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Web Service

A web service exposes a public api to communicate with. Usually they follow a standard specification such as REST or SOAP. For this example we expose a simple REST endpoint. These services are usually commentate with xml and json instead of human readable html.

JAX-RS

JAX-RS: Java API for RESTful Web Services (JAX-RS) is a Java programming language API spec that provides support in creating web services according to the Representational State Transfer (REST) architectural pattern. JAX-RS uses annotations for declaring what HTTP verbs and paths are associated with each method.

CXF

Apache CXF™ is an open source services framework. CXF helps you build and develop services using frontend programming APIs, like JAX-WS and JAX-RS. These services can speak a variety of protocols such as SOAP, XML/HTTP, RESTful HTTP, or CORBA and work over a variety of transports such as HTTP, JMS or JBI.

How It Works

Components

  1. @GET/POST/PUT/PATCH/DELETE
    • States what HTTP verb is used for this method.
  2. @PATH
    • The web server will invoke this method when the request matches this path and verb.
  3. @PRODUCES
    • The type of output the web service will display. This example will just be plain text.
  4. @PATHPARAM
    • The parameter taken from the URI that will be used by the program. In this case it is "name".

Setting Up a Web Service

  1. Specify a private Greeting interface variable and pass it into the public constructor as a parameter.

    •   private Greeting greetingService;
  
  public GreetingRest(Greeting greetingService) {
      this.greetingService = greetingService;
  }

  2. Specify JAX-RS annotations

    •   @GET
  @Path("/hello/{name}")
  @Produces(MediaType.TEXT_PLAIN)

  3. Use the given parameter "name" to return and pass it as a parameter into the hello function. This function then returns the the formatted string using "name".

    •   public String hello(@PathParam("name") String name) {
      return greetingService.hello(name);
  }

Blueprint definition

Add CXF and JAX-RS to the blueprint namespace

<blueprint xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0"
           xmlns:cxf="http://cxf.apache.org/blueprint/core"
           xmlns:jaxrs="http://cxf.apache.org/blueprint/jaxrs">
           ...
</blueprint>

Create the CXF Bus

The bus element is where you would configure CXF. You can add features and interceptors such as an authentication interceptor or a logging feature.

<cxf:bus>
    <cxf:features>
        <cxf:logging/>
    </cxf:features>
</cxf:bus>

Create the bean that will handle the web requests

<blueprint>
    <reference id="greetingService" interface="com.connexta.api.Greeting"/>
    <bean id="greetingServiceProxy" class="com.connexta.rest.GreetingRest">
        <argument refe="greetingService"/>
    </bean>
</blueprint>

Create the JAX-RS Server and tell it which bean handles requests

<jaxrs:server address="/greeting" id="greetingRest">
    <jaxrs:serviceBeans>
        <ref component-id="greetingServiceProxy"/>
    </jaxrs:serviceBeans>
</jaxrs:server>

Learn More About JAX-RS

Learn More About CXF