Microcontainer Inspector Tool Update

The Microcontainer Inspector Tool build did not work following the move to our new Maven repository at JBoss. I have updated the build and also changed the packaging to create a client jar and a server jar to be deployed. The Installation section of the original post have been updated with the new instructions.

This has made me wonder if the build will work for people who do NOT have the JBoss maven repositories set up as described here. If you are trying to build it and it does not work for you please leave me a comment and I'll fix the build.

JBoss User Group Belgium

I've been invited to talk at the Belgian JBoss User Group near Antwerp on 3rd June. The title of my talk will be "What's Cooking in JBoss AS 6" and I will talk about our current development model, ongoing optimizations and give a high-level overview of the new projects in AS 6 such as Weld, RestEasy, HornetQ and many more.

Hope to see you there!

JSR-330 and Qualifiers in the JBoss Microcontainer

The latest JBoss Microcontainer jboss-kernel 2.2.0.Alphas contain support for the @javax.inject.Inject and @javax.inject.Qualifier annotations from JSR-330.

While most of the use of the JBoss Microcontainer in JBoss AS uses explicitly named injection, e.g.

<?xml version="1.0" encoding="UTF-8"?>
<deployment xmlns="urn:jboss:bean-deployer:2.0">
   <bean name="MyDependency" class="org.jboss.test.Dependency"/>
   <bean name="MyBean" class="org.jboss.test.Bean">
      <property name="dependency"><inject bean="MyDependency"/></property>
   </bean>
</deployment>

The above means that when deploying the MyBean bean bean it will look up the MyDependency bean by name and inject that instance into MyBean's dependency property.

Contextual injection
We can also look up things by type, first let us see how to do this using xml. This has been supported by the Microcontainer for a while, so this might be familiar:

<?xml version="1.0" encoding="UTF-8"?>
<deployment xmlns="urn:jboss:bean-deployer:2.0">
   <bean name="MyDependency" class="org.jboss.test.Dependency"/>
   <bean name="MyBean" class="org.jboss.test.Bean">
      <property name="dependency"><inject/></property>
   </bean>
</deployment>

Now if the definition of MyBean's class is: package org.jboss.test;

public class Bean{
   Dependency dependency;

   public void setDependency(Dependency dependency){
      this.dependency = dependency;
   }
}

When creating MyBean this time, we have not given the name of the bean to use when configuring the dependency property. Instead the Microcontainer will check the type of the property, and find which beans are installed in the Microcontainer that can be cast to that type. In this case it finds MyDependency and uses that. If there had been more beans that could be cast to this type, an error would have been thrown. We'll see later how qualifiers can be used to resolve the ambiguities.

Using @javax.inject.Inject 
Now let us do the same using annotations. We first need to install the beans into the MC, the simplest way is to use an xml file to define the beans:

<?xml version="1.0" encoding="UTF-8"?>
<deployment xmlns="urn:jboss:bean-deployer:2.0">
   <bean name="MyDependency" class="org.jboss.test.Dependency"/>
   <bean name="MyBean" class="org.jboss.test.Bean"/> 
</deployment>

Notice that we did not define any injection for the dependency property in this case, instead we use @javax.inject.Inject on MyBean's class to define the injection:

package org.jboss.test; 

import javax.inject.Inject; 

public class Bean{

   Dependency dependency;

   @Inject
   public void setDependency(Dependency dependency){ 
      this.dependency = dependency;
   } 
} 

What happens now is that when MyBean is deployed we find the @javax.inject.Inject annotation on the dependency property and this causes a lookup of the bean to be found. As in the last example it looks up the bean by type, and throws an error if more that one can be found.

