When Logback's in use, route JBoss Logging straight into SLF4J

Prior to this change, when using spring-boot-starter-logging, JBoss
Logging would route like this:

JBoss Logging -> Log4j2 API -> SLF4J -> Logback

This is inefficient as there's no need for it to go via the Log4j2
API.

This commit updates the Logback logging system to configure a system
property that controls JBoss's routing. With this change in place,
JBoss Logging will route like this:

JBoss Logging -> SLF4J -> Logback

Closes gh-33155

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

@@ -20,6 +20,7 @@
 import java.util.function.BiConsumer;
 
 import ch.qos.logback.core.util.FileSize;
+import org.flywaydb.core.internal.util.ClassUtils;
 
 import org.springframework.boot.logging.LogFile;
 import org.springframework.boot.logging.LoggingSystemProperties;
@@ -37,6 +38,9 @@
  */
 public class LogbackLoggingSystemProperties extends LoggingSystemProperties {
 
+	private static final boolean JBOSS_LOGGING_PRESENT = ClassUtils.isPresent("org.jboss.logging.Logger",
+			LogbackLoggingSystemProperties.class.getClassLoader());
+
 	/**
 	 * The name of the System property that contains the rolled-over log file name
 	 * pattern.
@@ -85,6 +89,17 @@ protected Charset getDefaultCharset() {
 	@Override
 	protected void apply(LogFile logFile, PropertyResolver resolver) {
 		super.apply(logFile, resolver);
+		applyJBossLoggingProperties();
+		applyRollingPolicyProperties(resolver);
+	}
+
+	private void applyJBossLoggingProperties() {
+		if (JBOSS_LOGGING_PRESENT) {
+			setSystemProperty("org.jboss.logging.provider", "slf4j");
+		}
+	}
+
+	private void applyRollingPolicyProperties(PropertyResolver resolver) {
 		applyRollingPolicy(resolver, ROLLINGPOLICY_FILE_NAME_PATTERN, "logging.logback.rollingpolicy.file-name-pattern",
 				"logging.pattern.rolling-file-name");
 		applyRollingPolicy(resolver, ROLLINGPOLICY_CLEAN_HISTORY_ON_START,

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/logging/logback/LogbackLoggingSystemTests.java

@@ -55,6 +55,7 @@
 import org.springframework.boot.logging.LoggingInitializationContext;
 import org.springframework.boot.logging.LoggingSystem;
 import org.springframework.boot.logging.LoggingSystemProperties;
+import org.springframework.boot.testsupport.classpath.ClassPathOverrides;
 import org.springframework.boot.testsupport.system.CapturedOutput;
 import org.springframework.boot.testsupport.system.OutputCaptureExtension;
 import org.springframework.core.convert.ConversionService;
@@ -118,6 +119,22 @@ void cleanUp() {
 		((LoggerContext) LoggerFactory.getILoggerFactory()).stop();
 	}
 
+	@Test
+	@ClassPathOverrides("org.jboss.logging:jboss-logging:3.5.0.Final")
+	void jbossLoggingRoutesThroughLog4j2ByDefault() {
+		org.jboss.logging.Logger jbossLogger = org.jboss.logging.Logger.getLogger(getClass());
+		assertThat(jbossLogger.getClass().getName()).isEqualTo("org.jboss.logging.Log4j2Logger");
+	}
+
+	@Test
+	@ClassPathOverrides("org.jboss.logging:jboss-logging:3.5.0.Final")
+	void jbossLoggingRoutesThroughSlf4jWhenLoggingSystemIsInitialized() {
+		this.loggingSystem.beforeInitialize();
+		initialize(this.initializationContext, null, null);
+		assertThat(org.jboss.logging.Logger.getLogger(getClass()).getClass().getName())
+				.isEqualTo("org.jboss.logging.Slf4jLocationAwareLogger");
+	}
+
 	@Test
 	void noFile(CapturedOutput output) {
 		this.loggingSystem.beforeInitialize();
@@ -523,6 +540,7 @@ void initializeShouldApplyLogbackSystemPropertiesToTheContext() {
 		ReflectionUtils.doWithFields(LogbackLoggingSystemProperties.class,
 				(field) -> expectedProperties.add((String) field.get(null)), this::isPublicStaticFinal);
 		expectedProperties.removeAll(Arrays.asList("LOG_FILE", "LOG_PATH"));
+		expectedProperties.add("org.jboss.logging.provider");
 		assertThat(properties).containsOnlyKeys(expectedProperties);
 		assertThat(properties).containsEntry("CONSOLE_LOG_CHARSET", Charset.defaultCharset().name());
 	}