Custom ClassLoader

[irbash]

Hi All,

I am trying to create a custom classloader which I can use to load few classes in my war (may be complete war in future).

I found this article which explains how a custom classloader can be created:

(Custom ClassLoader (classloader-beans.xml)) http://java.dzone.com/articles/a-look-inside-jboss-microconta-0

I have few clarifications in this:

1) Where should I put the content of classloader-beans.xml ? (I have currently put it in jboss-beans.xml and placed it in WEB-INF)

2) Correct me if am wrong: The bean CB2 will be loaded using the customClassLoader... right ?

This is how my jboss-beans.xml looks like:

<deployment xmlns="urn:jboss:bean-deployer:2.0">

          <classloader>

                    <inject bean="custom-classloader:0.0.0" />

          </classloader>

          <classloader name="custom-classloader" xmlns="urn:jboss:classloader:1.0"

                    export-all="NON_EMPTY" import-all="true" />

          <bean name="CustomCL" class="com.beans.CustomClassLoader">

                    <constructor>

                              <parameter>

                                        <inject bean="custom-classloader:0.0.0" />

                              </parameter>

                    </constructor>

          </bean>

          <bean name="CB1" class="com.Sample">

          <classloader>

                    <inject bean="CustomCL" />

          </classloader>

</bean>

</deployment>

And I have the class CustomeClassLoader which just extends ClassLoader:

public class CustomClassLoader extends ClassLoader

{

   private Pattern pattern;

   public CustomClassLoader(ClassLoader parent)

   {

      super(parent);

   }

   public Class<?> loadClass(String name) throws ClassNotFoundException

   {

      if (pattern == null || pattern.matcher(name).matches())

         return super.loadClass(name);

      else

         throw new ClassNotFoundException("Name '" + name + "' doesn't match pattern: " + pattern);

   }

   public void setPattern(String regexp)

   {

      pattern = Pattern.compile(regexp);

   }

}

and when I start JBoss I get this following error:

08:28:51,677 ERROR [AbstractKernelController] Error installing to PreInstall: na

me=CustomCL state=Real

java.lang.ClassNotFoundException: com.beans.CustomClassLoader

        at java.net.URLClassLoader$1.run(Unknown Source)

        at java.net.URLClassLoader$1.run(Unknown Source)

        at java.security.AccessController.doPrivileged(Native Method)

        at java.net.URLClassLoader.findClass(Unknown Source)

        at java.lang.ClassLoader.loadClass(ClassLoader.java:428)

        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)

        at java.lang.ClassLoader.loadClass(ClassLoader.java:360)

        at java.lang.Class.forName0(Native Method)

        at java.lang.Class.forName(Unknown Source)

        at org.jboss.classloader.spi.base.BaseClassLoaderDomain.loadClass(BaseCl

assLoaderDomain.java:304)

        at org.jboss.classloader.spi.base.BaseClassLoaderDomain.loadClass(BaseCl

assLoaderDomain.java:1172)

        at org.jboss.classloader.spi.base.BaseClassLoader.loadClassFromDomain(Ba

seClassLoader.java:1264)

        at org.jboss.classloader.spi.base.BaseClassLoader.doLoadClass(BaseClassL

oader.java:549)

        at org.jboss.classloader.spi.base.BaseClassLoader.loadClass(BaseClassLoa

der.java:497)

        at java.lang.ClassLoader.loadClass(ClassLoader.java:360)

        at java.lang.Class.forName0(Native Method)

        at java.lang.Class.forName(Unknown Source)

        at org.jboss.reflect.plugins.introspection.IntrospectionTypeInfoFactoryI

mpl.resolveComplexTypeInfo(IntrospectionTypeInfoFactoryImpl.java:419)

        at org.jboss.reflect.plugins.introspection.IntrospectionTypeInfoFactoryI

mpl.getTypeInfo(IntrospectionTypeInfoFactoryImpl.java:388)

        at org.jboss.reflect.plugins.introspection.IntrospectionTypeInfoFactory.

