Java Tip #5 - Avoid 64KB method limit on JSP

Ok, this is hard to do on purpose with plain old java, but I've seen plenty of JSPs that when compiled had a method that exceeded the 64KB limit. Depending on the VM it may just barf and end with a hotspot error or it might give you some kind of useful message. I find it's just a hotspot error. Tomcat describes this problem in their release notes.

The simplest way to fix this is to break the page into parts so that each compiles separately using a jsp include. Avoiding big, monolithic JSPs is easy if you use Struts with Tiles. Of course, this shows how behind I am now since I'm not using one of the newer frameworks.

This seems to be less of a problem as container vendors have improved. They all generate different code, so it varied in our environment from Tomcat, SilverStream, and BEA. At one time or another, we had JSPs that exhibited the problem on one of the three platforms, but not the other two. I am happy to say we now target only one vendor, BEA.

Here is the blurb from section 4.10 of the Java Language Specification (JLS).

The amount of code per non-native, non-abstract method is limited to 65536 bytes by the sizes of the indices in the exception_table of the Code attribute (§4.7.3), in the LineNumberTable attribute (§4.7.8), and in the LocalVariableTable attribute (§4.7.9).

Note that using the @include file directive does not solve the problem, since it just inlines the JSP. You need to use a jsp include or tiles or similar.