Introduction

Smalltalk Exchange is a multi-tiered application that demonstrates how VisualAge Smalltalk applications can be integrated with systems constructed in other languages like Java. The application exploits the RMI and XML capabilities of VisualAge Smalltalk V5.5 to leverage business functionality from various sources.

The overall application is broken down into 4 separate features.

1. Web browser client interface
2. Smalltalk ULC Java application client interface
3. Smalltalk RMI server/XML requester
4. Smalltalk Web Connection/XML server

Browser client interface

The web browser interface is constructed using HTML and JSP files that were developed outside of the Smalltalk environment. The JSPs are used to present the dynamic model content generated by Smalltalk to the user.

Java servlets were developed as facades to the Smalltalk applications. Their sole purpose is to route requests from the WebSphere (or Tomcat) application server to Smalltalk. Java RMI (remote method invocation) was the technique used to communicate between Java and Smalltalk.

NOTE: The same user interface could have easily been constructed VisualAge Web Connection. However, we use servlets and Java Server Pages merely to demonstrate the interoperability between Smalltalk and Java and to demonstrate how Smalltalk can leverage other enterprise tools.

ULC (Ultra Light Client) interface

Smalltalk Exchange also ships with a user interface developed using the Ultra Light Client. ULC technology facilitates the development of rich user interfaces that have increased usability relative to a standard HTML page rendered with a web browser. Usage of ULC in the Smalltalk Exchange application demonstrates how various front-ends can be used to communicate with Smalltalk server applications. A ULC front end might be added to an application to provide custom behavior for a subset of users. For example, the Smalltalk Exchange application uses ULC to deliver a rich user interface that might be used by a stockbroker for managing his/her customers. Developers of ULC clients should be aware of the pros and cons of using this technology. Further, performance and scalability testing should be considered an integral part of the development cycle.

Smalltalk RMI server / XML requester

This portion of the application performs the following sequential operations:

• Accepts incoming RMI requests
• Creates XML request string using the XML serialization API of Visual Smalltalk
• Passes the XML request to a Smalltalk (Web Connection) server via an HTTP POST
• Processes the XML result of the HTTP request
• Returns resulting objects to Java client (servlet)

This section of the Smalltalk Exchange is the controlling layer of the application. Requests are accepted via RMI and then ‘repackaged’ in XML and sent to their proper destination. Likewise, information sent back to this Smalltalk control layer is properly converted from XML to an RMI call. This call chain represents a typical example of how information is transformed throughout distributed systems in order to leverage specialized services.

Smalltalk Web Connection/XML server

An XML request handler is invoked via the WSI (Web Server Interface) of Web Connection. This server performs the following operations:

• Parses incoming XML stream and maps from DOM into Smalltalk object
• Processes the request represented by the incoming XML
• Formats response as XML
• Sets the HTTP response and returns control to the client

This portion of the application demonstrates usage of the XML parser, highlighting the object serialization framework.

Setting up the demo

This section discusses the steps required to configure the Smalltalk Exchange application.

Deploying HTML and Java components

Tomcat

• Stop the Tomcat server
• Copy the file 'vastock.war' to the \webapps subdirectory of your Tomcat installation
• Start the Tomcat server

The server automatically expands the contents of the 'vastock.war' file during startup. All required resources should be in place after the server has successfully started.

· Edit the file <tomcat root>\webapps\vastock\login.html and modify the 'value' attribute in the line below to contain the server where the Smalltalk RMI layer will execute.

<input type="hidden" name="registryloc" value="smalltalk-host">

WebSphere

Users of WebSphere 3.5.2 (3.5 with Fixpack-2) can use the supplied WebSphere tools to import the contents of the 'vastock.war' file into the WebSphere environment. This is accomplished using the WebSphere Administrator menu option 'Console->Tasks->Convert a War File'.

