Chap-5. Les Frameworks REST

1Chapitre 5. Les frameworks REST

Chapitre 5

Les Frameworks REST

Les frameworks REST

2M.Romdhani, INSAT, Dcembre 2015

Sommaire

Qu'est ce que REST ?

Le format JSON

Mise en uvre de REST avec JAX-RS et Jersey

Mise en uvre de REST avec Apache-CXF

Mise en uvre de REST avec REST-Easy de JBoss

Mise en uvre de REST avec Spring MVC


Qu'est ce que REST ?

Les frameworks REST


Qu'est ce que REST?

"The motivation for developing REST was to createan architectural model for how the Web should work,

such that it could serve as the guiding framework for the Web protocol standards

Roy Fielding

REST (Representational state transfer) est une manire de construire une application pour les systmes distribus comme le Web. Le terme a t inventpar Roy Fielding en 2000.

REST n'est ni un protocole ni un format, c'est un style darchitecture, bti sur quelques principes simples : L'URI est fondamentale : connatre l'URI doit suffire pour accder la ressource ; HTTP fournit toutes les oprations ncessaires (GET, POST, PUT et DELETE,

essentiellement) ; Chaque opration est auto-suffisante : il n'y a pas d'tat ; Utilisation des standards hypermedia : HTML ou XML qui permettent de faire des

liens vers d'autres ressources et d'assurer ainsi la navigation dans l'application REST.


Les frameworks REST


Architecture oriente ressource

Linformation de base, dans une architecture REST, est appele ressource. Dans un systme hypermedia, une ressource est tout ce qui peut tre rfrenc par un lien.

Une ressource est identifie par un identificateur de ressource. Sur le web ces identificateurs sont les URI (Uniform Resource Identifier).

Enfin, les composants de larchitecture manipulent ces ressources en transfrant des reprsentations de ces ressources ( format HTML ou XML).

Les frameworks REST


Architecture oriente ressource


Les frameworks REST


REST et le Web

REST est le style architectural original du Web !

Tous les services Web que nous utilisons depuis des annes ,services de commande des livres , services de recherche ,dictionnaire en lignesont des Web services bass sur REST.

Donc, vous tes entrain dutiliser REST sans le savoir !

Les frameworks REST


Pourquoi lappellation Representational state transfer?

Le client rfrencie une ressource Web grace une URL.Il reoit unereprsentation de la ressource(ici un doc HTML).

La nouvelle reprsentation (Boeing747.html) place lapplication clientedans un autre tat(state).

Ainsi, lapplication cliente change(transfers) dtat avec chaquereprsentation

ResourceClienthttp://www.boeing.com/aircraft/747

Boeing747.html

Fuel ncessaireMaintenance prvue.


Les frameworks REST


Caractristiques du modle REST

Client-Server: La sparation des concepts amliore la portabilit de l'interface

utilisateur travers les diverses plates-formes. Permettre aux composants d'voluer indpendamment.

Stateless: (sans tat) L'tat de la session est entirement dtenu par le client. La fiabilit est amliore car il est plus simple de faire face des checs

partiels (restauration) La possibilit de monte en charge est meilleure.

Cache: Offre la possibilit dliminer tout ou une partie de certaines interactions Amliore l'efficacit, la monte en charge et rduit la latence moyenne

dans une srie d'interactions.

Les frameworks REST


Caractristiques du modle REST

Uniform interface: Toutes les ressouces sont manipules par une interface gnrique

(HTTP GET, POST, PUT, DELETE).

Code la demande: REST permet lextension des fonctionnalits dun client en tlchargeant et excutant

du code sous forme d'applet ou de scripts. Amliore l'extensibilit du systme grce la possibilit de tlcharger des

fonctionnalits aprs le dploiement.


Les frameworks REST


REST et les web services

Un web service qui suit larchitecture REST est dit RESTful

Le web doit son succs ce style darchitecture oriente ressource. Il na pas t conu comme un BUS XML pour transfrer des messages entre applications (cas du SOAP).

Les qualits recherches pour le web rejoignent celles des web services : sparation des tches, simplicit, interoprabilit, performances rseaux, ...

Les frameworks REST


REST Web-services

HTTP methods GET defines a reading access of the resource without side-effects. The

resource is never changed via a GET request, e.g. the request has no side effects (idempotent).

