Need Support : class loading
Dear All
Is there a way to know the classes loaded in memory
( in the JRE ) at any time
Is there a tool or a code sample to do that
Any Help
Highly appreciated
thanx all
Hi!
Use -verbose flag when you run your program. Like this:
java -verbose YourClass
This prints full class names into the console at tha time, classes are loaded. Example print follows
[Loaded org.apache.xpath.objects.XNodeSet]
[Loaded org.apache.xpath.objects.XBoolean]
[Loaded org.apache.xpath.objects.XRTreeFrag]
[Loaded org.apache.xpath.objects.Comparator]
[Loaded org.apache.xpath.objects.NotEqualComparator]
-Raine-
Similar Messages
-
Help Needed on a similar but not same class loader problem
Hi,
Please help...
There is a ClassLoader called MyLoader that overrides default findClass() method to decrypt already encrypted class files available in a separate jar file.
MyClass also contains a public static method launchMe() method that starts off with a call similar to loadClass("ApplicationMainClass");
The MyLoader class is also encrypted
I modified the default launcher (c) code to:
First find the encrypted MyLoader file then decrypt it and create a byte array.
The byte array, along with the system class loader and other required arguments, is passed to DefineClass native method (defined in jvm.dll)
Note: The system class loader class has been instantiated using static method ClassLoader.getSystemClassLoader() through Java's invocation API.
The DefineClass succeeds and I'm able to instantiate MyLoader and later call launchMe() to start application.
Now i come to the problem:
I'm not able to use any class other that those in rt.jar (i.e.standard classes) in MyLoader class. I end up with a runtime error ClassDefNotFoundError while trying to load any third party jar.
The classes i need are present in class path and also in the local jre's ext that i use to launch my app.
Although i can avoid using third party jar in MyLoader but if there is any way...
Piyushmake sure that third party jar resides in your library.....
or else put rt.jar and external jars under same folder
this is matter of path.... no else than this.......
cheers
Rajesh42 -
Class Loader Hierarchy in Weblogic 7.0
I have read the BEA documentation on the class loader hierarchy in Weblogic Server,
and I have some questions regarding some behavior I am seeing.
I am running Weblogic Server 7.0.
I have an ear file that contains 3 web apps (wars) and several utility jars. The
web apps' manifests contain the Class-Path entry for the utility jars. My understanding
of this is that each web app SHOULD have its own class loader. Also, the utility
jars will be scoped in a separate class loader and WILL NOT have visibility to
the web app classes. The web app classes should have visibility to the utility
jars.
Is this correct????
I added a static segment of code in each web app and printed the class loader
for each servlet when it was loaded. I also printed the class loader from a class
that is DEFINITELY contained in one of the utility jars. Here is the result:
Utility Class ClassLoader: sun.misc.Launcher$AppClassLoader@b9d04 Utility Class
Parent ClassLoader: sun.misc.Launcher$ExtClassLoader@71732b
Servlet 1 ClassLoader: sun.misc.Launcher$AppClassLoader@b9d04 Servlet 1 Parent
ClassLoader: sun.misc.Launcher$ExtClassLoader@71732b
Servlet 2 ClassLoader: sun.misc.Launcher$AppClassLoader@b9d04 Servlet 2 Parent
ClassLoader: sun.misc.Launcher$ExtClassLoader@71732b
I'm a little confused.... I expected to see 3 different class loaders (i.e. one
for each class above). I believe the above printout says that all 3 classes are
being loaded by the SAME class loader instance (Launcher$AppClassLoader@b9d04).
Am I interpreting this correctly? If so, what's going on?I rechecked the classpath for the user that starts Weblogic, and in the classpath
I found the project "src" directory (must have missed it earlier). When we did
our build, the classes are placed in the src structure then copied to the build
area. That's the reason I was not seeing the appropriate class loader hierarchy.
Thanks for all of the comments.
"Sanjeev Chopra" <[email protected]> wrote:
>
"Mark Cotherman" <[email protected]> wrote in message
news:[email protected]...
Thanks for your comments again Mark. I'm just trying to get a goodhandle
on how
this is working.
I'll assume that somehow my web app classes are being loaded into theroot
classloader.
The next question is... why??Just to be sure - is there any way these classes are sneaking into the
system classpath ?
My ear file contains the following:
a.war
b.war
c.war
lib/util1.jar
lib/util2.jar
lib/util3.jar
lib/util4.jar
The manifest in all three wars reference all util jars. This ear deployssuccessfully
on Weblogic with no errors.
How could these separate servlets (one in each war) not have seperateclass loaders
seperate from the root where the utils should reside. I don't thinkthat
I have
any control over where Weblogic loads the war classes, or do I?
See comments below....
Mark Spotswood <[email protected]> wrote:
Mark Cotherman wrote:
Thanks for the follow-up.
I want to make sure I follow what you are saying. All classes in
the
manifest
Class-Path of WARs are exported to the parent classloader.That's right.
