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Application Reuse Through Portal Frameworks: 

Application Reuse Through Portal Frameworks Mark Baker and Rahim Lakhoo

Outline: 

Outline Introduction. Motivation. Technologies: JSR-223, PHP-JavaBridge, PortletBridge-Portlet, Other Bridging Technologies. System Architecture. Demonstration Applications. Issue. Conclusions.

Introduction: 

Introduction Portsmouth and Reading’s role in the Sakai VRE project is to develop and deploy a number of portlet-based tools and services. In particular we are looking at: Collaborative tools based on NaradaBrokering, Semantic Web tools based on RDF, Bridging technologies to enable legacy applications, Peer-to-Peer technologies. We will make these tools available, either via a native JSR-168 capability, or via the WSRP consumer developed within the Sakai project. In this talk we will recount our experiences investigating, deploying and testing a range of emerging portal bridging technologies.

Legacy Applications: 

Legacy Applications Motivation: Investigate whether script-based Web applications, such as PHP can be reused in Java-based environment, Investigate if PHP applications can be reused as a portlets, Test by deploying a number of PHP applications as portlets, Add useful tools/utilities to the Sakai Demonstrator.

Bridging Technologies: 

Bridging Technologies JSR-223: Reference implementation available, Allows Java to communicate objects with script-based languages and vice versa, To be included with the next release of Sun JDK “Mustang” (JDK 1.6). PHP-JavaBridge: Described as an XML-based network protocol, Allows communications between Java and PHP, Provides a suitable environment to execute PHP scripts under Apache Tomcat. PortletBridge-Portlet: Renders Web pages into a JSR-168 portlet, Proxies links and other external resources contained in a Web page, Can load multiple instances, with different configurations.

Bridges - JSR-223 (1): 

Bridges - JSR-223 (1) JSR-223 specification is lead by Zend Technologies and Sun, amongst others. Allows script-based languages to be used in Java server-side applications and vice versa. Defines a new API, javax.script.*. New API includes scripting-engines for different languages. Reference implementation includes support for Rhino, PHP and Groovy.

Bridges - JSR-223 (2): 

Bridges - JSR-223 (2) Reference Implementation:

Bridges - JSR-223 (3): 

Bridges - JSR-223 (3) Reference implementation of JSR-223 includes a pre-compiled skeleton installation of PHP5. JSR-223 API includes some scripting engines for PHP, Groovy and Rhino. Also includes a script to invoke Java classes, which contain script-based calls, from the command-line. Samples scripts/programs are available for PHP, Groovy amongst others: Command-line and Web capabilities.

Bridges - PHP-JavaBridge (1): 

Bridges - PHP-JavaBridge (1) Described as an XML-based network protocol. Designed to communicate with native scripting engines, which have a Java or ECMA 335 virtual machine. Provides a suitable environment for PHP applications to run under Apache Tomcat. Allows Java and PHP to share sessions, in a J2EE environment. Has a number of configurations for installation and connections to existing Web servers.

Bridges - PHP-JavaBridge (2): 

Bridges - PHP-JavaBridge (2)

Bridges - PHP-JavaBridge (3): 

Bridges - PHP-JavaBridge (3) Includes PHP5-CGI binaries and configurations files. Although the PHP-JavaBridge is not limited to the included CGI environment, it can use the PHP environment of the hosting server. The PHP-JavaBridge can connect to an existing Apache Web Server, executing PHP applications. Has a number of different modes: Request - Created/destroyed on every request/response, Dynamic - Starts/stops synchronously with a HTTP server, System - Installed from a RPM as a system service, J2EE - Installed into a J2EE server, such as Apache Tomcat. If the PHP instance crashes with the PHP-JavaBridge the backend Java server/servlet is unaffected.

Bridges - PortletBridge-Portlet (1): 

Bridges - PortletBridge-Portlet (1) Generic method of rendering Web sites into a JSR-168 portlet, developed by Jamie McCrindle. Tested in various portlet containers, including GridSphere, JetSpeed and JBoss. Proxies a Web sites content, so that a user may use the application from within a portlet. Uses XSLT to rewrite downstream content from Web sites. Includes remote proxy server settings for complex network set-ups. Allows for multiple instances with different configurations.

