Question

I’ve the following closure:

def myData = {
    mkp.xmlDeclaration()
    OneEntry() {
        SecondInnerEntry()
    }
}

I can serialize its XML representation with StreamingMarkupBuilder (import omitted):

System.out << XmlUtil.serialize(new StreamingMarkupBuilder().bind(myData))

Which give me:

<?xml version="1.0" encoding="UTF-8"?>
<OneEntry>
  <SecondInnerEntry/>
</OneEntry>

But now i want to add a new entry before calling the bind() method of StreamingMarkupBuilder to obtain:

<?xml version="1.0" encoding="UTF-8"?>
<OneEntry>
  <FirstInnerEntry/>
  <SecondInnerEntry/>
</OneEntry>

How can i do this (i.e manipulate the closure to insert a new node, I don’t want to recreate the whole myData to just insert one element) ?

Answer 1

Without changing myData (as erimerturk says), or performing two passes, ie:

1. generate the xml with myData
2. parse this xml with XmlParser
3. insert a node at the desired location
4. write this new xml out

I don’t think this is possible.. The question boils down to:

How can I insert statements in the middle of an existing closure

To which the simple answer is “You can’t”*

(* it might be possible to do what you are trying by means of an AST Transformation, but I get the feeling it may not be possible in this case)