--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/artifacts/src/main/java/org/dive4elements/river/wsplgen/Scheduler.java	Thu Apr 25 15:23:37 2013 +0200
@@ -0,0 +1,111 @@
+package org.dive4elements.river.wsplgen;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.Future;
+import java.util.concurrent.ScheduledThreadPoolExecutor;
+
+import org.apache.log4j.Logger;
+
+import org.dive4elements.artifacts.CallContext;
+import org.dive4elements.river.artifacts.model.map.WSPLGENJob;
+
+
+/**
+ * The Scheduler is used to retrieve new WSPLGENJob. The incoming jobs are added
+ * to a ScheduledThreadPoolExecutor. This thread pool has a number of worker
+ * threads that processes the WSPLGENJobs. The number of worker threads can be
+ * set using a System property <i>wsplgen.max.threads</i> ; its default value is
+ * 1.
+ *
+ * @author <a href="mailto:ingo.weinzierl@intevation.de">Ingo Weinzierl</a>
+ */
+public class Scheduler {
+
+    private class FutureJob {
+        public Future     future;
+        public WSPLGENJob job;
+
+        public FutureJob(Future future, WSPLGENJob job) {
+            this.future = future;
+            this.job    = job;
+        }
+    }
+
+    public static final int MAX_WSPLGEN_PROCESSES =
+        Integer.getInteger("wsplgen.max.threads", 1);
+
+
+    protected ScheduledThreadPoolExecutor pool;
+    protected Map<String, FutureJob> jobs;
+
+
+    private static Scheduler INSTANCE;
+
+    private static final Logger logger = Logger.getLogger(Scheduler.class);
+
+
+
+    private Scheduler() {
+        jobs = new HashMap<String, FutureJob>();
+        pool = new ScheduledThreadPoolExecutor(MAX_WSPLGEN_PROCESSES);
+    }
+
+
+    public static Scheduler getInstance() {
+        if (INSTANCE == null) {
+            logger.info("Create new WSPLGEN Scheduler...");
+
+            INSTANCE = new Scheduler();
+        }
+
+        return INSTANCE;
+    }
+
+
+    public void addJob(final WSPLGENJob job) {
+        synchronized (jobs) {
+            WSPLGENFuture f = new WSPLGENFuture(new WSPLGENCallable(this, job));
+            pool.execute(f);
+
+            jobs.put(job.getArtifact().identifier(), new FutureJob(f, job));
+
+            logger.info("New WSPLGEN job successfully added.");
+        }
+    }
+
+
+    /**
+     * Cancels a running (or queued) job.
+     *
+     * @param jobId The id of the job (which is the identifier of an Artifact).
+     */
+    public void cancelJob(String jobId) {
+        logger.debug("Search job in queue: " + jobId);
+
+        synchronized (jobs) {
+            FutureJob fj = jobs.get(jobId);
+
+            if (fj != null) {
+                logger.info("Try to cancel job: " + jobId);
+
+                fj.future.cancel(true);
+
+                removeJob(jobId);
+
+                fj.job.getCallContext().afterBackground(
+                    CallContext.STORE);
+
+                logger.info("Canceled job: " + jobId);
+            }
+        }
+    }
+
+
+    protected void removeJob(String id) {
+        synchronized (jobs) {
+            jobs.remove(id);
+        }
+    }
+}
+// vim:set ts=4 sw=4 si et sta sts=4 fenc=utf-8 :