To me this is the correct behavior since the manifest Class-Path
is
meant to provide
a way to share common utility classes among several web apps. AllEJB jars and
manifest Class-Path entries should be loaded by the same class loader.Its a way to share class definitions, but not necessarilly class
instances. I don't think that a web application should be extending
the classpath of its parent's classloader. This leads to namespace
problems as well as reloadability issues.
Ok, you lost me here. Shouldn't delegation handle the namespacecollisions??
If the web app class loader has a class definition (webapp:com.xyz.ClassA) with
exactly the same name in the same package as the root class loader(rootloader:
com.xyz.ClassA), I thought the web app would use (delegate loading)the
class
definition from the root class loader when PreferWebInf is set to false.
Isn't this why the PreferWebInf attribute, when set to true, can causeClassCastExceptions??
The web app when creating an instance of (webapp: com.xyz.ClassA)from
the web
app class loader can potentially pass a reference to this instanceto a
class
instance loaded from the root loader. The root class loader has adifferent class
definition for ClassA.
REALLY what makes since is that all common jar files be defined
in
the manifest
Class-Path OF THE ear FILE (if the WAR(s) are in an ear). These
jar
files should
then be loaded by the same class loader as the EJB jars. There shouldbe no need
for the WARs to have any reference to the utility jars since the
EJB
class loader
is the parent of the WAR class loaders.The ear file doesn't have a manifest classpath, but what you are getting
at makes sense. If you add a manifest to any EJBs in your app, theall
webapps (as well as all other EJBs) will be able to see it, sincewith
our structure, EJBs are loaded into the application's root classloader.
My problem is that the ACTUAL SERVLET classes are NOT being loadedby a separate
class loader from the EJB and common jar class loader. This is
completely
against
what is being said in the Weblogic documentation. The Manifest
Class-Path
should
have nothing to do with where the classes that reside in
WEB-INF/classes
of my
servlet are loaded.Classloaders will ask their parent for the class first before loading
it
themselves. So if the parent classloader somehow has visibility to
classes that your webpapp references, then it will get loaded by the
parent classloader.
I am in the middle of migrating an app from an older version of
Weblogic,
and
it would be helpful to have the ACTUAL class loading hierarchy welldocumented.
The basic hierarchy is all EJBs are in a root shared classloader and
each web application is loaded by a classloader that is a child of
that root.
Again, am I missing something here???My suspicion is that somehow these servlets are in the classpath ofthe
root classloader, so when the webapp classloaders delegate to thatone,
it will come up with the class.
mark
Mark Spotswood <[email protected]> wrote:
I believe what you are seeing is a bug in the servlet container.
The classloader organization is what you expect, but each webapp
is exporting the classpath information from its manifest to the
classloader above its classloader (which is common to all
three webapps) rather than to its own classloader. So because
of the delegation that happens with classloading, the common
parent classloader is the one that loads the class.
I believe that this behavior exists as an attempt to avoid
ClassCastExceptions, but I don't think that it is the right
solution to this problem. In our 8.1 release, this behavior
has been changed. That is, web applications no longer export
manifest classpath information to the parent of their classloader.
This change has not been ported back to the 7.x line, but a bug
report has been created (CR099889). You should be able to follow
up with support with this CR number.
mark
Mark Cotherman wrote:
I have read the BEA documentation on the class loader hierarchy
in
Weblogic Server,
and I have some questions regarding some behavior I am seeing.
I am running Weblogic Server 7.0.
I have an ear file that contains 3 web apps (wars) and several
utility
jars. The
web apps' manifests contain the Class-Path entry for the utility
jars.
My understanding
of this is that each web app SHOULD have its own class loader.
Also,
the utility
jars will be scoped in a separate class loader and WILL NOT have
visibility
to
the web app classes. The web app classes should have visibility
to
the utility
jars.
Is this correct????
I added a static segment of code in each web app and printed the
class
loader
for each servlet when it was loaded. I also printed the class loaderfrom a class
that is DEFINITELY contained in one of the utility jars. Here is
the
result:
Utility Class ClassLoader: sun.misc.Launcher$AppClassLoader@b9d04
Utility
Class
Parent ClassLoader: sun.misc.Launcher$ExtClassLoader@71732b
Servlet 1 ClassLoader: sun.misc.Launcher$AppClassLoader@b9d04 Servlet1 Parent
ClassLoader: sun.misc.Launcher$ExtClassLoader@71732b
Servlet 2 ClassLoader: sun.misc.Launcher$AppClassLoader@b9d04 Servlet2 Parent
ClassLoader: sun.misc.Launcher$ExtClassLoader@71732b
I'm a little confused.... I expected to see 3 different class loaders(i.e. one
for each class above). I believe the above printout says that all
3
classes are
being loaded by the SAME class loader instance
(Launcher$AppClassLoader@b9d04).
Am I interpreting this correctly? If so, what's going on? -
Hi all,
Couple of questions. Is dynamic class loading using classloaders supported in any, if not all versions of J2ME? I guess I should ask first, what exactly does J2ME cover? I see KVM, but do watches and PDA's, set top boxes, refrigerators and so forth all run the same J2ME JVM? Or are their "less feature full" versions? I was hoping the J2ME spec would be the "lowest common denominator" to program for, but I thought I read somewhere that small devices like watches may even have a "smaller" J2ME JVM or something, less capable. So can I write code for J2ME and it will run on all small devices like cell phones, pda's, and so forth? Or is there another J2ME version, perhaps small than J2ME.
