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Posted to users@tomcat.apache.org by Guy Verbist <gu...@prosumersolutions.com> on 2001/09/11 13:04:06 UTC
Problem with loading classes dynamically, new objects can't "see"
things in webapp.
Hi all.
I hope I'm not being too dumb here.
My servlet code wants to load classes dynamically at runtime. Instances of
these classes will call back into the servlet code.
So, my server.xml looks like this:
<Context path="/prosumer"
docBase="c:\Products\suite\current\peng\webapp"
with all the class files under ...\webapp\WEB-INF\classes
Mostly it works fine.
However when I try to execute this line:
Class c = Class.forName("com.psl.test.customtags.ProsumerTestTag");
where ProsumerTestTag is defined thusly:
public class ProsumerTestTag implements CustomTag {
tomcat keels over with:
java.lang.NoClassDefFoundError: com/psl/customtags/CustomTag
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:486)
at
java.security.SecureClassLoader.defineClass(SecureClassLoader.java:111)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:248)
at java.net.URLClassLoader.access$100(URLClassLoader.java:56)
at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:297)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:286)
at java.lang.ClassLoader.loadClass(ClassLoader.java:253)
at
org.apache.tomcat.loader.AdaptiveClassLoader.loadClass(AdaptiveClassLoader.j
ava:446)
at java.lang.ClassLoader.loadClass(ClassLoader.java:253)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:313)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:120)
left in the jvm.stderr
I guess it can't find the "CustomTag" that ProsumerTestTag implements.
However com/psl/customtags/CustomTag *realy is* in the webapp.
I'm running tomcat 3.2.2 as a service on a Win2k server box, and if I add
the whole of the webapp code to the classpath for the jvm for tomcat by
editing the ...wrapper.properties for jk_nt_service.exe, then the whole
thing works. However this workaround seems to be suboptimal.
My question is why can't a class loaded by Class.forName() see things in
webapp/WEB-INF/classes, only things in the regular JVM classpath, when the
rest of the webapp can see things in the webapp/WEB-INF/classes?
I guess my call to Class.forName() is creating a different context for the
new class to what is created for the rest of the servlet, but is there some
way I can resolve the differences?
Thanks very much.
Guy
Re: Problem with loading classes dynamically, new objects can't
"see" things in webapp.
Posted by "Craig R. McClanahan" <cr...@apache.org>.
Because you got NoClassDefFoundError instead of ClassNotFoundException, it
is *not* ProsumerTestTag that is the missing one. Instead, check the
sources of ProsumerTag for references to *other* classes, and make sure
all of *those* classes are also available in your web app.
Craig McClanahan
On Tue, 11 Sep 2001, Guy Verbist wrote:
> Date: Tue, 11 Sep 2001 12:04:06 +0100
> From: Guy Verbist <gu...@prosumersolutions.com>
> Reply-To: tomcat-user@jakarta.apache.org
> To: "'tomcat-user@jakarta.apache.org'" <to...@jakarta.apache.org>
> Subject: Problem with loading classes dynamically,
> new objects can't "see" things in webapp.
>
> Hi all.
>
> I hope I'm not being too dumb here.
>
> My servlet code wants to load classes dynamically at runtime. Instances of
> these classes will call back into the servlet code.
>
> So, my server.xml looks like this:
>
> <Context path="/prosumer"
> docBase="c:\Products\suite\current\peng\webapp"
>
> with all the class files under ...\webapp\WEB-INF\classes
>
> Mostly it works fine.
> However when I try to execute this line:
>
> Class c = Class.forName("com.psl.test.customtags.ProsumerTestTag");
>
> where ProsumerTestTag is defined thusly:
>
> public class ProsumerTestTag implements CustomTag {
>
> tomcat keels over with:
>
> java.lang.NoClassDefFoundError: com/psl/customtags/CustomTag
> at java.lang.ClassLoader.defineClass0(Native Method)
> at java.lang.ClassLoader.defineClass(ClassLoader.java:486)
> at
> java.security.SecureClassLoader.defineClass(SecureClassLoader.java:111)
> at java.net.URLClassLoader.defineClass(URLClassLoader.java:248)
> at java.net.URLClassLoader.access$100(URLClassLoader.java:56)
> at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
> at java.security.AccessController.doPrivileged(Native Method)
> at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
> at java.lang.ClassLoader.loadClass(ClassLoader.java:297)
> at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:286)
> at java.lang.ClassLoader.loadClass(ClassLoader.java:253)
> at
> org.apache.tomcat.loader.AdaptiveClassLoader.loadClass(AdaptiveClassLoader.j
> ava:446)
> at java.lang.ClassLoader.loadClass(ClassLoader.java:253)
> at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:313)
> at java.lang.Class.forName0(Native Method)
> at java.lang.Class.forName(Class.java:120)
>
> left in the jvm.stderr
>
> I guess it can't find the "CustomTag" that ProsumerTestTag implements.
> However com/psl/customtags/CustomTag *realy is* in the webapp.
>
> I'm running tomcat 3.2.2 as a service on a Win2k server box, and if I add
> the whole of the webapp code to the classpath for the jvm for tomcat by
> editing the ...wrapper.properties for jk_nt_service.exe, then the whole
> thing works. However this workaround seems to be suboptimal.
>
> My question is why can't a class loaded by Class.forName() see things in
> webapp/WEB-INF/classes, only things in the regular JVM classpath, when the
> rest of the webapp can see things in the webapp/WEB-INF/classes?
>
> I guess my call to Class.forName() is creating a different context for the
> new class to what is created for the rest of the servlet, but is there some
> way I can resolve the differences?
>
> Thanks very much.
>
> Guy
>