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Posted to dev@tomcat.apache.org by Marc Saegesser <ma...@apropos.com> on 2001/04/26 01:39:46 UTC
Tomcat 3.2.2 and Thread synchronization
I've made some pretty major changes to JspServlet.java to clean up lots of
thread synchroniztion problems. The commit message summarizes most of the
changes. Because this is a major change very late in the beta cycle I would
appreciate it if other developers would give this a through review. Be
kind, my head is still spinning from all this synchronization stuff.
If no one has any complaints I'll cut a new (and hopfully final) beta
release for Tomcat 3.2.2 in a couple days.
> -----Original Message-----
> From: marcsaeg@apache.org [mailto:marcsaeg@apache.org]
> Sent: Wednesday, April 25, 2001 6:30 PM
> To: jakarta-tomcat-cvs@apache.org
> Subject: cvs commit: jakarta-tomcat/src/share/org/apache/jasper/servlet
> JspServlet.java
>
>
> marcsaeg 01/04/25 16:29:30
>
> Modified: src/share/org/apache/jasper/resources Tag: tomcat_32
> messages.properties messages_es.properties
> messages_fr.properties
> src/share/org/apache/jasper/servlet Tag: tomcat_32
> JspServlet.java
> Log:
> This is a fairly major update. There were numerous thread
> synchronization
> problems involving compiling JSP files. These problems were
> most apparent
> on systems running under load in which page re-compilations might
> happen while pages are being executed and where new requests
> arrive while
> a page compilation is underway.
>
> I've made lots of changes so I'll just summarize the major differences
> here.
>
> 1) The thread synchronization in doLoadJSP() is quite different. The
> comments before that method describe the synchronization model
> in detail.
>
> 2) The synchronization in doLoadJSP() is now based on the
> JspServletWrapper object instead of the JspServlet object.
>
> 3) The class loading and the object instantiation used to be
> split between
> doLoadJSP() and the JspServletWrapper. They are now combined into a
> single synchronization block inside doLoadJSP().
>
> 4) In JspServletWrapper, the data member theServlet was used directly by
> several methods. Access to this is now provided only through a
> synchronized accessor method(). Any method that needs to obtain the
> servlet must call getServlet() and store the result in a stack variable
> (or other per-thread storage). Multiple threads of execution through
> JspServletWrapper may be executing different servlet classes if a page
> compilation happened while other requests were being processed.
>
> 5) When a new JSP implementation class replaces an existing class, the
> original classes destroy() method should be called so that any
> jspDestroy() method on the page will be executed. However, the
> destroy()
> method can't be invoked until we know that there are no more requests
> being processed on that instance. To support this, the JSP
> implementation
> class is wrapped inside a new class called JspCountedServlet.
> This class
> provides simple reference counting in the service() method. If the
> classes destroy method is called it flags the class for destruction but
> does not call the servlet's destroy() method until it
> determines that the
> service method has completed on all threads running in the class.
>
> PR: 1280
>
> Revision Changes Path
> No revision
>
>
> No revision
>
>
> 1.17.2.9 +3 -1
> jakarta-tomcat/src/share/org/apache/jasper/resources/messages.properties
>
> Index: messages.properties
> ===================================================================
> RCS file:
> /home/cvs/jakarta-tomcat/src/share/org/apache/jasper/resources/mes
> sages.properties,v
> retrieving revision 1.17.2.8
> retrieving revision 1.17.2.9
> diff -u -r1.17.2.8 -r1.17.2.9
> --- messages.properties 2001/01/12 04:47:00 1.17.2.8
> +++ messages.properties 2001/04/25 23:29:28 1.17.2.9
> @@ -1,4 +1,4 @@
> -# $Id: messages.properties,v 1.17.2.8 2001/01/12 04:47:00 larryi Exp $
> +# $Id: messages.properties,v 1.17.2.9 2001/04/25 23:29:28
> marcsaeg Exp $
> #
> # Default localized string information
> # Localized this the Default Locale as is en_US
> @@ -214,3 +214,5 @@
> jsp.error.unterminated.user.tag=Unterminated user-defined tag:
> ending tag {0} not found or incorrectly nested
> jsp.error.invalid.javaEncoding=Invalid java encodings. Tried
> {0} and then {1}. Both failed.
> jsp.error.needAlternateJavaEncoding=Default java encoding {0}
> is invalid on your java platform. An alternate can be specified
> via the 'javaEncoding' parameter of JspServlet.
> +jsp.error.badcount=Internal error. Attempted to decrement the
> reference count for an unreferenced JSP.
> +
>
>
>
> 1.3.2.7 +3 -1
> jakarta-tomcat/src/share/org/apache/jasper/resources/messages_es.p
> roperties
>
> Index: messages_es.properties
> ===================================================================
> RCS file:
> /home/cvs/jakarta-tomcat/src/share/org/apache/jasper/resources/mes
> sages_es.properties,v
> retrieving revision 1.3.2.6
> retrieving revision 1.3.2.7
> diff -u -r1.3.2.6 -r1.3.2.7
> --- messages_es.properties 2001/01/12 04:47:00 1.3.2.6
> +++ messages_es.properties 2001/04/25 23:29:29 1.3.2.7
> @@ -1,4 +1,4 @@
> -# $Id: messages_es.properties,v 1.3.2.6 2001/01/12 04:47:00
> larryi Exp $
> +# $Id: messages_es.properties,v 1.3.2.7 2001/04/25 23:29:29
> marcsaeg Exp $
> #
> # Default localized string information
> # Localized para Locale es_ES
> @@ -204,3 +204,5 @@
> jspc.error.emptyWebApp=-webapp necesita un argumento de archivo
> jsp.error.no.more.content=Final del contenido alcanzado
> mientras se requeria mas entrada: anidamiento de tag s erroneo o
> tag no terminado
> jsp.error.unterminated.user.tag=Tag definida por el usuario no
> terminada: tag de finalizacion {0} no encontrado o incorrectamente anidado
> +jsp.error.badcount=Internal error. Attempted to decrement the
> reference count for an unreferenced JSP.
> +
>
>
>
> 1.1.2.3 +3 -1
> jakarta-tomcat/src/share/org/apache/jasper/resources/messages_fr.p
> roperties
>
> Index: messages_fr.properties
> ===================================================================
> RCS file:
> /home/cvs/jakarta-tomcat/src/share/org/apache/jasper/resources/mes
> sages_fr.properties,v
> retrieving revision 1.1.2.2
> retrieving revision 1.1.2.3
> diff -u -r1.1.2.2 -r1.1.2.3
> --- messages_fr.properties 2001/01/12 04:47:00 1.1.2.2
> +++ messages_fr.properties 2001/04/25 23:29:29 1.1.2.3
> @@ -1,4 +1,4 @@
> -# $Id: messages_fr.properties,v 1.1.2.2 2001/01/12 04:47:00
> larryi Exp $
> +# $Id: messages_fr.properties,v 1.1.2.3 2001/04/25 23:29:29
> marcsaeg Exp $
> #
> # Default localized string information
> # Localized this the Default Locale as is fr_FR
> @@ -208,3 +208,5 @@
> jspc.error.emptyWebApp=-webapp nécessite un argument suivant
> de type fichier
> jsp.error.no.more.content=Fin de contenu atteinte alors que
> plus d''analyse est nécessaire: Un tag non terminé ou une erreur
> de tag imbriqué?
> jsp.error.unterminated.user.tag=Tag utilisateur non terminé:
> Le tag de fermeture {0} est introuvable ou incorrectement imbriqué
> +jsp.error.badcount=Internal error. Attempted to decrement the
> reference count for an unreferenced JSP.
