespace must not change (files might contain spaces, tabs, or both)</li> <li>comments must be preserved</li> <li>windows vs. unix-style line separators must be preserved</li> <li>the xml declaration at the top must not be added or removed</li> <li>attributes in tags must retain their order</li> </ul> <p>So far, after trying many combinations of XmlParser, DOMBuilder, XmlNodePrinter, XmlUtil.serialize(), and so on, I've landed on reading each file line-by-line and applying an ugly hybrid of the xml utilities and regular expressions.</p> <p>Reading and writing each file:</p> <pre><code>files.each { File file -&gt; def lineEnding = file.text.contains('\r\n') ? '\r\n' : '\n' def newLineAtEof = file.text.endsWith(lineEnding) def lines = file.readLines() file.withWriter { w -&gt; lines.eachWithIndex { line, index -&gt; line = update(line) w.write(line) if (index &lt; lines.size-1) w.write(lineEnding) else if (newLineAtEof) w.write(lineEnding) } } } </code></pre> <p>Searching for and updating URLs within a line:</p> <pre><code>def matcher = (line =~ urlTagRegexp) //matches a &lt;url&gt; element and its contents matcher.each { groups -&gt; def urlNode = new XmlParser().parseText(line) def url = urlNode.text() def newUrl = translate(url) if (newUrl) { urlNode.value = newUrl def replacement = nodeToString(urlNode) line = matcher.replaceAll(replacement) } } def nodeToString(node) { def writer = new StringWriter() writer.withPrintWriter { printWriter -&gt; def printer = new XmlNodePrinter(printWriter) printer.preserveWhitespace = true printer.print(node) } writer.toString().replaceAll(/[\r\n]/, '') } </code></pre> <p>This mostly works, except it can't handle a tag split over multiple lines, and messing with newlines when writing the files back out is cumbersome.</p> <p>I'm new to groovy, but I feel like there must be a groovier way of doing this.</p>
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    1. COIt's not Groovy related issue but more general one. If you want to parse XML and write it back again I see no way to preserve formatting, whitespaces and everything (unless there is some special lib for that). You can either don't parse and just replace URLs itself with a shifty regexp (full file scan) or parse and build XML again while setting desired formatting (desired but altered).
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    2. COIT IS Groovy related issue. More particularly, it relates to Groovy JDK. The question should be interpreted as such: "is there a class in Groovy JDK, that allows easy reading of XML files WITHOUT losing comments, whitespaces, etc.?" If so, the answer is: "no". XmlSlurper ignores lot of things, I stumbled on it myself. Solution would be to use non-groovy classes for that. If files are not big (say, under 50 MB), it is reasonable (and, probably, easiest) to load them with JDOM2 class SAXBuilder. The result is DOM-tree, which you can: 1. iterate and search via XPath 2. modify 3. save to file.
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    3. CO@topr yes, I suppose my question boils down to "is there some special lib for that?"
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