Qualifiers to the rescue
If we deploy the following beans:

<?xml version="1.0" encoding="UTF-8"?>
<deployment xmlns="urn:jboss:bean-deployer:2.0">
   <bean name="SomeDependency" class="org.jboss.test.SomeDependency"/>
   <bean name="TestDependency" class="org.jboss.test.TestDependency"/>
   <bean name="MyBean" class="org.jboss.test.Bean"/>
</deployment>

with the following classes

package org.jboss.test;

public class SomeDependency extends Dependency{
}
- - - - - - - - -
package org.jboss.test;

public class TestDependency extends Dependency{
}
- - - - - - - - -
package org.jboss.test;

import javax.inject.Inject;

public class Bean{
   Dependency dependency;

   @Inject
   public void setDependency(Dependency dependency){
      this.dependency = dependency;
   }
}

Now we have an ambiguity since both TestDependency and SomeDependency can be cast to org.jboss.test.Dependency. To give the Microcontainer a hint about which of these instances should be used we can use a qualifier. A qualifier is any annotation that has been annotated with the @javax.inject.Qualifier annotation. For example:

package org.jboss.test;

import javax.inject.Qualifier;

@Qualifier
@Retention(RUNTIME)
public @interface Test{
}

Now we can use this qualifier on our beans by adding it to TestDependency's class and to the Bean.dependency injection point:

package org.jboss.test;

@Test
public class TestDependency extends Dependency{
}
- - - - - - - - -
package org.jboss.test;

import javax.inject.Inject;

public class Bean{
   Dependency dependency;

   @Inject @Test
   public void setDependency(Dependency dependency){
      this.dependency = dependency;
   }
}

Now the Microcontainer will look up all beans that can be cast to org.jboss.test.Dependency AND that have the @org.jboss.test.Test annotation. In this case only TestDependency satisfies those criteria and is used for injection.

Qualifiers via xml
As part of implementing qualifiers in the Microcontainer we built in native support for qualifiers and came up with something somewhat more powerful that what is indicated by JSR-330. First let's deploy the classes from the previous example without any annotations:

package org.jboss.test;

public class SomeDependency extends Dependency{
}
- - - - - - - - -
package org.jboss.test;

public class TestDependency extends Dependency{
}
- - - - - - - - -
package org.jboss.test;

import javax.inject.Inject;

public class Bean{
   Dependency dependency;

   public void setDependency(Dependency dependency){
      this.dependency = dependency;
   }
}

This time the injection and qualifier annotations are driven by xml:

<?xml version="1.0" encoding="UTF-8"?>
<deployment xmlns="urn:jboss:bean-deployer:2.0">
   <bean name="SomeDependency" class="org.jboss.test.SomeDependency"/>
   <bean name="TestDependency" class="org.jboss.test.TestDependency">
      <qualifier content="Annotation">@org.jboss.test.Test</qualifier>
   </bean>
   <bean name="MyBean" class="org.jboss.test.Bean">
      <property name="dependency">
         <inject>
            <qualifier content="Annotation" type="Required">@org.jboss.Test</qualifier>
         </inject>
      </property>
   </bean>
</deployment>

Now, we're saying that TestDependency provides the @org.jboss.test.Test qualifier, and when injecting Bean.dependency we want to inject any bean that is of type Dependency and that has the @org.jboss.test.Test qualifier. As when using "real" annotations it will pick out the TestDependency bean. The qualifier content is Annotation which means the parser will try to create an annotation from the body of the qualifier annotation. When qualifier annotations are applied in this way, they do not need to be annotated with @javax.inject.Inject.

A qualifier does not have to be an annotation, simple strings can be used by omitting the content attribute:

<?xml version="1.0" encoding="UTF-8"?>
<deployment xmlns="urn:jboss:bean-deployer:2.0">
   <bean name="SomeDependency" class="org.jboss.test.SomeDependency"/>
   <bean name="TestDependency" class="org.jboss.test.TestDependency">
      <qualifier>test</qualifier>
   </bean>
   <bean name="MyBean" class="org.jboss.test.Bean">
      <property name="dependency">
         <inject>
            <qualifier type="Required">test</qualifier>
         </inject>
      </property>
   </bean>
</deployment>

Qualifiers can also be used in other places supporting the inject element, such as parameters to constructors and install methods.

