how to create RESTful web services with Groovy on Grails

2. Vüqar Süleymanov
Java Developer at Cybernet

3. RESTful
• What is Web Services?
• About RESTful
• RESTful with Groovy & Grails

4. Web Service is online API which we call from code.
Web Service
What is Web Sevices?

5. Difference between java local api and online api.
Client App
Library
Library
Library

6. Web Services
Web ServiceWeb ServiceClient

7. Post to your wallApps
Games

8. http://www.twitter.com http://api.twitter.com
HTML XML / JSON

9. Web Service Types
REST Web Services
SOAP Web Services

10. Client Server
HTTP request
HTTP response
HTTP exchange

11. Client Web Service
Data
<html…>
…
</html>
HTTP exchange

12. Protocol
Client Web Service
Message format
SOAP
Simple Object Access Protocol

13. Protocol
Client
SOAP
Web Service
SOAP protocol
Client
REST
Web Service
XML
JSON
Text
…

14. What is RESTful Web Sevices?
• RESTful services was first introduced in the year 2000
by Roy Fielding at the university of California.
But RESTful was popular only the last few years.
• Many developers found SOAP hard to use.
For example, working with SOAP in JavaScript means writing
a ton of code to perform extremely simple tasks because you
must create the required XML structure absolutely every time.
• REST provides a lighter weight alternative. Instead of using XML
to make a request, REST relies on a simple URL in many cases.

15. • Resource based URIs
• HTTP methods
• HTTP status codes
• Message headers
What we need?

16. RESTful with Groovy on Grails
Different approaches
• Using just @Resource.
• With uri attribute.
• With explicit UrlMappings
• Using Controller

17. package com.grailsbaki
import grails.rest.Resource
@Resource
class Job {
String name
static constraints = {
}
}
package com.grailsbaki
import grails.rest.Resource
@Resource(uri=‘/category’)
class Category {
String name
static hasMany = [jobs: Job]
static constraints = {
}
}

18. <?xml version="1.0" encoding="UTF-8"?>
<list>
<category id="1">
<jobs />
<name>Information Technology</name>
</category>
<category id="2">
<jobs />
<name>Sales &amp; Marketing</name>
</category>
<category id="3">
<jobs />
<name>Banking &amp; Finance</name>
</category>
</list>
http://localhost:8080/RESTfulOnGrails/category

19. <?xml version="1.0" encoding="UTF-8"?>
<list>
<category id="1">
<jobs />
<name>Information Technology</name>
</category>
<category id="2">
<jobs />
<name>Sales &amp; Marketing</name>
</category>
<category id="3">
<jobs />
<name>Banking &amp; Finance</name>
</category>
</list>
http://localhost:8080/RESTfulOnGrails/categories

20. package com.grailsbaki
import grails.rest.Resource
@Resource(uri=‘/category’, formats=[‘json’], readOnly = true)
class Category {
String name
static hasMany = [jobs: Job]
static constraints = {
}
} [
{
"class": "com.grailsbaku.Category",
"id": 1,
"jobs": [],
"name": "Information Technology"
},
{
"class": "com.grailsbaku.Category",
"id": 2,
"jobs": [],
"name": "Sales & Marketing"
},
{
"class": "com.grailsbaku.Category",
"id": 3,
"jobs": [],
"name": "Banking & Finance"
}

21. grails> url-mappings-report

22. "/categories" (resources: "category"){
"/jobs" (resources: "job")
}
Url
Mapping
http://localhost:8080/RESTfulOnGrails/categories/1/jobs
<?xml version="1.0" encoding="UTF-8"?>
<list>
<job id="1">
<name>Java Developer</name>
</job>
<job id="2">
<name>C# Developer</name>
</job>
<job id="3">
<name>Php Developer</name>
</job>
</list>

23. Using Controller
def save(params) {
new Person(name: params.name, surname: params.surname).save(flush: true)
}
def update() {
print("update method")
}
def delete() {
print("delete method")
}
def list() {
def people = Person.list()
respond people, [formats:['xml','json']]
request.withFormat {
json {
render people as JSON
}
}
}
static allowedMethods = [save:'POST',delete:['POST', 'DELETE'],
update:'POST', list:'GET']

24. POSTMAN

25. The End