Added an implementation of a spin lock that can be used to lock a directory.

Former-commit-id: 97cb3752808ae32f6a9a6d5d88418350f139c1f8

dependency-check-core/src/test/java/org/owasp/dependencycheck/concurrency/DirectorySpinLockTest.java

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+/*
+ * This file is part of dependency-check-core.
+ *
+ * Dependency-check-core is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation, either version 3 of the License, or (at your option) any
+ * later version.
+ *
+ * Dependency-check-core is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * dependency-check-core. If not, see http://www.gnu.org/licenses/.
+ *
+ * Copyright (c) 2013 Jeremy Long. All Rights Reserved.
+ */
+package org.owasp.dependencycheck.concurrency;
+
+import java.io.File;
+import java.net.URL;
+import org.junit.After;
+import org.junit.AfterClass;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import static org.junit.Assert.*;
+
+/**
+ *
+ * @author Jeremy Long (jeremy.long@owasp.org)
+ */
+public class DirectorySpinLockTest {
+
+    public DirectorySpinLockTest() {
+    }
+
+    @BeforeClass
+    public static void setUpClass() {
+    }
+
+    @AfterClass
+    public static void tearDownClass() {
+    }
+
+    @Before
+    public void setUp() {
+    }
+
+    @After
+    public void tearDown() {
+    }
+
+    /**
+     * Test of obtainSharedLock method, of class DirectorySpinLock.
+     * Specifically, this test uses the SpinLockTask to obtain an exclusive lock
+     * that is held for 5 seconds. We then try to obtain a shared lock while
+     * that task is running. It should take longer then 5 seconds to obtain the
+     * shared lock.
+     */
+    @Test
+    public void testObtainSharedLock_withContention() throws Exception {
+        URL location = this.getClass().getProtectionDomain().getCodeSource().getLocation();
+        File directory = new File(location.getFile());
+        DirectorySpinLock instance = new DirectorySpinLock(directory);
+        SpinLockTask task = new SpinLockTask(directory, 5000, false, 2);
+        long start = System.currentTimeMillis();
+        task.run();
+        instance.obtainSharedLock();
+        long end = System.currentTimeMillis();
+        instance.close();
+        if (task.getException() != null) {
+            throw task.getException();
+        }
+        long timeElapsed = end - start;
+        assertTrue("no lock contention occured?", timeElapsed >= 5000);
+        //no exceptions means everything worked.
+    }
+
+    /**
+     * Test of obtainSharedLock method, of class DirectorySpinLock. This method
+     * obtains two shared locks by using the SpinLockTask to obtain a lock in
+     * another thread.
+     */
+    @Test
+    public void testObtainSharedLock() throws Exception {
+        URL location = this.getClass().getProtectionDomain().getCodeSource().getLocation();
+        File directory = new File(location.getFile());
+        DirectorySpinLock instance = new DirectorySpinLock(directory);
+        SpinLockTask task = new SpinLockTask(directory, 1000, true, 2);
+        task.run();
+        instance.obtainSharedLock();
+        instance.close();
+        if (task.getException() != null) {
+            throw task.getException();
+        }
+        //no exceptions means everything worked.
+    }
+
+    /**
+     * Test of obtainExclusiveLock method, of class DirectorySpinLock.
+     */
+    @Test
+    public void testObtainExclusiveLock() throws Exception {
+        URL location = this.getClass().getProtectionDomain().getCodeSource().getLocation();
+        File directory = new File(location.getFile());
+        DirectorySpinLock instance = new DirectorySpinLock(directory);
+        SpinLockTask task = new SpinLockTask(directory, 1000, true, 1);
+        instance.obtainExclusiveLock();
+        task.run();
+        instance.close();
+        assertNotNull("No exception thrown due to exclusive lock failure?", task.getException());
+        assertEquals("Incorrect exception when obtaining exclusive lock", "Unable to obtain lock", task.getException().getMessage());
+    }
+}

dependency-check-core/src/test/java/org/owasp/dependencycheck/concurrency/SpinLockTask.java

@@ -0,0 +1,82 @@
+/*
+ * This file is part of dependency-check-core.
+ *
+ * Dependency-check-core is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation, either version 3 of the License, or (at your option) any
+ * later version.
+ *
+ * Dependency-check-core is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * dependency-check-core. If not, see http://www.gnu.org/licenses/.
+ *
+ * Copyright (c) 2013 Jeremy Long. All Rights Reserved.
+ */
+package org.owasp.dependencycheck.concurrency;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+/**
+ *
+ * @author Jeremy Long (jeremy.long@owasp.org)
+ */
+public class SpinLockTask implements Runnable {
+
+    DirectorySpinLock lock = null;
+    int holdLockFor;
+    long maxWait;
+    boolean shared;
+    private Exception exception = null;
+
+    /**
+     * Get the value of exception
+     *
+     * @return the value of exception
+     */
+    public Exception getException() {
+        return exception;
+    }
+
+    /**
+     * Set the value of exception
+     *
+     * @param exception new value of exception
+     */
+    public void setException(Exception exception) {
+        this.exception = exception;
+    }
+
+    public SpinLockTask(File directory, int holdLockFor, boolean shared, long maxWait) throws InvalidDirectoryException, DirectoryLockException {
+        this.holdLockFor = holdLockFor;
+        this.shared = shared;
+        this.maxWait = maxWait;
+        lock = new DirectorySpinLock(directory);
+    }
+
+    @Override
+    public void run() {
+        try {
+            lock.obtainLock(shared, maxWait);
+            Thread.sleep(holdLockFor);
+        } catch (DirectoryLockException ex) {
+            exception = ex;
+        } catch (InterruptedException ex) {
+            exception = ex;
+        } finally {
+            if (lock != null) {
+                try {
+                    lock.close();
+                } catch (IOException ex) {
+                    exception = ex;
+                }
+            }
+        }
+    }
+}