The document discusses REST (Representational State Transfer) and how to implement RESTful web services and clients in Grails. Some key points: - REST is an architectural style for building web services using plain text, XML, or JSON over HTTP. It uses standard HTTP methods like GET, PUT, POST, and DELETE to perform CRUD operations on resources. - In Grails, RESTful controllers can be generated and mapped to HTTP methods automatically or explicitly. Data can be returned in XML or JSON format. - Clients can access REST services using HTTPBuilder or by submitting HTML forms. Content negotiation allows returning different formats. - Additional topics covered include RSS/Atom feeds, custom XML output, and

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Grails : REST and Web Service
@somkiat

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REST
• Not really a Technology
• More an Architecture
• Simple
• Communication via plain text, xml, json
• Combine with HTTP method
• Resource-Oriented

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Mapping HTTP Method
HTTP Method Action
GET Read ( R )
PUT Update ( U )
POST Create ( C )
DELETE Delete ( D )

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Mapping REST in Grails
• Example
static mappings = {
"/product/$id?"( resource:"product" )
}
HTTP Method Action
GET show
PUT update
POST save
DELETE delete

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Mapping REST in Grails
• Example
static mappings = {
"/product/$id"(controller:"product",
parseRequest:true ){
action = [
GET:"show",
PUT:"update",
DELETE:"delete",
POST:"save“
]
}
}
Automatic XML
or JSON
Marshaling

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Create REST Controller
• grails create-controller product
class ProductController {
def show = {
render “show from rest”
}
def save = {
render “save from rest”
}
def update = {
render “update from rest”
}
def delete = {
render “delete from rest”
}
}

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REST Client
• Groovy HTTPBuilder
import groovyx.net.http.*
import static groovyx.net.http.ContentType.HTML
def url = "http://localhost:8080/example1/product/1"
def http = new HTTPBuilder( url )
http.request(Method.GET, HTML) {
response.success = {resp, html ->
println html
}
}

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REST Client
• GSP Form
<g:form controller="product" method="PUT">
<g:submitButton name="Test" />
</g:form>

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REST Controller :: Switch on HTTP method
• grails create-controller product
class ProductController {
def index = {
switch(request.method){
case "POST": render "Create"
break
case "GET": render "Retrieve"
break
case "PUT": render "Update"
break
case "DELETE": render "Delete"
break
}
}
}

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Communication via XML
• grails create-controller product
import grails.converters.*
class ProductController {
def list = {
render Product.list() as XML
}
def show = {
render Product.get( params.id ) as XML
}
}

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Domain class :: Product
• grails create-domain-class product
class Product {
String name
Double price
String toString() {
return "id=${id}|name=${name}|price=${price}"
}
}

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Insert data for Test
• File /conf/BootStap.groovy
class BootStrap {
def init = { servletContext ->
if( !Product.count() ) {
new Product(
name:"Product 1",
price:12.9 ).save( failOnError:true )
new Product(
name:"Product 2",
price:20.5 ).save( failOnError:true )
}
}
def destroy = { }
}

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XML Result
<list>
<product id="1">
<name>Product 1</name>
<price>12.9</price>
</product>
<product id="2">
<name>Product 2</name>
<price>20.5</price>
</product>
</list>

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Custom XML
<products>
<product id="1">
<product-name>product 1</name>
<product-price>12.9</price>
</product>
<product id="2">
<product-name>product 2</name>
<product-price>20.5</price>
</product>
</products>

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Communication via XML
def listXmlCustom = {
def productList = Product.list()
render( contentType:"text/xml" ) {
products{
for( temp in productList ) {
product( id:temp.id ){
"product-name"(temp.name)
"product-price"(temp.price)
}
}
}
}
}
Using Groovy
Markup Builder
http://groovy.codehaus.org/Creating+XML+using+Groovy's+MarkupBuilder

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Communication via JSON
• grails create-controller product
import grails.converters.*
class ProductController {
def list = {
render Product.list() as JSON
}
def show = {
render Product.get( params.id ) as JSON
}
}

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JSON Result
[
{ "class":"example1.Product",
"id":1,
"name":"Product 1",
"price":12.9
},
{
"class":"example1.Product",
"id":2,
"name":"Product 2",
"price":20.5
}
]

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Content Negotiation
• Allow to return different format based on the request.
• All format in file /conf/Config.groovy
grails.mime.types =
[
html: ['text/html','application/xhtml+xml'],
xml: ['text/xml', 'application/xml'],
text: 'text/plain',
js: 'text/javascript',
rss: 'application/rss+xml',
atom: 'application/atom+xml',
css: 'text/css',
csv: 'text/csv',
all: '*/*',
json: ['application/json','text/json'],
form: 'application/x-www-form-urlencoded',
multipartForm: 'multipart/form-data'
]

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Using withFormat
def list = {
if(!params.max) params.max = 10
def productList = Product.list( params )
withFormat {
html { render productList }
xml { render productList as XML }
json { render productList as JSON }
}
}
Default format
html

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How to call ?
• Default
• http://localhost:8080/example/product/list
• URL Extension
• http://localhost:8080/example/product/list.html
• Format request parameter
• http://localhost:8080/example/product/list?format=html

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URL Extension
• Disable/Enable in file /conf/Config.groovy
grails.mime.file.extensions = true // Enable ( Default )
grails.mime.file.extensions = false // Disable

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Define Format parameter in URL Mapping
• Set default format = xml
"/product2/list2" (controller:"product2", action:"list2") {
format = "xml"
}

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How to call ?
• http://localhost:8080/example/product/list.xml
• http://localhost:8080/example/product/list?format=xml

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RSS and Atom
• Using Feed plug-in
•http://docs.codehaus.org/display/GRAILS/Feeds+Plugin
• ROME Library
•https://rome.dev.java.net/

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RSS
• Install plug-in > grails install-plugin feeds
withFormat {
rss {
render(feedType:"rss", feedVersion:"2.0") {
title = "My test feed"
link = "http://www.grails66.com/feed"
description = “Grails 66 feed"
productList.each() { product ->
entry(product.name) {
link ="http://grails66.com//${product.id}"
product.name
}
}
}
}
}

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Result
• http://localhost:8080/example/product/list.rss
• http://localhost:8080/example/product/list?format=rss

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Demo :: REST with DOJO
grails create-app example2
cd example2
grails install-plugin dojo
grails install-dojo
grails create-domain-class product
grails create-controller product

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Web Service
• Web API
• Access via HTTP
• Executed on remote system
• SOA ( Service-Oriented Architecture )

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Grails Plug-in
• XFire
• http://xfire.codehaus.org/
• CFX
• http://grails.org/plugin/cxf/
• Axis2
• http://grails.org/plugin/axis2
• Metro
• https://jax-ws-commons.dev.java.net/grails/

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Thank you