The following repository contains a relatively straight forward Apache Tomcat Web Application employing Java Servlets and JSP as well as a RMI Service for querying dictionary definitions. The web client presents a basic user interface in which a user can enter a search string and submit it to be processed by the application. The application has been setup to simulate a delay of requests being added to a queueing system. This effectively demonstrates the asynchronous communication. Message Queues are implemented using RabbitMQ and the system also employs multiple RMI Client threads.

The following diagram depicts the overall system architecture and flow of execution:

• Apache Tomcat
• Maven
• RabbitMQ

If you are on OSX Homebrew makes it easy to install various dependencies and manage services with Brew Services such as RabbitMQ as well as various other dependencies such as databases - i.e. CouchDB or MySQL. To get started with RabbitMQ follow these instructions.

1. Update HomeBrew

brew update

2. Brew Install

brew install rabbitmq

3. Start the RabbitMQ Server

brew services start rabbitmq

To get setup using RabbitMQ on Windows please follow the instructions on the RabbitMQ Installation Documentation. RabbitMQ offers a basic .exe installer that can be used to manage services - stopping, starting.

Running a Maven Install inside the directory will generate the target directory and the associated war file - (Web Application Archieve). However this isn't necessary as I've included the associated war file and also the RMI Server Application jar file in this repository to avoid complications with different system environments and dependencies.

To use the application simply:

1. Clone this Respository

git clone https://github.com/damiannolan/dictionary-service-RMI.git

2. Start RabbitMQ as previously mentioned above

• Getting Started with RabbitMQ

3. Start the RMI Server Application

java -cp ./dictionary-service.jar ie.gmit.sw.server.ServiceSetup

4. Drag and Drop Dictionary-Service-Webapp.war into an Apache Tomcat Installation directory under the folder named webapps.

5. Start your Tomcat Server and navigate to http://localhost:8080/Dictionary-Service-Webapp/

brew services start tomcat

-> C:\dev\tomcat\bin> startup.bat

As previously mentioned running an Maven Install will also generate the war file and target directory as well as download and install the dependencies needed for the application. You can also import the project into Eclipse and use the Maven plugin associated.

mvn install

Eclipse -> File -> Import -> Maven -> Existing Maven Projects

The application employs two Java Servlets - DictionaryServlet and PollingServlet for handling requests made by the client and polling of the server for a response respectively. HTML form information is sent to a servlet that adds the client request to an InQueue which is then in turn pulled from the queue and dispatched to an RMI Client Worker thread. The worker thread handles processing of the request and communications with an RMI Dictionary Service in order to fetch a number of defintions. The response is then added to an OutQueue and returned to the client via a PollingServlet which employs short polling every 10 seconds.

Application source code is packaged under the name ie.gmit.sw and ie.gmit.sw.server.

• IDictionaryService
• DictionaryService
• ServiceSetup

• DictionaryServlet
• PollingServlet
• Request / Response
• InQueueService
• OutQueueService
• RMIClient