In this recipe, we will learn how to update and delete nodes of a parsed XML document using the XmlParser.
Let's start by parsing the following XML with the XmlParser (see the Reading XML using XmlParser recipe):
def carXml = '''
<?xml version="1.0" ?>
<cool-cars>
<car manufacturer="Ferrari">
<model>430 Scuderia</model>
</car>
<car manufacturer="Porsche">
<model>911</model>
</car>
<car manufacturer="Lotus">
<model>Elan</model>
</car>
<car manufacturer="Pagani">
<model>Huayra</model>
</car>
</cool-cars>
'''
def coolCars = new XmlParser().parseText(carXml)The simplest way to change the value of a node is to reference it using the position of the node itself.
- For instance, if we want to change the model of the Lotus brand to Elise, we can reference the model node as showed in the example:
coolCars.car[2].model[0].value = 'Elise'
- Alternatively, it is possible to find a node by its contents and alter it:
coolCars.find { it.@manufacturer == 'Ferrari' }.model[0].value = 'Testarossa'Instead of referencing the node by its position, we use the
findmethod to reference the attribute of the node. - What about modifying an attribute of a node?
coolCars.car[1].@manufacturer = 'Ford'
- Finally, to delete nodes, you can use a very similar approach:
coolCars.remove(coolCars.car[3]) coolCars.remove(coolCars.car[1])
or even better:
coolCars.findAll { [email protected]('P') } .each { coolCars.remove(it) }This previous example deletes every car's manufacturer, whose name starts with the letter P.
- Now we can print the result:
new XmlNodePrinter().print(coolCars)
- The output will be as follows:
<cool-cars> <car manufacturer="Ferrari"> <model> Testarossa </model> </car> <car manufacturer="Lotus"> <model> Elise </model> </car> </cool-cars>
Thanks to Groovy's dynamic typing and metaprogramming capabilities, we can access the members of our document directly by name, as shown in several other recipes from this chapter: Reading XML using XmlSlurper, Searching in XML with GPath, and Constructing XML content.
In most cases, we operate directly on the groovy.util.Node classes or collections of nodes. The full power of the Groovy Collection API can be applied easily to navigate and modify the document tree.
In the previous code, we also made use of the .@ operator, which gives access to an attribute of an XML element.
In the last step, we print out the resulting in-memory node tree to the standard output with the help of the XmlNodePrinter class. This class pretty prints a groovy.util.Node including all children in XML format.