> +
>
>
>
> No revision
>
>
> No revision
>
>
> 1.3.2.6 +181 -51
> jakarta-tomcat/src/share/org/apache/jasper/servlet/JspServlet.java
>
> Index: JspServlet.java
> ===================================================================
> RCS file:
> /home/cvs/jakarta-tomcat/src/share/org/apache/jasper/servlet/JspSe
> rvlet.java,v
> retrieving revision 1.3.2.5
> retrieving revision 1.3.2.6
> diff -u -r1.3.2.5 -r1.3.2.6
> --- JspServlet.java 2001/04/25 21:58:41 1.3.2.5
> +++ JspServlet.java 2001/04/25 23:29:30 1.3.2.6
> @@ -91,14 +91,97 @@
> *
> * @author Anil K. Vijendran
> * @author Harish Prabandham
> + * @author Marc A. Saegesser
> */
> public class JspServlet extends HttpServlet {
>
> + /**
> + * Adds reference counting to the JSP implementation servlet. This
> + * is required to handle the case where a JSP
> implementation servlet
> + * is executing requests on several threads when a new
> implementation
> + * arrives (the JSP source was updated). We need to wait until all
> + * the requests complete before calling the implementation
> servlet's
> + * destroy() method.
> + */
> + class JspCountedServlet extends HttpServlet
> + {
> + private Servlet servlet = null;
> + private int threadCount = 0;
> + private boolean destroyed = false;
> +
> + public JspCountedServlet(Servlet servlet)
> + {
> + this.servlet = servlet;
> + }
> +
> + public void init(ServletConfig config) throws
> ServletException, JasperException
> + {
> + try{
> + servlet.init(config);
> + }catch(NullPointerException e){
> + throw new JasperException(e);
> + }
> + }
> +
> + public void service(HttpServletRequest req,
> HttpServletResponse res) throws ServletException, IOException,
> JasperException
> + {
> + try{
> + incrementCount();
> + servlet.service(req, res);
> + }catch(NullPointerException e){
> + throw new JasperException(e);
> + }finally{
> + decrementCount();
> + }
> + }
> +
> + /*
> + * Flags this servlet for destrction once all active
> requests have completed.
> + * After calling this method it is invalid to call service().
> + */
> + public void destroy()
> + {
> + destroyed = true;
> + if(getCount() == 0)
> + doDestroy();
> + }
> +
> + private void doDestroy()
> + {
> + try{
> + servlet.destroy();
> + servlet = null;
> + }catch(NullPointerException e){
> + }
> + }
> +
> + private synchronized void incrementCount()
> + {
> + threadCount++;
> + }
> +
> + private synchronized void decrementCount()
> + {
> + if(threadCount <= 0){
> + Constants.message("jsp.error.badcount", Logger.ERROR);
> + return;
> + }
> +
> + --threadCount;
> + if(threadCount == 0 && destroyed)
> + doDestroy();
> + }
> +
> + private synchronized int getCount()
> + {
> + return threadCount;
> + }
> + }
> +
> class JspServletWrapper {
> - Servlet theServlet;
> + JspCountedServlet theServlet;
> String jspUri;
> boolean isErrorPage;
> - // ServletWrapper will set this
> Class servletClass;
>
> JspServletWrapper(String jspUri, boolean isErrorPage) {
> @@ -107,23 +190,46 @@
> this.theServlet = null;
> }
>
> - private void load() throws JasperException, ServletException {
> + public synchronized void instantiateServlet(Class
> servletClass) throws JasperException, ServletException
> + {
> try {
> - // Class servletClass = (Class) loadedJSPs.get(jspUri);
> - // This is to maintain the original protocol.
> - destroy();
> + this.servletClass = servletClass;
> +
> + // If we're replacing an existing JSP
> Implementation class, then
> + // schedule it for destruction
> + if(theServlet != null)
> + theServlet.destroy();
> +
> + // Create an instance of the JSP implementation class
> + Servlet servlet = (Servlet) servletClass.newInstance();
> + // Set the class loader
> + if(servlet instanceof HttpJspBase) {
> +
> ((HttpJspBase)servlet).setClassLoader(JspServlet.this.parentClassLoader);
> + }
> +
> + // Wrap this servlet in a counted servlet
> + theServlet = new JspCountedServlet(servlet);
> +
> + // Call the JSP Implementation servlet's
> init() method. This
> + // will cause the page's jspInit() method to
> be invoked if one exists.
> + theServlet.init(JspServlet.this.config);
>
> - theServlet = (Servlet) servletClass.newInstance();
> } catch(Exception ex) {
> throw new JasperException(ex);
> }
> - theServlet.init(JspServlet.this.config);
> - if(theServlet instanceof HttpJspBase) {
> - HttpJspBase h = (HttpJspBase) theServlet;
> - h.setClassLoader(JspServlet.this.parentClassLoader);
> - }
> +
> }
>
> + public synchronized Servlet getServlet()
> + {
> + return theServlet;
> + }
> +
> + public synchronized boolean isInstantiated()
> + {
> + return theServlet != null;
> + }
> +
> private void loadIfNecessary(HttpServletRequest req,
> HttpServletResponse res)
> throws JasperException, ServletException,
> FileNotFoundException
> {
> @@ -149,10 +255,7 @@
> },
> Logger.INFORMATION);
>
> - if(loadJSP(jspUri, cp, isErrorPage, req, res)
> - || theServlet == null) {
> - load();
> - }
> + loadJSP(jspUri, cp, isErrorPage, req, res);
> }
>
> public void service(HttpServletRequest request,
> @@ -160,21 +263,23 @@
> boolean precompile)
> throws ServletException, IOException, FileNotFoundException
> {
> + Servlet servlet = null;
> try {
> loadIfNecessary(request, response);
> + servlet = getServlet();
>
> // If a page is to only to be precompiled return.
> if(precompile)
> return;
>
> - if(theServlet instanceof SingleThreadModel) {
> + if(servlet instanceof SingleThreadModel) {
> // sync on the wrapper so that the freshness
> // of the page is determined right before servicing
> synchronized (this) {
> - theServlet.service(request, response);
> + servlet.service(request, response);
> }
> } else {
> - theServlet.service(request, response);
> + servlet.service(request, response);
> }
>
> } catch(FileNotFoundException ex) {
> @@ -216,7 +321,8 @@
> }
> }
>
> - public void destroy() {
> + public void destroy()
> + {
> if(theServlet != null)
> theServlet.destroy();
> }
> @@ -272,7 +378,6 @@
> "<none>"
> }, Logger.DEBUG);
> }
> - // System.out.println("JspServlet: init " +
> config.getServletName() );
> if( loader==null ) {
> if( jdk12 ) {
> try {
> @@ -307,11 +412,18 @@
> throws ServletException, IOException
> {
> boolean isErrorPage = exception != null;
> + JspServletWrapper wrapper = null;
>
> - JspServletWrapper wrapper = (JspServletWrapper)
> jsps.get(jspUri);
> - if(wrapper == null) {
> - wrapper = new JspServletWrapper(jspUri, isErrorPage);
> - jsps.put(jspUri, wrapper);
> + /*
> + * Several threads may be handling requests for the
> same jspUri.
> + * Only one of them is allowed to create the JspServletWrapper.
> + */
> + synchronized(this){
> + wrapper = (JspServletWrapper) jsps.get(jspUri);
> + if(wrapper == null) {
> + wrapper = new JspServletWrapper(jspUri, isErrorPage);
> + jsps.put(jspUri, wrapper);
> + }
> }
>
> wrapper.service(request, response, precompile);
> @@ -437,6 +549,36 @@
> * @param classpath explicitly set the JSP compilation path.
> * @return true if JSP files is newer
> */
> +
> + /*
> + * A word about the thread synchronization below. The call to
> + * compiler.isOutDated() is outside the synchronization
> block on purpose.
> + * The expectation is that for the vast majority of cases
> the JSP source file
> + * will not have changed and there will be no need to
> recompile the
> + * implementation class. For those cases when a compile
> is required, we
> + * enter a block that is synchronized on the
> JspServletWrapper object for
> + * this JSP page. Because the initial out dated check is
> unsynchronized, it
> + * is possible for more than one request to attempt to
> enter the synchronized
> + * compile block. The compile() method contains performs
> an outdated check
> + * of its own. The first thread into the block will cause
> a compile, the
> + * subsequent threads will essentially skip the
> compilation and instantiation
> + * steps.