So, from what I have found so far, it appears dynamic class loading is done at startup from a DB (of sorts) as opposed to being able to dynamically find/load classes. If this is so, is there any way to support downloading and reloading new classes like you can with J2SE, such as the hot-swap feature of web servers? Does Class.forName() at least work in that you can "replace" a class with a new version, even if it is not able to have a separate classloader instance? My guess is that J2ME supports only a single classloader space, but I thought I read somewhere that Class.forName() is available. J2ME API shows it I believe, but I could be wrong.
Any help on this topic would be appreciated.
Thanks.Dynamic class loading is not available in most (if not all) J2ME profiles and configurations. Class.forName() is available (at least in the MID profile), but not to be used for dynamic class loading. It can be used when using device-specific APIs where you can try to load a class containing device specific methods (for example a class that works only on certain Nokia phones, and has methods playSound() and vibrate(), which are not available in MIDP), and if you catch a ClassNotFound exception you can load a class that doesn't use the device specific APIs and contains stubs of the methods, or you can disable certain features in you application that need those features. For an example implementation you can have a look at Nokia's Block Game example (available from their developer site - http://www.forum.nokia.com/main.html).
As for your other more general questions about different JVM's and such, you should read all about the different configurations and profiles available in J2ME (plenty of information using in the J2ME link on this site). -
Dynamic Class Loading and Stubs
How Dynamic Class Loading is used on Java RMI, since stubs are generated on clients using Reflection API?
I was reading Dynamic code downloading using JavaTM RMI (http://java.sun.com/javase/6/docs/technotes/guides/rmi/codebase.html), it seems to be out of date.
For example, "The client requests the class definition from the codebase. The codebase the client uses is the URL that was annotated to the stub instance when the stub class was loaded by the registry. Back in step 1, the annotated stub for the exported object was then registered with the Java RMI registry bound to a name.""Enhancements in J2SETM 5.0
Dynamic Generation of Stub Classes
This release adds support for the dynamic generation of stub classes at runtime, obviating the need to use the Java(tm) Remote Method Invocation (Java RMI) stub compiler, rmic, to pregenerate stub classes for remote objects. *Note that rmic must still be used to pregenerate stub classes for remote objects that need to support clients running on _earlier versions_.*
When an application exports a remote object (using the constructors or static exportObject methods(1) of the classes java.rmi.server.UnicastRemoteObject or java.rmi.activation.Activatable) and a pregenerated stub class for the remote object's class cannot be loaded, the remote object's stub will be a java.lang.reflect.Proxy instance (whose class is dynamically generated) with a java.rmi.server.RemoteObjectInvocationHandler as its invocation handler.
An existing application can be deployed to use dynamically generated stub classes unconditionally (that is, whether or not pregenerated stub classes exist) by setting the system property java.rmi.server.ignoreStubClasses to "true". If this property is set to "true", pregenerated stub classes are never used.
Notes:
* If a remote object has pre-5.0 clients, that remote object should use a stub class pregenerated with rmic or the client will get an ClassNotFoundException deserializing the remote object's stub. Pre-5.0 clients will not be able to load an instance of a dynamically generated stub class, because such a class contains an instance of RemoteObjectInvocationHandler, which was not available prior to this release.
* Prior to the J2SE 5.0 release, exporting a remote object would throw a java.rmi.StubNotFoundException if the pregenerated stub class for the remote object's class could not be loaded. With the added support for dynamically generated stub classes, exporting a remote object that has no pregenerated stub class will silently succeed instead. A user deploying a server application to support pre-5.0 clients must still make sure to pregenerate stub classes for the server's remote object classes, even though missing stub classes are no longer reported at export time. Such errors will instead be reported to a pre-5.0 client when it deserializes a dynamically generated stub class.
(1) The static method UnicastRemoteObject.exportObject(Remote) is declared to return java.rmi.server.RemoteStub and therefore cannot be used to export a remote object to use a dynamically generated stub class for its stub. An instance of a dynamically generated stub class is a java.lang.reflect.Proxy instance which is not assignable to RemoteStub."
http://java.sun.com/j2se/1.5.0/docs/guide/rmi/relnotes.html -
I am getting the following error even though the corresponding file is present in the app.jar.
This happens when hibernates are getting loaded , when i start the oracle app server.
Does anyone knows why its so.
