Breathing new life into JSP with OSGi!

Outline

• JSP!!! What’s the meaning of this?
• Bytecode is Better
• Initial Problems
• Compiling
• Designing a Solution
• Key Java EE OSGi Bundles
• Jasper*
• Compilation - javax.tools
• OSGi Support - org.osgi.framework.wiring
• Phidias
• Liferay JSP Compiler
• Some Details
• Demo Time

JSP!!! What’s the meaning of this?

• Isn’t JSP a dead tech?
• Enterprises use JSP a lot
  • find -type f -regex .*\.jspf? | wc -l
    • Eclipse = 59
    • Liferay = 1696
    • Liferay Plugins = 669

Bytecode is Better

• Compiled to Bytecode view templates still most efficient server side
  • w.r.t. memory consumption and performance
  • Other _compiled to bytecode_ view tech not as widely known
    • Play Scala Templates
    • Google Soy Templates

Initial Problems

• Java EE instantiation model (ServiceLoader, Class.forName, TCCL)
• Limitations to the existing JSP servlet impls required ugly hacks
• Compilation dependencies lead to complex runtime dependencies

Compiling

• Traditionally - JDT _load the world_ compilation strategy
  • JDT is not a small dependency
• Other compilation options non-existent
• OSGi had no way to natively support compilation process

Designing a Solution

• Re-use existing tech when possible
• Use JDK compiler API (since Java 6)
• Avoid lots of hacks
• Keep a small footprint
• Limit usage requirements

Key Java EE OSGi Bundles

• Key API/RIs are OSGi bundles ** Servlet ** JSP ** JSTL ** EL

Jasper

• Proven and stable
• Has limited dependencies
• Recently solved issues enabling easier OSGi use

Thanks Glassfish!

Java SE Support - javax.tools

• Since Java SE 6
• Full blown compiler support
• .. complicated to use

OSGi Support - org.osgi.framework.wiring

• Since Core R4.3
• Deep classloader & wiring resource access

Phidias

• Small OSS bundle which crosses
  • javax.tools
  • org.osgi.framework.wiring
• Provides simplified OSGi aware compiler support
• Alpha (0.3.4)

Liferay JSP Compiler

• Extends Jasper with custom
  • JSP compiler which uses Phidias
  • JSP servlet which transparently handles classloading concerns

Some Details

• Entire JSP support ~ 1.3MB
• Most modern versions of JSP, JSTL, EL available
• No need to declare any JSP related imports in JSP enabled bundles
• No need to include any libs or standard TLDs
• No need to WAB your bundles
  • Can use regular old jar layout + web fragment subtree
    • Place JSPs in META-INF/resources/

OSGi Aware Compilation

• Does this open the door for other interesting topics?
  • Limit compile time view of the world to public APIs?