Register Logback's pattern conversion rule using Suppliers

This commit makes use of a feature introduced in LogBack 1.5.15 that
allows converter to be specified using a supplier rather than a fully
qualified class name.

Closes gh-43588

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,8 @@
 
 package org.springframework.boot.logging.logback;
 
+import java.util.function.Supplier;
+
 import ch.qos.logback.classic.Level;
 import ch.qos.logback.classic.LoggerContext;
 import ch.qos.logback.classic.spi.ILoggingEvent;
@@ -38,10 +40,10 @@ class DebugLogbackConfigurator extends LogbackConfigurator {
 	}
 
 	@Override
-	@SuppressWarnings("rawtypes")
-	public void conversionRule(String conversionWord, Class<? extends Converter> converterClass) {
+	<T extends Converter<?>> void conversionRule(String conversionWord, Class<T> converterClass,
+			Supplier<T> converterSupplier) {
 		info("Adding conversion rule of type '" + converterClass.getName() + "' for word '" + conversionWord + "'");
-		super.conversionRule(conversionWord, converterClass);
+		super.conversionRule(conversionWord, converterClass, converterSupplier);
 	}
 
 	@Override

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2024 the original author or authors.
+ * Copyright 2012-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -99,11 +99,12 @@ void apply(LogbackConfigurator config) {
 
 	private void defaults(LogbackConfigurator config) {
 		deprecatedDefaults(config);
-		config.conversionRule("clr", ColorConverter.class);
-		config.conversionRule("correlationId", CorrelationIdConverter.class);
-		config.conversionRule("esb", EnclosedInSquareBracketsConverter.class);
-		config.conversionRule("wex", WhitespaceThrowableProxyConverter.class);
-		config.conversionRule("wEx", ExtendedWhitespaceThrowableProxyConverter.class);
+		config.conversionRule("clr", ColorConverter.class, ColorConverter::new);
+		config.conversionRule("correlationId", CorrelationIdConverter.class, CorrelationIdConverter::new);
+		config.conversionRule("esb", EnclosedInSquareBracketsConverter.class, EnclosedInSquareBracketsConverter::new);
+		config.conversionRule("wex", WhitespaceThrowableProxyConverter.class, WhitespaceThrowableProxyConverter::new);
+		config.conversionRule("wEx", ExtendedWhitespaceThrowableProxyConverter.class,
+				ExtendedWhitespaceThrowableProxyConverter::new);
 		putProperty(config, "CONSOLE_LOG_PATTERN", CONSOLE_LOG_PATTERN);
 		putProperty(config, "CONSOLE_LOG_CHARSET", "${CONSOLE_LOG_CHARSET:-" + DEFAULT_CHARSET + "}");
 		putProperty(config, "CONSOLE_LOG_THRESHOLD", "${CONSOLE_LOG_THRESHOLD:-TRACE}");
@@ -124,7 +125,7 @@ private void defaults(LogbackConfigurator config) {
 
 	@SuppressWarnings("removal")
 	private void deprecatedDefaults(LogbackConfigurator config) {
-		config.conversionRule("applicationName", ApplicationNameConverter.class);
+		config.conversionRule("applicationName", ApplicationNameConverter.class, ApplicationNameConverter::new);
 	}
 
 	void putProperty(LogbackConfigurator config, String name, String val) {

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2024 the original author or authors.
+ * Copyright 2012-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,6 +19,7 @@
 import java.util.HashMap;
 import java.util.Map;
 import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Supplier;
 
 import ch.qos.logback.classic.Level;
 import ch.qos.logback.classic.Logger;
@@ -54,17 +55,18 @@ ReentrantLock getConfigurationLock() {
 		return this.context.getConfigurationLock();
 	}
 
-	@SuppressWarnings({ "rawtypes", "unchecked" })
-	void conversionRule(String conversionWord, Class<? extends Converter> converterClass) {
+	@SuppressWarnings("unchecked")
+	<T extends Converter<?>> void conversionRule(String conversionWord, Class<T> converterClass,
+			Supplier<T> converterSupplier) {
 		Assert.hasLength(conversionWord, "Conversion word must not be empty");
-		Assert.notNull(converterClass, "Converter class must not be null");
-		Map<String, String> registry = (Map<String, String>) this.context
-			.getObject(CoreConstants.PATTERN_RULE_REGISTRY);
+		Assert.notNull(converterSupplier, "Converter supplier must not be null");
+		Map<String, Supplier<?>> registry = (Map<String, Supplier<?>>) this.context
+			.getObject(CoreConstants.PATTERN_RULE_REGISTRY_FOR_SUPPLIERS);
 		if (registry == null) {
 			registry = new HashMap<>();
-			this.context.putObject(CoreConstants.PATTERN_RULE_REGISTRY, registry);
+			this.context.putObject(CoreConstants.PATTERN_RULE_REGISTRY_FOR_SUPPLIERS, registry);
 		}
-		registry.put(conversionWord, converterClass.getName());
+		registry.put(conversionWord, converterSupplier);
 	}
 
 	void appender(String name, Appender<?> appender) {

spring-boot-project/spring-boot/src/main/resources/org/springframework/boot/logging/logback/defaults.xml

@@ -8,7 +8,7 @@ Default logback configuration provided for import
 	<conversionRule conversionWord="applicationName" class="org.springframework.boot.logging.logback.ApplicationNameConverter"/>
 	<conversionRule conversionWord="clr" class="org.springframework.boot.logging.logback.ColorConverter"/>
 	<conversionRule conversionWord="correlationId" class="org.springframework.boot.logging.logback.CorrelationIdConverter"/>
-	<conversionRule  conversionWord="esb" class="org.springframework.boot.logging.logback.EnclosedInSquareBracketsConverter" />
+	<conversionRule conversionWord="esb" class="org.springframework.boot.logging.logback.EnclosedInSquareBracketsConverter" />
 	<conversionRule conversionWord="wex" class="org.springframework.boot.logging.logback.WhitespaceThrowableProxyConverter" />
 	<conversionRule conversionWord="wEx" class="org.springframework.boot.logging.logback.ExtendedWhitespaceThrowableProxyConverter" />