AbstractLogService: fix notification of LogListerners

The method notifyListeners should only notify the log listeners.
It must NOT be used for overloading or to output log messages.

Author: maarzt

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

@@ -90,6 +90,8 @@ public void setLevelForLogger(final String source, final int level) {
 		rootLogger.getSource().subSource(source).setLogLevel(level);
 	}
 
+	abstract protected void messageLogged(LogMessage message);
+
 	// -- Logger methods --
 
 	@Override
@@ -184,7 +186,7 @@ private Map<String, Integer> setupMapFromProperties(Properties properties,
 	private class RootLogger extends DefaultLogger {
 
 		public RootLogger() {
-			super(AbstractLogService.this::notifyListeners, LogSource.newRoot(),
+			super(AbstractLogService.this::messageLogged, LogSource.newRoot(),
 				LogLevel.NONE);
 		}
 

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

@@ -61,7 +61,7 @@ public void setPrintStreams(Function<Integer, PrintStream> levelToStream) {
 	}
 
 	@Override
-	public void notifyListeners(LogMessage message) {
+	protected void messageLogged(LogMessage message) {
 		final PrintStream out = levelToStream.apply(message.level());
 		out.print(message);
 	}

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

@@ -2,6 +2,8 @@
 
 import org.junit.Test;
 
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Properties;
 import java.util.function.BiConsumer;
 import java.util.function.Function;
@@ -200,6 +202,15 @@ public void testListener() {
 		listener.hasLogged(m -> msg2.equals(m.text()));
 	}
 
+	@Test
+	public void testLogListenerIsNotifiedOnce() {
+		List<LogMessage> list = new ArrayList<>();
+		LogService logService = new TestableLogService();
+		logService.addLogListener(list::add);
+		logService.error("dummy");
+		assertEquals(1, list.size());
+	}
+
 	// -- Helper classes --
 
 	private static class MyTestClass {
@@ -241,7 +252,7 @@ public Throwable exception() {
 		}
 
 		@Override
-		public void notifyListeners(LogMessage message) {
+		protected void messageLogged(LogMessage message) {
 			this.message = message.toString();
 			this.exception = message.throwable();
 		}