Format log messages using LogMessage.toString

And test that the method works as expected.

Signed-off-by: Curtis Rueden <ctrueden@wisc.edu>

Author: maarzt

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

@@ -31,6 +31,8 @@
 
 package org.scijava.log;
 
+import java.io.PrintWriter;
+import java.io.StringWriter;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Date;
@@ -109,7 +111,20 @@ public void attach(Object value) {
 
 	@Override
 	public String toString() {
-		return "LogMessage {" + level + ", " + message + ", " + throwable + "}";
+		return format(this);
 	}
 
+	// -- Utility methods --
+
+	public static String format(final LogMessage message) {
+		final StringWriter sw = new StringWriter();
+		final PrintWriter printer = new PrintWriter(sw);
+		printer.print("[" + message.time() + "] ");
+		printer.print("[" + LogLevel.prefix(message.level()) + "] ");
+		printer.println(message.text());
+		if (message.throwable() != null) {
+			message.throwable().printStackTrace(printer);
+		}
+		return sw.toString();
+	}
 }

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

@@ -32,6 +32,8 @@
 
 package org.scijava.log;
 
+import java.io.PrintStream;
+
 import org.scijava.Priority;
 import org.scijava.plugin.Plugin;
 import org.scijava.service.Service;
@@ -52,11 +54,7 @@ public class StderrLogService extends AbstractLogService {
 
 	@Override
 	public void alwaysLog(final int level, final Object msg, final Throwable t) {
-		final String prefix = LogLevel.prefix(level);
-		final String message = (prefix == null ? "" : prefix + " ") + msg;
-		// NB: Emit severe messages to stderr, and less severe ones to stdout.
-		if (level <= LogLevel.WARN) System.err.println(message);
-		else System.out.println(message);
-		if (t != null) t.printStackTrace();
+		final PrintStream out = (level <= LogLevel.WARN) ? System.err : System.out;
+		out.print(new LogMessage(level, msg, t));
 	}
 }

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

@@ -0,0 +1,71 @@
+/*
+ * #%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.Assert;
+import org.junit.Test;
+
+/**
+ * Tests {@link LogMessage}.
+ * 
+ * @author Matthias Arzt
+ */
+public class LogMessageTest {
+
+	/** Tests {@link LogMessage#toString()}. */
+	@Test
+	public void testToString() {
+		String nameOfThisMethod = "testToString";
+		// setup
+		LogMessage message = new LogMessage(LogLevel.DEBUG, 42, new NullPointerException());
+		// process
+		String s = message.toString();
+		//test
+		Assert.assertTrue("Log message contains level", s.contains(LogLevel.prefix(message.level())));
+		Assert.assertTrue("Log message contains msg", s.contains(message.text()));
+		Assert.assertTrue("Log message contains throwable", s.contains(message.throwable().toString()));
+		Assert.assertTrue("Log message contains stack trace", s.contains(nameOfThisMethod));
+	}
+
+	@Test
+	public void testToStringOptionalParameters() {
+		// setup
+		LogMessage message = new LogMessage(LogLevel.WARN, null, null);
+
+		// process
+		// Can it still format the message if optional parameters are null?
+		String s = message.toString();
+
+		// test
+		Assert.assertTrue("Log message contains level", s.contains(LogLevel.prefix(message.level())));
+	}
+}