Caused by: org.hibernate.MappingException: entity class not found: com.iflex.fcr.app.deposit.td.us.dto.DepositRateHistoryDTOCheckNew
at org.hibernate.mapping.PersistentClass.getMappedClass(PersistentClass.java:99)
at org.hibernate.tuple.PropertyFactory.getGetter(PropertyFactory.java:166)
at org.hibernate.tuple.PropertyFactory.buildIdentifierProperty(PropertyFactory.java:44)
at org.hibernate.tuple.EntityMetamodel.<init>(EntityMetamodel.java:115)
at org.hibernate.persister.entity.AbstractEntityPersister.<init>(AbstractEntityPersister.java:412)
at org.hibernate.persister.entity.SingleTableEntityPersister.<init>(SingleTableEntityPersister.java:108)
at org.hibernate.persister.PersisterFactory.createClassPersister(PersisterFactory.java:55)
at org.hibernate.impl.SessionFactoryImpl.<init>(SessionFactoryImpl.java:216)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1176)
at com.iflex.fcr.infra.das.orm.hibernate.SessionFactoryLoader.<clinit>(Unknown Source)
... 5 more
Caused by: oracle.classloader.util.AnnotatedClassNotFoundException:
Missing class: com.iflex.fcr.app.deposit.td.us.dto.DepositRateHistoryDTOCheckNew
Dependent class: org.hibernate.util.ReflectHelper
Loader: global.libraries:1.0
Code-Source: /D:/product/10.1.3.1/OracleAS_3/j2ee/FSI_RETAIL/applib/hibernate313.jar
Configuration: <code-source> in /D:/product/10.1.3.1/OracleAS_3/j2ee/FSI_RETAIL/config/server.xml
This load was initiated at global.libraries:1.0 using the Class.forName() method.
The missing class is not available from any code-source or loader in the system.
at oracle.classloader.PolicyClassLoader.handleClassNotFound(PolicyClassLoader.java:2078)
at oracle.classloader.PolicyClassLoader.internalLoadClass(PolicyClassLoader.java:1679)
at oracle.classloader.PolicyClassLoader.loadClass(PolicyClassLoader.java:1635)
at oracle.classloader.PolicyClassLoader.loadClass(PolicyClassLoader.java:1620)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:164)
at org.hibernate.util.ReflectHelper.classForName(ReflectHelper.java:108)
at org.hibernate.mapping.PersistentClass.getMappedClass(PersistentClass.java:96)
... 14 moreNeither, not using Oracle HTTP Server nor using JDK 1.4 incluence the behaviour of OC4J. It is your application deployment. As it should be with every Java EE server you provide an EAR file structure with modules like WAR files or EJB jar files. Each of these modules has more or less its own class loading environment.
OC4J however supports application and global shared libraries. Application shared libraries can be packaged in the EAR file using the Java EE 5 library mechanism. In essence your libraries must be known by the class loader of the Java EE module otherwise your application doesn't work.
What I need to know is what type of application (WAR, EJB, combo of both) you're using and how the files are laid out in the directory structure.
To have an example, see this blog entry: http://blogs.oracle.com/olaf/2007/07/25
--olaf -
Hi all!
Let me explain my problem.
I have an EJB which has in its same Java package some support classes
& also a startup class. I created an EJB jar file (containing the home,
remote, bean, the deployment descriptors & the container generated stubs)
for deployment. I also compiled all the support classes & the startup class
into the /weblogic/myserver/serverclasses directory. I also added the
required entries in the weblogic.properties file for the startup class.
Now the problem is that the support classes & the startup class contain
methods & constructors which have package level access (i.e the default
access in Java). At runtime, when my bean tries to access one of these
methods, an IllegalAccessException is thrown.
I understand that this exception is thrown when one tries to access a
method which should not be accessed (like private/protected/cross-package
access). However, both the EJB & these classes are in the same package.
So this should not be thrown.
Now the next thing I thought is that the EJB & the support classes are
being loaded by 2 different classloaders. I guess the classes under
/weblogic/myserver/serverclasses are being loaded by the WebLogic
Server ClassLoader & the EJB bean classes are being loaded by the
specialized EJB ClassLoader.
Now my question is,
1) Is it the case that the WebLogic Server does not recognize that the
EJB Bean class is in the same package as the support classes because
they are loaded by 2 separate class loaders? Please note that the EJB
jar file does not contain any support classes - so there is no
duplicate classes here.
2) Is this a bug?
3) What should I do to prevent this problem?
Some workarounds that I have done are:
1) Copied the Bean.class (implementation class of EJB bean) into the
serverclasses directory. Now the server does not throw any
IllegalAccessException. -- This, however, does not appeal as a solution
since it looks like the Bean class is now being loaded by the WebLogic
Class Loader instead of from the EJB jar file.
2) I changed all the default package access methods to public methods.
Works like a charm. -- Problem is that this is a third party set of classes
which I would like to avoid modifying.
Hope this is not too confusing. Please let me know if you need any further info.
Thanks much in advance,
--DasYou have to tell WLAS where to load your new classes. You can change
workingDir of your JSP configuration in weblogic.properties to point to your
new class directory.
Cheers - Wei
Hyung-Jin Kim <[email protected]> wrote in message
news:[email protected]..
> It seems that if I compile a class that a JSP uses while Weblogic is
> running, Weblogic's class loader has this nasty habit of caching/writing
> the class that already has loaded into memory into:
>
> weblogic/myServer/classfiles
>
> Weblogic then refers to the older class file under the above directory
> when the server is started again. Is there any way to turn this "class
> loader caching" off in Weblogic? Thanks!
