Add/insert elements into Groovy MarkupBuilder object after initial creation

Question

I understand how to create XML in Groovy using MarkupBuilder. How do you add/insert elements into a MarkupBuilder object after the initial creation? For example, start with:

def builder = new MarkupBuilder(writer)
  def items = builder.items{
        item(name: "book")
  }

Which would produce:

<items> 
   <item name="book/> 
 </items>

I am trying to create an extensible base XML message, using a core class to wrap the builder and inheritance to add specific tags. Building on the above example, here is my base class:

Class ItemBuilder{
   def name;
   def builder = new MarkupBuilder(writer)
   public Object getXML(){
     def items = builder.items{
            item(name: this.name)
      }
     return items;
   }
}

Here is an example extended message builder:

Class SubItemBuilder extends ItemBuilder{
       def type;

       public Object getXML(){
         def items = super.getXML();
         //do something here to add a subitem child tag....
         return items;
       }
    }

If I was working with JSON in JavaScript, I would do something like:

items.item.subitem = "foo"

I ultimately want SubItemBuilder.getXML to generate:

<items> 
     <item name="book>
       <subitem type="paperback"/>
      </item>
 </items>

Is there any easy way to achieve this? Seems like one option is to subclass MarkupBuilder and add public methods to insert child nodes. Is there a better approach to achieve the result I'm looking for?

Answer 1

The cookbook example Using MarkupBuilder for Agile XML Creation shows how to create something close to what I need.

For example:

import groovy.xml.MarkupBuilder

def writer = new StringWriter()
def builder = new MarkupBuilder(writer)  

def subitem (builder){
    builder.subitem(type: "paperback")
}


def items = builder.items{
    item(name: "book")
    subitem(builder)
}

println writer.toString()​