Conditionally take out elements on Groovy Closure - groovy

Question

I am using a Groovy library call ws-lite for web service testing. The way it works is it takes a closure and generate XML and send it to a web service end point.
See below for a simple example of what this closure looks like:
def bookXml = {
books {
book(available: "20", id: "1") {
title("Don Xijote")
author(id: "1", "Manuel De Cervantes")
}
book(available: "14", id: "2") {
title("Catcher in the Rye")
author(id: "2", "JD Salinger")
}
book(available: "13", id: "3") {
title("Alice in Wonderland")
author(id: "3", "Lewis Carroll")
}
}
}
Will generate XML in the request as below:
<?xml version="1.0" encoding="UTF-8"?>
<books>
<book available="20" id="1">
<title>Don Xijote</title>
<author id="1">Manuel De Cervantes</author>
</book>
<book available="14" id="2">
<title>Catcher in the Rye</title>
<author id="2">JD Salinger</author>
</book>
<book available="13" id="3">
<title>Alice in Wonderland</title>
<author id="3">Lewis Carroll</author>
</book>
</books>
In order to make my clients more flexible, I normally pass the data structure from my test to the client as a map:
def bookMap = [
books: [[
id : "1",
available: "20",
title : "Don Xijote",
author : [
id : "1",
name: "Manuel De Cervantes"
]
], [
id : "2",
available: "14",
title : "Catcher in the Rye",
author : [
id : "2",
name: "JD Salinger"
]
], [
id : "3",
available: "13",
title : "Alice in Wonderland",
author : [
id : "3",
name: "Lewis Carroll"
]
]
]
]
This is how the client looks like now:
def bookXml = {
books {
bookMap.books.book.each {
book(available: it.available, id: it.id) {
title(it.available.title)
author(id: it.author.id, it.author.name)
}
}
}
}
One thing I want to do is in the bookXml closure, is there a way that I can take out a tag, if the value in my data structure is null?
For example, if title of my first book is null in the map, then in the closure, it won't create this tag title for book one.
I know how this can be done in groovy collection using collectentries for map and collect for list, but I don't know much about transforming closure.
Can you please share some insight with me?
Thanks.

Answer 1

I do not have much knowledge of builders, but it seems that the question is about how to ignore keys will null values in a map.
This can be achieved by using the each() method with a two-arg closure. The two arguments passed to the closure in this case will be each entry's key and value.
To demonstrate -
def book = [
id : "1",
available: "20",
title : null
]
book.each {key, value->
if (value) {
println "$key->$value"
}
}

Answer 2

I highly doubt you can do what you want in a simple way. If you are not into ASTs, then a closure is not a data structure which you can manipulate easily.
IMO, you should make your input map consistent before passing it to bookXml. Other than that, stick to #diveshpremdeep answer.