Chapter 8. JBoss EAP MBean Services
A managed bean, sometimes simply referred to as an MBean, is a type of JavaBean that is created with dependency injection. MBean services are the core building blocks of the JBoss EAP server.
8.1. Writing JBoss MBean Services
Writing a custom MBean service that relies on a JBoss service requires the service interface method pattern. A JBoss MBean service interface method pattern consists of a set of life cycle operations that inform an MBean service when it can create, start, stop, and destroy itself.
You can manage the dependency state using any of the following approaches:
- If you want specific methods to be called on your MBean, declare those methods in your MBean interface. This approach allows your MBean implementation to avoid dependencies on JBoss specific classes.
-
If you are not bothered about dependencies on JBoss specific classes, then you can have your MBean interface extend the
ServiceMBeaninterface andServiceMBeanSupportclass. TheServiceMBeanSupportclass provides implementations of the service lifecycle methods like create, start, and stop. To handle a specific event like thestart()event, you need to overridestartService()method provided by theServiceMBeanSupportclass.
8.1.1. A Standard MBean Example
This section develops two example MBean services packaged together in a service archive (.sar).
ConfigServiceMBean interface declares specific methods like the start, getTimeout, and stop methods to start, hold, and stop the MBean correctly without using any JBoss specific classes. ConfigService class implements ConfigServiceMBean interface and consequently implements the methods used within that interface.
The PlainThread class extends the ServiceMBeanSupport class and implements the PlainThreadMBean interface. PlainThread starts a thread and uses ConfigServiceMBean.getTimeout() to determine how long the thread should sleep.
Example: MBean Services Class
package org.jboss.example.mbean.support;
public interface ConfigServiceMBean {
int getTimeout();
void start();
void stop();
}
package org.jboss.example.mbean.support;
public class ConfigService implements ConfigServiceMBean {
int timeout;
@Override
public int getTimeout() {
return timeout;
}
@Override
public void start() {
//Create a random number between 3000 and 6000 milliseconds
timeout = (int)Math.round(Math.random() * 3000) + 3000;
System.out.println("Random timeout set to " + timeout + " seconds");
}
@Override
public void stop() {
timeout = 0;
}
}
package org.jboss.example.mbean.support;
import org.jboss.system.ServiceMBean;
public interface PlainThreadMBean extends ServiceMBean {
void setConfigService(ConfigServiceMBean configServiceMBean);
}
package org.jboss.example.mbean.support;
import org.jboss.system.ServiceMBeanSupport;
public class PlainThread extends ServiceMBeanSupport implements PlainThreadMBean {
private ConfigServiceMBean configService;
private Thread thread;
private volatile boolean done;
@Override
public void setConfigService(ConfigServiceMBean configService) {
this.configService = configService;
}
@Override
protected void startService() throws Exception {
System.out.println("Starting Plain Thread MBean");
done = false;
thread = new Thread(new Runnable() {
@Override
public void run() {
try {
while (!done) {
System.out.println("Sleeping....");
Thread.sleep(configService.getTimeout());
System.out.println("Slept!");
}
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
}
});
thread.start();
}
@Override
protected void stopService() throws Exception {
System.out.println("Stopping Plain Thread MBean");
done = true;
}
}
The jboss-service.xml descriptor shows how the ConfigService class is injected into the PlainThread class using the inject tag. The inject tag establishes a dependency between PlainThreadMBean and ConfigServiceMBean, and thus allows PlainThreadMBean to use ConfigServiceMBean easily.
Example: jboss-service.xml Service Descriptor
<server xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:jboss:service:7.0 jboss-service_7_0.xsd"
xmlns="urn:jboss:service:7.0">
<mbean code="org.jboss.example.mbean.support.ConfigService" name="jboss.support:name=ConfigBean"/>
<mbean code="org.jboss.example.mbean.support.PlainThread" name="jboss.support:name=ThreadBean">
<attribute name="configService">
<inject bean="jboss.support:name=ConfigBean"/>
</attribute>
</mbean>
</server>
After writing the MBeans example, you can package the classes and the jboss-service.xml descriptor in the META-INF/ folder of a service archive (.sar).
8.2. Deploying JBoss MBean Services
Example: Deploy and Test MBeans in a Managed Domain
Use the following command to deploy the example MBeans (ServiceMBeanTest.sar) in a managed domain:
deploy ~/Desktop/ServiceMBeanTest.sar --all-server-groups
Example: Deploy and Test MBeans on a Standalone Server
Use the following command to build and deploy the example MBeans (ServiceMBeanTest.sar) on a standalone server:
deploy ~/Desktop/ServiceMBeanTest.sar
Example: Undeploy the MBeans Archive
Use the following command to undeploy the MBeans example:
undeploy ServiceMBeanTest.sar
