Fail fast when a Logback configuration file is missing or malformed

Closes gh-3309

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

@@ -206,10 +206,11 @@ public class LoggingApplicationListener implements GenericApplicationListener {
 				system.initialize(logConfig, logFile);
 			}
 			catch (Exception ex) {
-				this.logger.warn("Logging environment value '" + logConfig
+				System.err
-						+ "' cannot be opened and will be ignored "
+						.println("Logging system failed to initialize using configuration from '"
-						+ "(using default location instead)");
+								+ logConfig + "'");
-				system.initialize(null, logFile);
+				ex.printStackTrace(System.err);
+				throw new IllegalStateException(ex);
 			}
 		}
 		else {

spring-boot/src/main/java/org/springframework/boot/logging/logback/LogbackLoggingSystem.java

@@ -21,6 +21,7 @@ import java.security.CodeSource;
 import java.security.ProtectionDomain;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import org.slf4j.ILoggerFactory;
@@ -40,6 +41,7 @@ import ch.qos.logback.classic.LoggerContext;
 import ch.qos.logback.classic.turbo.TurboFilter;
 import ch.qos.logback.classic.util.ContextInitializer;
 import ch.qos.logback.core.spi.FilterReply;
+import ch.qos.logback.core.status.Status;
 
 /**
  * {@link LoggingSystem} for <a href="http://logback.qos.ch">logback</a>.
@@ -122,6 +124,22 @@ public class LogbackLoggingSystem extends Slf4JLoggingSystem {
 			throw new IllegalStateException("Could not initialize Logback logging from "
 					+ location, ex);
 		}
+		List<Status> statuses = context.getStatusManager().getCopyOfStatusList();
+		if (containsError(statuses)) {
+			for (Status status : statuses) {
+				System.err.println(status);
+			}
+			throw new IllegalStateException("Logback configuration error detected");
+		}
+	}
+
+	private boolean containsError(List<Status> statuses) {
+		for (Status status : statuses) {
+			if (status.getLevel() == Status.ERROR) {
+				return true;
+			}
+		}
+		return false;
 	}
 
 	@Override

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

@@ -29,6 +29,7 @@ import org.junit.After;
 import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 import org.junit.rules.TemporaryFolder;
 import org.slf4j.bridge.SLF4JBridgeHandler;
 import org.springframework.boot.SpringApplication;
@@ -56,6 +57,9 @@ public class LoggingApplicationListenerTests {
 
 	private static final String[] NO_ARGS = {};
 
+	@Rule
+	public ExpectedException thrown = ExpectedException.none();
+
 	@Rule
 	public TemporaryFolder temporaryFolder = new TemporaryFolder();
 
@@ -129,14 +133,23 @@ public class LoggingApplicationListenerTests {
 	public void overrideConfigDoesNotExist() throws Exception {
 		EnvironmentTestUtils.addEnvironment(this.context,
 				"logging.config: doesnotexist.xml");
+		this.thrown.expect(IllegalStateException.class);
+		this.outputCapture
+				.expect(containsString("Logging system failed to initialize using configuration from 'doesnotexist.xml'"));
+		this.initializer.initialize(this.context.getEnvironment(),
+				this.context.getClassLoader());
+	}
+
+	@Test
+	public void overrideConfigBroken() throws Exception {
+		EnvironmentTestUtils.addEnvironment(this.context,
+				"logging.config: classpath:logback-broken.xml");
+		this.thrown.expect(IllegalStateException.class);
+		this.outputCapture
+				.expect(containsString("Logging system failed to initialize using configuration from 'classpath:logback-broken.xml'"));
+		this.outputCapture.expect(containsString("ConsolAppender"));
 		this.initializer.initialize(this.context.getEnvironment(),
 				this.context.getClassLoader());
-		// Should not throw
-		this.logger.info("Hello world");
-		String output = this.outputCapture.toString().trim();
-		assertTrue("Wrong output:\n" + output, output.contains("Hello world"));
-		assertFalse("Wrong output:\n" + output, output.contains("???"));
-		assertFalse(new File(tmpDir() + "/spring.log").exists());
 	}
 
 	@Test

spring-boot/src/test/resources/logback-broken.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+	<appender name="CONSOLE" class="ch.qos.logback.core.ConsolAppender">
+		<encoder>
+			<pattern>${LOG_FILE} [%t] ${PID:-????} %c{1}: %m%n BOOTBOOT</pattern>
+		</encoder>
+	</appender>
+	<root level="INFO">
+		<appender-ref ref="CONSOLE" />
+	</root>
+</configuration>