RAP/Equinox WAR products
This document is a proposal for the GSoC 2010 project: WAR deployment for Equinox based applications and was created by Holger Staudacher as part of his GSoC application. This is a living document. Feel free to edit or add things.
WAR deployment for Equinox based applications
The purpose of the RAP project is to enable developers to build rich, Ajax-enabled Web applications using the Eclipse development model, plug-ins and a Java-only API. After completing a RAP application the next step is generally to publish the application on a web server, i.e. in a servlet container or application server. But this step, also known as deployment, sounds simpler than it is in the real world. When searching the RAP newsgroup for "WAR deployment" 210 threads appear. The reason for this is that many developers have problems deploying a RAP application. These problems exist because RAP products build on top of Server-Side Equinox. Equinox has special requirements for the deployable archive. To making things easier for beginners and to simplify the deployment process a good approach and tooling is needed. The goal of this GSoC 2010 project is to provide this approach and tooling.
How does this fit in the RAP context
RAP is probably the biggest consumer of the Server-Side Equinox technology. With this fact it's in the interest of the RAP community to have a good concept and tooling for users. This project will be mentored by the lead of the RAP team (Rüdiger Herrmann) and initially hosted at the RAP CVS. While doing this project as part of Eclipse RAP we can recognize user needs because there is a bunch of people at the RAP community which are interested in a good concept and tooling for deploying Equinox and RAP based applications. At a later stage, the results can hopefully be contributed to PDE (aka "Equinox Tooling"), though this is outside the scope of this project.
Why does Equinox have special deployment requirements?
While deploying a Server-Side Equinox Application, Equinox and all bundles required by the application need to be integrated in a servlet-contianer. The incoming requests must be forwarded from the Equinox instance to the participating resources. This creates certain requirements for successfully deploying an Equinox based application as a WAR. The requirements are:
- All dependencies need to be resolved for the bundles that are being deployed.
- The config.ini must be set up properly.
- The javax.servlet bundle must be excluded from the deployment.
- The servletbridge (both sides) must be present.
- A bundle that provides the HttpService must be present.
- The basic folder structure must be intact (WEB-INF folder, web.xml, etc.).
How can the deployment process be improved?
A good approach for building eclipse based applications is the RCP product approach. With this approach developers can create product configurations. These configurations are the basis for exporting RCP applications as executable products. To improve the server-side Equinox deployment process this approach can be adopted. A concept called the WAR product should be introduced. With this concept developers can create WAR product configurations which hold the necessary information for exporting an Equinox based application as a deployable WAR.
Having a good approach is one thing, but the right tooling is needed as well. Decent tooling exists for the RCP product. PDE comes with wizards for creating product configurations and for exporting a product. In addition, a configuration editor is available to help avoid syntax errors. Similar tooling for the WAR product will be needed. This tooling will make the deployment process much simpler and avoid errors during deployment. The following images show the RCP product tooling. This tooling can act as the basis for the WAR product tooling and will make RCP developers feel at home.
- let the user choose the name of the .warproduct configuration
- make the workspace bundles selectable (basic settings)
- provide a way to start from an osgi/rap launch configuration (take all bundles and so on)
- Investigate which parts can be reused from the PDE product editor and how to make it pluggable.
- bundle validation
- make sure all added bundles can be resolved (if not show error marker)
- make sure the javax.servlet bundle is not contained into the used bundles
- make sure a bundle which provides an HTTP service is present (maybe hardcoded org.eclipse.equinox.http.servlet?)
- make sure that the needed equinox bundles are included (servletbridge and so on). The equinox bundles should not be deletable from the definition. Maybe they can be resolved from the target platform (show error marker if they can't be resolved)
- make sure all bundle dependencies can be resolved (if not show error marker)
- library management
- web.xml configuration - provide a way which make's web.xml configuring easy (maybe these things can be distributed over the whole editor e.g. meta info on the overview tab and so on)
- let the user choose which commandline arguments will be used (-console and so on). Only allow valid arguments.
- let the user choose if the framework controls should be enabled
- make the framework launcher exchangeable (default should be org.eclipse.equinox.servletbridge.FrameworkLauncher)
- let the user define own init-params with key/value pairs
- make meta data editable (display-name, servlet-class, servlet-name and so on)
- let the user choose a servlet mapping (/* by default, what about the .jsp mapping?)
- config.ini configuration
- make it possible to start the export within the editor
- let the user choose which .warproduct configuration should be used
- validate the .warproduct file (there should be errors e.g. if the bundle dependencies could not be resolved)
- provide a way to define a destination for the .war file
- make sure the exported file ends with .war
- make it optional if an ant script should be generated for the used configuration (nice to have if it's enough time left)
- create WEB-INF structure defined with the options within the .warproduct configuration
- create the config.ini on the fly
- add launch.ini with static content (the default content)
- add all libraries to the lib folder
- put all plugins/features into the eclipse folder (plugins/feature folder)
- create the configured web.xml and put it into the WEB-INF folder
The described functionality may change during the coding period.