PUT creates a new resource, must also be idempotent.

DELETE removes the resources. The operations are idempotent, they can get repeated without leading to different results.

POST updates an existing resource or creates a new resource.


Les frameworks REST


REST Web-services

Example base URI for the web service: http://example.com/resources/

Resource GET PUT POST DELETE

Collection URI, such ashttp://example.com/resourc

es/

List the URIs and perhaps other details of the collection's members.

Replace the entire collection with another collection.

Create a new entry in the collection. The new entry's URL is assigned automatically and is usually returned by the operation.

Delete the entirecollection.

Element URI, such ashttp://example.com/resourc

es/item17

Retrieve a representation of the addressed member of the collection, expressed in an appropriate Internet media type.

Replace the addressed member of the collection, or if it doesn't exist, create it.

Not generally used. Treat the addressed member as a collection in its own right and create a new entry in it.

Delete the addressed member of the collection.

Le format JSON


Les frameworks REST


JSON Notation

A lightweight data-interchange format

A subset of the object literal notation of JavaScript (or ECMA-262). A JSON string must be enclosed by double quotes.

Comparison of JSON and XML Similarities:

Both are human readable/Both have very simple syntax Both are hierarchical/Both are language independent Both can be used by Ajax

Differences: Syntax is different JSON is less verbose JSON includes arrays Names in JSON must not be JavaScript reserved words XML can be validated JavaScript is not typically used on the server side

Les frameworks REST


JSON example

JSON stands for JavaScript Object Notation Despite the name, JSON is a (mostly) language-independent way of specifying

objects as name-value pairs

Example (http://secretgeek.net/json_3mins.asp):{"skillz": {

"web":[{ "name": "html", "years": 5

},{ "name": "css", "years": 3

}]"database":[

{ "name": "sql", "years": 7

}]}}


Les frameworks REST


JSON syntax, I

An object is an unordered set of name/value pairs The pairs are enclosed within braces, { } There is a colon between the name and the value Pairs are separated by commas Example: { "name": "html", "years": 5 }

An array is an ordered collection of values The values are enclosed within brackets, [ ] Values are separated by commas Example: [ "html", xml", "css" ]

Les frameworks REST


JSON syntax, II

A value can be: A string, a number, true, false, null, an object, or an array Values can be nested

Strings are enclosed in double quotes, and can contain the usual assortment of escaped characters

Numbers have the usual C/C++/Java syntax, including exponential (E) notation All numbers are decimal--no octal or hexadecimal

Whitespace can be used between any pair of tokens

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Chapitre 5. Les frameworks REST

Les frameworks REST


Using JSON in JavaScript

JSON encoded data JavaScript object var myObject = Eval('(' + myJSONtext + ')'); var myObject = JSON.Parse(myJSONtext);

JavaScript value JSON encoded data var myJSONText = JSON.stringify(myObject);

Les frameworks REST


Using JSON with XmlHttpRequest

Sending JSON encoded data to the server Use HTTP POST method and send the JSON encoded data in the body of

the request// xmlhttp is an XmlHttpRequest objectxmlhttp.setRequestHeader(

'Content-type','application/x-www-form-urlencoded;charset=UTF-8;'

);xmlhttp.send('jsondata=' + escape(myJSONText));

Handling JSON encoded data from the server Server should set the content type to "text/plain" In the handler function of xmlhttp object, read xmlhttp.responseText

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Mise en uvre de REST avec JAX-RS et Jersey

Les frameworks REST


JAX-RS

JSR-311: JAX-RS: The Java API for RESTful Web Services

Introduced in Java SE 5: annotation-based

Objective: simplify the development and deployment of web service clients and endpoints.

Part of Java EE 6

No configuration is necessary to start using JAX-RS

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Les frameworks REST


JAX-RS API

Specifications Annotations to aid in mapping a resource class (a Plain Old

Java Object) as a web resource. @Path specifies the relative path for a resource class or method. @GET, @PUT, @POST, @DELETE and @HEAD specify the HTTP request type of a

resource.

@Produces specifies the response MIME media types. @Consumes specifies the accepted request media types.

Annotations to method parameters to pull information out of the request. All the @*Param annotations take a key of some form which is used to look up the value required.

