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Posted to commits@commons.apache.org by oh...@apache.org on 2009/11/22 17:57:40 UTC
svn commit: r883100 - in /commons/proper/lang/trunk/src:
java/org/apache/commons/lang/concurrent/CallableBackgroundInitializer.java
test/org/apache/commons/lang/concurrent/CallableBackgroundInitializerTest.java
Author: oheger
Date: Sun Nov 22 16:57:39 2009
New Revision: 883100
URL: http://svn.apache.org/viewvc?rev=883100&view=rev
Log:
[LANG-501] Added CallableBackgroundInitializer class with unit tests.
Added:
commons/proper/lang/trunk/src/java/org/apache/commons/lang/concurrent/CallableBackgroundInitializer.java (with props)
commons/proper/lang/trunk/src/test/org/apache/commons/lang/concurrent/CallableBackgroundInitializerTest.java (with props)
Added: commons/proper/lang/trunk/src/java/org/apache/commons/lang/concurrent/CallableBackgroundInitializer.java
URL: http://svn.apache.org/viewvc/commons/proper/lang/trunk/src/java/org/apache/commons/lang/concurrent/CallableBackgroundInitializer.java?rev=883100&view=auto
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--- commons/proper/lang/trunk/src/java/org/apache/commons/lang/concurrent/CallableBackgroundInitializer.java (added)
+++ commons/proper/lang/trunk/src/java/org/apache/commons/lang/concurrent/CallableBackgroundInitializer.java Sun Nov 22 16:57:39 2009
@@ -0,0 +1,127 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.commons.lang.concurrent;
+
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+
+/**
+ * <p>
+ * A specialized {@link BackgroundInitializer} implementation that wraps a
+ * {@code Callable} object.
+ * </p>
+ * <p>
+ * An instance of this class is initialized with a {@code Callable} object when
+ * it is constructed. The implementation of the {@link #initialize()} method
+ * defined in the super class delegates to this {@code Callable} so that the
+ * {@code Callable} is executed in the background thread.
+ * </p>
+ * <p>
+ * The {@code java.util.concurrent.Callable} interface is a standard mechanism
+ * of the JDK to define tasks to be executed by another thread. The {@code
+ * CallableBackgroundInitializer} class allows combining this standard interface
+ * with the background initializer API.
+ * </p>
+ * <p>
+ * Usage of this class is very similar to the default usage pattern of the
+ * {@link BackgroundInitializer} class: Just create an instance and provide the
+ * {@code Callable} object to be executed, then call the initializer's
+ * {@link #start()} method. This causes the {@code Callable} to be executed in
+ * another thread. When the results of the {@code Callable} are needed the
+ * initializer's {@link #get()} method can be called (which may block until
+ * background execution is complete). The following code fragment shows a
+ * typical usage example:
+ *
+ * <pre>
+ * // a Callable that performs a complex computation
+ * Callable<Integer> computationCallable = new MyComputationCallable();
+ *
+ * // setup the background initializer
+ * CallableBackgroundInitializer<Integer> initializer =
+ * new CallableBackgroundInitializer(computationCallable);
+ * initializer.start();
+ *
+ * // Now do some other things. Initialization runs in a parallel thread
+ * ...
+ * // Wait for the end of initialization and access the result
+ * Integer result = initializer.get();
+ * </pre>
+ *
+ * </p>
+ *
+ * @version $Id: $
+ * @param <T> the type of the object managed by this initializer class
+ */
+public class CallableBackgroundInitializer<T> extends BackgroundInitializer<T> {
+ /** The Callable to be executed. */
+ private final Callable<T> callable;
+
+ /**
+ * Creates a new instance of {@code CallableBackgroundInitializer} and sets
+ * the {@code Callable} to be executed in a background thread.
+ *
+ * @param call the {@code Callable} (must not be <b>null</b>)
+ * @throws IllegalArgumentException if the {@code Callable} is <b>null</b>
+ */
+ public CallableBackgroundInitializer(Callable<T> call) {
+ checkCallable(call);
+ callable = call;
+ }
+
+ /**
+ * Creates a new instance of {@code CallableBackgroundInitializer} and
+ * initializes it with the {@code Callable} to be executed in a background
+ * thread and the {@code ExecutorService} for managing the background
+ * execution.
