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diff --git a/BKULocal/src/main/java/at/gv/egiz/bku/local/stal/ExclusiveAccessSTAL.java b/BKULocal/src/main/java/at/gv/egiz/bku/local/stal/ExclusiveAccessSTAL.java
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+++ b/BKULocal/src/main/java/at/gv/egiz/bku/local/stal/ExclusiveAccessSTAL.java
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+/*
+* Copyright 2009 Federal Chancellery Austria and
+* Graz University of Technology
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+* http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+package at.gv.egiz.bku.local.stal;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import at.gv.egiz.stal.ErrorResponse;
+import at.gv.egiz.stal.STAL;
+import at.gv.egiz.stal.STALRequest;
+import at.gv.egiz.stal.STALResponse;
+
+public class ExclusiveAccessSTAL implements STAL {
+
+ private final Logger log = LoggerFactory.getLogger(ExclusiveAccessSTAL.class);
+
+ private Lock lock = new ReentrantLock(true);
+
+ private long timeout = 30;
+
+ private STAL stal;
+
+ public ExclusiveAccessSTAL(STAL stal) {
+ if (stal == null) {
+ throw new NullPointerException("Argument 'stal' must not be null.");
+ }
+ this.stal = stal;
+ }
+
+ @Override
+ public List<STALResponse> handleRequest(
+ List<? extends STALRequest> aRequestList) {
+
+ try {
+ if (lock.tryLock(timeout, TimeUnit.SECONDS)) {
+ try {
+ return stal.handleRequest(aRequestList);
+ } finally {
+ lock.unlock();
+ }
+ } else {
+ // time out
+ log.info("Timeout while waiting for exclusive access to STAL.");
+ ErrorResponse response = new ErrorResponse(6000);
+ return Collections.singletonList((STALResponse) response);
+ }
+ } catch (InterruptedException e) {
+ // interrupted
+ ErrorResponse response = new ErrorResponse(6000);
+ return Collections.singletonList((STALResponse) response);
+ }
+
+ }
+
+}