Developing Hello World Restful Service with Fuse

Introduction:

Fuse ESB Enterprise's embedded Web and RESTful services framework is based on Apache CXF. They provide a small footprint engine for creating reusable web services and for service-enabling new and legacy applications as part of an integration solution.

RESTful Service Development Pattern

Overview

Representational State Transfer (REST) describes a stateless client-server architecture in which web services are treated as resources that can be identified by their URLs.

In RESTful systems, servers use URIs to expose resources, and clients use the four HTTP verbs GET, POST, PUT, and DELETE to access them. As they receive a representation of a resource, client applications enter a state. When they access another resource, typically by following a link, client applications change their state.

Because RESTful systems can take full advantage of HTTP's scalability features, such as caching and proxies, they are highly scalable and highly flexible. Changes made to servers do not impact clients because:

·         Resources are accessed and manipulated using the four HTTP verbs.

·         Resources are exposed using a URI.

·         Resources are represented using standard grammars.

Today's Web architecture is an example of a system designed on RESTful principles. Web browser clients access resources hosted on Web servers. The resources are represented using HTML or XML grammars understood and navigable by all web browsers.

JAX-RS development

Fuse ESB Enterprise supports JAX-RS (JSR-311), the Java API for RESTful Web Services. JAX-RS provides a standard way to build RESTful services in Java, using annotations to simplify the development and deployment of web service clients and endpoints.

Using JAX-RS to develop restful services has several benefits:

·         The URI bindings are local to the resource beans, which can be arbitrarily nested. This feature simplifies refactoring.

·         Loose coupling between providers and the objects returned by the resource methods makes it easy to drop in support for new representations, without having to change the code of the resource beans (or controllers). Instead, you need only modify an annotation.

·         Static typing can be useful when binding URIs and parameters to the controller. For example, using String, integer, and Date fields frees the controller from having to explicitly convert parameter values.

JSON data bindings

 JavaScript Object Notation (JSON), a lightweight data format for data exchange, is provided as an alternative to JAXB. JSON is a text-based and human-readable format for representing simple data structures and associative arrays (called objects).

Implementation:

Suppose you want to create a RESTfull web service using CXF for hello world.  You would typically want to perform following operations.

Ø  Create Fuse Project

Ø  Create Java classes

Ø  Create Camel Context

Ø  Deploy in Fuse Server

Ø  Test Hello world

Create Fuse Project:

Step 1: Go to Fileà New à Fuse Project.

Step 2: Give Project name as ‘FuseHelloWorldRSService’ and click on next.

Step 3: Select the artifact ID: camel-archetype-spring-dm and Group ID: org.apache.camel.archetypes and give the details as shown below and click on finish.

Create Java classes

Step 4: Create  HelloWorldReqest , HelloWorldResponse, HelloWorldImpl and HelloWorldResponseTransformer classes and generate setter and getter methods.

Step 5: Open POM.xml fine and add the following dependencies, so that incase of any errors in our Java classes will resolve these dependencies.

Create Camel Context

Step 6: Open the blueprint.xml under camel Contexts folder. Delete the content on blueprint.xml

Step 7: Click on source to edit the blueprint.xml file and add the schema locations.

Step 8: Add Bean entries for classes and service endpoint to blueprint.xml.

Step 9: Add the routes in blueprint.xml

Deploy in Fuse Server

Step 10: Right click on pom.xml à Run As à Maven Install

Once the build successful we can see the success build message in console.

Step 11: Start Fuse server. Run the below command in Fuse server command prompt.

osgi:install -s mvn:com.eai.helloworldrs/helloworldrs/1.0.0-SNAPSHOT

Run the list command to check the status of the service. You can see below the service is in run status with Bundle ID 273.

Test Hello world

Now our service is running on Fuse server. We need to test now.

Open Mozilla Browser and Install the Rest Client plug-in which is under Mozilla plug-in’s. This plug in is used for test the rest services.

Enter the ‘http://localhost:9090/getHelloWorld/getHelloWorld?name=Ameer’ under url, select as GET method and click on Send. We can see the response under Response Body(Raw) tab as shown below.

Summary:

We have learnt how to develop simple hello world program with restful services with Fuse. I will soon post new post with advance usage/ implementations with restful services in Fuse.

Downlad:

S. No	File Name	Download
1	Developing HelloWorld Restful Service.pdf	Download
2	FuseHelloWorldRSService.zip	Download