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From "Daryl Beattie" <dar...@date.com>
Subject RE: Memory Leak in ELEvaluator (cont'd...)
Date Thu, 12 May 2005 21:14:12 GMT
Hi folks,

	Did anybody ever follow up with this?
	For what it's worth, I've been using JSTL 1.1 for a while now
and have noticed no leak. Honestly I haven't profiled anything to be
sure, but I think it's safe enough to close the bug as it no longer
applies to the JSTL 1.1+ -- or maybe mark it as "WON'T FIX" for version
1.0?

Sincerely,

	Daryl.


> -----Original Message-----
> From: Kris Schneider [mailto:kris@dotech.com] 
> Sent: Sunday, February 27, 2005 1:51 PM
> To: Tag Libraries Developers List
> Subject: Re: Memory Leak in ELEvaluator (cont'd...)
> 
> 
> Or just use the setAccessible hack:
> 
> elcache.jsp:
> ------------
> <%@ page import="java.io.*" %>
> <%@ page import="java.lang.reflect.*" %>
> <%@ page import="java.util.*" %>
> <%@ page import="org.apache.taglibs.standard.lang.jstl.*" %>
> <%@ taglib prefix="c" uri="http://java.sun.com/jstl/core" %>
> 
> <%
> String genPath = 
> pageContext.getServletContext().getRealPath("/generated.jsp");
> PrintStream ps = null;
> try {
>      ps = new PrintStream(new BufferedOutputStream(new 
> FileOutputStream(genPath, false), 4096));
> 
>      ps.println("<%" + "@ taglib prefix=\"c\" 
> uri=\"http://java.sun.com/jstl/core\" %\>");
>      ps.println("<html><head>");
>      ps.println("<meta http-equiv=\"refresh\" content=\"3; 
> URL=elcache.jsp\">");
>      ps.println("<title>Generated</title>");
>      ps.println("</head><body><ul>");
> 
>      long time = System.currentTimeMillis();
>      for (int i = 0; i < 100; i++) {
>          long value = time + i;
>          String var = "v_" + value;
>          ps.print("<li>");
>          ps.print("<c:set var='" + var + "' value='${" + 
> value + "}'/>");
>          ps.print("<c:out value='${pageScope." + var + "}'/>");
>          ps.println("</li>");
>      }
> 
>      ps.println("</ul></body></html>");
> } catch (FileNotFoundException exc) {
>      exc.printStackTrace();
> } finally {
>      if (ps != null) {
>          ps.close();
>      }
> }
> 
> Field cachedExpressionStringsField = 
> ELEvaluator.class.getDeclaredField("sCachedExpressionStrings");
> cachedExpressionStringsField.setAccessible(true);
> Map cachedExpressionStrings = 
> (Map)cachedExpressionStringsField.get(ELEvaluator.class);
> %>
> 
> <html>
> 
>      <head>
>          <meta http-equiv="refresh" content="3; URL=generated.jsp">
>          <title>EL Cache Test</title>
>      </head>
> 
>      <body>
>          <p>Number cached expr strings: <%= 
> cachedExpressionStrings.size() 
> %></p>
>      </body>
> 
> </html>
> 
> It should increase by 200 each time elcache.jsp is accessed. 
> The reason for 
> the non-zero refresh is that a newly generated.jsp only seemed to be 
> recognized for every request by introducing a slight delay. I ran TC 
> 4.1.31's Jasper in dev mode so it would check for mods on 
> every request as 
> well as setting it not to fork compiles. Of course, JSP 
> compilation could 
> still be performed in a background thread within the same 
> JVM, which might 
> explain why the delay was required...
> 
> Daryl Beattie wrote:
> > Yeah, that's basically it! Dunno why I never thought of using a
> > scriptlet instead of writing a custom tag... It's probably because
> > scriptlets are so frowned-upon where I currently work that 
> I hardly ever
> > consider using them.
> > 
> > One thing I did in one of my tests was actually to print 
> out the size of
> > the cache in the JSP. So as my JSP refreshed every second, 
> I could watch
