Groovy XmlUtil.serialze() is throwing a 'Content is not allowed in prolog' error when trying to serialize a GPathResult

Question

Hi all,
I've encountered a strange issue with Groovy's (1.7.3) XmlUtil.serialize( GPathResult ) method. It throws a 'Content is not allowed in prolog' error when I call it with a GPathResult, but groovy.util.Node is serializing just fine. Here is the very simple Groovy Script I am trying:

import groovy.xml.XmlUtil
import groovy.xml.StreamingMarkupBuilder

def xmlStr = """<?xml version="1.0" encoding="UTF-8"?><stuff>ver="1.0"><properties><foo>bar</foo></properties></stuff>"""

//to pretty print GPathResult -- NOT WORKING
def gpr = new XmlSlurper().parseText( xmlStr )
println XmlUtil.serialize( gpr )

println 'trying groovy.util.Node'
//to pretty print groovy.util.Node -- WORKS
def node = new XmlParser().parseText( xmlStr )
println( XmlUtil.serialize( node ) )  

This is the output I get:

[Fatal Error] :1:1: Content is not allowed in prolog.
ERROR:  'Content is not allowed in prolog.'
<?xml version="1.0" encoding="UTF-8"?>
trying groovy.util.Node
<?xml version="1.0" encoding="UTF-8"?>
<stuff ver="1.0">
 <properties>
  <foo>bar</foo>
 </properties>
</stuff>

I am using Groovy Version: 1.7.3 JVM: 1.6.0_20 on Mac OS X Snow Leopard

Is anyone else experiencing this?

Answer 1

Looks like a bug where Groovy is selecting the wrong serialize method to execute in XmlUtil

If we hard-cast it, it seems to work for me (does it for you?)

println XmlUtil.serialize( (groovy.util.slurpersupport.GPathResult)gpr )

I've added it to the JIRA here: http://jira.codehaus.org/browse/GROOVY-4285 So hopefully, it will be fixed in future releases, and you won't need the cast

[edit] The JIRA now states that a fix has gone into trunk, and will be generally available in 1.7.4+

Answer 2

You could just use Simple as an alternative to Groovy XmlUtil.