PI92335: JavaServer Pages (JSP) performance difference between JSP 2.2 and JSP 2.3

APAR status

• Closed as suggestion for future release.

Error description

• Profiling shows there is a outstanding hot spot related to EL
  resolver difference between the two versions of WebSphere.
  
  The difference comes down to class AstIdentifier. To be EL 3.0
  spec. section 1.5.1 Evaluating Identifiers. compliant, this
  class needed to be modified in order to support Lamba
  expressions, variables, ELResolvers, and statically imported
  fields. This set of new checks is generating the behavior
  reported in the PMR.
  
  After evaluating the issue the particular ELResolver causing
  the biggest performance difference is ScopedAttributeELResolver
  (javax.servlet.jsp.el). This class is included in WAS from the
  JSP API classes provided by Oracle. It was modified for JSP
  2.3 to support EL 3.0 static fields for imported classes.
  

Local fix

• We can recommend a workaround that, depending on your
  application, could improve the performance when resolving EL
  expressions. The workaround is to set a value for each EL
  variables that you're using in a page. If a variable is null, a
  check in the classloader will be made and here is where we
  start seeing the performance difference. To set the value for a
  variable you can use any of the following scopes: page,
  request, session, and application (the most efficient would be
  the page scope, but you need to evaluate if that makes sense
  for the application).
  

Problem summary

Problem conclusion

Temporary fix

Comments

• APAR PI92335 is being closed SUG because the JavaServer Pages
  (JSP) 2.3 specification has a dependency on EL 3.0. This
  dependency has the potential to cause a performance degradation
  between JSP 2.2 and JSP 2.3 due to the EL 3.0 static variable
  resolution feature. A new action has been added to JSP 2.3 when
  resolving EL expression; if an EL expression variable is not fou
  on any of the scopes (page, request, session, or application),
  then the JSP engine will need to verify if the variable is a
  statically imported field in order to be compliant with the EL 3
  specification. This new check might have a performance differenc
  when compared to just checking the scopes (as in JSP 2.2) as
  classloading operations will happen.
  
  A JSP 2.3 issue is open in the Java Enterprise Edition issue
  tracker. The title of the issue is "JSP spec. needs to define a
  mechanism to support EL 3.0 static fields for imported classes".
  
  Update: We can now recommend the fix for APAR PH31416,
  which improves the performance of resolving EL 3.0 expressions
  of the type described here.
  

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

Applicable component levels