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500 Servlet Exception - java.lang.NullPointerException

843810Oct 25 2005 — edited Nov 24 2007
Hi,

I went to this site : http://www.arco.ifema.es/index.jsp# and then clicked on "English version". Then I got the following page:

500 Servlet Exception

java.lang.NullPointerException
at idioma_jsp._jspService(/idioma.jsp:15)
at com.caucho.jsp.JavaPage.service(JavaPage.java:75)
at com.caucho.jsp.Page.subservice(Page.java:497)
at com.caucho.server.http.FilterChainPage.doFilter(FilterChainPage.java:182)
at com.caucho.server.http.Invocation.service(Invocation.java:312)
at com.caucho.server.http.CacheInvocation.service(CacheInvocation.java:135)
at com.caucho.server.http.RunnerRequest.handleRequest(RunnerRequest.java:342)
at com.caucho.server.http.RunnerRequest.handleConnection(RunnerRequest.java:272)
at com.caucho.server.TcpConnection.run(TcpConnection.java:137)
at java.lang.Thread.run(Thread.java:534)

Resin 2.1.6 (built Fri Nov 8 08:18:18 PST 2002)

Any idea on how to fix this? I have java installed. Any help or suggestion is welcome. Thanks

Comments

843811
Such optimization are done by JIT compiler (not by javac).
C++ have just the same problems, exceptions make CFG analisis more difficult but not impossible.
PS You can read JLS about volatile variables there some additional restrictions on them.
843811
zhmur is right, this makes optimization harder not impossible.

There are sicentific papers aimed at making more analysis/optimization in the presence of many try/catch blocks. For instance, JIT can reorder statements, and then put compensation code into the catch body, recovering program state back if an exception was thrown.

General principle is simple: exceptions are rare. So JIT optimizes the "normal" control flow by the cost of more complex catch body.

You may also look/post to the comp.compilers newsgroup regarding compilers and optimization techniques

Denis

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Locked on Dec 22 2007
Added on Oct 25 2005
#java-errors-and-error-handling-developer-tool-apis
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