1 files changed, 309 insertions, 0 deletions
diff --git a/src/test/java/org/apache/commons/lang3/concurrent/BackgroundInitializerTest.java b/src/test/java/org/apache/commons/lang3/concurrent/BackgroundInitializerTest.java
new file mode 100644
index 000000000..d1a80da81
--- /dev/null
+++ b/src/test/java/org/apache/commons/lang3/concurrent/BackgroundInitializerTest.java
@@ -0,0 +1,309 @@
+/*
+ * 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.lang3.concurrent;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.time.Duration;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicReference;
+
+import org.apache.commons.lang3.AbstractLangTest;
+import org.apache.commons.lang3.ThreadUtils;
+import org.junit.jupiter.api.Test;
+
+public class BackgroundInitializerTest extends AbstractLangTest {
+    /**
+     * Helper method for checking whether the initialize() method was correctly
+     * called. start() must already have been invoked.
+     *
+     * @param init the initializer to test
+     */
+    private void checkInitialize(final BackgroundInitializerTestImpl init) throws ConcurrentException {
+        final Integer result = init.get();
+        assertEquals(1, result.intValue(), "Wrong result");
+        assertEquals(1, init.initializeCalls, "Wrong number of invocations");
+        assertNotNull(init.getFuture(), "No future");
+    }
+
+    /**
+     * Tests whether initialize() is invoked.
+     */
+    @Test
+    public void testInitialize() throws ConcurrentException {
+        final BackgroundInitializerTestImpl init = new BackgroundInitializerTestImpl();
+        init.start();
+        checkInitialize(init);
+    }
+
+    /**
+     * Tries to obtain the executor before start(). It should not have been
+     * initialized yet.
+     */
+    @Test
+    public void testGetActiveExecutorBeforeStart() {
+        final BackgroundInitializerTestImpl init = new BackgroundInitializerTestImpl();
+        assertNull(init.getActiveExecutor(), "Got an executor");
+    }
+
+    /**
+     * Tests whether an external executor is correctly detected.
+     */
+    @Test
+    public void testGetActiveExecutorExternal() throws InterruptedException, ConcurrentException {
+        final ExecutorService exec = Executors.newSingleThreadExecutor();
+        try {
+            final BackgroundInitializerTestImpl init = new BackgroundInitializerTestImpl(
+                    exec);
+            init.start();
+            assertSame(exec, init.getActiveExecutor(), "Wrong executor");
+            checkInitialize(init);
+        } finally {
+            exec.shutdown();
+            exec.awaitTermination(1, TimeUnit.SECONDS);
+        }
+    }
+
+    /**
+     * Tests getActiveExecutor() for a temporary executor.
+     */
+    @Test
+    public void testGetActiveExecutorTemp() throws ConcurrentException {
+        final BackgroundInitializerTestImpl init = new BackgroundInitializerTestImpl();
+        init.start();
+        assertNotNull(init.getActiveExecutor(), "No active executor");
+        checkInitialize(init);
+    }
+
+    /**
+     * Tests the execution of the background task if a temporary executor has to
+     * be created.
+     */
+    @Test
+    public void testInitializeTempExecutor() throws ConcurrentException {
+        final BackgroundInitializerTestImpl init = new BackgroundInitializerTestImpl();
+        assertTrue(init.start(), "Wrong result of start()");
+        checkInitialize(init);
+        assertTrue(init.getActiveExecutor().isShutdown(), "Executor not shutdown");
+    }
+
+    /**
+     * Tests whether an external executor can be set using the
+     * setExternalExecutor() method.
+     */
+    @Test
+    public void testSetExternalExecutor() throws ConcurrentException {
+        final ExecutorService exec = Executors.newCachedThreadPool();
+        try {
+            final BackgroundInitializerTestImpl init = new BackgroundInitializerTestImpl();
+            init.setExternalExecutor(exec);
+            assertEquals(exec, init.getExternalExecutor(), "Wrong executor service");
+            assertTrue(init.start(), "Wrong result of start()");
+            assertSame(exec, init.getActiveExecutor(), "Wrong active executor");
+            checkInitialize(init);
+            assertFalse(exec.isShutdown(), "Executor was shutdown");
+        } finally {
+            exec.shutdown();
+        }
+    }
+
+    /**
+     * Tests that setting an executor after start() causes an exception.
+     *
+     * @throws org.apache.commons.lang3.concurrent.ConcurrentException because the test implementation may throw it
+     */
+    @Test
+    public void testSetExternalExecutorAfterStart() throws ConcurrentException, InterruptedException {
+        final BackgroundInitializerTestImpl init = new BackgroundInitializerTestImpl();
+        init.start();
+        final ExecutorService exec = Executors.newSingleThreadExecutor();
+        try {
+            assertThrows(IllegalStateException.class, () -> init.setExternalExecutor(exec));
+            init.get();
+        } finally {
+            exec.shutdown();
+            exec.awaitTermination(1, TimeUnit.SECONDS);
+        }
+    }
+
+    /**
+     * Tests invoking start() multiple times. Only the first invocation should
+     * have an effect.