+ *
+ * @param call the {@code Callable} (must not be <b>null</b>)
+ * @param exec an external {@code ExecutorService} to be used for task
+ * execution
+ * @throws IllegalArgumentException if the {@code Callable} is <b>null</b>
+ */
+ public CallableBackgroundInitializer(Callable<T> call, ExecutorService exec) {
+ super(exec);
+ checkCallable(call);
+ callable = call;
+ }
+
+ /**
+ * Performs initialization in a background thread. This implementation
+ * delegates to the {@code Callable} passed at construction time of this
+ * object.
+ *
+ * @return the result of the initialization
+ * @throws Exception if an error occurs
+ */
+ @Override
+ protected T initialize() throws Exception {
+ return callable.call();
+ }
+
+ /**
+ * Tests the passed in {@code Callable} and throws an exception if it is
+ * undefined.
+ *
+ * @param call the object to check
+ * @throws IllegalArgumentException if the {@code Callable} is <b>null</b>
+ */
+ private void checkCallable(Callable<T> call) {
+ if (call == null) {
+ throw new IllegalArgumentException("Callable must not be null!");
+ }
+ }
+}
Propchange: commons/proper/lang/trunk/src/java/org/apache/commons/lang/concurrent/CallableBackgroundInitializer.java
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Added: commons/proper/lang/trunk/src/test/org/apache/commons/lang/concurrent/CallableBackgroundInitializerTest.java
URL: http://svn.apache.org/viewvc/commons/proper/lang/trunk/src/test/org/apache/commons/lang/concurrent/CallableBackgroundInitializerTest.java?rev=883100&view=auto
==============================================================================
--- commons/proper/lang/trunk/src/test/org/apache/commons/lang/concurrent/CallableBackgroundInitializerTest.java (added)
+++ commons/proper/lang/trunk/src/test/org/apache/commons/lang/concurrent/CallableBackgroundInitializerTest.java Sun Nov 22 16:57:39 2009
@@ -0,0 +1,99 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.commons.lang.concurrent;
+
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+import junit.framework.TestCase;
+
+/**
+ * Test class for {@code CallableBackgroundInitializer}
+ *
+ * @version $Id$
+ */
+public class CallableBackgroundInitializerTest extends TestCase {
+ /** Constant for the result of the call() invocation. */
+ private static final Integer RESULT = 42;
+
+ /**
+ * Tries to create an instance without a Callable. This should cause an
+ * exception.
+ */
+ public void testInitNullCallable() {
+ try {
+ new CallableBackgroundInitializer<Object>(null);
+ fail("Could create instance without a Callable!");
+ } catch (IllegalArgumentException iex) {
+ // ok
+ }
+ }
+
+ /**
+ * Tests whether the executor service is correctly passed to the super
+ * class.
+ */
+ public void testInitExecutor() {
+ ExecutorService exec = Executors.newSingleThreadExecutor();
+ CallableBackgroundInitializer<Integer> init = new CallableBackgroundInitializer<Integer>(
+ new TestCallable(), exec);
+ assertEquals("Executor not set", exec, init.getExternalExecutor());
+ }
+
+ /**
+ * Tries to pass a null Callable to the constructor that takes an executor.
+ * This should cause an exception.
+ */
+ public void testInitExecutorNullCallable() {
+ ExecutorService exec = Executors.newSingleThreadExecutor();
+ try {
+ new CallableBackgroundInitializer<Integer>(null, exec);
+ fail("Could create instance without a Callable!");
+ } catch (IllegalArgumentException iex) {
+ // ok
+ }
+ }
+
+ /**
+ * Tests the implementation of initialize().
+ */
+ public void testInitialize() throws Exception {
+ TestCallable call = new TestCallable();
+ CallableBackgroundInitializer<Integer> init = new CallableBackgroundInitializer<Integer>(
+ call);
+ assertEquals("Wrong result", RESULT, init.initialize());
+ assertEquals("Wrong number of invocations", 1, call.callCount);
+ }
+
+ /**
+ * A test Callable implementation for checking the initializer's
+ * implementation of the initialize() method.
+ */
+ private static class TestCallable implements Callable<Integer> {
+ /** A counter for the number of call() invocations. */
+ int callCount;
+
+ /**
+ * Records this invocation and returns the test result.
+ */
+ public Integer call() throws Exception {
+ callCount++;
+ return RESULT;
+ }
+ }
+}
Propchange: commons/proper/lang/trunk/src/test/org/apache/commons/lang/concurrent/CallableBackgroundInitializerTest.java
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