@PathParam binds the parameter to a path segment. @QueryParam binds the parameter to the value of an HTTP query parameter. @MatrixParam binds the parameter to the value of an HTTP matrix parameter. @HeaderParam binds the parameter to an HTTP header value. @CookieParam binds the parameter to a cookie value. @FormParam binds the parameter to a form value. @DefaultValue specifies a default value for the above bindings when the key is not

found. @Context returns the entire context of the object. Ex.(@Context HttpServletRequest

request)

Les frameworks REST


JAX-RS API

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Les frameworks REST


JAX-RS implementations

Implementations Jersey, from Sun/Oracle (Java EE 6 reference implementation) Apache, CFX from Apache RESTeasy, from JBoss Restlet, created by Jerome Louvel, a pioneer in REST frameworks.

Les frameworks REST


Jersey

Jersey is the reference implementation for the JSR 311 specification. The Jersey implementation provides a library to implement Restful

webservices in a Java servlet container. On the server side Jersey provides a servlet implementation which

scans predefined classes to identify RESTful resources. In your web.xml configuration file your register this servlet for your web

application. The Jersey implementation also provides a client library to communicate

with a RESTful webservice. JAX-RS supports the creation of XML and JSON via the Java

Architecture for XML Binding (JAXB).

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Les frameworks REST


Mise en uvre de REST avec Jersey

Steps Setup of Jersey libraries either manually or using a depedency

management tools like Maven or Gradle Create a web application and register the Jersey Servlet dispatcher

in web.xml

Jersey REST Serviceorg.glassfish.jersey.servlet.ServletContainer

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Les frameworks REST


Mise en uvre de REST Apache-CXF

Steps Create the Web App using Maven and download the Apache CXF

dependencies Configure Apache CXF in the Web App

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Mise en uvre de REST avec REST-Easy

Les frameworks REST


Mise en uvre de REST Easy

Steps Create the Web App using Maven and download the Apache CXF

dependencies

org.jboss.resteasyresteasy-jaxrs2.2.1.GA

Configure Apache CXF in the Web App

org.jboss.resteasy.plugins.server.servlet.ResteasyBootstrap

resteasy-servlet

org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher

resteasy-servlet/rest/*

Contd

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Les frameworks REST


Mise en uvre de REST Easy

Steps (Contd) Create the Web App using Maven and download the Apache CXF

dependencies

org.jboss.resteasyresteasy-jaxrs2.2.1.GA

Configure Apache CXF in the Web App

org.jboss.resteasy.plugins.server.servlet.ResteasyBootstrap

resteasy-servlet org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher

resteasy-servlet/rest/*

Create the Service Implementation on the App Test out the service


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Les frameworks REST



Spring MVC 4 annotations supporting REST @RestController : Spring 4s new @RestController annotation. This annotation eliminates the

need of annotating each method with @ResponseBody. Under the hood, @RestController isitself annotated with @ResponseBody, and can be considered as combination of @Controller and @ResponseBody.

@RequestBody : If a method parameter is annotated with @RequestBody, Spring will bind the incoming HTTP request body(for the URL mentioned in @RequestMapping for that method) to that parameter. While doing that, Spring will [behind the scenes] use HTTP Message convertersto convert the HTTP request body into domain object [deserialize request body to domainobject], based on ACCEPT or Content-Type header present in request.

@ResponseBody : If a method is annotated with @ResponseBody, Spring will bind the return value to outgoing HTTP response body. While doing that, Spring will [behind the scenes] use HTTP Message converters to convert the return value to HTTP response body [serialize the object to response body], based on Content-Type present in request HTTP header. As alreadymentioned, in Spring 4, you may stop using this annotation.

ResponseEntity is a real deal. It represents the entire HTTP response. Good thing about it isthat you can control anything that goes into it. You can specify status code, headers, and body. It comes with several constructors to carry the information you want to sent in HTTP Response.

@PathVariable This annotation indicates that a method parameter should be bound to a URI template variable [the one in '{}'].

Basically, @RestController , @RequestBody, ResponseEntity & @PathVariable are all you need to know to implement a REST API in Spring 4. Additionally, spring provides several support classes to help you implement something customized.

Les frameworks REST



Steps Create the Web App using Maven and download the Spring mvc

dependencies Configure the dispatcher servlet in the Web App Create the Service Implementation on the App Test out the service

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Chap-5. Les Frameworks REST