controller.groovy

def save() {
        def item = new Page(params)
        if(item.validate()) {
            item.save(flush:true)
            respond item
        }
        else {
            render(status: 422, item.errors as JSON)
        }
    }

errors

| Error 2014-05-22 15:12:03,762 [http-bio-8080-exec-1] ERROR errors.GrailsExceptionResolver  - PSQLException occurred when processing request: [POST] /api/page - parameters:
content: asjdajhdlaslkjdha
title: foo
pageName: tech
secured: 1
ERROR: duplicate key value violates unique constraint "page_page_name_key"
  Detail: Key (page_name)=(tech) already exists.. Stacktrace follows:
Message: ERROR: duplicate key value violates unique constraint "page_page_name_key"
  Detail: Key (page_name)=(tech) already exists.

Page.groovy

package no.cipr.safari.auxiliary

class Page {

    String pageName, title, content

    Boolean secured

    static constraints = {
        pageName(unique: true, blank: false)
        title(blank: false)
        content(blank: false)

    }
}