Bean level qualifiers
In the previous example we applied qualifiers to a particular property. As a convenience you can choose default qualifiers that should be applied when doing injection at bean level. This is useful when you have a lot of properties that need injecting, here is an example:

<?xml version="1.0" encoding="UTF-8"?>
<deployment xmlns="urn:jboss:bean-deployer:2.0">
   <bean name="SomeDependency" class="org.jboss.test.SomeDependency"/>
   <bean name="TestDependency" class="org.jboss.test.TestDependency">
      <qualifier>test</qualifier>
   </bean>
   <bean name="SomeOtherDependency" class="org.jboss.test.SomeOtherDependency">
      <qualifier>test</qualifier>
   </bean>
   <bean name="TestOtherDependency" class="org.jboss.test.TestOtherDependency">
      <qualifier>test</qualifier>
      <qualifier>other</qualifier>
   </bean>
   <bean name="MyBean" class="org.jboss.test.Bean">
      <qualifier type="Required">test</qualifier>
      <qualifier type="Optional">other</qualifier>
      <property name="dependency"><inject/></property>
      <property name="otherDependency"><inject/></property>
   </bean>
</deployment>

Now we are saying that when doing contextual injection into MyBean's properties, the candidate beans MUST have the test qualifier, and that the other qualifier can be used to further strip out ambiguities. If we have the following bean classes:

package org.jboss.test;

public class SomeDependency extends Dependency{
}
- - - - - - - - -
package org.jboss.test;

public class TestDependency extends Dependency{
}
- - - - - - - - -
package org.jboss.test;

public class SomeOtherDependency extends OtherDependency{
}
- - - - - - - - -
package org.jboss.test;

public class TestOtherDependency extends OtherDependency{
}
- - - - - - - - -
package org.jboss.test;

import javax.inject.Inject;

public class Bean{
   Dependency dependency;

   OtherDependency otherDependency;

   public void setDependency(Dependency dependency){
      this.dependency = dependency;
   }

   public void setOtherDependency(OtherDependency otherDependency){
      this.otherDependency = otherDependency;
   }
}

then TestDependency is used for MyBean.dependency and TestOtherDependency is used for injection into MyBean.otherDependency.

Custom qualifiers
If the above qualifiers are not enough to narrow down what you want to inject, you can create custom qualifiers as shown in this simple example. If we deploy the following beans we end up with Dependency3 being injected into MyBean.dependency:

<?xml version="1.0" encoding="UTF-8"?>
<deployment xmlns="urn:jboss:bean-deployer:2.0">
   <bean name="TestMatcherAndParser"
      class="org.jboss.test.kernel.qualifiers.support.TestMatcherAndParser"/>
      <bean name="QualifierMatchers" class="org.jboss.kernel.spi.qualifier.QualifierMatchers">
         <constructor factoryMethod="getInstance">
      </constructor>
      <install method="addParser">
         <parameter><inject bean="TestMatcherAndParser"/></parameter>
      </install>
      <install method="addMatcher">
         <parameter><inject bean="TestMatcherAndParser"/></parameter>
      </install>
      </bean> 
      <bean name="Dependency1" class="org.jboss.test.SomeDependency">
         <qualifier>test</qualifier>
      <qualifier content="Test">Hello-xxx</qualifier>
      </bean>
      <bean name="Dependency2" class="org.jboss.test.Dependency">
         <qualifier>test</qualifier>
      </bean>
      <bean name="Dependency3" class="org.jboss.test.TestDependency">
         <qualifier>test</qualifier>
         <qualifier content="Test">Hola-xxx</qualifier>
      </bean>
      <bean name="MyBean" class="org.jboss.test.Bean">
         <qualifier type="Required">test</qualifier>
      <qualifier type="Required" content="Test">xxx-Hola</qualifier>
    </bean>
</deployment>

The magic behind understanding content="Test" lives in the TestMatcherAndParser bean which is installed via the QualifierParser singleton:

package org.jboss.test.kernel.qualifiers.support;

import java.util.Set;
import org.jboss.beans.metadata.api.model.QualifierContent;
import org.jboss.dependency.spi.ControllerContext;
import org.jboss.kernel.spi.qualifier.QualifierMatcher;
import org.jboss.kernel.spi.qualifier.QualifierParser;

public class TestMatcherAndParser implements QualifierMatcher, QualifierParser{
   public TestMatcherAndParser(){
   }