getTypeInfo(IntrospectionTypeInfoFactory.java:54)

        at org.jboss.classadapter.plugins.BasicClassAdapterFactory.getClassAdapt

er(BasicClassAdapterFactory.java:61)

        at org.jboss.config.plugins.AbstractConfiguration.getBeanInfo(AbstractCo

nfiguration.java:86)

        at org.jboss.kernel.plugins.config.AbstractKernelConfig.getBeanInfo(Abst

ractKernelConfig.java:80)

        at org.jboss.kernel.plugins.config.AbstractKernelConfigurator.getBeanInf

o(AbstractKernelConfigurator.java:77)

        at org.jboss.kernel.plugins.config.AbstractKernelConfigurator.getBeanInf

o(AbstractKernelConfigurator.java:96)

        at org.jboss.kernel.plugins.dependency.PreInstallAction.installActionInt

ernal(PreInstallAction.java:90)

        at org.jboss.kernel.plugins.dependency.InstallsAwareAction.installAction

(InstallsAwareAction.java:54)

        at org.jboss.kernel.plugins.dependency.InstallsAwareAction.installAction

(InstallsAwareAction.java:42)

        at org.jboss.dependency.plugins.action.SimpleControllerContextAction.sim

pleInstallAction(SimpleControllerContextAction.java:62)

        at org.jboss.dependency.plugins.action.AccessControllerContextAction.ins

tall(AccessControllerContextAction.java:71)

        at org.jboss.dependency.plugins.AbstractControllerContextActions.install

(AbstractControllerContextActions.java:51)

        at org.jboss.dependency.plugins.AbstractControllerContext.install(Abstra

ctControllerContext.java:348)

        at org.jboss.dependency.plugins.AbstractController.install(AbstractContr

oller.java:1631)

        at org.jboss.dependency.plugins.AbstractController.incrementState(Abstra

ctController.java:934)

        at org.jboss.dependency.plugins.AbstractController.resolveContexts(Abstr

actController.java:1082)

        at org.jboss.dependency.plugins.AbstractController.resolveContexts(Abstr

actController.java:984)

        at org.jboss.dependency.plugins.AbstractController.install(AbstractContr

oller.java:774)

        at org.jboss.dependency.plugins.AbstractController.install(AbstractContr

oller.java:540)

        at org.jboss.deployers.vfs.deployer.kernel.BeanMetaDataDeployer.deploy(B

eanMetaDataDeployer.java:121)

        at org.jboss.deployers.vfs.deployer.kernel.BeanMetaDataDeployer.deploy(B

eanMetaDataDeployer.java:51)

        at org.jboss.deployers.spi.deployer.helpers.AbstractSimpleRealDeployer.i

nternalDeploy(AbstractSimpleRealDeployer.java:62)

        at org.jboss.deployers.spi.deployer.helpers.AbstractRealDeployer.deploy(

AbstractRealDeployer.java:50)

        at org.jboss.deployers.plugins.deployers.DeployerWrapper.deploy(Deployer

Wrapper.java:171)

        at org.jboss.deployers.plugins.deployers.DeployersImpl.doDeploy(Deployer

sImpl.java:1439)

        at org.jboss.deployers.plugins.deployers.DeployersImpl.doInstallParentFi

rst(DeployersImpl.java:1157)

        at org.jboss.deployers.plugins.deployers.DeployersImpl.doInstallParentFi

rst(DeployersImpl.java:1178)

        at org.jboss.deployers.plugins.deployers.DeployersImpl.install(Deployers

Impl.java:1098)

        at org.jboss.dependency.plugins.AbstractControllerContext.install(Abstra

ctControllerContext.java:348)

        at org.jboss.dependency.plugins.AbstractController.install(AbstractContr

oller.java:1631)

        at org.jboss.dependency.plugins.AbstractController.incrementState(Abstra

ctController.java:934)

        at org.jboss.dependency.plugins.AbstractController.resolveContexts(Abstr

actController.java:1082)

        at org.jboss.dependency.plugins.AbstractController.resolveContexts(Abstr

actController.java:984)

        at org.jboss.dependency.plugins.AbstractController.change(AbstractContro

ller.java:822)

        at org.jboss.dependency.plugins.AbstractController.change(AbstractContro

ller.java:553)

        at org.jboss.deployers.plugins.deployers.DeployersImpl.process(Deployers

Impl.java:781)

        at org.jboss.deployers.plugins.main.MainDeployerImpl.process(MainDeploye

rImpl.java:702)

        at org.jboss.system.server.profileservice.repository.MainDeployerAdapter

.process(MainDeployerAdapter.java:117)

        at org.jboss.system.server.profileservice.repository.ProfileDeployAction

.install(ProfileDeployAction.java:70)