+     */
+    @Test
+    public void testStartMultipleTimes() throws ConcurrentException {
+        final BackgroundInitializerTestImpl init = new BackgroundInitializerTestImpl();
+        assertTrue(init.start(), "Wrong result for start()");
+        for (int i = 0; i < 10; i++) {
+            assertFalse(init.start(), "Could start again");
+        }
+        checkInitialize(init);
+    }
+
+    /**
+     * Tests calling get() before start(). This should cause an exception.
+     */
+    @Test
+    public void testGetBeforeStart() {
+        final BackgroundInitializerTestImpl init = new BackgroundInitializerTestImpl();
+        assertThrows(IllegalStateException.class, init::get);
+    }
+
+    /**
+     * Tests the get() method if background processing causes a runtime
+     * exception.
+     */
+    @Test
+    public void testGetRuntimeException() {
+        final BackgroundInitializerTestImpl init = new BackgroundInitializerTestImpl();
+        final RuntimeException rex = new RuntimeException();
+        init.ex = rex;
+        init.start();
+        final Exception ex = assertThrows(Exception.class, init::get);
+        assertEquals(rex, ex, "Runtime exception not thrown");
+    }
+
+    /**
+     * Tests the get() method if background processing causes a checked
+     * exception.
+     */
+    @Test
+    public void testGetCheckedException() {
+        final BackgroundInitializerTestImpl init = new BackgroundInitializerTestImpl();
+        final Exception ex = new Exception();
+        init.ex = ex;
+        init.start();
+        final ConcurrentException cex = assertThrows(ConcurrentException.class, init::get);
+        assertEquals(ex, cex.getCause(), "Exception not thrown");
+    }
+
+    /**
+     * Tests the get() method if waiting for the initialization is interrupted.
+     *
+     * @throws InterruptedException because we're making use of Java's concurrent API
+     */
+    @Test
+    public void testGetInterruptedException() throws InterruptedException {
+        final ExecutorService exec = Executors.newSingleThreadExecutor();
+        final BackgroundInitializerTestImpl init = new BackgroundInitializerTestImpl(
+                exec);
+        final CountDownLatch latch1 = new CountDownLatch(1);
+        init.shouldSleep = true;
+        init.start();
+        final AtomicReference<InterruptedException> iex = new AtomicReference<>();
+        final Thread getThread = new Thread() {
+            @Override
+            public void run() {
+                try {
+                    init.get();
+                } catch (final ConcurrentException cex) {
+                    if (cex.getCause() instanceof InterruptedException) {
+                        iex.set((InterruptedException) cex.getCause());
+                    }
+                } finally {
+                    assertTrue(isInterrupted(), "Thread not interrupted");
+                    latch1.countDown();
+                }
+            }
+        };
+        getThread.start();
+        getThread.interrupt();
+        latch1.await();
+        exec.shutdownNow();
+        exec.awaitTermination(1, TimeUnit.SECONDS);
+        assertNotNull(iex.get(), "No interrupted exception");
+    }
+
+    /**
+     * Tests isStarted() before start() was called.
+     */
+    @Test
+    public void testIsStartedFalse() {
+        final BackgroundInitializerTestImpl init = new BackgroundInitializerTestImpl();
+        assertFalse(init.isStarted(), "Already started");
+    }
+
+    /**
+     * Tests isStarted() after start().
+     */
+    @Test
+    public void testIsStartedTrue() {
+        final BackgroundInitializerTestImpl init = new BackgroundInitializerTestImpl();
+        init.start();
+        assertTrue(init.isStarted(), "Not started");
+    }
+
+    /**
+     * Tests isStarted() after the background task has finished.
+     */
+    @Test
+    public void testIsStartedAfterGet() throws ConcurrentException {
+        final BackgroundInitializerTestImpl init = new BackgroundInitializerTestImpl();
+        init.start();
+        checkInitialize(init);
+        assertTrue(init.isStarted(), "Not started");
+    }
+
+    /**
+     * A concrete implementation of BackgroundInitializer. It also overloads
+     * some methods that simplify testing.
+     */
+    private static class BackgroundInitializerTestImpl extends
+            BackgroundInitializer<Integer> {
+        /** An exception to be thrown by initialize(). */
+        Exception ex;
+
+        /** A flag whether the background task should sleep a while. */
+        boolean shouldSleep;
+
+        /** The number of invocations of initialize(). */
+        volatile int initializeCalls;
+
+        BackgroundInitializerTestImpl() {
+        }
+
+        BackgroundInitializerTestImpl(final ExecutorService exec) {
+            super(exec);
+        }
+
+        /**
+         * Records this invocation. Optionally throws an exception or sleeps a
+         * while.
+         *
+         * @throws Exception in case of an error
+         */
+        @Override
+        protected Integer initialize() throws Exception {
+            if (ex != null) {
+                throw ex;
+            }
+            if (shouldSleep) {
+                ThreadUtils.sleep(Duration.ofMinutes(1));
+            }
+            return Integer.valueOf(++initializeCalls);
+        }
+    }
+}