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8.1.6 XML and JSON Responses - Reference Documentation

Authors: Graeme Rocher, Peter Ledbrook, Marc Palmer, Jeff Brown, Luke Daley, Burt Beckwith, Lari Hotari

Version: 3.1.6

8.1.6 XML and JSON Responses

Using the render method to output XML

Grails supports a few different ways to produce XML and JSON responses. The first is the render method.

The render method can be passed a block of code to do mark-up building in XML:

def list() {

def results = Book.list()

render(contentType: "text/xml") { books { for (b in results) { book(title: b.title) } } } }

The result of this code would be something like:

<books>
    <book title="The Stand" />
    <book title="The Shining" />
</books>

Be careful to avoid naming conflicts when using mark-up building. For example this code would produce an error:

def list() {

def books = Book.list() // naming conflict here

render(contentType: "text/xml") { books { for (b in results) { book(title: b.title) } } } }

This is because there is local variable books which Groovy attempts to invoke as a method.

Using the render method to output JSON

The render method can also be used to output JSON:

def list() {

def results = Book.list()

render(contentType: "application/json") { books = array { for (b in results) { book title: b.title } } } }

In this case the result would be something along the lines of:

[
    {"title":"The Stand"},
    {"title":"The Shining"}
]

The same dangers with naming conflicts described above for XML also apply to JSON building.

Automatic XML Marshalling

Grails also supports automatic marshalling of domain classes to XML using special converters.

To start off with, import the grails.converters package into your controller:

import grails.converters.*

Now you can use the following highly readable syntax to automatically convert domain classes to XML:

render Book.list() as XML

The resulting output would look something like the following::

<?xml version="1.0" encoding="ISO-8859-1"?>
<list>
  <book id="1">
    <author>Stephen King</author>
    <title>The Stand</title>
  </book>
  <book id="2">
    <author>Stephen King</author>
    <title>The Shining</title>
  </book>
</list>

For more information on XML marshalling see the section on REST

Automatic JSON Marshalling

Grails also supports automatic marshalling to JSON using the same mechanism. Simply substitute XML with JSON:

render Book.list() as JSON

The resulting output would look something like the following:

[
    {"id":1,
     "class":"Book",
     "author":"Stephen King",
     "title":"The Stand"},
    {"id":2,
     "class":"Book",
     "author":"Stephen King",
     "releaseDate":new Date(1194127343161),
     "title":"The Shining"}
 ]