Polish contribution

- Extract the logic that coerces the string into a LogLevel into a
  separate method.
- Add a test that verifies that false is mapped to LogLevel.OFF

Closes gh-3628

Author: wilkinsona

spring-boot/src/main/java/org/springframework/boot/logging/LoggingApplicationListener.java

@@ -246,18 +246,20 @@ private void setLogLevel(LoggingSystem system, Environment environment, String n
 				name = null;
 			}
 			level = environment.resolvePlaceholders(level);
-			if (Boolean.toString(false).equalsIgnoreCase(level)) {
-				system.setLogLevel(name, LogLevel.OFF);
-			}
-			else {
-				system.setLogLevel(name, LogLevel.valueOf(level.toUpperCase()));
-			}
+			system.setLogLevel(name, coerceLogLevel(level));
 		}
 		catch (RuntimeException ex) {
 			this.logger.error("Cannot set level: " + level + " for '" + name + "'");
 		}
 	}
 
+	private LogLevel coerceLogLevel(String level) {
+		if ("false".equalsIgnoreCase(level)) {
+			return LogLevel.OFF;
+		}
+		return LogLevel.valueOf(level.toUpperCase());
+	}
+
 	public void setOrder(int order) {
 		this.order = order;
 	}

spring-boot/src/test/java/org/springframework/boot/logging/LoggingApplicationListenerTests.java

@@ -258,6 +258,18 @@ public void parseLevelsNone() throws Exception {
 		assertThat(this.outputCapture.toString(), not(containsString("testatfatal")));
 	}
 
+	@Test
+	public void parseLevelsMapsFalseToOff() throws Exception {
+		EnvironmentTestUtils.addEnvironment(this.context,
+				"logging.level.org.springframework.boot=false");
+		this.initializer.initialize(this.context.getEnvironment(),
+				this.context.getClassLoader());
+		this.logger.debug("testatdebug");
+		this.logger.fatal("testatfatal");
+		assertThat(this.outputCapture.toString(), not(containsString("testatdebug")));
+		assertThat(this.outputCapture.toString(), not(containsString("testatfatal")));
+	}
+
 	@Test
 	public void parseArgsDisabled() throws Exception {
 		this.initializer.setParseArgs(false);