Start Threshold filters in DefaultLogbackConfiguration

Closes gh-36741

Author: mhalbritter

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

@@ -100,6 +100,7 @@ private Appender<ILoggingEvent> consoleAppender(LogbackConfigurator config) {
 		ConsoleAppender<ILoggingEvent> appender = new ConsoleAppender<>();
 		ThresholdFilter filter = new ThresholdFilter();
 		filter.setLevel(resolve(config, "${CONSOLE_LOG_THRESHOLD}"));
+		filter.start();
 		appender.addFilter(filter);
 		PatternLayoutEncoder encoder = new PatternLayoutEncoder();
 		encoder.setPattern(resolve(config, "${CONSOLE_LOG_PATTERN}"));
@@ -114,6 +115,7 @@ private Appender<ILoggingEvent> fileAppender(LogbackConfigurator config, String
 		RollingFileAppender<ILoggingEvent> appender = new RollingFileAppender<>();
 		ThresholdFilter filter = new ThresholdFilter();
 		filter.setLevel(resolve(config, "${FILE_LOG_THRESHOLD}"));
+		filter.start();
 		appender.addFilter(filter);
 		PatternLayoutEncoder encoder = new PatternLayoutEncoder();
 		encoder.setPattern(resolve(config, "${FILE_LOG_PATTERN}"));

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

@@ -21,6 +21,7 @@
 import java.lang.reflect.Modifier;
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
+import java.nio.file.Path;
 import java.util.Arrays;
 import java.util.EnumSet;
 import java.util.HashSet;
@@ -87,6 +88,7 @@
  * @author Robert Thornton
  * @author Eddú Meléndez
  * @author Scott Frederick
+ * @author Moritz Halbritter
  */
 @ExtendWith(OutputCaptureExtension.class)
 class LogbackLoggingSystemTests extends AbstractLoggingSystemTests {
@@ -706,6 +708,29 @@ void whenConfigLocationIsXmlAndHasQueryParametersThenIllegalArgumentExceptionSho
 			.satisfies((ex) -> assertThat(ex.getCause()).isNotInstanceOf(IllegalArgumentException.class));
 	}
 
+	@Test
+	void shouldRespectConsoleThreshold(CapturedOutput output) {
+		this.environment.setProperty("logging.threshold.console", "warn");
+		this.loggingSystem.beforeInitialize();
+		initialize(this.initializationContext, null, null);
+		this.logger.info("Some info message");
+		this.logger.warn("Some warn message");
+		assertThat(output).doesNotContain("Some info message").contains("Some warn message");
+	}
+
+	@Test
+	void shouldRespectFileThreshold() {
+		this.environment.setProperty("logging.threshold.file", "warn");
+		this.loggingSystem.beforeInitialize();
+		initialize(this.initializationContext, null, getLogFile(null, tmpDir()));
+		this.logger.info("Some info message");
+		this.logger.warn("Some warn message");
+		Path file = Path.of(tmpDir(), "spring.log");
+		assertThat(file).content(StandardCharsets.UTF_8)
+			.doesNotContain("Some info message")
+			.contains("Some warn message");
+	}
+
 	private void initialize(LoggingInitializationContext context, String configLocation, LogFile logFile) {
 		this.loggingSystem.getSystemProperties((ConfigurableEnvironment) context.getEnvironment()).apply(logFile);
 		this.loggingSystem.initialize(context, configLocation, logFile);