>
> -hjk
>
-
Class loader: saaj-api conflict
I need to load saaj-api from my application which is newer than the one that comes w/ith oc4j 10.1.3 which is loaded by the system class loader with name api from webservices/lib/saaj-api.jar.
remove-inherited doesn't seem to do the trick.
Any suggestions would be appreciated.
Thanks,
Jindong.While I understand where you're coming from, it sounded to me that oc4j lacks the flexibility to allow application to use newer version of certain component.
For example, certain JDK level supports certain JAXP, but there is indeed an extension mechnism to allow application plug in newer JAXP?
I believe other j2ee contains are a lot flexbile in terms of this...I don't think J2EE spec says that applications running in its container can not use newer software components?
I think it only makes sense that the minimum supported level is j2ee 1.4, but nothing should stop applications from having their own version of any thing.
I strongly suggest that this to be considered for what ever release you guys are working on or a work around can be provided for the current version we're using.
Jindong. -
Hi!
I have developed an application that use CLASS LOADER methods to download classes when needed in the application.
I would like to know if there exist any way to use a JRE cache for using these classes and download it when it changes.
Thank you very much for any help!
Jose Monzon.Hi,
Class is put into the cache of the class loader in the
defineClass() method and may be retrieved from the cache with the findLoadedClass() method.
Check the above methods for caching.
I hope this helped.
Roopasri Vittal
Developer Technical Support
Sun Microsystems
http://sun.com/developers/support -
EP 6.20 Class loader issues with irj application
Hi All,
I have a servlet to interface with the SAP UM API. I had deployed this as a WAR, but the SAP UM cannot be initialised outside of the irj application (SAP Support advised this it is abailable outside the irj application in 6.40).
As a result, I tried to deploy it within the irj application - I copied my jars to the WEB-INF\lib directory, and modified the WEB-INF\web.xml to include a new servlet and servlet-mapping.
I also had to copy some other SAP supporting jars into WEB-INF\lib (the XML parser impls).
This works fine for the UM stuff. Ideally I'd like to redeploy the irj application so I don't have to hack the files and it would allow me to specify the additional libaries required, however there is now way I've found in the Deploy Tool to do this (you need the WAR of the irj application, or the project file). So this is problem 1.
Problem 2. The next extension included support for user mapping data.
Using -
IUserMapping iUserMapping = UMFactory.getUserMapping();
iUserMapping.getUserMappingData(systemAlias, iUser, mapLogonData);
I was able to read the mapping data, but this required knowing beforehand, all the system aliases. With a response from SAP Security, it was suggested
IUserMappingService iums = (IUserMappingService)PortalRuntime.getRuntimeResources().getService(IUserMappingService.KEY);
IUserMappingData mappingData = iums.getMappingData (systemAlias, iUser);
be used to obtain mapping data, and that
com.sap.portal.pcm.system.ISystems sysSrv = (ISystems)PortalRuntime.getRuntimeResources().getService(ISystems.KEY);
String[] systemAliases = sysSrv.getAliases();
be used to obtain the system aliases.
The problem is with the class loader. If I copy the jars with the classes for the IUserMappingService and the ISystems, to the irj WEB-INF\lib I cause a class def not found with other EP6 applications. This is also the case when I add them to the JVM classpath (I know this is bad - but it was a last resort!).
Hoping someone can help me redeploy irj with my application that will resolve problem 2! If not, maybe some advice on problem 2?
Cheers,
Scott...Hi Scott,
THis isnt an answer to ur Question, but could u tell me which jar files are needed for the packages:
com.sap.portal.pcm.system.ISystems
com.sap.portal.pcm.system.ISystem
and under which path I coul dfind them.
Thnx
Regards
Meesum. -
How to load a class dynamically in the current/system class loader
I need to dynamically load a new jdbc driver jar to the current/system class loader... Please note that creating a new classloader will not help since the DriverManager refers to the systemclassloader itself.
Restarting the application by appending the jar to its classpath will solve the problem but I want to avoid doing this.Did you then create a ClassLoader to load the JDBC
driver and then install it into the system as
directed by the JDBC specification (ie
Class.forName(someClassName))?
And then try to use it from a class loaded fromsome
other ClassLoader (i.e. the system class loader)?
If you did not try this please explain why not.O.K. I just looked at the source to
java.sql.DriverManager. I did not know what I was
talking about, as what I suggested above will not
work.
This is my new Idea:
Create a URLClassLoader to load the JDBC driver also
in this ClassLoader you need to place a helper class
that does the following:
public class Helper {
public Driver getJDBCDriver(String driverClassName,
String url) {
try {
Class.forName(driverClassName);
Driver d = DriverManager.getDriver(url);
return d;
catch(Exception ex) {
ex.printStackTrace();
return null;
}Now create an instance of the Helper class in the new
ClassLoader, and call its getJDBCDriver method to get
an instance of the driver (you will probably have to
create an interface in the root class loader that the
Helper implements so that you can easily call it).
Now from the root classloader you can make calls
directly to the returned Driver and bypass the
DriverManager and its restrictions on cross
ClassLoader access.