   //QualifierParser methods
   public QualifierContent getHandledContent(){
      return QualifierContent.getContent("Test");
   }

   public Object parseSupplied(ClassLoader cl, Object rawQualifier){
      return new Supplied((String)rawQualifier);
   }

   public Object parseWanted(ClassLoader cl, Object object){
      return new Wanted((String)object);
   }

   //QualifierMatcher methods
   public Class getHandledType(){
      return Wanted.class;
   }

   public boolean matches(ControllerContext context, Set<Object> suppliedQualifiers, Wanted qualifier){
      for (Object supplied : suppliedQualifiers){
         if (supplied instanceof Supplied)
            return qualifier.getString().equals(((Supplied)supplied).getString());
      }
      return false;
   }

   private static class Supplied{
      String string;

      public Supplied(String string){
         int i = string.indexOf("-xxx");
         if (i >= 0)
            string = string.substring(0, i);
            this.string = string;
      }

      public String getString(){
         return string;
      }
   }
}
- - - - - - - - -
package org.jboss.test.kernel.qualifiers.support;

public class Wanted{
   String string;
   public Wanted(String string){
      this.string = string;
      if (string.startsWith("xxx-"))
         string = string.substring(4);
         this.string = string;
      }

   public String getString(){
      return string;
   }
}

TestMatcherAndParser implements the QualifierParser and QualifierMatcher interfaces. The getHandledContent() method is what links this parser to content="Test". When parsing a qualifier with that content type supplied from from a bean (e.g. the qualifier entries in Dependency1 and Dependency3) we end up in the parseSupplied() method which creates an instance of Supplied. Similarly when parsing a qualifier with that content type from a bean wanting to inject something we end up in the parseWanted() method which creates an instance of Wanted.

So for Dependency1 we end up with a Supplied containing the string Hello and for Dependency3 we end up with a Supplied containing the string Hola. We end up with a Wanted containing the string Hola for MyBean.
Next when checking the qualifiers when doing injection into MyBean and checking

<qualifier type="Required" content="Test">xxx-Hola</qualifier>

behind the scenes the microcontainer finds all the contexts that are of the correct type and which have supplied qualifiers where type content="Test", i.e. the contexts Dependency1 and Dependency3. Then for each of these contexts it calls matches() with all the qualifiers for the candidate bean along with the parsed Wanted qualifier for MyBean.

When checking Dependency1 it calls matches() with the Supplied containing Hello and the Wanted containing Hola which does not match, and for Dependency2 it calls matches() with the Supplied containing Hello and the Wanted containing Hola which matches, meaning that only Dependency1 matches all the criteria. When calling matches() the ControllerContext (with information about the candidate bean's name, type, instance and other things) is passed in as well.

In the provided example we are only doing a silly little check where the Supplied gets rid of the final -xxx and the Wanted gets rid of the leading -xxx. The point here is that it is simple to implement more advanced qualifier checking than is provided out-of-the-box, and this mechanism has already been used to provide support for matching OSGi properties.

Microcontainer Inspector Tool

For those of you familiar with the Twiddle application, which allows you to inspect the JMX MBeans in JBoss Application Server, I have created a similar tool for use with the JBoss Microcontainer. This means that you can now manage and inspect ALL the beans in the JBoss Application Server (or in a standalone Microcontainer application). I'll briefly outline the existing functionality below and how to use it. The functionality supported so far is quite basic, but hopefully it will be useful to somebody. I'll be adding more commands to it when I have the time.

Implementing commands to extend the feature set is very easy. If you would like to be a Microcontainer committer, this is a great opportunity to get involved by implementing something simple while you get to know the code and the team. If you are interested please contact me privately or via our forums.

Installation
If you want to run this in a standalone environment you simply create an instance of org.jboss.microcontainer.mcinspector.bean.McInspector and pass it your bootstrapped kernel as shown in the test cases. To install it into a JBoss Application Server installed to ~/jbossas/:

• Check out the source from http://anonsvn.jboss.org/repos/jbossas/projects/mc-tools/mcinspector/trunk/ 
• Build it by going to the checkout directory and run mvn install
• Copy target/mcinspector-server.jar to ~/jbossas/server/default/deploy
• Copy target/mcinspector.jar to ~/jbossas/bin
• Copy src/main/resources/mcinspector.sh to ~/jbossas/bin
• chmod 755 ~/jbossas/bin/mcinspector.sh

That's all, now start up JBoss as normal, and in another terminal: cd ~/jbossas/bin. This last terminal is the one we will be using to try out the commands in the rest of this demo.

