79 lines
1.5 KiB
Java
79 lines
1.5 KiB
Java
package org.gcube.smartgears.handlers;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* An ordered list {@link Handler}s that handle related events.
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*
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* @author Fabio Simeoni
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*
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* @param <E> the type of events
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* @param <H> the type of handlers
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*
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*
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*/
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public abstract class Pipeline<E,H extends Handler<E>> {
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//private static Logger log = LoggerFactory.getLogger(Pipeline.class);
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private final List<H> handlers;
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private int cursor = 0;
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/**
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* Creates an instance with a given list of handlers.
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* <p>
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* Modification to the input list do not affect the pipeline.
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*
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* @param handlers the handlers
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*/
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public Pipeline(List<H> handlers) {
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this.handlers = new ArrayList<H>(handlers); // defensive copy
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}
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/**
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* Returns the handlers in this pipeline.
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* <p>
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* Modification to the input list do not affect the pipeline.
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*
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* @return the handlers
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*/
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public List<H> handlers() {
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return new ArrayList<H>(handlers); // defensive copy
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}
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/**
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* Forwards an event through the pipeline.
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*
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* @param event the event
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*/
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public void forward(E event) {
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if (cursor >= handlers.size()) {
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reset();
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return;
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}
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H handler = handlers.get(cursor);
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cursor++;
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//log.trace("forwarding {} to {}", event, handler);
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try {
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handler.onEvent(event);
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}
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catch(RuntimeException e) {
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reset();
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throw e;
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}
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forward(event); //make sure it's the last thing we do, or it will keep acting as recursion retracts
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}
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private void reset() {
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cursor=0;
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}
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}
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