(Quick Reference)

request

Purpose

The request object is an instance of the Servlet API's HttpServletRequest class

Examples

class BookController {
    def list = {
        log.info "User agent: " + request.getHeader("User-Agent")

render(view:actionName) } }

Description

The HttpServletRequest class is useful for, amongst other things, obtaining request headers, storing request scoped attributes and establishing information about the client. Refer to the Servlet API's javadocs for further information.

Grails enhances the HttpServletRequest instance by adding the following new properties and methods:

  • XML - An instance of XmlSlurper's GPathResult class that allows parsing of an incoming XML request (useful for REST).
  • JSON - An instance of Grails' JSONObject class that allows parsing of an incoming JSON request (useful for JSON based REST).
  • forwardURI - Useful for obtaining the current request URI since the request objects requestURI property returns the original URI, not the matched one.
  • get - Returns true if the current request is an HTTP GET request.
  • post - Returns true if the current request is an HTTP POST request.
  • each - Implementation of Groovy's each method for iterating over request attributes.
  • find - Implementation of Groovy's default find method for searching request attributes.
  • findAll - Implementation of Groovy's default findAll method for searching request attributes.
  • format - The request format, used for content negotiation.
  • withFormat(Closure) - The withFormat method, used for content negotiation.
  • xhr - Returns true if the current request is an XML-HTTP (AJAX) request.

The XML and JSON properties are useful for XML APIs and can be used to parse incoming XML or JSON packages. For example given a request body of:

<book>
   <title>The Stand</title>
</book>

This can be parsed trivially:

def title = request.XML?.book?.title
render "The Title is $title"

Request attributes which are normally accessible via the getAttribute can also be indexed into using the array index operator or de-reference operator:

def user = request['user']

request['user'] = 'John'

asset 'John' == request.user