The only catch here is that you would have to call to
the returned Driver directly and not use the Driver
Manager.This sounds like will work but I did not want to load DriverManager in a new classloader.. I did a hack
I unzip the jar dynamically in a previously known location (which I included in my classpath when launching the app). The classLoader finds the class now though it did not exist when the app was launched !
A hack of-course but works eh .. -
How can I make server use single class loader for several applications
I have several web/ejb applications. These applications use some common libraries and should share instances of classes from those libraries.
But applications are being deployed independently thus packaging all them to EAR is not acceptable.
I suppose the problem is that each application uses separate class loader.
How can I make AS use single class loader for a set of applications?
Different applications depend on different libraries so I need a way that will not share library for all applications on the domain but only for some exact applications.
When I placed common jar to *%domain%/lib* - all works. But that jar is shared between all applications on the domain.
When I tried to place common jar to *%domain%/lib/applibs* and specified --libraries* attribute on deploying I got exception
java.lang.ClassCastException: a.FirstDao cannot be cast to a.FirstDaoHere http://download.oracle.com/docs/cd/E19879-01/820-4336/6nfqd2b1t/index.html I read:
If multiple applications or modules refer to the same libraries, classes in those libraries are automatically shared.
This can reduce the memory footprint and allow sharing of static information.Does it mean that classes should be able to be casted ?You didn't specify which version of the application server you are using, but the config is similar as long as you know what to look for. Basically, you need to change the classloader delegation. Here's how it is done in 8.2
http://download.oracle.com/docs/cd/E19830-01/819-4721/beagb/index.html -
How can I get a dynamic list of Classes Loaded
I assume this may need to use some sort of reflection. Does
anyone have code or ideas where I can:
a) I can get a list of all Classes loaded and their
properties. This would probably be all instances of Class
b) A list of all
global instance variables. (This may not even be possible. I
know it can be done in other languages)
I assume this may need to use some sort of reflection.
Thank youAdobe Newsbot hopes that the following resources helps you.
NewsBot is experimental and any feedback (reply to this post) on
its utility will be appreciated:
mx.controls.List (Flex 3):
If the data is incorrect, you can call the preventDefault()
method to stop Flex from passing the new data back to the list
control and from closing the
Link:
http://livedocs.adobe.com/flex/3/langref/mx/controls/List.html
Displaying icons in a Flex List control at Flex Examples:
http://blog.flexexamples.com/2007/08/17/displaying-icons-in-a-flex-list-control/
--> <mx:Application xmlns:mx="
http://www.adobe.com/2006/mxml"
Link:
http://blog.flexexamples.com/2007/08/17/displaying-icons-in-a-flex-list-control/
Populate the list -- Flex 2.01:
You populate a list-based form control with the
<mx:dataProvider> child tag. The <mx:dataProvider> tag
lets you specify list items in several ways.
Link:
http://livedocs.adobe.com/flex/201/html/tutorial_controls_019_4.html
Smooth Scroll for Horizontal List - Flex India Community |
Google:
I have created image gallery with Horizontal List[Flex 2.0].
Just as below ref site. My Problem is i need a smooth scroll for
Horizontal List. where images
Link:
http://groups.google.com/group/flex_india/browse_thread/thread/a12441143b98d32c?hide_quote s=no
Creating a List control -- Flex 2.01:
The following example code adds a handler for a change event
to the List control. Flex broadcasts a mx.ListEvent.CHANGE event
when the value of the control
Link:
http://livedocs.adobe.com/flex/201/html/dpcontrols_062_03.html
Disclaimer: This response is generated automatically by the
Adobe NewsBot based on Adobe
Community
Engine. -
Dynamic class loading problem using unknown JAR archive and directory names
I read the following article, which enlightened me a lot:
Ted Neward: Understanding Class.forName().
However, it took me some while to understand that my problem is the other way around:
I know the name of the class, I know the name of the method,
but my program/JVM does not know where to load the classes from.
Shortly, my problem is that the server engine that I am writing
uses two different versions of the same library.
So I am trying out the following solution:
My program is named TestClassPathMain.java
Assume the two libraries are named JAR1.jar and JAR2.jar
and the class/instance method that should
be exposed to TestClassPathMain.java by them is named
TestClass1.testMethod().
As long as I was depending on just one library,
I put JAR1.jar in the classpath before starting java,
and I was happy for a while.
At the moment I got the need to use another version of
TestClass1.testMethod() packaged in JAR2.jar,
a call would always access JAR1.jar's
TestClass1.testMethod().
I then decided to remove JAR1.jar from the classpath,
and programmatically define two separate ClassLoaders, one for use
with JAR1.jar and the other for use with JAR2.jar.
However, the problem is only partly solved.
Please refer to the enclosed code for details.
(The code in the JAR1.jar/JAR2.jar is extremely simple,
it just tells (by hardcoding) the name of the jar it is packaged in
and instantiates another class packaged in the same jar using
the "new" operator and calls a method on it. I don't enclose it.)