> + *
> + * One other thing to note is that there is a window of
> time between the
> + * compiler.compile() call and the end of the synchronized
> block where a new
> + * thread entering doLoadJSP() will be told that that
> implementation class is
> + * up to date even though the code in the synchronized
> block has not
> + * completed loading and instantiating the class. In this
> case doLoadJSP()
> + * will return false without attempting to compile the
> class. This is OK
> + * because the JspServletWrapper.getServlet() method used by the
> + * JspServletWrapper.service() method is synchronized.
> Thus, the service
> + * method will not receive the servlet class until it has
> been completely loaded and
> + * instantiated.
> + *
> + * The bottom line is that we avoid synchronizing a fairly
> expensive
> + * operation (isOutDated) but pay a small price of some
> unnecessary
> + * compilation attempts in the atypical case of a modified
> JSP file.
> + */
> protected boolean doLoadJSP(String jspUri, String classpath,
> boolean isErrorPage,
> HttpServletRequest req, HttpServletResponse res)
> throws JasperException, FileNotFoundException
> @@ -445,25 +587,26 @@
> if( jsw==null ) {
> throw new JasperException("Can't happen -
> JspServletWrapper=null");
> }
> - // Class jspClass = (Class) loadedJSPs.get(jspUri);
> - boolean firstTime = jsw.servletClass == null;
> JspCompilationContext ctxt = new
> JspEngineContext(loader, classpath,
>
> context, jspUri,
>
> isErrorPage, options,
> req, res);
> boolean outDated = false;
>
> - Compiler compiler = null;
> - synchronized(this){
> - compiler = ctxt.createCompiler();
> - }
> + Compiler compiler = ctxt.createCompiler();
>
> try {
> +
> +
> outDated = compiler.isOutDated();
> - if( (jsw.servletClass == null) || outDated ) {
> - synchronized ( this ) {
> - if((jsw.servletClass == null) ||
> (compiler.isOutDated() )) {
> - outDated = compiler.compile();
> + if(!jsw.isInstantiated() || outDated ) {
> + synchronized(jsw){
> + outDated = compiler.compile();
> + if(!jsw.isInstantiated() || outDated) {
> + if( null ==ctxt.getServletClassName() ) {
> + compiler.computeServletClassName();
> + }
> +
> jsw.instantiateServlet(loader.loadClass(ctxt.getFullClassName()));
> }
> }
> }
> @@ -472,25 +615,12 @@
> throw ex;
> } catch(JasperException ex) {
> throw ex;
> + } catch(ClassNotFoundException cex) {
> + throw new
> JasperException(Constants.getString("jsp.error.unable.load"),
> + cex);
> } 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 {
> - if( null ==ctxt.getServletClassName() ) {
> - compiler.computeServletClassName();
> - }
> - jsw.servletClass =
> loader.loadClass(ctxt.getFullClassName());
> - //loadClass(ctxt.getFullClassName(), true);
> - } catch(ClassNotFoundException cex) {
> - throw new
> JasperException(Constants.getString("jsp.error.unable.load"),
> - cex);
> - }
> -
> - // loadedJSPs.put(jspUri, jspClass);
> }
>
> return outDated;
>
>
>
RE: Tomcat 3.2.2 and Thread synchronization
Posted by Marc Saegesser <ma...@apropos.com>.
JspServlet, in 3.2.x, takes on some of the responsibilities of a servlet
container in that it controls the lifecycle of the implementation servlet
classes (instantiates them, calls init(), service() and destroy()). We
really should be delegating this stuff to a real servlet container and I
think the Jasper34 refactoring is a going to do that. I just couldn't go
that far in 3.2.2 because we're too close to release to make those kinds of
changes.
> -----Original Message-----
> From: cmanolache@yahoo.com [mailto:cmanolache@yahoo.com]
> Sent: Wednesday, April 25, 2001 7:07 PM
> To: tomcat-dev@jakarta.apache.org
> Subject: Re: Tomcat 3.2.2 and Thread synchronization
>
>
>
> One quick comment - this should be provided by the servlet container.
> ( i.e. make sure that destroy() is not called while a servlet is in
> progress ). Of course, JspServlet is overriding the container and manage
> it's own servlets.
>
> I'll look at the code and try to port it to 3.3 - and send more comments
> as I go. ( if anyone wants to help - the fix should go in the container,
> since in 3.3 jsp-generated servlets are treated as normal servlets ).
> ( for 3.3 JspServlet - probably a cvs merge will work fine )
>
> Costin
>
>
> On Wed, 25 Apr 2001, Marc Saegesser wrote:
>
> > I've made some pretty major changes to JspServlet.java to clean
> up lots of
> > thread synchroniztion problems. The commit message summarizes
> most of the
> > changes. Because this is a major change very late in the beta
> cycle I would
> > appreciate it if other developers would give this a through review. Be
> > kind, my head is still spinning from all this synchronization stuff.
> >
> > If no one has any complaints I'll cut a new (and hopfully final) beta
> > release for Tomcat 3.2.2 in a couple days.
> >
> >
> > > -----Original Message-----
> > > From: marcsaeg@apache.org [mailto:marcsaeg@apache.org]
> > > Sent: Wednesday, April 25, 2001 6:30 PM
> > > To: jakarta-tomcat-cvs@apache.org
> > > Subject: cvs commit:
> jakarta-tomcat/src/share/org/apache/jasper/servlet
> > > JspServlet.java
> > >
> > >
> > > marcsaeg 01/04/25 16:29:30
> > >
> > > Modified: src/share/org/apache/jasper/resources Tag: tomcat_32
> > > messages.properties messages_es.properties
> > > messages_fr.properties
> > > src/share/org/apache/jasper/servlet Tag: tomcat_32
> > > JspServlet.java
> > > Log:
> > > This is a fairly major update. There were numerous thread
> > > synchronization
> > > problems involving compiling JSP files. These problems were
> > > most apparent
> > > on systems running under load in which page re-compilations might
> > > happen while pages are being executed and where new requests
> > > arrive while
> > > a page compilation is underway.
> > >
> > > I've made lots of changes so I'll just summarize the major
> differences
> > > here.
> > >
> > > 1) The thread synchronization in doLoadJSP() is quite
> different. The
> > > comments before that method describe the synchronization model
> > > in detail.
> > >
> > > 2) The synchronization in doLoadJSP() is now based on the
> > > JspServletWrapper object instead of the JspServlet object.
> > >
> > > 3) The class loading and the object instantiation used to be
> > > split between
> > > doLoadJSP() and the JspServletWrapper. They are now combined into a
> > > single synchronization block inside doLoadJSP().
> > >
> > > 4) In JspServletWrapper, the data member theServlet was
> used directly by
> > > several methods. Access to this is now provided only through a
> > > synchronized accessor method(). Any method that needs to obtain the
> > > servlet must call getServlet() and store the result in a
> stack variable
> > > (or other per-thread storage). Multiple threads of
> execution through
> > > JspServletWrapper may be executing different servlet
> classes if a page
> > > compilation happened while other requests were being processed.
> > >
> > > 5) When a new JSP implementation class replaces an existing
> class, the
> > > original classes destroy() method should be called so that any
> > > jspDestroy() method on the page will be executed. However, the
> > > destroy()
> > > method can't be invoked until we know that there are no
> more requests
> > > being processed on that instance. To support this, the JSP
> > > implementation
> > > class is wrapped inside a new class called JspCountedServlet.
> > > This class
> > > provides simple reference counting in the service() method. If the
> > > classes destroy method is called it flags the class for
> destruction but
> > > does not call the servlet's destroy() method until it
> > > determines that the
> > > service method has completed on all threads running in the class.
