LogService: tweak getCallingClass method

Extract code for calling class detection to new class CallingClassUtils.
Classes that should be ignored by the calling class detection should be
annotated with IgnoreAsCallingClass.

Author: maarzt

src/main/java/org/scijava/log/AbstractLogService.java

@@ -44,6 +44,7 @@
  * @author Johannes Schindelin
  * @author Curtis Rueden
  */
+@IgnoreAsCallingClass
 public abstract class AbstractLogService extends AbstractService implements
 	LogService
 {
@@ -88,7 +89,7 @@ public AbstractLogService(final Properties properties) {
 	public int getLevel() {
 		if (!classAndPackageLevels.isEmpty()) {
 			// check for a custom log level for calling class or its parent packages
-			String classOrPackageName = callingClass();
+			String classOrPackageName = CallingClassUtils.getCallingClass().getName();
 			while (classOrPackageName != null) {
 				final Integer level = classAndPackageLevels.get(classOrPackageName);
 				if (level != null) return level;
@@ -119,16 +120,6 @@ protected String getPrefix(final int level) {
 
 	// -- Helper methods --
 
-	private String callingClass() {
-		final String thisClass = AbstractLogService.class.getName();
-		for (final StackTraceElement element : new Exception().getStackTrace()) {
-			final String className = element.getClassName();
-			// NB: Skip stack trace elements from other methods of this class.
-			if (!thisClass.equals(className)) return className;
-		}
-		return null;
-	}
-
 	private String parentPackage(final String classOrPackageName) {
 		final int dot = classOrPackageName.lastIndexOf(".");
 		if (dot < 0) return null;

src/main/java/org/scijava/log/CallingClassUtils.java

@@ -0,0 +1,67 @@
+/*
+ * #%L
+ * SciJava Common shared library for SciJava software.
+ * %%
+ * Copyright (C) 2009 - 2017 Board of Regents of the University of
+ * Wisconsin-Madison, Broad Institute of MIT and Harvard, and Max Planck
+ * Institute of Molecular Cell Biology and Genetics.
+ * %%
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ * #L%
+ */
+
+package org.scijava.log;
+
+/**
+ * Utility class for getting the calling class of a method.
+ *
+ * @author Matthias Arzt
+ */
+
+@IgnoreAsCallingClass
+public final class CallingClassUtils {
+
+	private CallingClassUtils() {
+		// prevent instantiation of utility class
+	}
+
+	/**
+	 * Inspects the stack trace to return the class that calls this method, but
+	 * ignores every class annotated with @IgnoreAsCallingClass.
+	 *
+	 * @throws IllegalStateException if every method on the stack, is in a class
+	 *           annotated with @IgnoreAsCallingClass.
+	 */
+	public static Class<?> getCallingClass() {
+		try {
+			StackTraceElement[] stackTrace = Thread.currentThread().getStackTrace();
+			for (int i = 1; i < stackTrace.length - 1; i++) {
+				Class<?> clazz = Class.forName(stackTrace[i].getClassName());
+				if (!clazz.isAnnotationPresent(IgnoreAsCallingClass.class))
+					return clazz;
+			}
+		}
+		catch (ClassNotFoundException ignore) {}
+		throw new IllegalStateException();
+	}
+
+}

src/main/java/org/scijava/log/IgnoreAsCallingClass.java

@@ -0,0 +1,44 @@
+/*
+ * #%L
+ * SciJava Common shared library for SciJava software.
+ * %%
+ * Copyright (C) 2009 - 2017 Board of Regents of the University of
+ * Wisconsin-Madison, Broad Institute of MIT and Harvard, and Max Planck
+ * Institute of Molecular Cell Biology and Genetics.
+ * %%
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ * #L%
+ */
+
+package org.scijava.log;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/**
+ * Classes annotated with {@link IgnoreAsCallingClass} are ignored by
+ * {@link CallingClassUtils#getCallingClass()}.
+ *
+ * @author Matthias Arzt
+ */
+@Retention(RetentionPolicy.RUNTIME)
+public @interface IgnoreAsCallingClass {}

src/main/java/org/scijava/log/Logger.java

@@ -48,6 +48,7 @@
  * @see LogLevel
  * @see LogService
  */
+@IgnoreAsCallingClass
 public interface Logger {
 
 	default void debug(final Object msg) {

src/test/java/org/scijava/log/CallingClassUtilsTest.java

@@ -0,0 +1,68 @@
+/*
+ * #%L
+ * SciJava Common shared library for SciJava software.
+ * %%
+ * Copyright (C) 2009 - 2017 Board of Regents of the University of
+ * Wisconsin-Madison, Broad Institute of MIT and Harvard, and Max Planck
+ * Institute of Molecular Cell Biology and Genetics.
+ * %%
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ * #L%
+ */
+
+package org.scijava.log;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Tests {@link CallingClassUtils}.
+ * 
+ * @author Matthias Arzt
+ */
+public class CallingClassUtilsTest {
+	@Test
+	public void testGetCallingClass() {
+		Class<?> callingClass = CallingClassUtils.getCallingClass();
+		assertEquals(this.getClass(), callingClass);
+	}
+
+	@Test
+	public void testIgnoreAsCallingClass() {
+		assertEquals(ClassA.class, ClassA.returnGetCallingClass());
+		assertEquals(this.getClass(), ClassB.returnGetCallingClass());
+	}
+
+	public static class ClassA {
+		static Class<?> returnGetCallingClass() {
+			return CallingClassUtils.getCallingClass();
+		}
+	}
+
+	@IgnoreAsCallingClass
+	private static class ClassB {
+		static Class<?> returnGetCallingClass() {
+			return CallingClassUtils.getCallingClass();
+		}
+	}
+}