The TestClassPathMain.java/UC1.java/UC2.java code suite was
successfully compiled with an arbitrary of JAR1 or JAR2 in the classpath,
however removed from the classpath at runtime.
(I know that this could have been done (more elegantly...?) by producing an Interface,
but I think the main problem principle is still untouched by this potential lack of elegancy(?))
1) This problem should not be unknown to you experts out there,
how is it generally and/or most elegantly solved?
The "*** UC2: Variant 2" is the solution I would like best, had it only worked.
2) And why arent "*** UC2: Variant 2" and
"*** static UC2: Variant 2" working,
while "*** Main: Variant 2" is?
3) And a mal-apropos:
Why can't I catch the NoClassDefFoundError?
The output:
*** Main: Variant 1 JAR 1 ***:
Entering TestClass1.testMethod() packaged in JAR1.jar
About to instantiate TestClass2 with the new operator
About to call TestClass2.testMethod()
Entering TestClass2.testMethod() packaged in JAR1.jar
*** Main: Variant 1 JAR 2 ***:
Entering TestClass1.testMethod() packaged in JAR2.jar
About to instantiate TestClass2 with the new operator
About to call TestClass2.testMethod()
Entering TestClass2.testMethod() packaged in JAR2.jar
*** Main: Variant 2 JAR 1 ***:
Entering TestClass1.testMethod() packaged in JAR1.jar
About to instantiate TestClass2 with the new operator
About to call TestClass2.testMethod()
Entering TestClass2.testMethod() packaged in JAR1.jar
*** Main: Variant 2 JAR 2 ***:
Entering TestClass1.testMethod() packaged in JAR2.jar
About to instantiate TestClass2 with the new operator
About to call TestClass2.testMethod()
Entering TestClass2.testMethod() packaged in JAR2.jar
*** UC1: Variant 1 JAR 1 ***:
Entering TestClass1.testMethod() packaged in JAR1.jar
About to instantiate TestClass2 with the new operator
About to call TestClass2.testMethod()
Entering TestClass2.testMethod() packaged in JAR1.jar
*** UC1: Variant 1 JAR 2 ***:
Entering TestClass1.testMethod() packaged in JAR2.jar
About to instantiate TestClass2 with the new operator
About to call TestClass2.testMethod()
Entering TestClass2.testMethod() packaged in JAR2.jar
*** static UC2: Variant 2 JAR 1 ***:
Exception in thread "main" java.lang.NoClassDefFoundError: TestClass1
at UC2.runFromJarVariant2_static(UC2.java:56)
at TestClassPathMain.main(TestClassPathMain.java:52)
TestClassPathMain.java
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
public class TestClassPathMain {
public static void main(final String args[]) throws MalformedURLException, ClassNotFoundException, InstantiationException, SecurityException, NoSuchMethodException, IllegalArgumentException, IllegalAccessException, InvocationTargetException {
// Commented out because I cannot catch the NoClassDefFoundError.
// Why?
try {
final TestClass1 testClass1 = new TestClass1();
System.out.println(
"\nThe class TestClass1 is of some unexplicable reason available." +
"\nFor the purpose of the test, it shouldn't have been!" +
"\nExiting");
System.exit(1);
} catch (NoClassDefFoundError e) {
System.out.println("\nPositively confirmed that the class TestClass1 is not available:\n" + e);
System.out.println("\n\nREADY FOR THE TEST: ...");
// Works fine
System.out.println("\n*** Main: Variant 1 JAR 1 ***:");
runFromJarVariant1("file:/W:/java/eclipse/workspaces/simped_test/CP1/JAR1.jar");
System.out.println("\n*** Main: Variant 1 JAR 2 ***:");
runFromJarVariant1("file:/W:/java/eclipse/workspaces/simped_test/CP2/JAR2.jar");
// Works fine
System.out.println("\n*** Main: Variant 2 JAR 1 ***:");
runFromJarVariant1("file:/W:/java/eclipse/workspaces/simped_test/CP1/JAR1.jar");
System.out.println("\n*** Main: Variant 2 JAR 2 ***:");
runFromJarVariant1("file:/W:/java/eclipse/workspaces/simped_test/CP2/JAR2.jar");
// Works fine
final UC1 uc1 = new UC1();
System.out.println("\n*** UC1: Variant 1 JAR 1 ***:");
uc1.runFromJarVariant1("file:/W:/java/eclipse/workspaces/simped_test/CP1/JAR1.jar");
System.out.println("\n*** UC1: Variant 1 JAR 2 ***:");
uc1.runFromJarVariant1("file:/W:/java/eclipse/workspaces/simped_test/CP2/JAR2.jar");
// Crashes
System.out.println("\n*** static UC2: Variant 2 JAR 1 ***:");
UC2.runFromJarVariant2_static("file:/W:/java/eclipse/workspaces/simped_test/CP1/JAR1.jar");
System.out.println("\n*** static UC2: Variant 2 JAR 2 ***:");
UC2.runFromJarVariant2_static("file:/W:/java/eclipse/workspaces/simped_test/CP2/JAR2.jar");
// Crashes
final UC2 uc2 = new UC2();
System.out.println("\n*** UC2: Variant 2 JAR 1 ***:");
uc2.runFromJarVariant2("file:/W:/java/eclipse/workspaces/simped_test/CP1/JAR1.jar");
System.out.println("\n*** UC2: Variant 2 JAR 2 ***:");
uc2.runFromJarVariant2("file:/W:/java/eclipse/workspaces/simped_test/CP2/JAR2.jar");
private static void runFromJarVariant1(final String jarFileURL)
