[jboss-user] [Microcontainer] - How to emulate ServiceMBeanSupport using AOP
I got this to work, it's pretty slick actually... Thanks Ales.
Service.java :
| /**
| * Interface defines the basic operations for a service.
| */
| public interface Service {
|
| /**
| * Possible states for a service.
| */
| enum State {
| /**
| * Initial state; no lifecycle methods called.
| */
| INITIAL,
| /**
| * Created state; dependencies not ready.
| */
| CREATED,
| /**
| * Started state; dependencies in started state.
| */
| STARTED,
| /**
| * Stopped state; dependencies also stopped.
| */
| STOPPED,
| /**
| * Destroyed state.
| */
| DESTROYED
| }
|
| /**
| * Starts the service
| * @throws Exception if this lifecycle method failed
| */
| public void start() throws Exception;
|
| /**
| * Starts the service
| * @throws Exception if this lifecycle method failed
| */
| public void stop() throws Exception;
|
| /**
| * Creates the service
| * @throws Exception if this lifecycle method failed
| */
| public void create() throws Exception;
|
| /**
| * Destroys the service
| * @throws Exception if this lifecycle method failed
| */
| public void destroy() throws Exception;
|
| /**
| * Returns the service state; or null if not known.
| */
| public State getState();
|
| /**
| * Returns the service name; or null if not known.
| */
| public String getName();
| }
|
LifecycleInterceptor.java:
| public class LifecycleInterceptor {
|
| private Log log = LogFactory.getLog(getClass());
|
| private Kernel kernel;
|
| /**
| * Maps the service method names to controller states.
| */
| private enum Methods {
|
| start(ControllerState.INSTALLED),
| stop(ControllerState.CREATE),
| create(ControllerState.CREATE),
| destroy(ControllerState.INSTANTIATED);
|
| private ControllerState cs;
|
| Methods(ControllerState cs) {
| this.cs = cs;
| }
|
| public ControllerState getState() {
| return cs;
| }
| };
|
| private boolean calledByKernel() {
| // The following detects if the kernel is calling us
| StackTraceElement[] sta = Thread.currentThread().getStackTrace();
| for (StackTraceElement se : sta) {
| String c = se.getClassName();
| if (c.startsWith("org.jboss.kernel"))
| return true;
| }
| return false;
| }
|
| /**
| * Determines the controller context, by method name chooses
| * and sets new controller state in the kernel.
| *
| * If called by the kernel, returns.
| *
| * @param inv method invocation
| */
| public Object handle(Invocation inv) throws Throwable {
| Service target = (Service) inv.getTargetObject();
|
| if (calledByKernel())
| return inv.invokeNext();
|
| KernelController controller = kernel.getController();
| ControllerContext context;
| MethodInvocation minv = (MethodInvocation)inv;
| String mname = minv.getMethod().getName();
| context = kernel.getController().getContext(target.getName(), null);
| if (context == null) {
| log.debug("service not installed " + target.getName());
| return inv.invokeNext();
| }
|
| // We assume the method call is a lifecycle method (by configuration)
| ControllerState state = Methods.valueOf(mname).getState();
| log.debug("controller change " + target.getName() + " to " +
state.getStateString() + " for " + mname + "()");
| controller.change(context, state);
| return null;
| }
|
| /**
| * Returns kernel.
| */
| public Kernel getKernel() {
| return kernel;
| }
|
| /**
| * Sets kernel.
| */
| public void setKernel(Kernel kernel) {
| this.kernel = kernel;
| }
|
| }
|
-beans.xml declaration:
| <aop:aspect xmlns:aop="urn:jboss:aop-beans:1.0"
| name="LifecycleAdvice"
| class="LifecycleInterceptor"
| method="handle"
| pointcut="execution(public void
com.autodesk.lbs.service.Service->*())">
| <property name="kernel">
| <inject bean="jboss.kernel:service=Kernel" />
| </property>
| <depends>LifecycleCallback</depends>
| </aop:aspect>
|
One weakness is that the Name has to be stored in the target, there's no way, given a
Service to find its name in the Microcontainer. (That I know of.)
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