Thanks for the comments Kin-Man. Given those comments and a look at the jasper2
code I have come up with the patch below. After profiling jasper2 I saw that
there was indeed a speed improvement over Jasper. However the excessive creation
of File objects and getting files from URL's was still a problem.
I did as you suggested and used the JspServletWrapper object to hold all of
the
required data. As well I set up this version to fall back to reading JSP's from
a URL if reading the File object doesn't work.
I found in my testing that the jasper engine used ~15% of the request time in
loadJSP, jasper2 used ~12%, and my change uses ~1%. The only thing my code does
not do is force a reload of the .class file if it is deleted. My code only
causes a recompile if the jsp changes. I can look into modifying it to handle
this situation as well if required. I look forward to your feedback.
Kin-Man Chung wrote:
> Duncan, I looked at your patch carefully, looks like Remy's work on
> jasper2 already addressed the issues that you are trying to solved.
> In fact, Remy only creates a compiler for the container, whereas you
> would have created a compiler for each jsp page. OTOH, you save the
> modification date for each page in a hashtable, so is potentially
> faster when checking whether a jsp needs to be send to the compiler.
> I may incoporate your idea on this one later, maybe reusing the
> JspServletWrapper class instead of using another hashtabl, since that
> **IS** a per page object.
>
> Thanks again for the patch. If you wish, you should try running with
> japser2, and compare its performance with the one you patched.
>
>
>
--- JspServlet.java.orig Mon Apr 29 20:50:33 2002
+++ JspServlet.java Mon Apr 29 17:34:28 2002
@@ -129,6 +129,11 @@
JspCompilationContext ctxt = null;
String outDir = null;
long available = 0L;
+
+
File jspFile = null;
+ long nLastModified = 0;
+ boolean bCompiling = false;
+
boolean bInWar = false;
JspServletWrapper(String jspUri, boolean isErrorPage) {
this.jspUri = jspUri;
@@ -276,6 +281,103 @@
if (theServlet != null)
theServlet.destroy();
}
+
+
/**
+
* This function takes the relative name of a jsp file and tries
+
* to determine whether it has changed since the last time this
+
* was called.
+
*/
+
private boolean hasJspChanged() {
+
try {
+
//get the last time the file was modified and the
+
//last time it was modified that we compiled
+
long
nMod = getModifiedTime();
+
+
//if we have not compiled before, or the file has changed.
+
if (nMod == 0 || (nLastModified != nMod && !isCompiling(nMod))) {
+
return true;
+
}
+
+
waitForCompile();
+
+
return false;
+
} catch(IOException ioEx) {
+
//ignore so that the normal logic will kick in.
+
}
+
+
return true;
+
}
+
+
/**
+
* Gets the time that a particular JSP file was last modified.
+
*/
+
private long getModifiedTime()
+
throws IOException {
+
if (bInWar) {
+
return nLastModified;
+
}
+
+
if (jspFile == null)
+
{
+
//if is FAR faster to create a file object and get its
+
//last modified time than to open a URL connection to
+
//the file and get the last modified time that way.
+
String strPath =
getServletConfig().getServletContext().getRealPath(jspUri);
+
jspFile = new File(strPath);
+
}
+
+
try {
+
//this will return 0 if the file does not exist.
+
long nRet = jspFile.lastModified();
+
+
if (nRet != 0){
+
return nRet;
+
}
+
} catch(Exception ex) {
+
//ignore and fall back.
+
}
+
+
try {
+
URL jspUrl = ctxt.getResource(jspUri);
+
if (jspUrl != null)
+
{
+
bInWar = true;
+
return jspUrl.openConnection().getLastModified();
+
}
+
} catch (Exception e) {
+
//ignore
+
}
+
+
return 0;
+
}
+
+
/**
+
* This function determines if the jsp this represents is
+
* already being compiled. If it is not then the new modification
+
* time is saved, and false is returned meaning the caller is
+
* allowed to compile the JSP.