throws MalformedURLException,
ClassNotFoundException,
InstantiationException,
IllegalArgumentException,
IllegalAccessException,
InvocationTargetException,
SecurityException,
NoSuchMethodException {
final URL url = new URL(jarFileURL);
final URLClassLoader cl =
new URLClassLoader(new URL[]{url},
Thread.currentThread().getContextClassLoader());
final Class clazz = cl.loadClass("TestClass1");
final Object testClass1 = clazz.newInstance();
final Method testMethod1 = clazz.getMethod("testMethod", null);
testMethod1.invoke(testClass1, null);
private static void runFromJarVariant2(final String jarFileURL)
throws MalformedURLException,
ClassNotFoundException,
InstantiationException,
IllegalArgumentException,
IllegalAccessException,
InvocationTargetException,
SecurityException,
NoSuchMethodException {
final URL url = new URL(jarFileURL);
final URLClassLoader cl =
new URLClassLoader(new URL[]{url},
Thread.currentThread().getContextClassLoader());
final Class clazz = cl.loadClass("TestClass1");
final TestClass1 testClass1 = new TestClass1();
testClass1.testMethod();
UC1.java
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
public class UC1 {
public void runFromJarVariant1(final String jarFileURL)
throws MalformedURLException,
ClassNotFoundException,
InstantiationException,
IllegalArgumentException,
IllegalAccessException,
InvocationTargetException,
SecurityException,
NoSuchMethodException {
final URL url = new URL(jarFileURL);
final URLClassLoader cl =
new URLClassLoader(new URL[]{url},
Thread.currentThread().getContextClassLoader());
final Class clazz = cl.loadClass("TestClass1");
final Object testClass1 = clazz.newInstance();
final Method testMethod1 = clazz.getMethod("testMethod", null);
testMethod1.invoke(testClass1, null);
UC2.java
import java.lang.reflect.InvocationTargetException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
public class UC2 {
public void runFromJarVariant2(final String jarFileURL)
throws MalformedURLException,
ClassNotFoundException,
InstantiationException,
IllegalArgumentException,
IllegalAccessException,
InvocationTargetException,
SecurityException,
NoSuchMethodException {
final URL url = new URL(jarFileURL);
final URLClassLoader cl =
new URLClassLoader(new URL[]{url},
Thread.currentThread().getContextClassLoader());
final Class clazz = cl.loadClass("TestClass1");
final TestClass1 testClass1 = new TestClass1();
testClass1.testMethod();
* Identic to the "runFromJarVariant2" method,
* except that it is static
public static void runFromJarVariant2_static(final String jarFileURL)
throws MalformedURLException,
ClassNotFoundException,
InstantiationException,
IllegalArgumentException,
IllegalAccessException,
InvocationTargetException,
SecurityException,
NoSuchMethodException {
final URL url = new URL(jarFileURL);
final URLClassLoader cl =
new URLClassLoader(new URL[]{url},
Thread.currentThread().getContextClassLoader());
final Class clazz = cl.loadClass("TestClass1");
final TestClass1 testClass1 = new TestClass1();
testClass1.testMethod();
}2. i need to load the class to the same JVM (i.e. to
the same environment) of the current running
aplication, so that when the loaded class is run, it
would be able to invoke methods on it!!!
ClassLoader(s) do this. Try the URLClassLoader.
(I was talking about relatively esoteric "security"
issues when I mentioned the stuff about Class objects
"scope".) You might use the URLClassLoader kind of
like this.
Pseudo-code follows:
// setup the class loader
URL[] urls = new URL[1];
urls[0] = new URL("/path/to/dynamic/classes");
URLClassLoader ucl = new URLClassLoader(urls);
// load a class & use make an object with the default constructor
Object tmp = ucl.loadClass("dynamic.class.name").newInstance();
// Cast the object to a know interface so that you can use it.
// This may be used to further determine which interface to cast
// the class to. Or it may simply be the interface to which all
// dynamic classes have to conform in your program.
InterfaceImplementedByDynamicClass loadedObj =
(InterfaceImplementedByDynamicClass)tmp;It's really not as hard as it sounds, just write a little test of
this and you will see how it works. -
Dynamic class loading over a network
hi,
Im tryin to run a simple little "Hello World" type app using RMI. What i want to know is what permissions i need to grant inorder to dynamically load (client side) the stubs and skeletons from my server. Currently i get an UnmarshalException with a nested ClassNotFoundException and the helpful message "access denied to class loader". Any help is appreciated.
Thanks in advance,
AlexIt is hard to tell what the problem is with out a stack trace from the exception. Perhaps in the future you would be kind enough to supply one.
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