> > the size of the cache climb. This, of course, requires a change to
> > ELEvaluator.java so that the size of the cache is publicly 
> visible --
> > perhaps by adding a "getCacheSize()" method.
> > 
> > Although I don't like to have my test JSPs actually display 
> their own
> > results, the problem with this kind of test is that it 
> can't be easily
> > converted to a "unit" test; it's results are somewhat subjective.
> > Because of that, I found that adding the cache size to the 
> JSP eased my
> > results.
> > 
> > By adding this to ELEvaluator.java:
> > public static int getELCacheSize() {
> > 	return ELEvaluator.sCachedExpressionStrings.size();
> > }
> > 
> > You can then change the body of the JSP to:
> > <body>
> > 	<p>EL Cache Test</p>
> > 	<p>EL Cache Size: <%=ELEvaluator.getELCacheSize()%></p>
> > </body>
> > 
> > Then you just load the JSP and watch it climb; if it climbs
> > indefinitely, you've got a bug in the cache. If it climbs to a fixed
> > size and stops there's no bug. ...And I would personally 
> put the refresh
> > delay down to 0 just so that the cache is filled up 
> faster... cuz I'm
> > impatient. :)
> > 
> > - Daryl Beattie
> > 
> > 
> > 
> >>-----Original Message-----
> >>From: Kris Schneider [mailto:kris@dotech.com] 
> >>Sent: Friday, February 25, 2005 1:57 PM
> >>To: Tag Libraries Developers List
> >>Subject: Re: Memory Leak in ELEvaluator (cont'd...)
> >>
> >>
> >>Here's an approach to dynamically generating unique 
> >>expressions that might work as a test.
> >>
> >>elcache.jsp:
> >>------------
> >><%@ page import="java.io.*" %>
> >><%@ taglib prefix="c" uri="http://java.sun.com/jstl/core" %>
> >>
> >><%
> >>String genPath = 
> >>pageContext.getServletContext().getRealPath("/generated.jsp");
> >>PrintStream ps = null;
> >>try {
> >>    ps = new PrintStream(new BufferedOutputStream(new 
> >>FileOutputStream(genPath, false), 4096));
> >>
> >>    ps.println("<%" + "@ taglib prefix=\"c\" 
> >>uri=\"http://java.sun.com/jstl/core\" %\>");
> >>    ps.println("<html><head>");
> >>    ps.println("<meta http-equiv=\"refresh\" content=\"3; 
> >>URL=elcache.jsp\">");
> >>    ps.println("<title>Generated</title>");
> >>    ps.println("</head><body><ul>");
> >>
> >>    long time = System.currentTimeMillis();
> >>    for (int i = 0; i < 100; i++) {
> >>        long value = time + i;
> >>        String var = "v_" + value;
> >>        ps.print("<li>");
> >>        ps.print("<c:set var='" + var + "' value='${" + value 
> >>+ "}'/>");
> >>        ps.print("<c:out value='${pageScope." + var + "}'/>");
> >>        ps.println("</li>");
> >>    }
> >>
> >>    ps.println("</ul></body></html>");
> >>} catch (FileNotFoundException exc) {
> >>    exc.printStackTrace();
> >>} finally {
> >>    if (ps != null) {
> >>        ps.close();
> >>    }
> >>}
> >>%>
> >>
> >><html>
> >>
> >>    <head>
> >>        <meta http-equiv="refresh" content="3; URL=generated.jsp">
> >>        <title>EL Cache Test</title>
> >>    </head>
> >>
> >>    <body>
> >>        <p>EL Cache Test</p>
> >>    </body>
> >>
> >></html>
> >>
> >>If you drop this into TC's $CATALINA_HOME/webapps/ROOT and 
> >>add the JSTL libs to $CATALINA_HOME/webapps/ROOT/WEB-INF/lib, 
> >>it should do what you want. I tested this with TC 4.1.31 and 
> >>Standard 1.0.6, but didn't do any sort of profiling. If you 
> >>don't see the output from generated.jsp change for each 
> >>request, try increasing the refresh interval.
> >>
> >>-- 
> >>Kris Schneider <mailto:kris@dotech.com>
> >>D.O.Tech       <http://www.dotech.com/>
> 
> -- 
> Kris Schneider <mailto:kris@dotech.com>
> D.O.Tech       <http://www.dotech.com/>
> 
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