A field trial for the automatically named logger.

Can be enabled with -Dorg.slf4j.LoggerFactory.autoNamedLoggerFieldTrial=true.

Prints an error (and stacktrace) to stderr when a mismatch between custom and automatic logger names is detected.

slf4j-api/src/main/java/org/slf4j/LoggerFactory.java

@@ -82,6 +82,13 @@ public final class LoggerFactory {
   static SubstituteLoggerFactory TEMP_FACTORY = new SubstituteLoggerFactory();
   static NOPLoggerFactory NOP_FALLBACK_FACTORY = new NOPLoggerFactory();
 
+  // Support for the automatically-named logger field trial.
+  static final String AUTO_NAMED_LOGGER_FIELD_TRIAL_PROPERTY =
+      "org.slf4j.LoggerFactory.autoNamedLoggerFieldTrial";
+  static boolean AUTO_NAMED_LOGGER_FIELD_TRIAL =
+      Boolean.getBoolean(AUTO_NAMED_LOGGER_FIELD_TRIAL_PROPERTY);
+
+
   /**
    * It is LoggerFactory's responsibility to track version changes and manage
    * the compatibility list.
@@ -293,8 +300,21 @@ public final class LoggerFactory {
    * @return logger
    */
   @Nonnull
-  public static Logger getLogger(@Nonnull Class clazz) {
-    return getLogger(clazz.getName());
+  public static Logger getLogger(@Nonnull Class<?> clazz) {
+    Logger logger = getLogger(clazz.getName());
+    if (AUTO_NAMED_LOGGER_FIELD_TRIAL) {
+      String autoName = Util.getCallingClassName();
+      if (!logger.getName().equals(autoName)) {
+        IllegalStateException exception = new IllegalStateException(String.format(
+            "Auto-named logger field trial: mismatch detected between " +
+            "given logger name and automatic logger name. Given name: \"%s\"; " +
+            "automatic name: \"%s\". If this is unexpected, please file a bug " +
+            "against slf4j. Set property %s to \"false\" to disable this check.",
+            logger.getName(), autoName, AUTO_NAMED_LOGGER_FIELD_TRIAL_PROPERTY));
+        exception.printStackTrace(System.err);
+      }
+    }
+    return logger;
   }
 
   /**

slf4j-api/src/main/java/org/slf4j/helpers/Util.java

@@ -31,8 +31,48 @@ package org.slf4j.helpers;
  *
  * @author Ceki Gülcü
  */
-public class Util {
-    
+public final class Util {
+
+  private Util() {}
+
+  /**
+   * In order to call {@link SecurityManager#getClassContext()}, which is a
+   * protected method, we add this wrapper which allows the method to be visible
+   * inside this package.
+   */
+  private static final class ClassContextSecurityManager extends SecurityManager {
+    protected Class<?>[] getClassContext() {
+      return super.getClassContext();
+    }
+  };
+  private static final ClassContextSecurityManager SECURITY_MANAGER =
+      new ClassContextSecurityManager();
+
+  /**
+   * Returns the name of the class which called the invoking method.
+   * @return the name of the class which called the invoking method.
+   */
+  public static String getCallingClassName() {
+    Class<?>[] trace = SECURITY_MANAGER.getClassContext();
+    String thisClassName = Util.class.getName();
+
+    // Advance until Util is found
+    int i;
+    for (i = 0 ; i < trace.length ; i++) {
+      if (thisClassName.equals(trace[i].getName()))
+        break;
+    }
+
+    // trace[i] = Util; trace[i+1] = caller; trace[i+2] = caller's caller
+    if (i >= trace.length || i + 2 >= trace.length) {
+      throw new IllegalStateException(
+          "Failed to find org.slf4j.helpers.Util or its caller in the stack; " +
+          "this should not happen");
+    }
+
+    return trace[i+2].getName();
+  }
+
   static final public void report(String msg, Throwable t) {
     System.err.println(msg);
     System.err.println("Reported exception:");