Help
To get help you enter: ./mcinspector.sh help, which gives you an overview of the commands available. The command and its output are shown below:
$./mcinspector.sh help
Available commands:
  help   Prints the list of available commands.
  list   Lists all the available contexts.
  change Changes the state of the context.
  bean   Inspect a particular bean.
For more information about a particular command, enter 'help '.
Handled in 1026ms

You can also get more information about a particular command, e.g.:
$./mcinspector.sh help list
Lists all the contexts in the controller.
Usage: list [-o | -v] [ []*]
If no state arguments are passed in all states will be checked for contexts. Otherwise
only the passed in states will be checked
Options:
-o Overview. Show all the states in the controller with the number of contexts in each
   Normally only states with contexts will be shown
-e Error. Show only the contexts which are in the error state. Can not be used in combination  
   with state arguments.
-v Verbose. Show extra information for each context. Contexts with unresolved dependencies
   will have a '*' after their name. Additional information is in the format 
   (ControllerMode, Current state)
Handled in 523ms

List
Let's try out the list command. As promised in the help section, it lists all the states, in ascending order, in the Application Server's main controller and displays the number of beans found in each state:

$./mcinspector.sh list -o
NOT INSTALLED: 0 contexts
PREPARSE: 0 contexts
PARSE: 0 contexts
POSTPARSE: 0 contexts
PREDESCRIBE: 0 contexts
DESCRIBE: 0 contexts
CLASSLOADER: 0 contexts
POSTCLASSLOADER: 0 contexts
PREREAL: 0 contexts
REAL: 0 contexts
PREINSTALL: 0 contexts
DESCRIBED: 33 contexts
INSTANTIATED: 0 contexts
CONFIGURED: 0 contexts
CREATE: 0 contexts
START: 0 contexts
INSTALLED: 997 contexts
Handled in 509ms

To view which beans are in the different states we execute ./mcinspector.sh list. Since there are lot of beans in the Application Server I have deleted most of the output below:

DESCRIBED:
JBossLogManagerContextSelectorService
org.jboss.netty.channel.socket.nio.NioClientSocketChannelFactory
org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory
org.jboss.netty.channel.socket.nio.NioDatagramChannelFactory
org.jboss.netty.channel.socket.oio.OioClientSocketChannelFactory
org.jboss.netty.channel.socket.oio.OioServerSocketChannelFactory
org.jboss.netty.channel.socket.oio.OioDatagramChannelFactory
org.jboss.netty.channel.local.DefaultLocalClientChannelFactory
org.jboss.netty.channel.local.DefaultLocalServerChannelFactory
ModClusterListener
ModClusterService
...
INSTALLED:
JBossServer
ClassLoaderSystem
ClassLoaderDomain
ClassLoading
bootstrap-classloader:0.0.0$MODULE
bootstrap-classloader:0.0.0
stdio-classloader:0.0.0$MODULE
stdio-classloader:0.0.0
JBossStdioSystemOutStream
JBossStdioSystemErrStream
…
McInspectorCommands
McInspector
org.jboss.kernel:service=McInspector
McInspectorHelpCommand
McInspectorListCommand
McInspectorChangeCommand
McInspectorBeanCommand
file:///Users/kabir/sourcecontrol/jbossas/trunk/subversion/build/target/jboss-6.0.0-SNAPSHOT/server/default/deploy/mcinspector.jar
Handled in 596ms

To get more information about the contexts for a given state, you can do ./mcinspector.sh list -v DESCRIBED. The verbose output currently shows the controller mode of the beans' contexts, along with the current state of the bean. The * means that the context has unresolved dependencies.