> > >
> > > PR: 1280
> > >
> > > Revision Changes Path
> > > No revision
> > >
> > >
> > > No revision
> > >
> > >
> > > 1.17.2.9 +3 -1
> > >
> jakarta-tomcat/src/share/org/apache/jasper/resources/messages.properties
> > >
> > > Index: messages.properties
> > > ===================================================================
> > > RCS file:
> > > /home/cvs/jakarta-tomcat/src/share/org/apache/jasper/resources/mes
> > > sages.properties,v
> > > retrieving revision 1.17.2.8
> > > retrieving revision 1.17.2.9
> > > diff -u -r1.17.2.8 -r1.17.2.9
> > > --- messages.properties 2001/01/12 04:47:00 1.17.2.8
> > > +++ messages.properties 2001/04/25 23:29:28 1.17.2.9
> > > @@ -1,4 +1,4 @@
> > > -# $Id: messages.properties,v 1.17.2.8 2001/01/12 04:47:00
> larryi Exp $
> > > +# $Id: messages.properties,v 1.17.2.9 2001/04/25 23:29:28
> > > marcsaeg Exp $
> > > #
> > > # Default localized string information
> > > # Localized this the Default Locale as is en_US
> > > @@ -214,3 +214,5 @@
> > > jsp.error.unterminated.user.tag=Unterminated user-defined tag:
> > > ending tag {0} not found or incorrectly nested
> > > jsp.error.invalid.javaEncoding=Invalid java encodings. Tried
> > > {0} and then {1}. Both failed.
> > > jsp.error.needAlternateJavaEncoding=Default java encoding {0}
> > > is invalid on your java platform. An alternate can be specified
> > > via the 'javaEncoding' parameter of JspServlet.
> > > +jsp.error.badcount=Internal error. Attempted to decrement the
> > > reference count for an unreferenced JSP.
> > > +
> > >
> > >
> > >
> > > 1.3.2.7 +3 -1
> > > jakarta-tomcat/src/share/org/apache/jasper/resources/messages_es.p
> > > roperties
> > >
> > > Index: messages_es.properties
> > > ===================================================================
> > > RCS file:
> > > /home/cvs/jakarta-tomcat/src/share/org/apache/jasper/resources/mes
> > > sages_es.properties,v
> > > retrieving revision 1.3.2.6
> > > retrieving revision 1.3.2.7
> > > diff -u -r1.3.2.6 -r1.3.2.7
> > > --- messages_es.properties 2001/01/12 04:47:00 1.3.2.6
> > > +++ messages_es.properties 2001/04/25 23:29:29 1.3.2.7
> > > @@ -1,4 +1,4 @@
> > > -# $Id: messages_es.properties,v 1.3.2.6 2001/01/12 04:47:00
> > > larryi Exp $
> > > +# $Id: messages_es.properties,v 1.3.2.7 2001/04/25 23:29:29
> > > marcsaeg Exp $
> > > #
> > > # Default localized string information
> > > # Localized para Locale es_ES
> > > @@ -204,3 +204,5 @@
> > > jspc.error.emptyWebApp=-webapp necesita un argumento de archivo
> > > jsp.error.no.more.content=Final del contenido alcanzado
> > > mientras se requeria mas entrada: anidamiento de tag s erroneo o
> > > tag no terminado
> > > jsp.error.unterminated.user.tag=Tag definida por el usuario no
> > > terminada: tag de finalizacion {0} no encontrado o
> incorrectamente anidado
> > > +jsp.error.badcount=Internal error. Attempted to decrement the
> > > reference count for an unreferenced JSP.
> > > +
> > >
> > >
> > >
> > > 1.1.2.3 +3 -1
> > > jakarta-tomcat/src/share/org/apache/jasper/resources/messages_fr.p
> > > roperties
> > >
> > > Index: messages_fr.properties
> > > ===================================================================
> > > RCS file:
> > > /home/cvs/jakarta-tomcat/src/share/org/apache/jasper/resources/mes
> > > sages_fr.properties,v
> > > retrieving revision 1.1.2.2
> > > retrieving revision 1.1.2.3
> > > diff -u -r1.1.2.2 -r1.1.2.3
> > > --- messages_fr.properties 2001/01/12 04:47:00 1.1.2.2
> > > +++ messages_fr.properties 2001/04/25 23:29:29 1.1.2.3
> > > @@ -1,4 +1,4 @@
> > > -# $Id: messages_fr.properties,v 1.1.2.2 2001/01/12 04:47:00
> > > larryi Exp $
> > > +# $Id: messages_fr.properties,v 1.1.2.3 2001/04/25 23:29:29
> > > marcsaeg Exp $
> > > #
> > > # Default localized string information
> > > # Localized this the Default Locale as is fr_FR
> > > @@ -208,3 +208,5 @@
> > > jspc.error.emptyWebApp=-webapp nécessite un argument suivant
> > > de type fichier
> > > jsp.error.no.more.content=Fin de contenu atteinte alors que
> > > plus d''analyse est nécessaire: Un tag non terminé ou une erreur
> > > de tag imbriqué?
> > > jsp.error.unterminated.user.tag=Tag utilisateur non terminé:
> > > Le tag de fermeture {0} est introuvable ou incorrectement imbriqué
> > > +jsp.error.badcount=Internal error. Attempted to decrement the
> > > reference count for an unreferenced JSP.
> > > +
> > >
> > >
> > >
> > > No revision
> > >
> > >
> > > No revision
> > >
> > >
> > > 1.3.2.6 +181 -51
> > > jakarta-tomcat/src/share/org/apache/jasper/servlet/JspServlet.java
> > >
> > > Index: JspServlet.java
> > > ===================================================================
> > > RCS file:
> > > /home/cvs/jakarta-tomcat/src/share/org/apache/jasper/servlet/JspSe
> > > rvlet.java,v
> > > retrieving revision 1.3.2.5
> > > retrieving revision 1.3.2.6
> > > diff -u -r1.3.2.5 -r1.3.2.6
> > > --- JspServlet.java 2001/04/25 21:58:41 1.3.2.5
> > > +++ JspServlet.java 2001/04/25 23:29:30 1.3.2.6
> > > @@ -91,14 +91,97 @@
> > > *
> > > * @author Anil K. Vijendran
> > > * @author Harish Prabandham
> > > + * @author Marc A. Saegesser
> > > */
> > > public class JspServlet extends HttpServlet {
> > >
> > > + /**
> > > + * Adds reference counting to the JSP implementation
> servlet. This
> > > + * is required to handle the case where a JSP
> > > implementation servlet
> > > + * is executing requests on several threads when a new
> > > implementation
> > > + * arrives (the JSP source was updated). We need to
> wait until all
> > > + * the requests complete before calling the implementation
> > > servlet's
> > > + * destroy() method.
> > > + */
> > > + class JspCountedServlet extends HttpServlet
> > > + {
> > > + private Servlet servlet = null;
> > > + private int threadCount = 0;
> > > + private boolean destroyed = false;
> > > +
> > > + public JspCountedServlet(Servlet servlet)
> > > + {
> > > + this.servlet = servlet;
> > > + }
> > > +
> > > + public void init(ServletConfig config) throws
> > > ServletException, JasperException
> > > + {
> > > + try{
> > > + servlet.init(config);
> > > + }catch(NullPointerException e){
> > > + throw new JasperException(e);
> > > + }
> > > + }
> > > +
> > > + public void service(HttpServletRequest req,
> > > HttpServletResponse res) throws ServletException, IOException,
> > > JasperException
> > > + {
> > > + try{
> > > + incrementCount();
> > > + servlet.service(req, res);
> > > + }catch(NullPointerException e){
> > > + throw new JasperException(e);
> > > + }finally{
> > > + decrementCount();
> > > + }
> > > + }
> > > +
> > > + /*
> > > + * Flags this servlet for destrction once all active
> > > requests have completed.
> > > + * After calling this method it is invalid to call
> service().
