de.skuzzle.inject.async

Interface TriggerStrategy

All Known Implementing Classes:

CronTriggerStrategy, DelayedTriggerStrategy, SimpleTriggerStrategy

public interface TriggerStrategy

Defines how a certain Trigger annotation is handled in order to extract scheduling meta information and to actually schedule method invocations.

The framework searches for implementations of this class using the Java's ServiceLoader. In order to implement your own trigger, just follow these steps:

1. Create a new Trigger annotation which will hold scheduling meta information:

    @Trigger
    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.METHOD)
    public @interface CustomTrigger {
        // meta information fields
    }
    

2. Create an implementation of this interface to handle the new annotation:

    public class CustomTriggerStrategy implements TriggerStrategy {
   
        // Field injection is allowed
        @Inject
        private Injector injector;
   
        // public no-argument constructor required (because of the ServiceLoader)!
   
        @Override
        public Class<CustomTrigger> getTriggerType() {
            return CustomTrigger.class;
        }
   
        @Override
        public void schedule(Method method, Object self,
                ScheduledExecutorService executor) {
   
            // read trigger annotation from the method
            CustomTrigger trigger = method.getAnnotation(getTriggerType());
   
            // use meta information from the trigger to schedule the execution with the
            // provided executor (might want to use InjectedMethodInvocation class)
            executor.schedule(...);
        }
    }
    

3. Register your implementation for the ServiceLoader. Create the folder structure 'META-INF/services'. Within the services folder create a file named 'de.skuzzle.inject.async.TriggerStrategy'. Put a single line which contains the full qualified class name of your CustomTriggerStrategy into that file.

Author:

Simon Taddiken

Method Summary

Modifier and Type	Method and Description
Class<? extends Annotation>	getTriggerType() Returns the annotation type that this strategy can handle.
ScheduledContext	schedule(Method method, Object self, ScheduledExecutorService executor, ExceptionHandler handler) Extracts scheduling information from the provided Method and then schedules invocations of that method according to the information.

Method Detail

getTriggerType

Class<? extends Annotation> getTriggerType()

Returns the annotation type that this strategy can handle.

Returns:

The annotation type.

schedule

ScheduledContext schedule(Method method,
                          Object self,
                          ScheduledExecutorService executor,
                          ExceptionHandler handler)

Extracts scheduling information from the provided Method and then schedules invocations of that method according to the information.

To support invocation of parameterized methods, implementors can refer to InjectedMethodInvocation to inject actual parameters of a method.

Parameters:

method - The method to schedule.

self - The object to invoke the method on. This will be null in case that the method is static.

executor - The executor to use for scheduling.

handler - The exception handler to be used.

Returns:

The ScheduledContext.