$./mcinspector.sh list -v DESCRIBED
DESCRIBED:
JBossLogManagerContextSelectorService* (ON_DEMAND, DESCRIBED)
org.jboss.netty.channel.socket.nio.NioClientSocketChannelFactory* (ON_DEMAND, DESCRIBED)
org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory* (ON_DEMAND, DESCRIBED)
org.jboss.netty.channel.socket.nio.NioDatagramChannelFactory* (ON_DEMAND, DESCRIBED)
org.jboss.netty.channel.socket.oio.OioClientSocketChannelFactory* (ON_DEMAND, DESCRIBED)
org.jboss.netty.channel.socket.oio.OioServerSocketChannelFactory* (ON_DEMAND, DESCRIBED)
org.jboss.netty.channel.socket.oio.OioDatagramChannelFactory* (ON_DEMAND, DESCRIBED)
org.jboss.netty.channel.local.DefaultLocalClientChannelFactory (ON_DEMAND, DESCRIBED)
org.jboss.netty.channel.local.DefaultLocalServerChannelFactory (ON_DEMAND, DESCRIBED)
ModClusterListener* (ON_DEMAND, DESCRIBED)
ModClusterService* (ON_DEMAND, DESCRIBED)
HAModClusterService* (ON_DEMAND, DESCRIBED)
ModClusterConfig* (ON_DEMAND, DESCRIBED)
DynamicLoadBalanceFactorProvider* (ON_DEMAND, DESCRIBED)
AverageSystemLoadMetric* (ON_DEMAND, DESCRIBED)
OperatingSystemLoadMetricSource (ON_DEMAND, DESCRIBED)
BusyConnectorsLoadMetric* (ON_DEMAND, DESCRIBED)
ThreadPoolLoadMetricSource* (ON_DEMAND, DESCRIBED)
SimpleLoadBalanceFactorProvider* (ON_DEMAND, DESCRIBED)
SystemMemoryUsageLoadMetric* (ON_DEMAND, DESCRIBED)
HeapMemoryUsageLoadMetric* (ON_DEMAND, DESCRIBED)
RequestCountLoadMetric* (ON_DEMAND, DESCRIBED)
ReceiveTrafficLoadMetric* (ON_DEMAND, DESCRIBED)
SendTrafficLoadMetric* (ON_DEMAND, DESCRIBED)
RequestProcessorLoadMetricSource* (ON_DEMAND, DESCRIBED)
ActiveSessionsLoadMetric* (ON_DEMAND, DESCRIBED)
SessionLoadMetricSource* (ON_DEMAND, DESCRIBED)
ConnectionPoolUsageMetric* (ON_DEMAND, DESCRIBED)
ConnectionPoolLoadMetricSource* (ON_DEMAND, DESCRIBED)
MBeanAttributeLoadMetric* (ON_DEMAND, DESCRIBED)
MBeanAttributeRatioLoadMetric* (ON_DEMAND, DESCRIBED)
MBeanQueryLoadMetricSource* (ON_DEMAND, DESCRIBED)
XnioProvider* (ON_DEMAND, DESCRIBED)
Handled in 479ms

Bean
To get more information about one or more beans in particular, you can run the bean command. e.g.:
$./mcinspector.sh bean ModClusterListener ModClusterService
Name='ModClusterListener'
  bean type=org.jboss.modcluster.catalina.CatalinaEventHandlerAdapter
  mode=ON_DEMAND
  state=DESCRIBED
  required state=DESCRIBED
  context type=org.jboss.kernel.plugins.dependency.AbstractKernelControllerContext
  unresolved dependencies=1
Name='ModClusterService'
  bean type=org.jboss.modcluster.ModClusterService
  mode=ON_DEMAND
  state=DESCRIBED
  required state=DESCRIBED
  context type=org.jboss.kernel.plugins.dependency.AbstractKernelControllerContext
  unresolved dependencies=5
Handled in 485ms

To get some more information about the dependencies, you can pass in the -d flag
$./mcinspector.sh bean -d ModClusterListener
Name='ModClusterListener'
  bean type=org.jboss.modcluster.catalina.CatalinaEventHandlerAdapter
  mode=ON_DEMAND
  state=DESCRIBED
  required state=DESCRIBED
  context type=org.jboss.kernel.plugins.dependency.AbstractKernelControllerContext
  unresolved dependencies=1
  Resolved dependencies:
  Unresolved dependencies:
    iDependOn=ModClusterService; whenRequired=INSTANTIATED; dependentState=INSTALLED