> > > + */
> > > + public void destroy()
> > > + {
> > > + destroyed = true;
> > > + if(getCount() == 0)
> > > + doDestroy();
> > > + }
> > > +
> > > + private void doDestroy()
> > > + {
> > > + try{
> > > + servlet.destroy();
> > > + servlet = null;
> > > + }catch(NullPointerException e){
> > > + }
> > > + }
> > > +
> > > + private synchronized void incrementCount()
> > > + {
> > > + threadCount++;
> > > + }
> > > +
> > > + private synchronized void decrementCount()
> > > + {
> > > + if(threadCount <= 0){
> > > + Constants.message("jsp.error.badcount",
> Logger.ERROR);
> > > + return;
> > > + }
> > > +
> > > + --threadCount;
> > > + if(threadCount == 0 && destroyed)
> > > + doDestroy();
> > > + }
> > > +
> > > + private synchronized int getCount()
> > > + {
> > > + return threadCount;
> > > + }
> > > + }
> > > +
> > > class JspServletWrapper {
> > > - Servlet theServlet;
> > > + JspCountedServlet theServlet;
> > > String jspUri;
> > > boolean isErrorPage;
> > > - // ServletWrapper will set this
> > > Class servletClass;
> > >
> > > JspServletWrapper(String jspUri, boolean isErrorPage) {
> > > @@ -107,23 +190,46 @@
> > > this.theServlet = null;
> > > }
> > >
> > > - private void load() throws JasperException,
> ServletException {
> > > + public synchronized void instantiateServlet(Class
> > > servletClass) throws JasperException, ServletException
> > > + {
> > > try {
> > > - // Class servletClass = (Class)
> loadedJSPs.get(jspUri);
> > > - // This is to maintain the original protocol.
> > > - destroy();
> > > + this.servletClass = servletClass;
> > > +
> > > + // If we're replacing an existing JSP
> > > Implementation class, then
> > > + // schedule it for destruction
> > > + if(theServlet != null)
> > > + theServlet.destroy();
> > > +
> > > + // Create an instance of the JSP
> implementation class
> > > + Servlet servlet = (Servlet)
> servletClass.newInstance();
> > > + // Set the class loader
> > > + if(servlet instanceof HttpJspBase) {
> > > +
> > >
> ((HttpJspBase)servlet).setClassLoader(JspServlet.this.parentClassLoader);
> > > + }
> > > +
> > > + // Wrap this servlet in a counted servlet
> > > + theServlet = new JspCountedServlet(servlet);
> > > +
> > > + // Call the JSP Implementation servlet's
> > > init() method. This
> > > + // will cause the page's jspInit() method to
> > > be invoked if one exists.
> > > + theServlet.init(JspServlet.this.config);
> > >
> > > - theServlet = (Servlet) servletClass.newInstance();
> > > } catch(Exception ex) {
> > > throw new JasperException(ex);
> > > }
> > > - theServlet.init(JspServlet.this.config);
> > > - if(theServlet instanceof HttpJspBase) {
> > > - HttpJspBase h = (HttpJspBase) theServlet;
> > > -
> h.setClassLoader(JspServlet.this.parentClassLoader);
> > > - }
> > > +
> > > }
> > >
> > > + public synchronized Servlet getServlet()
> > > + {
> > > + return theServlet;
> > > + }
> > > +
> > > + public synchronized boolean isInstantiated()
> > > + {
> > > + return theServlet != null;
> > > + }
> > > +
> > > private void loadIfNecessary(HttpServletRequest req,
> > > HttpServletResponse res)
> > > throws JasperException, ServletException,
> > > FileNotFoundException
> > > {
> > > @@ -149,10 +255,7 @@
> > > },
> > > Logger.INFORMATION);
> > >
> > > - if(loadJSP(jspUri, cp, isErrorPage, req, res)
> > > - || theServlet == null) {
> > > - load();
> > > - }
> > > + loadJSP(jspUri, cp, isErrorPage, req, res);
> > > }
> > >
> > > public void service(HttpServletRequest request,
> > > @@ -160,21 +263,23 @@
> > > boolean precompile)
> > > throws ServletException, IOException, FileNotFoundException
> > > {
> > > + Servlet servlet = null;
> > > try {
> > > loadIfNecessary(request, response);
> > > + servlet = getServlet();
> > >
> > > // If a page is to only to be precompiled return.
> > > if(precompile)
> > > return;
> > >
> > > - if(theServlet instanceof SingleThreadModel) {
> > > + if(servlet instanceof SingleThreadModel) {
> > > // sync on the wrapper so that the freshness
> > > // of the page is determined right
> before servicing
> > > synchronized (this) {
> > > - theServlet.service(request, response);
> > > + servlet.service(request, response);
> > > }
> > > } else {
> > > - theServlet.service(request, response);
> > > + servlet.service(request, response);
> > > }
> > >
> > > } catch(FileNotFoundException ex) {
> > > @@ -216,7 +321,8 @@
> > > }
> > > }
> > >
> > > - public void destroy() {
> > > + public void destroy()
> > > + {
> > > if(theServlet != null)
> > > theServlet.destroy();
> > > }
> > > @@ -272,7 +378,6 @@
> > > "<none>"
> > > }, Logger.DEBUG);
> > > }
> > > - // System.out.println("JspServlet: init " +
> > > config.getServletName() );
> > > if( loader==null ) {
> > > if( jdk12 ) {
> > > try {
> > > @@ -307,11 +412,18 @@
> > > throws ServletException, IOException
> > > {
> > > boolean isErrorPage = exception != null;
> > > + JspServletWrapper wrapper = null;
> > >
> > > - JspServletWrapper wrapper = (JspServletWrapper)
> > > jsps.get(jspUri);
> > > - if(wrapper == null) {
> > > - wrapper = new JspServletWrapper(jspUri, isErrorPage);
> > > - jsps.put(jspUri, wrapper);
> > > + /*
> > > + * Several threads may be handling requests for the
> > > same jspUri.
> > > + * Only one of them is allowed to create the
> JspServletWrapper.
> > > + */
> > > + synchronized(this){
> > > + wrapper = (JspServletWrapper) jsps.get(jspUri);
> > > + if(wrapper == null) {
> > > + wrapper = new JspServletWrapper(jspUri,
> isErrorPage);
> > > + jsps.put(jspUri, wrapper);
> > > + }
> > > }
> > >
> > > wrapper.service(request, response, precompile);
> > > @@ -437,6 +549,36 @@
> > > * @param classpath explicitly set the JSP compilation path.
> > > * @return true if JSP files is newer
> > > */
> > > +
> > > + /*
> > > + * A word about the thread synchronization below. The call to
> > > + * compiler.isOutDated() is outside the synchronization
> > > block on purpose.
> > > + * The expectation is that for the vast majority of cases
> > > the JSP source file
> > > + * will not have changed and there will be no need to
> > > recompile the
> > > + * implementation class. For those cases when a compile
> > > is required, we
> > > + * enter a block that is synchronized on the
> > > JspServletWrapper object for
> > > + * this JSP page. Because the initial out dated check is
> > > unsynchronized, it
> > > + * is possible for more than one request to attempt to
> > > enter the synchronized
> > > + * compile block. The compile() method contains performs
> > > an outdated check
> > > + * of its own. The first thread into the block will cause
> > > a compile, the
> > > + * subsequent threads will essentially skip the
> > > compilation and instantiation
> > > + * steps.
> > > + *
> > > + * One other thing to note is that there is a window of
> > > time between the
> > > + * compiler.compile() call and the end of the synchronized
> > > block where a new
> > > + * thread entering doLoadJSP() will be told that that
> > > implementation class is
> > > + * up to date even though the code in the synchronized
> > > block has not
> > > + * completed loading and instantiating the class. In this
> > > case doLoadJSP()
> > > + * will return false without attempting to compile the
> > > class. This is OK
> > > + * because the JspServletWrapper.getServlet() method
> used by the
> > > + * JspServletWrapper.service() method is synchronized.
> > > Thus, the service
> > > + * method will not receive the servlet class until it has
> > > been completely loaded and
> > > + * instantiated.
> > > + *
> > > + * The bottom line is that we avoid synchronizing a fairly
> > > expensive
> > > + * operation (isOutDated) but pay a small price of some
> > > unnecessary
> > > + * compilation attempts in the atypical case of a modified
> > > JSP file.