        at org.jboss.system.server.profileservice.repository.AbstractProfileActi

on.install(AbstractProfileAction.java:53)

        at org.jboss.system.server.profileservice.repository.AbstractProfileServ

ice.install(AbstractProfileService.java:361)

        at org.jboss.dependency.plugins.AbstractControllerContext.install(Abstra

ctControllerContext.java:348)

        at org.jboss.dependency.plugins.AbstractController.install(AbstractContr

oller.java:1631)

        at org.jboss.dependency.plugins.AbstractController.incrementState(Abstra

ctController.java:934)

        at org.jboss.dependency.plugins.AbstractController.resolveContexts(Abstr

actController.java:1082)

        at org.jboss.dependency.plugins.AbstractController.resolveContexts(Abstr

actController.java:984)

        at org.jboss.dependency.plugins.AbstractController.change(AbstractContro

ller.java:822)

        at org.jboss.dependency.plugins.AbstractController.change(AbstractContro

ller.java:553)

        at org.jboss.system.server.profileservice.repository.AbstractProfileServ

ice.activateProfile(AbstractProfileService.java:306)

        at org.jboss.system.server.profileservice.ProfileServiceBootstrap.start(

ProfileServiceBootstrap.java:271)

        at org.jboss.bootstrap.AbstractServerImpl.start(AbstractServerImpl.java:

461)

        at org.jboss.Main.boot(Main.java:221)

        at org.jboss.Main$1.run(Main.java:556)

DEPLOYMENTS MISSING DEPENDENCIES:

  Deployment "CB1" is missing the following dependencies:

    Dependency "CustomCL" (should be in state "PreInstall", but is actually in s

tate "**ERROR**")

DEPLOYMENTS IN ERROR:

  Deployment "CustomCL" is in error due to the following reason(s): java.lang.Cl

assNotFoundException: com.beans.CustomClassLoader, **ERROR**

Can anyone help in solving this problem.

From the above error, it seems that the baseClassLoader doesn't know where com.beans.CustomClassLoader is located.

Thanks in advance,

Irfan

[alesj]

classloader element takes explicit roots -- paths to jars, etc.

* http://anonsvn.jboss.org/repos/jbossas/projects/jboss-cl/branches/Branch_2_0/classloading-vfs/src/main/java/org/jboss/classloading/spi/vfs/metadata/VFSClassLoaderFactory.java

Just create CustomCL bean -- no need for classloader element, and set this as classloader to other beans.

Having classloader per whole deployment (whole -beans.xml) is a bit trickier,

as it's chicken-n-egg problem.

[alesj]

Your last post somehow got removed ...

But no, completely remove <classloader name element.

Plain CL bean should do.

[irbash]

Thanks Ales...

I deleted the last post because I got it working soon after I posted it.

Thanks once again...

Regards,

Irfan

[alesj]

I deleted the last post because I got it working soon after I posted it.

Can you post the solution, so others can learn as well?

[irbash]

Solution:

1. Add jboss-beans.xml to WEB-INF:

<deployment xmlns="urn:jboss:bean-deployer:2.0">

         <classloader name="custom-classloader" xmlns="urn:jboss:classloader:1.0"

                    export-all="NON_EMPTY" import-all="true" />

          <bean name="CustomCL" class="com.beans.CustomClassLoader">

                    <constructor>

                              <parameter>

                                        <inject bean="custom-classloader:0.0.0" />

                              </parameter>

                    </constructor>

          </bean>

          <bean name="CB1" class="com.Sample">

          <classloader>

                    <inject bean="CustomCL" />

          </classloader>

</bean>

</deployment>

2. Create a CustomClassLoader (com.beans.CustomClassLoader):

public class CustomClassLoader extends ClassLoader

{

   public CustomClassLoader(ClassLoader parent)

   {

      super(parent);

   }

   public Class<?> loadClass(String name) throws ClassNotFoundException

   {    

          //This simply calls super's loadClass (if run from jboss, it calls BaseClassLoader

         return super.loadClass(name);    

   }

}

Run JBoss, keep a breakpoint in CustomClassLoader.loadClass method. when class com.Sample has to be loaded the breakpoint will be hit.

Regards,

Irfan

[alesj]

Hmmm, how does CustomCL see com.Sample class?

Afair, <classloader> then has zero roots, meaning it only sees system classpath.