The -u flag is the same as -d apart from it does not look for resolved dependencies:

$./mcinspector.sh bean -d ModClusterListener
Name='ModClusterListener'
  bean type=org.jboss.modcluster.catalina.CatalinaEventHandlerAdapter
  mode=ON_DEMAND
  state=DESCRIBED
  required state=DESCRIBED
  context type=org.jboss.kernel.plugins.dependency.AbstractKernelControllerContext
  unresolved dependencies=1
  Unresolved dependencies:
    iDependOn=ModClusterService; whenRequired=INSTANTIATED; dependentState=INSTALLED
Handled in 492ms

Change
Finally there is the change command which attempts to change the state of a bean, so it can for example be used to temporarily disable a bean. Only do this if you know what you are doing! For example, let us try to stop the bean that implements the MC Inspector's bean command:

$./mcinspector.sh change INSTANTIATED McInspectorBeanCommand
Changed 'McInspectorBeanCommand' to INSTANTIATED
Handled in 473ms

This has stopped the bean implementing the bean command, so bean no longer appears in the list of available commands:
$./mcinspector.sh help
Available commands:
  help Prints the list of available commands.
  list Lists all the available contexts.
  change Changes the state of the context.
  For more information about a particular command, enter 'help '.
Handled in 497ms
And it appears in the INSTANTIATED state:
$./mcinspector.sh list INSTANTIATED -v
INSTANTIATED:
McInspectorBeanCommand (AUTOMATIC, INSTANTIATED)
Handled in 488ms

Let us make it installed again:
$./mcinspector.sh change INSTALLED McInspectorBeanCommand
Changed 'McInspectorBeanCommand' to INSTALLED
Handled in 474ms
Now bean appears in the list of available commands again:
$./mcinspector.sh help
Available commands:
  help Prints the list of available commands.
  list Lists all the available contexts.
  change Changes the state of the context.
  bean Inspect a particular bean.
For more information about a particular command, enter 'help '.
Handled in 480ms

Optimizing the JBoss Microcontainer

Ales linked to the ongoing optimization work before I had planned on writing anything, so here is a very rushed overview of what is going on :-) 

For JBoss Application Server 6.0.0.M2 a lot of work went in to optimizing the boot time. Some of the work done by the AS team that really made a difference was optimizing the algorithm to add the deployers, and to make things like the admin console start when first accessed rather than use eager loading.

As part of this, for JBoss Kernel 2.2.0.Alpha6 I took a look at optimizing the dependency resolution algorithm of the Microcontainer, which is used to install and wire together the services the core of the application server. The dependency resolution algorithm is used to determine if the beans implementing the services can be moved through the states on the way from being put into the Microcontainer to being fully up and running. Initially I did work on a fully optimized prototype, but this was too big and risky an undertaking for the short timeframe and did not yield the expected results. This prototype is far from "finished" and there is plenty of room for improvement, so I might come back to it at some later stage.

So instead I went through and used JProfiler to see what is taking the time in the dependency resolution algorithm that we have today. What really made a difference here was that I found that when a bean can not be moved to the next state we were looking up its unresolved dependency three times in the Microcontainer. Wrapping these three calls into one gave a lot less overhead. That was the main optimization we had time for for JBoss Kernel 2.2.0.Alpha6 which is what is used in AS 6.0.0.M2. 

Since then I have been working on quite a few other optimizations that you can see on the Microcontainer Development Forum, more specifically here, which so far significantly improve the boot time of 6.0.0.M2 in my local benchmarks, and I am nowhere not done yet. The fixes are mainly making sure that objects used in maps are properly hashed, and making objects that are expensive to create less expensive to create. All these fixes will all go into the next community release of JBoss AS: 6.0.0.M3.

Another thing is that John Bailey is currently integrating JBoss Virtual File System 3 into AS. VFS is used as an abstraction layer to read files from several different sources, and VFS 3 promises to really speed things up when reading from zipped archives. This is something that happens a lot in the application server, when scanning archives for deployment descriptors and annotations, and loading classes and so on. So it will be very exciting to see this in JBoss AS 6.0.0.M3!