> > > + */
> > > protected boolean doLoadJSP(String jspUri, String classpath,
> > > boolean isErrorPage,
> > > HttpServletRequest req, HttpServletResponse res)
> > > throws JasperException, FileNotFoundException
> > > @@ -445,25 +587,26 @@
> > > if( jsw==null ) {
> > > throw new JasperException("Can't happen -
> > > JspServletWrapper=null");
> > > }
> > > - // Class jspClass = (Class) loadedJSPs.get(jspUri);
> > > - boolean firstTime = jsw.servletClass == null;
> > > JspCompilationContext ctxt = new
> > > JspEngineContext(loader, classpath,
> > >
> > > context, jspUri,
> > >
> > > isErrorPage, options,
> > >
> req, res);
> > > boolean outDated = false;
> > >
> > > - Compiler compiler = null;
> > > - synchronized(this){
> > > - compiler = ctxt.createCompiler();
> > > - }
> > > + Compiler compiler = ctxt.createCompiler();
> > >
> > > try {
> > > +
> > > +
> > > outDated = compiler.isOutDated();
> > > - if( (jsw.servletClass == null) || outDated ) {
> > > - synchronized ( this ) {
> > > - if((jsw.servletClass == null) ||
> > > (compiler.isOutDated() )) {
> > > - outDated = compiler.compile();
> > > + if(!jsw.isInstantiated() || outDated ) {
> > > + synchronized(jsw){
> > > + outDated = compiler.compile();
> > > + if(!jsw.isInstantiated() || outDated) {
> > > + if( null ==ctxt.getServletClassName() ) {
> > > + compiler.computeServletClassName();
> > > + }
> > > +
> > > jsw.instantiateServlet(loader.loadClass(ctxt.getFullClassName()));
> > > }
> > > }
> > > }
> > > @@ -472,25 +615,12 @@
> > > throw ex;
> > > } catch(JasperException ex) {
> > > throw ex;
> > > + } catch(ClassNotFoundException cex) {
> > > + throw new
> > > JasperException(Constants.getString("jsp.error.unable.load"),
> > > + cex);
> > > } 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 {
> > > - if( null ==ctxt.getServletClassName() ) {
> > > - compiler.computeServletClassName();
> > > - }
> > > - jsw.servletClass =
> > > loader.loadClass(ctxt.getFullClassName());
> > > - //loadClass(ctxt.getFullClassName(), true);
> > > - } catch(ClassNotFoundException cex) {
> > > - throw new
> > > JasperException(Constants.getString("jsp.error.unable.load"),
> > > - cex);
> > > - }
> > > -
> > > - // loadedJSPs.put(jspUri, jspClass);
> > > }
> > >
> > > return outDated;
> > >
> > >
> > >
> >
Re: Tomcat 3.2.2 and Thread synchronization
Posted by cm...@yahoo.com.
One quick comment - this should be provided by the servlet container.
( i.e. make sure that destroy() is not called while a servlet is in
progress ). Of course, JspServlet is overriding the container and manage
it's own servlets.
I'll look at the code and try to port it to 3.3 - and send more comments
as I go. ( if anyone wants to help - the fix should go in the container,
since in 3.3 jsp-generated servlets are treated as normal servlets ).
( for 3.3 JspServlet - probably a cvs merge will work fine )
Costin
On Wed, 25 Apr 2001, Marc Saegesser wrote:
> I've made some pretty major changes to JspServlet.java to clean up lots of
> thread synchroniztion problems. The commit message summarizes most of the
> changes. Because this is a major change very late in the beta cycle I would
> appreciate it if other developers would give this a through review. Be
> kind, my head is still spinning from all this synchronization stuff.
>
> If no one has any complaints I'll cut a new (and hopfully final) beta
> release for Tomcat 3.2.2 in a couple days.
>
>
> > -----Original Message-----
> > From: marcsaeg@apache.org [mailto:marcsaeg@apache.org]
> > Sent: Wednesday, April 25, 2001 6:30 PM
> > To: jakarta-tomcat-cvs@apache.org
> > Subject: cvs commit: jakarta-tomcat/src/share/org/apache/jasper/servlet
> > JspServlet.java
> >
> >
> > marcsaeg 01/04/25 16:29:30
> >
> > Modified: src/share/org/apache/jasper/resources Tag: tomcat_32
> > messages.properties messages_es.properties
> > messages_fr.properties
> > src/share/org/apache/jasper/servlet Tag: tomcat_32
> > JspServlet.java
> > Log:
> > This is a fairly major update. There were numerous thread
> > synchronization
> > problems involving compiling JSP files. These problems were
> > most apparent
> > on systems running under load in which page re-compilations might
> > happen while pages are being executed and where new requests
> > arrive while
> > a page compilation is underway.
> >
> > I've made lots of changes so I'll just summarize the major differences
> > here.
> >
> > 1) The thread synchronization in doLoadJSP() is quite different. The
> > comments before that method describe the synchronization model
> > in detail.
> >
> > 2) The synchronization in doLoadJSP() is now based on the
> > JspServletWrapper object instead of the JspServlet object.
> >
> > 3) The class loading and the object instantiation used to be
> > split between
> > doLoadJSP() and the JspServletWrapper. They are now combined into a
> > single synchronization block inside doLoadJSP().
> >
> > 4) In JspServletWrapper, the data member theServlet was used directly by
> > several methods. Access to this is now provided only through a
> > synchronized accessor method(). Any method that needs to obtain the
> > servlet must call getServlet() and store the result in a stack variable
> > (or other per-thread storage). Multiple threads of execution through
> > JspServletWrapper may be executing different servlet classes if a page
> > compilation happened while other requests were being processed.
> >
> > 5) When a new JSP implementation class replaces an existing class, the
> > original classes destroy() method should be called so that any
> > jspDestroy() method on the page will be executed. However, the
> > destroy()
> > method can't be invoked until we know that there are no more requests
> > being processed on that instance. To support this, the JSP
> > implementation
> > class is wrapped inside a new class called JspCountedServlet.
> > This class
> > provides simple reference counting in the service() method. If the
> > classes destroy method is called it flags the class for destruction but
> > does not call the servlet's destroy() method until it
> > determines that the
> > service method has completed on all threads running in the class.
> >
> > PR: 1280
> >
> > Revision Changes Path
> > No revision
> >
> >
> > No revision
> >
> >
> > 1.17.2.9 +3 -1
> > jakarta-tomcat/src/share/org/apache/jasper/resources/messages.properties
> >
> > Index: messages.properties
> > ===================================================================
> > RCS file:
> > /home/cvs/jakarta-tomcat/src/share/org/apache/jasper/resources/mes
> > sages.properties,v
> > retrieving revision 1.17.2.8
> > retrieving revision 1.17.2.9
> > diff -u -r1.17.2.8 -r1.17.2.9
> > --- messages.properties 2001/01/12 04:47:00 1.17.2.8
> > +++ messages.properties 2001/04/25 23:29:28 1.17.2.9
> > @@ -1,4 +1,4 @@
> > -# $Id: messages.properties,v 1.17.2.8 2001/01/12 04:47:00 larryi Exp $
> > +# $Id: messages.properties,v 1.17.2.9 2001/04/25 23:29:28
> > marcsaeg Exp $
> > #
> > # Default localized string information
> > # Localized this the Default Locale as is en_US
> > @@ -214,3 +214,5 @@
> > jsp.error.unterminated.user.tag=Unterminated user-defined tag:
> > ending tag {0} not found or incorrectly nested
> > jsp.error.invalid.javaEncoding=Invalid java encodings. Tried
> > {0} and then {1}. Both failed.
> > jsp.error.needAlternateJavaEncoding=Default java encoding {0}
> > is invalid on your java platform. An alternate can be specified
> > via the 'javaEncoding' parameter of JspServlet.
> > +jsp.error.badcount=Internal error. Attempted to decrement the
> > reference count for an unreferenced JSP.