Bridges - PortletBridge-Portlet (2): 

Bridges - PortletBridge-Portlet (2)

Bridges - PortletBridge-Portlet (3): 

Bridges - PortletBridge-Portlet (3) PorltetBridge-portlet, uses Apache’s httpclient to GET/POST from/to Web pages. Uses the CyberNeko HTML Parser. Web pages are transformed using XSLT, which rewrites links and other content, such as: CSS, JavaScript, Images, Forms, Headers, etc… Uses Regex for defining the proxy scope. PortletBridge defines a Memento for storing users state, such as cookies.

Bridges - Others: 

Bridges - Others Apache Portals Bridges project aims to use common Web frameworks via portlets. Currently support is being developed for: Struts, JSF, Perl CGI Scripts, PHP, Velocity Templates. GridSphere 2.1.x portal includes the Struts Portals Bridge.

System Architecture (1): 

System Architecture (1) The PHP-JavaBridge provides the runtime environment for the PHP application. A PHP application is packaged and configured as a Web archive (WAR). Included in the WAR is a configured CGI environment, complete with PHP configuration files and extensions, per application. The PHP application can communicate with Java if extra functionality or a hybrid application is desired.

System Architecture (2): 

System Architecture (2)

System Architecture (3): 

System Architecture (3) The PortletBridge-Portlet is installed as a JSR-168 portlet under GridSphere. PortletBridge-Portlet instances are created and configured for each PHP application installed under the PHP-JavaBridge. If desired, XSL Style Sheets can be configured per PHP application. Once configured, the PHP applications are presented as individual portlets, which can be subscribed to by users.

Demonstration Applications: 

Demonstration Applications Using a combination of the PHP-JavaBridge and the PortletBridge-Portlet, we configured some PHP applications as portlets. These are the applications configured: BibAdmin - Bibtex database, YW Guest Book - PHP guest book application, FhImage - A simple image gallery. Deployment procedure: Applications are first deployed as WARs under Tomcat. Then an instance of the PortletBridge-Portlet is created and configured for each PHP application.

BibAdmin Portlet: 

BibAdmin Portlet

Guest Book Portlet: 

Guest Book Portlet

Guest Book Admin Portlet: 

Guest Book Admin Portlet

Image Gallery Portlet: 

Image Gallery Portlet

Demonstrated Applications: 

Demonstrated Applications The PHP applications tested with this technique have no real difference in terms of functionality when compared to native installations. Some PHP applications are easier to port to a portlet than others. Other PHP applications have a poor implementation/design, which can lead to issues within a portal environment.

Issues: 

Issues Login mechanisms can cause problems; simple PHP and PHP with JS logins were tested successfully: However, it is also feasible to disable logins of PHP applications in favor of utilising the portals security framework. Some applications need to have pre-defined PHP variables changed to reflect the J2EE environment, i.e. port number. PHP applications which load new windows have issues with the constraints imposed by a portal. Frames are not supported by the PortletBridge-Portlet. XHTML or mixed XHTML/HTML documents currently cause the proxy facility of the PortletBridge-Portlet to fail: The developers are working on this. There are some CSS leaks into the portal, currently this issue has been seen with GridSphere: Also, background colours cannot always be seen in the portlet versions.

Conclusions: 

Conclusions Although this technique is not without issues, it does present a viable solution for reusing existing PHP applications. The PortletBridge-Portlet is still a young project, which is being actively developed. Other bridging technologies, such as the Apache Portals Bridges project will be of interest, as they are starting to be included in portals, such as GridSphere. JSR-223 should see an increase in developers using the new API, as the release of Sun JDK 1.6 approaches. Bridging technologies should be an interesting alternative/addition for developing portlets and could be useful when combined with WSRP.

References: 

References http://portals.rdg.ac.uk http://www.jcp.org/aboutJava/communityprocess/edr/jsr223/index.html http://PHP-Java-Bridge.sourceforge.net http://www.portletbridge.org http://www.gridpshere.org http://portals.apache.org/bridges/

Slide28: 

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