Revert "Remove unnecessary code"

Fixes gh-24835

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

@@ -54,6 +54,7 @@
 import org.springframework.core.SpringProperties;
 import org.springframework.core.annotation.Order;
 import org.springframework.core.env.ConfigurableEnvironment;
+import org.springframework.core.env.Environment;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.ResourceUtils;
@@ -147,6 +148,13 @@ protected void loadDefaults(LoggingInitializationContext initializationContext,
 		}
 		LogbackConfigurator configurator = debug ? new DebugLogbackConfigurator(context)
 				: new LogbackConfigurator(context);
+		Environment environment = initializationContext.getEnvironment();
+		context.putProperty(LoggingSystemProperties.LOG_LEVEL_PATTERN,
+				environment.resolvePlaceholders("${logging.pattern.level:${LOG_LEVEL_PATTERN:%5p}}"));
+		context.putProperty(LoggingSystemProperties.LOG_DATEFORMAT_PATTERN, environment.resolvePlaceholders(
+				"${logging.pattern.dateformat:${LOG_DATEFORMAT_PATTERN:yyyy-MM-dd HH:mm:ss.SSS}}"));
+		context.putProperty(LoggingSystemProperties.ROLLING_FILE_NAME_PATTERN, environment
+				.resolvePlaceholders("${logging.pattern.rolling-file-name:${LOG_FILE}.%d{yyyy-MM-dd}.%i.gz}"));
 		new DefaultLogbackConfiguration(initializationContext, logFile).apply(configurator);
 		context.setPackagingDataEnabled(true);
 	}

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

@@ -20,9 +20,7 @@
 import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 import java.util.EnumSet;
-import java.util.HashSet;
 import java.util.List;
-import java.util.Set;
 import java.util.logging.Handler;
 import java.util.logging.LogManager;
 
@@ -89,13 +87,10 @@ class LogbackLoggingSystemTests extends AbstractLoggingSystemTests {
 
 	private LoggingInitializationContext initializationContext;
 
-	private Set<Object> systemPropertyNames;
-
 	@BeforeEach
 	void setup() {
 		System.getProperties().remove(LoggingSystemProperties.CONSOLE_LOG_CHARSET);
 		System.getProperties().remove(LoggingSystemProperties.FILE_LOG_CHARSET);
-		this.systemPropertyNames = new HashSet<>(System.getProperties().keySet());
 		this.loggingSystem.cleanUp();
 		this.logger = ((LoggerContext) StaticLoggerBinder.getSingleton().getLoggerFactory()).getLogger(getClass());
 		this.environment = new MockEnvironment();
@@ -106,7 +101,6 @@ void setup() {
 
 	@AfterEach
 	void cleanUp() {
-		System.getProperties().keySet().retainAll(this.systemPropertyNames);
 		this.loggingSystem.cleanUp();
 		((LoggerContext) StaticLoggerBinder.getSingleton().getLoggerFactory()).stop();
 	}
@@ -318,7 +312,6 @@ void testConsolePatternProperty(CapturedOutput output) {
 	@Test
 	void testLevelPatternProperty(CapturedOutput output) {
 		this.environment.setProperty("logging.pattern.level", "X%clr(%p)X");
-		new LoggingSystemProperties(this.environment).apply();
 		LoggingInitializationContext loggingInitializationContext = new LoggingInitializationContext(this.environment);
 		initialize(loggingInitializationContext, null, null);
 		this.logger.info("Hello world");
@@ -521,7 +514,6 @@ void initializationIsOnlyPerformedOnceUntilCleanedUp() {
 	@Test
 	void testDateformatPatternProperty(CapturedOutput output) {
 		this.environment.setProperty("logging.pattern.dateformat", "yyyy-MM-dd'T'hh:mm:ss.SSSZ");
-		new LoggingSystemProperties(this.environment).apply();
 		LoggingInitializationContext loggingInitializationContext = new LoggingInitializationContext(this.environment);
 		initialize(loggingInitializationContext, null, null);
 		this.logger.info("Hello world");