> > +
> >
> >
> >
> > 1.3.2.7 +3 -1
> > jakarta-tomcat/src/share/org/apache/jasper/resources/messages_es.p
> > roperties
> >
> > Index: messages_es.properties
> > ===================================================================
> > RCS file:
> > /home/cvs/jakarta-tomcat/src/share/org/apache/jasper/resources/mes
> > sages_es.properties,v
> > retrieving revision 1.3.2.6
> > retrieving revision 1.3.2.7
> > diff -u -r1.3.2.6 -r1.3.2.7
> > --- messages_es.properties 2001/01/12 04:47:00 1.3.2.6
> > +++ messages_es.properties 2001/04/25 23:29:29 1.3.2.7
> > @@ -1,4 +1,4 @@
> > -# $Id: messages_es.properties,v 1.3.2.6 2001/01/12 04:47:00
> > larryi Exp $
> > +# $Id: messages_es.properties,v 1.3.2.7 2001/04/25 23:29:29
> > marcsaeg Exp $
> > #
> > # Default localized string information
> > # Localized para Locale es_ES
> > @@ -204,3 +204,5 @@
> > jspc.error.emptyWebApp=-webapp necesita un argumento de archivo
> > jsp.error.no.more.content=Final del contenido alcanzado
> > mientras se requeria mas entrada: anidamiento de tag s erroneo o
> > tag no terminado
> > jsp.error.unterminated.user.tag=Tag definida por el usuario no
> > terminada: tag de finalizacion {0} no encontrado o incorrectamente anidado
> > +jsp.error.badcount=Internal error. Attempted to decrement the
> > reference count for an unreferenced JSP.
> > +
> >
> >
> >
> > 1.1.2.3 +3 -1
> > jakarta-tomcat/src/share/org/apache/jasper/resources/messages_fr.p
> > roperties
> >
> > Index: messages_fr.properties
> > ===================================================================
> > RCS file:
> > /home/cvs/jakarta-tomcat/src/share/org/apache/jasper/resources/mes
> > sages_fr.properties,v
> > retrieving revision 1.1.2.2
> > retrieving revision 1.1.2.3
> > diff -u -r1.1.2.2 -r1.1.2.3
> > --- messages_fr.properties 2001/01/12 04:47:00 1.1.2.2
> > +++ messages_fr.properties 2001/04/25 23:29:29 1.1.2.3
> > @@ -1,4 +1,4 @@
> > -# $Id: messages_fr.properties,v 1.1.2.2 2001/01/12 04:47:00
> > larryi Exp $
> > +# $Id: messages_fr.properties,v 1.1.2.3 2001/04/25 23:29:29
> > marcsaeg Exp $
> > #
> > # Default localized string information
> > # Localized this the Default Locale as is fr_FR
> > @@ -208,3 +208,5 @@
> > jspc.error.emptyWebApp=-webapp nécessite un argument suivant
> > de type fichier
> > jsp.error.no.more.content=Fin de contenu atteinte alors que
> > plus d''analyse est nécessaire: Un tag non terminé ou une erreur
> > de tag imbriqué?
> > jsp.error.unterminated.user.tag=Tag utilisateur non terminé:
> > Le tag de fermeture {0} est introuvable ou incorrectement imbriqué
> > +jsp.error.badcount=Internal error. Attempted to decrement the
> > reference count for an unreferenced JSP.
> > +
> >
> >
> >
> > No revision
> >
> >
> > No revision
> >
> >
> > 1.3.2.6 +181 -51
> > jakarta-tomcat/src/share/org/apache/jasper/servlet/JspServlet.java
> >
> > Index: JspServlet.java
> > ===================================================================
> > RCS file:
> > /home/cvs/jakarta-tomcat/src/share/org/apache/jasper/servlet/JspSe
> > rvlet.java,v
> > retrieving revision 1.3.2.5
> > retrieving revision 1.3.2.6
> > diff -u -r1.3.2.5 -r1.3.2.6
> > --- JspServlet.java 2001/04/25 21:58:41 1.3.2.5
> > +++ JspServlet.java 2001/04/25 23:29:30 1.3.2.6
> > @@ -91,14 +91,97 @@
> > *
> > * @author Anil K. Vijendran
> > * @author Harish Prabandham
> > + * @author Marc A. Saegesser
> > */
> > public class JspServlet extends HttpServlet {
> >
> > + /**
> > + * Adds reference counting to the JSP implementation servlet. This
> > + * is required to handle the case where a JSP
> > implementation servlet
> > + * is executing requests on several threads when a new
> > implementation
> > + * arrives (the JSP source was updated). We need to wait until all
> > + * the requests complete before calling the implementation
> > servlet's
> > + * destroy() method.
> > + */
> > + class JspCountedServlet extends HttpServlet
> > + {
> > + private Servlet servlet = null;
> > + private int threadCount = 0;
> > + private boolean destroyed = false;
> > +
> > + public JspCountedServlet(Servlet servlet)
> > + {
> > + this.servlet = servlet;
> > + }
> > +
> > + public void init(ServletConfig config) throws
> > ServletException, JasperException
> > + {
> > + try{
> > + servlet.init(config);
> > + }catch(NullPointerException e){
> > + throw new JasperException(e);
> > + }
> > + }
> > +
> > + public void service(HttpServletRequest req,
> > HttpServletResponse res) throws ServletException, IOException,
> > JasperException
> > + {
> > + try{
> > + incrementCount();
> > + servlet.service(req, res);
> > + }catch(NullPointerException e){
> > + throw new JasperException(e);
> > + }finally{
> > + decrementCount();
> > + }
> > + }
> > +
> > + /*
> > + * Flags this servlet for destrction once all active
> > requests have completed.
> > + * After calling this method it is invalid to call service().
> > + */
> > + public void destroy()
> > + {
> > + destroyed = true;
> > + if(getCount() == 0)
> > + doDestroy();
> > + }
> > +
> > + private void doDestroy()
> > + {
> > + try{
> > + servlet.destroy();
> > + servlet = null;
> > + }catch(NullPointerException e){
> > + }
> > + }
> > +
> > + private synchronized void incrementCount()
> > + {
> > + threadCount++;
> > + }
> > +
> > + private synchronized void decrementCount()
> > + {
> > + if(threadCount <= 0){
> > + Constants.message("jsp.error.badcount", Logger.ERROR);
> > + return;
> > + }
> > +
> > + --threadCount;
> > + if(threadCount == 0 && destroyed)
> > + doDestroy();
> > + }
> > +
> > + private synchronized int getCount()
> > + {
> > + return threadCount;
> > + }
> > + }
> > +
> > class JspServletWrapper {
> > - Servlet theServlet;
> > + JspCountedServlet theServlet;
> > String jspUri;
> > boolean isErrorPage;
> > - // ServletWrapper will set this
> > Class servletClass;
> >
> > JspServletWrapper(String jspUri, boolean isErrorPage) {
> > @@ -107,23 +190,46 @@
> > this.theServlet = null;
> > }
> >
> > - private void load() throws JasperException, ServletException {
> > + public synchronized void instantiateServlet(Class
> > servletClass) throws JasperException, ServletException
> > + {
> > try {
> > - // Class servletClass = (Class) loadedJSPs.get(jspUri);
> > - // This is to maintain the original protocol.
> > - destroy();
> > + this.servletClass = servletClass;
> > +
> > + // If we're replacing an existing JSP
> > Implementation class, then
> > + // schedule it for destruction
> > + if(theServlet != null)
> > + theServlet.destroy();
> > +
> > + // Create an instance of the JSP implementation class
> > + Servlet servlet = (Servlet) servletClass.newInstance();
> > + // Set the class loader
> > + if(servlet instanceof HttpJspBase) {
> > +
> > ((HttpJspBase)servlet).setClassLoader(JspServlet.this.parentClassLoader);
> > + }
> > +
> > + // Wrap this servlet in a counted servlet
> > + theServlet = new JspCountedServlet(servlet);
> > +
> > + // Call the JSP Implementation servlet's
> > init() method. This
> > + // will cause the page's jspInit() method to
> > be invoked if one exists.
