Using Dynamic Languages to Implement Services

Overview

JavaScriptJavascript, also known by its formal name ECMAScript, is one of the many dynamic languages that are growing in prevalence in development environments. It provides a quick and lightweight means of creating functionality that can be run on a number of platforms. Another strength of JavaScript is that applications can be quickly rewritten.

Celtix provides support for developing services using JavaScript and ECMAScript for XML(E4X). The pattern used to develop these services are similar to JAX-WS Providerimplementations that handle their requests and responses (either SOAP messages or SOAP payloads) as DOM documents.

Implementing a Service in JavaScript

Writing a service in JavaScript is a two step process:

1. Definethe JAX-WS style metadata.
2. Implementthe services business logic.

Defining the Metadata

Normal Java providers typically use Java annotations to specify JAX-WS metadata. Since JavaScript does not support annotations, you use ordinary JavaScript variables to specify metadata for JavaScript implementations. Celtix treats any JavaScript variable in your code whose name equals or begins withWebServiceProvideras a JAX-WS metadata variable.

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Example 1 shows a metadata description for a JavaScript service implementation.

Implementing the Service Logic

You implement the service's logic using the requiredinvokeproperty of the WebServiceProvidervariable. This variable is a function that accepts one input argument, a javax.xml.transform.dom.DOMSourcenode, and returns a document of the same type. The invokefunction can manipulate either the input or output documents using the regular Java DOMSourceclass interface just as a Java application would.

Example 2 shows an invokeproperty for a simple JavaScript service implementation.

Implementing a Service in ECMAScript for XML(E4X)

Writing a Celtix service using E4X is very similar to writing a service using JavaScript. You define the JAX-WS metadata using the same WebServiceProvidervariable in JavaScript. You also implement the service's logic in theWebServiceProvidervariable's invokeproperty.

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Example 3 shows an invokeproperty for a simple E4X service implementation.

Deploying Scripted Services

Celtix provides a lightweight container that allows you to deploy your Javascript and E4X services and take advantage of Celtix's pluggable transport infrastructure.Note:Script based services can work with SOAP messages. So, while they are multi-transport, they can only use the SOAP binding.
You deploy them into the container using the following command:java org.objectweb.celtix.js.rhino.ServerApp -aaddressURL -bbaseAddressURLfile.js file2.jsfile3.jsx ...
The org.objectweb.celtix.js.rhino.ServerAppclass, shorted to ServerAppbelow, takes one or more Javascript files, suffixed with a .js, or E4X files, suffixed with a .jsx, and loads them into the Celtix runtime. If ServerApplocates JAX-WS metadata in the files it creates and registers a JAX-WS Provider<DOMSource>object for each service. The Provider<DOMSource>object delegates the processing of requests to the implementation stored in the associated file. ServerAppcan also take the name of a directory containing Javascript and E4X files. It will load all of the scripts that contain JAX-WS metadata, load them, and publish a service endpoint for each one.

ServerApphas three optional arguments:

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