Otherwise, a new Web Application called 'vastock' should be created and the resources below should be added:

LoginServlet	com.ibm.vast.stockdemo.LoginServlet
LogoutServlet	com.ibm.vast.stockdemo.LogoutServlet
QueryServlet	com.ibm.vast.stockdemo.QueryServlet
TransactionServlet	com.ibm.vast.stockdemo.TransactionServlet
ErrorReporter	com.ibm.servlet.engine.webapp.DefaultErrorReporter
jsp11	org.apache.jasper.runtime.JspServlet
file	com.ibm.servlet.engine.webapp.SimpleFileServlet

The contents of '.\java\vastock.war' must be unzipped, and all web resources (servlets, JSPs, HTML files, images) must be copied to the proper directories in the application server. The directory structure of the WAR file should be preserved when unzipping and copying files.

Loading VisualAge Smalltalk code

Below is a summary of the configuration maps defined for the Smalltalk Exchange application along with the prerequisite VisualAge features. Make sure prerequisite features are loaded prior to attempting to load the Smalltalk Exchange maps.

Map name	Contents	Prerequisites
VaStockPortfolioBase	contains model classes	VA: XML support
VaStockXMLFixes	Fixes to VA: XML suppport feature. This map should only be loaded when running version 5.5. Subsequent VA releases already contain the fixes.	VA: XML support
VaStockPortfolioClient	RMI mappings, XML requester code	VaStockPortfolioBase ST: Server, SST
VaStockPortfolioServer	XML server	VaStockPortfolioBase
VaStockPortfolioULCClient	ULC front end logic and interface	VaStockPortfolioClient VA: ULC - Development..

• Copy required Smalltalk Exchange XML files to product directory. The XML files should be placed in directory <visualage>\xml\stock prior to loading application code. The files 'vastock.listings' and 'vastock.charts' should be copied to the 'image' subdirectory.
• If using the ULC client, copy the file .\bitmaps\banner.png to the Smalltalk .\bitmaps directory
• Start VisualAge Smalltalk
• From a configuration maps browser, import all configuration maps from the repository file '.\smalltalk\vastock.dat'
• Load prerequisite features required for the application maps to be loaded
• Load "Smalltalk Exchange" maps (use the 'Load With Required Maps' option to simplify loading)

Running the application

1. Start the 'Smalltalk Exchange' XML server. The server can run in the development image or via a packaged runtime image. A packaged runtime image is supplied as ..\image\vastock.icx.

1. Start a WSI listener to handle incoming XML requests (See Web Connection documentation for information about using WSI)

2. Set the URL for the XML client ie) VaStockXmlRequester current urlString: 'http://myserver/servlet/com.ibm.abt.web.servlet.Router/VaStockRequestHandler'

3. Reset/Export required RMI mappings

1. Reset the SST contexts using menu option 'Tools->SST->Clear...' (select all contexts, and click OK)
2. Export RMI mappings by executing 'VaStockManager export'

4. Start the web server and the web application if necessary. Check the instructions for your web server for the steps required to activate the 'Smalltalk Exchange' Java servlets.

5. Invoke the Smalltalk Exchange by invoking the 'login.html' file from a browser. The URL will be similar to http://myserver/vastock/login.html

6. Enter a valid userid (valid ids are '000001'-'000004'). Enter any value for the password (how's that for security?), and press the 'Login' button. The application should be intuitive

See the file 'vastock.ws' for some useful code snippets.

Running the ULC client

The main view for the ULC portion of the stock demo is 'VaStockBrokerView'. Prior to trying this view, you must first install and start the ULC UI engine. After starting the 'Smalltalk Exchange' XML server (described above), test the 'VaStockBrokerView' from the VisualAge Organizer.

Obtaining "Live" stock quotes

By default, the stock quote server obtains quotes and charts from previously saved files (.\image\vastock.listings and .\image\vastock.charts). The following tickers are represented: ARBA,BBY,C,DELL,GTW,IBM,MSFT,SUNW,YHOO

If you would like the server to obtain a "live" quote from the network, you must start the XML server image using the '-live:true' command line option.

ie) vastock -live:true