Using g.render in a grails service

I totally agree with John's argumentation - doing GSP in services is generally a bad design decision. But no rules without exceptions! If you still want to do this, try the following approach:

class MyService implements InitializingBean {
    boolean transactional = false
    def gspTagLibraryLookup  // being automatically injected by spring
    def g

    public void afterPropertiesSet() {
        g = gspTagLibraryLookup.lookupNamespaceDispatcher("g")
        assert g
    }

    def serviceMethod() {    
       // do anything with e.g. g.render
    }
}

Using the gspTagLibraryLookup bean you can of course access every other desired taglib in a service.

It's even simpler now in Grails 2 with the PageRenderer. e.g.:

class SomeService {
    def groovyPageRenderer

    void someMethod() {
        String html = groovyPageRenderer.render(view: '/email/someTemplateName')
    }
}

API - http://grails.org/doc/latest/api/grails/gsp/PageRenderer.html

More complete example - http://mrhaki.blogspot.com/2012/03/grails-goodness-render-gsp-views-and.html