18.10.1 Asking About Available Artefacts

As a plugin developer, it can be important for you to find out about what domain classes, controllers, or other types of artefact are available in an application. For example, the Elasticsearch plugin needs to know what domain classes exist so it can check them for any searchable properties and index the appropriate ones. So how does it do it? The answer lies with the grailsApplication object, and instance of GrailsApplication that’s available automatically in controllers and GSPs and can be injected everywhere else.

The grailsApplication object has several important properties and methods for querying artefacts. Probably the most common is the one that gives you all the classes of a particular artefact type:

for (cls in grailsApplication.<artefactType>Classes) {
    ...
}

In this case, artefactType is the property name form of the artefact type. With core Grails you have:

• domain

• controller

• tagLib

• service

• codec

• bootstrap

• urlMappings

So for example, if you want to iterate over all the domain classes, you use:

for (cls in grailsApplication.domainClasses) {
    ...
}

and for URL mappings:

for (cls in grailsApplication.urlMappingsClasses) {
    ...
}

You need to be aware that the objects returned by these properties are not instances of Class. Instead, they are instances of GrailsClass that has some particularly useful properties and methods, including one for the underlying Class:

• shortName - the class name of the artefact without the package (equivalent of Class.simpleName).

• logicalPropertyName - the artefact name in property form without the 'type' suffix. So MyGreatController becomes 'myGreat'.

• isAbstract() - a boolean indicating whether the artefact class is abstract or not.

• getPropertyValue(name) - returns the value of the given property, whether it’s a static or an instance one. This works best if the property is initialised on declaration, e.g. static transactional = true.

The artefact API also allows you to fetch classes by name and check whether a class is an artefact:

• getClass(String name)

• isClass(Class clazz)

The first method will retrieve the GrailsClass instance for the given name, e.g. 'MyGreatController'. The second will check whether a class is a particular type of artefact. For example, you can use grailsApplication.isControllerClass(org.example.MyGreatController) to check whether MyGreatController is in fact a controller.