+
*/
+
synchronized boolean isCompiling(long nNewModTime) {
+
if (bCompiling) {
+
return true;
+
}
+
+
nLastModified = nNewModTime;
+
bCompiling = true;
+
+
return false;
+
}
+
+
void doneCompile()
+
{
+
bCompiling = false;
+
}
+
+
void waitForCompile()
+
{
+
while (bCompiling)
+
Thread.yield();
+
}
}
@@ -594,57 +696,68 @@
jsw.outDir, isErrorPage, options,
req, res);
}
- JspCompilationContext ctxt = jsw.ctxt;
-
boolean outDated;
- Compiler compiler = ctxt.createCompiler();
-
- try {
-
synchronized(jsw) {
-
// Synchronizing on jsw enables simultaneous compilations of
-
// different pages, but not the same page.
-
outDated = compiler.isOutDated();
-
if (outDated)
-
compiler.compile();
- }
- } catch (FileNotFoundException ex) {
- compiler.removeGeneratedFiles();
- throw ex;
- } catch (JasperException ex) {
- throw ex;
- } catch (Exception ex) {
-
throw new JasperException(Constants.getString("jsp.error.unable.compile"),
- ex);
-
}
+
+ //this short circuits the need to create a copiler and do a test compile.
+ if (!jsw.hasJspChanged()) {
+
return false;
+ }
+
+
try{
+
JspCompilationContext ctxt = jsw.ctxt;
+
boolean outDated;
+
Compiler compiler = ctxt.createCompiler();
+
+
try {
+
synchronized(jsw) {
+
// Synchronizing on jsw enables simultaneous compilations of
+
// different pages, but not the same page.
+
outDated = compiler.compile();
+
}
+
} catch (FileNotFoundException ex) {
+
compiler.removeGeneratedFiles();
+
throw ex;
+
} catch (JasperException ex) {
+
throw ex;
+
} catch (Exception ex) {
+
throw new JasperException(Constants.getString("jsp.error.unable.compile"),
+
ex);
+
}
- // Reload only if it's outdated
-
if ((jsw.servletClass == null) || outDated) {
-
try {
-
synchronized (jsw) {
-
if (jsw.servletClass == null || outDated) {
-
URL [] urls = new URL[1];
-
File outputDir = new File(normalize(ctxt.getOutputDir()));
-
urls[0] = outputDir.toURL();
-
jsw.loader = new JasperLoader(
-
urls,ctxt.getServletClassName(),
-
parentClassLoader,
-
permissionCollection,
-
codeSource);
-
jsw.servletClass = jsw.loader.loadClass(
-
Constants.JSP_PACKAGE_NAME + "." +
-
ctxt.getServletClassName());
+
// Reload only if it's outdated
+
if ((jsw.servletClass == null) || outDated) {
+
try {
+
synchronized (jsw) {
+
if (jsw.servletClass == null || outDated) {
+
URL [] urls = new URL[1];
+
File outputDir = new File(normalize(ctxt.getOutputDir()));
+
urls[0] = outputDir.toURL();
+
+
jsw.loader = new JasperLoader(
+
urls,ctxt.getServletClassName(),
+
parentClassLoader,
+
permissionCollection,
+
codeSource);
+
jsw.servletClass = jsw.loader.loadClass(
+
Constants.JSP_PACKAGE_NAME + "." +
+
ctxt.getServletClassName());
+
}
+
}
+
} catch (ClassNotFoundException cex) {
+
System.out.println("Caught: " + cex);
+
throw new JasperException(
+
Constants.getString("jsp.error.unable.load"),cex);
+
} catch (MalformedURLException mue) {
+
System.out.println("Caught: " + mue);
+
throw new JasperException(
+
Constants.getString("jsp.error.unable.load"),mue);
}
+
+
}
+
+
return outDated;
+
} finally {
+
jsw.doneCompile();
}
-
} catch (ClassNotFoundException cex) {
-
throw new JasperException(
-
Constants.getString("jsp.error.unable.load"),cex);
-
} catch (MalformedURLException mue) {
- throw new JasperException(
-
Constants.getString("jsp.error.unable.load"),mue);
-
}
-
-
}
-
-
return outDated;
}
--
Duncan McLean
Hummingbird Ltd.
613-548-4355 x1539
http://www.hummingbird.com
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