Grails Training Day 1 => REST and Web Service

1. Page 1
Grails : REST and Web Service
@somkiat

2. Page 2
REST
• Not really a Technology
• More an Architecture
• Simple
• Communication via plain text, xml, json
• Combine with HTTP method
• Resource-Oriented

3. Page 3
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

6. Page 6
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”
}
}

7. Page 7
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