Using Legacy Applications via
Bridges
Mark Baker and Rahim Lakhoo
Outline
• Introduction.
• Motivation.
• Technologies:
– JSR-223,
– PHP-JavaBridge,
– PortletBridge-Portlet,
– Other Bridging Technologies.
• System Architecture.
• Demonstration Applications.
• Issue.
• Conclusions.
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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 bridging technologies.
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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.
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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:
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– 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.
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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.
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Bridges - JSR-223 (2)
• Reference Implementation:
Hosting Server
Apache Tomcat
JSR223 Reference Implementation
Compiled
PHP 5.01
PHP.INI
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Libs
Javax.script
API
CLI
Scripting
Engines
PHP
Engine
Groovy
Engine
Samples
PHP
Rhino
Engine
PHP
CLI
Groovy
PHP
Web
Groovy
Web
Groovy
CLI
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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.
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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.
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Bridges - PHP-JavaBridge (2)
Hosting Server
Apache Tomcat
Apache Web Server
PHP-JavaBridge
Socket Connection
Java Libs
Hosts CGI
Binary
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PHP CGI
Optional Binaries
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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.
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Bridges - PortletBridge-Portlet (1)
• Generic method of rendering Web sites into a JSR168 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.
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Bridges - PortletBridge-Portlet (2)
Hosting Server
Web Page/
Site
Apache Tomcat
Portal
PortletBridge-Portlet
Portlet
Web
Page/Site
Rendered
as a
Portlet
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PortletBridge Servlet
XSLT
Proxy
Scope
Memento
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Bridges - PortletBridge-Portlet (3)
• PorltetBridge-portlet, uses Apache’s httpclient to
GET/POST from/to Web pages.
• 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.
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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.
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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.
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System Architecture (2)
Hosting Server
GridSphere Portal
Apache Tomcat
PortletBridgePortlet
Exsiting Application
PHP Application
MySQL
Database
PHP-JavaBridge
CGI/FastCGI
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System Architecture (3)
• The PortletBridge-Portlet is installed as a JSR168 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.
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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.
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BibAdmin Portlet
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Guest Book Portlet
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Guest Book Admin Portlet
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Image Gallery Portlet
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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.
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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.
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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.
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References
• http://portals.dsg.port.ac.uk
• http://www.jcp.org/aboutJava/communit
yprocess/edr/jsr223/index.html
• http://PHP-Java-Bridge.sourceforge.net
• http://www.portletbridge.org
• http://www.gridpshere.org
• http://portals.apache.org/bridges/
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Questions?
http://dsg.port.ac.uk
http://acet.rdg.ac.uk
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