Where your CustomCL is created in deployment's CL, with zero-root CL as parent,

where you then try to load com.Sample ... beats me. :-)

Unless this zero-roots CL shares the same domain as deployment's CL.

[irbash]

I guess the zero-roots CL (as you say) shares the domain of deployment's CL.

Is that the reason why super.loadClass goes back to org.jboss.classloader.spi.base.BaseClassLoader ?

Is there any thing wrong in what I did ? (I am able to get the breakpoint in loadClass method, and here the parent classloader is BaseClassLoader of jboss)

What I am trying to do is:

My war has few encrypted classes (which can be decrypted only if a hardware dongle is available using the ClassLoader provided by the hardware dongle). And now since we use JBoss, the encrypted classes are not been loaded. (In tomcat it was possible to set the system classloader :  –Djava.system.class.loader in catalina.bat)

I first tried to load then using translator (the previous post from me), but if I use translator, the plain bytecode is available in translator (after translator decrypts the encrypted class)

So now I am trying to use this customClassLoader, and here use the ClassLoader provided the third party (the company which provides us the hardware dongle).

[alesj]

I guess the zero-roots CL (as you say) shares the domain of deployment's CL.

Can we somehow confirm this?

Is that the reason why super.loadClass goes back to org.jboss.classloader.spi.base.BaseClassLoader ?

If 1st paragraph holds, then yes.

Is there any thing wrong in what I did ? (I am able to get the breakpoint in loadClass method, and here the parent classloader is BaseClassLoader of jboss)

From 10.000ft atm, no. :-)

My war has few encrypted classes (which can be decrypted only if a hardware dongle is available using the ClassLoader provided by the hardware dongle). And now since we use JBoss, the encrypted classes are not been loaded. (In tomcat it was possible to set the system classloader :  –Djava.system.class.loader in catalina.bat)

I first tried to load then using translator (the previous post from me), but if I use translator, the plain bytecode is available in translator (after translator decrypts the encrypted class)

So now I am trying to use this customClassLoader, and here use the ClassLoader provided the third party (the company which provides us the hardware dongle).

I don't see how translator is different from classloader.

In both cases you can see the actual bytecode.

[irbash]

The translator is different from classloader:

If I use translator, I pass the encrypted bytecode to the translator and the translator decrypts it and sends back the actual bytecode. So once the translator decrypts it, the actual bytecode can be obtained easily. If anyone wants to get the actual bytecode, he/she can just get it from translator.

If I use classloader (provided by the third party security company, which decrypts the bytecode only if a hardware dongle is available), I just pass the classname to the ClassLoader and it returns me the Class after loading it. So with the Class, one cannot get the bytecode (at least thats what I believe). This secure ClassLoader somehow loads the class without calling the java.lang.ClassLoader, and the classloader itself is encrypted so it is pretty much safe. (I tested this by changing the code of java.lang.ClassLoader in rt.jar... surprisingly this secure classloader doesn't call the java.lang.ClassLoader... )

[alesj]

This secure ClassLoader somehow loads the class without calling the java.lang.ClassLoader

Hmmm, never heard of this, nor have some co-workers ...

and the classloader itself is encrypted so it is pretty much safe

How is then classloader decrypted?

Chicken-n-egg ...

Afaik, any JavaAgent should be able to read the bytes.

Unless there is some JVM extension / magic I don't know about.

[irbash]

Well, I must agree that I have just about 2 years of experience in java programming... and as far as my knowledge is, for java to execute a class it should first load it in memory (in jvm) and this can be done by ClassLoader. Hence any class which should be loaded should have gone through loadClass method of ClassLoader. (I suppose this also applies for classes loaded through reflection)

And the strange thing is, when I modified the code of java.lang.ClassLoader and dumped the bytecode to my local disk (from method loadClass), I didnot find the classes which are loaded through the secure classloader. Is there a way to load class into jvm from any other way without using java.lang.ClassLoader ?

[alesj]

Is there a way to load class into jvm from any other way without using java.lang.ClassLoader ?

Not that I'm aware of.

But I never looked JVM into details.

[irbash]

Anyway, Is there a way to extend the org.jboss.classloader.spi.base.BaseClassLoader ?

[alesj]

The idea behind extending MC's CL layer is to provide CL policy.

All ugly details are hidden behind CL policy usage.