slf4j-simple/src/test/java/org/slf4j/AutoNamedLoggerFieldTrialTest.java

@@ -0,0 +1,125 @@
+/**
+ * Copyright (c) 2004-2011 QOS.ch
+ * All rights reserved.
+ *
+ * Permission is hereby granted, free  of charge, to any person obtaining
+ * a  copy  of this  software  and  associated  documentation files  (the
+ * "Software"), to  deal in  the Software without  restriction, including
+ * without limitation  the rights to  use, copy, modify,  merge, publish,
+ * distribute,  sublicense, and/or sell  copies of  the Software,  and to
+ * permit persons to whom the Software  is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The  above  copyright  notice  and  this permission  notice  shall  be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE  SOFTWARE IS  PROVIDED  "AS  IS", WITHOUT  WARRANTY  OF ANY  KIND,
+ * EXPRESS OR  IMPLIED, INCLUDING  BUT NOT LIMITED  TO THE  WARRANTIES OF
+ * MERCHANTABILITY,    FITNESS    FOR    A   PARTICULAR    PURPOSE    AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE,  ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
+package org.slf4j;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+/**
+ * Tests that the automatically named logger field trial works and
+ * doesn't cause problems or trigger if disabled.
+ * <p>
+ * This test can't live inside slf4j-api because the NOP Logger doesn't
+ * remember its name.
+ */
+public class AutoNamedLoggerFieldTrialTest {
+
+  private static final String MISMATCH_STRING = "Auto-named logger field trial: mismatch detected";
+
+  private final ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
+  private final PrintStream oldErr = System.err;
+
+  @Before
+  public void setUp() {
+    System.setErr(new PrintStream(byteArrayOutputStream));
+  }
+
+  @After
+  public void tearDown() {
+    setTrialEnabled(false);
+    System.setErr(oldErr);
+  }
+
+  /*
+   * Pass in the wrong class to the Logger with the field trial disabled, and
+   * make sure there are no errors.
+   */
+  @Test
+  public void testNoTriggerWithoutProperty() {
+    setTrialEnabled(false);
+    Logger logger = LoggerFactory.getLogger(String.class);
+    assertEquals("java.lang.String", logger.getName());
+    assertIsMismatch(false);
+  }
+
+  /*
+   * Pass in the wrong class to the Logger with the field trial enabled, and
+   * make sure there ARE errors.
+   */
+  @Test
+  public void testTriggerWithProperty() {
+    setTrialEnabled(true);
+    LoggerFactory.getLogger(String.class);
+    assertIsMismatch(true);
+  }
+
+  /*
+   * Checks the whole error message to ensure all the names show up correctly.
+   */
+  @Test
+  public void testTriggerWholeMessage() {
+    setTrialEnabled(true);
+    LoggerFactory.getLogger(String.class);
+    assertTrue(String.valueOf(byteArrayOutputStream).contains(
+      "Auto-named logger field trial: mismatch detected between given logger " +
+      "name and automatic logger name. Given name: \"java.lang.String\"; " +
+      "automatic name: \"org.slf4j.AutoNamedLoggerFieldTrialTest\". If this " +
+      "is unexpected, please file a bug against slf4j. Set property " +
+      "org.slf4j.LoggerFactory.autoNamedLoggerFieldTrial to \"false\" to " +
+      "disable this check."));
+  }
+
+  /*
+   * Checks that there are no errors with the trial enabled if the
+   * class matches.
+   */
+  @Test
+  public void testPassIfMatch() {
+    setTrialEnabled(true);
+    Logger logger = LoggerFactory.getLogger(AutoNamedLoggerFieldTrialTest.class);
+    assertEquals("org.slf4j.AutoNamedLoggerFieldTrialTest", logger.getName());
+    assertIsMismatch(false);
+  }
+
+  private void assertIsMismatch(boolean isMismatch) {
+    assertEquals(
+        isMismatch,
+        String.valueOf(byteArrayOutputStream).contains(MISMATCH_STRING));
+  }
+
+  private static void setTrialEnabled(boolean enabled) {
+    // The system property is read into a static variable at initialization time
+    // so we cannot just reset the system property to test this feature.
+    // Therefore we set the variable directly.
+    LoggerFactory.AUTO_NAMED_LOGGER_FIELD_TRIAL = enabled;
+  }
+}