> > + theServlet.init(JspServlet.this.config);
> >
> > - theServlet = (Servlet) servletClass.newInstance();
> > } catch(Exception ex) {
> > throw new JasperException(ex);
> > }
> > - theServlet.init(JspServlet.this.config);
> > - if(theServlet instanceof HttpJspBase) {
> > - HttpJspBase h = (HttpJspBase) theServlet;
> > - h.setClassLoader(JspServlet.this.parentClassLoader);
> > - }
> > +
> > }
> >
> > + public synchronized Servlet getServlet()
> > + {
> > + return theServlet;
> > + }
> > +
> > + public synchronized boolean isInstantiated()
> > + {
> > + return theServlet != null;
> > + }
> > +
> > private void loadIfNecessary(HttpServletRequest req,
> > HttpServletResponse res)
> > throws JasperException, ServletException,
> > FileNotFoundException
> > {
> > @@ -149,10 +255,7 @@
> > },
> > Logger.INFORMATION);
> >
> > - if(loadJSP(jspUri, cp, isErrorPage, req, res)
> > - || theServlet == null) {
> > - load();
> > - }
> > + loadJSP(jspUri, cp, isErrorPage, req, res);
> > }
> >
> > public void service(HttpServletRequest request,
> > @@ -160,21 +263,23 @@
> > boolean precompile)
> > throws ServletException, IOException, FileNotFoundException
> > {
> > + Servlet servlet = null;
> > try {
> > loadIfNecessary(request, response);
> > + servlet = getServlet();
> >
> > // If a page is to only to be precompiled return.
> > if(precompile)
> > return;
> >
> > - if(theServlet instanceof SingleThreadModel) {
> > + if(servlet instanceof SingleThreadModel) {
> > // sync on the wrapper so that the freshness
> > // of the page is determined right before servicing
> > synchronized (this) {
> > - theServlet.service(request, response);
> > + servlet.service(request, response);
> > }
> > } else {
> > - theServlet.service(request, response);
> > + servlet.service(request, response);
> > }
> >
> > } catch(FileNotFoundException ex) {
> > @@ -216,7 +321,8 @@
> > }
> > }
> >
> > - public void destroy() {
> > + public void destroy()
> > + {
> > if(theServlet != null)
> > theServlet.destroy();
> > }
> > @@ -272,7 +378,6 @@
> > "<none>"
> > }, Logger.DEBUG);
> > }
> > - // System.out.println("JspServlet: init " +
> > config.getServletName() );
> > if( loader==null ) {
> > if( jdk12 ) {
> > try {
> > @@ -307,11 +412,18 @@
> > throws ServletException, IOException
> > {
> > boolean isErrorPage = exception != null;
> > + JspServletWrapper wrapper = null;
> >
> > - JspServletWrapper wrapper = (JspServletWrapper)
> > jsps.get(jspUri);
> > - if(wrapper == null) {
> > - wrapper = new JspServletWrapper(jspUri, isErrorPage);
> > - jsps.put(jspUri, wrapper);
> > + /*
> > + * Several threads may be handling requests for the
> > same jspUri.
> > + * Only one of them is allowed to create the JspServletWrapper.
> > + */
> > + synchronized(this){
> > + wrapper = (JspServletWrapper) jsps.get(jspUri);
> > + if(wrapper == null) {
> > + wrapper = new JspServletWrapper(jspUri, isErrorPage);
> > + jsps.put(jspUri, wrapper);
> > + }
> > }
> >
> > wrapper.service(request, response, precompile);
> > @@ -437,6 +549,36 @@
> > * @param classpath explicitly set the JSP compilation path.
> > * @return true if JSP files is newer
> > */
> > +
> > + /*
> > + * A word about the thread synchronization below. The call to
> > + * compiler.isOutDated() is outside the synchronization
> > block on purpose.
> > + * The expectation is that for the vast majority of cases
> > the JSP source file
> > + * will not have changed and there will be no need to
> > recompile the
> > + * implementation class. For those cases when a compile
> > is required, we
> > + * enter a block that is synchronized on the
> > JspServletWrapper object for
> > + * this JSP page. Because the initial out dated check is
> > unsynchronized, it
> > + * is possible for more than one request to attempt to
> > enter the synchronized
> > + * compile block. The compile() method contains performs
> > an outdated check
> > + * of its own. The first thread into the block will cause
> > a compile, the
> > + * subsequent threads will essentially skip the
> > compilation and instantiation
> > + * steps.
> > + *
> > + * One other thing to note is that there is a window of
> > time between the
> > + * compiler.compile() call and the end of the synchronized
> > block where a new
> > + * thread entering doLoadJSP() will be told that that
> > implementation class is
> > + * up to date even though the code in the synchronized
> > block has not
> > + * completed loading and instantiating the class. In this
> > case doLoadJSP()
> > + * will return false without attempting to compile the
> > class. This is OK
> > + * because the JspServletWrapper.getServlet() method used by the
> > + * JspServletWrapper.service() method is synchronized.
> > Thus, the service
> > + * method will not receive the servlet class until it has
> > been completely loaded and
> > + * instantiated.
> > + *
> > + * The bottom line is that we avoid synchronizing a fairly
> > expensive
> > + * operation (isOutDated) but pay a small price of some
> > unnecessary
> > + * compilation attempts in the atypical case of a modified
> > JSP file.
> > + */
> > protected boolean doLoadJSP(String jspUri, String classpath,
> > boolean isErrorPage,
> > HttpServletRequest req, HttpServletResponse res)
> > throws JasperException, FileNotFoundException
> > @@ -445,25 +587,26 @@
> > if( jsw==null ) {
> > throw new JasperException("Can't happen -
> > JspServletWrapper=null");
> > }
> > - // Class jspClass = (Class) loadedJSPs.get(jspUri);
> > - boolean firstTime = jsw.servletClass == null;
> > JspCompilationContext ctxt = new
> > JspEngineContext(loader, classpath,
> >
> > context, jspUri,
> >
> > isErrorPage, options,
> > req, res);
> > boolean outDated = false;
> >
> > - Compiler compiler = null;
> > - synchronized(this){
> > - compiler = ctxt.createCompiler();
> > - }
> > + Compiler compiler = ctxt.createCompiler();
> >
> > try {
> > +
> > +
> > outDated = compiler.isOutDated();
> > - if( (jsw.servletClass == null) || outDated ) {
> > - synchronized ( this ) {
> > - if((jsw.servletClass == null) ||
> > (compiler.isOutDated() )) {
> > - outDated = compiler.compile();
> > + if(!jsw.isInstantiated() || outDated ) {
> > + synchronized(jsw){
> > + outDated = compiler.compile();
> > + if(!jsw.isInstantiated() || outDated) {
> > + if( null ==ctxt.getServletClassName() ) {
> > + compiler.computeServletClassName();
> > + }
> > +
> > jsw.instantiateServlet(loader.loadClass(ctxt.getFullClassName()));
> > }
> > }
> > }
> > @@ -472,25 +615,12 @@
> > throw ex;
> > } catch(JasperException ex) {
> > throw ex;
> > + } catch(ClassNotFoundException cex) {
> > + throw new
> > JasperException(Constants.getString("jsp.error.unable.load"),
> > + cex);
> > } 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 {
> > - if( null ==ctxt.getServletClassName() ) {
> > - compiler.computeServletClassName();
> > - }
> > - jsw.servletClass =
> > loader.loadClass(ctxt.getFullClassName());
> > - //loadClass(ctxt.getFullClassName(), true);
> > - } catch(ClassNotFoundException cex) {
> > - throw new
> > JasperException(Constants.getString("jsp.error.unable.load"),
> > - cex);
> > - }
> > -
> > - // loadedJSPs.put(jspUri, jspClass);
> > }
> >
> > return outDated;
> >
> >
> >
>