Merge pull request #43575 from nosan

* pr/43575:
  Polish "Logback StructuredLogFormatter exceptions are not visible to the user"
  Logback StructuredLogFormatter exceptions are not visible to the user

Closes gh-43575

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

@@ -0,0 +1,80 @@
+/*
+ * 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.logging.logback;
+
+import ch.qos.logback.core.spi.ContextAwareBase;
+import ch.qos.logback.core.spi.LifeCycle;
+import ch.qos.logback.core.status.Status;
+import ch.qos.logback.core.status.StatusListener;
+
+/**
+ * Logback {@link StatusListener} that filters {@link Status} by its logging level and
+ * delegates to the underlying {@code StatusListener}.
+ *
+ * @author Dmytro Nosan
+ */
+class FilteringStatusListener extends ContextAwareBase implements StatusListener, LifeCycle {
+
+	private final StatusListener delegate;
+
+	private final int levelThreshold;
+
+	/**
+	 * Creates a new {@link FilteringStatusListener}.
+	 * @param delegate the {@link StatusListener} delegate to
+	 * @param levelThreshold the minimum log level accepted for delegation
+	 */
+	FilteringStatusListener(StatusListener delegate, int levelThreshold) {
+		this.delegate = delegate;
+		this.levelThreshold = levelThreshold;
+	}
+
+	@Override
+	public void addStatusEvent(Status status) {
+		if (status.getLevel() >= this.levelThreshold) {
+			this.delegate.addStatusEvent(status);
+		}
+	}
+
+	@Override
+	public boolean isResetResistant() {
+		return this.delegate.isResetResistant();
+	}
+
+	@Override
+	public void start() {
+		if (this.delegate instanceof LifeCycle lifeCycle) {
+			lifeCycle.start();
+		}
+	}
+
+	@Override
+	public void stop() {
+		if (this.delegate instanceof LifeCycle lifeCycle) {
+			lifeCycle.stop();
+		}
+	}
+
+	@Override
+	public boolean isStarted() {
+		if (this.delegate instanceof LifeCycle lifeCycle) {
+			return lifeCycle.isStarted();
+		}
+		return true;
+	}
+
+}

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

@@ -36,6 +36,7 @@ import ch.qos.logback.classic.turbo.TurboFilter;
 import ch.qos.logback.core.joran.spi.JoranException;
 import ch.qos.logback.core.spi.FilterReply;
 import ch.qos.logback.core.status.OnConsoleStatusListener;
+import ch.qos.logback.core.status.OnErrorConsoleStatusListener;
 import ch.qos.logback.core.status.Status;
 import ch.qos.logback.core.status.StatusUtil;
 import ch.qos.logback.core.util.StatusListenerConfigHelper;
@@ -234,6 +235,9 @@ public class LogbackLoggingSystem extends AbstractLoggingSystem implements BeanF
 			if (debug) {
 				StatusListenerConfigHelper.addOnConsoleListenerInstance(loggerContext, new OnConsoleStatusListener());
 			}
+			else {
+				addOnErrorConsoleStatusListener(loggerContext);
+			}
 			Environment environment = initializationContext.getEnvironment();
 			// Apply system properties directly in case the same JVM runs multiple apps
 			new LogbackLoggingSystemProperties(environment, getDefaultValueResolver(environment),
@@ -487,6 +491,16 @@ public class LogbackLoggingSystem extends AbstractLoggingSystem implements BeanF
 		}
 	}
 
+	private void addOnErrorConsoleStatusListener(LoggerContext context) {
+		FilteringStatusListener listener = new FilteringStatusListener(new OnErrorConsoleStatusListener(),
+				Status.ERROR);
+		listener.setContext(context);
+		boolean effectivelyAdded = context.getStatusManager().add(listener);
+		if (effectivelyAdded) {
+			listener.start();
+		}
+	}
+
 	void setStatusPrinterStream(PrintStream stream) {
 		this.statusPrinter.setPrintStream(stream);
 	}

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

@@ -0,0 +1,121 @@
+/*
+ * 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.logging.logback;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import ch.qos.logback.core.spi.LifeCycle;
+import ch.qos.logback.core.status.ErrorStatus;
+import ch.qos.logback.core.status.InfoStatus;
+import ch.qos.logback.core.status.Status;
+import ch.qos.logback.core.status.StatusListener;
+import ch.qos.logback.core.status.WarnStatus;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link FilteringStatusListener}.
+ *
+ * @author Dmytro Nosan
+ */
+class FilteringStatusListenerTests {
+
+	private final DelegateStatusListener delegate = new DelegateStatusListener();
+
+	@Test
+	void shouldFilterOutInfoStatus() {
+		FilteringStatusListener listener = createListener(Status.WARN);
+		InfoStatus info = new InfoStatus("info", getClass());
+		WarnStatus warn = new WarnStatus("warn", getClass());
+		ErrorStatus error = new ErrorStatus("error", getClass());
+		listener.addStatusEvent(info);
+		listener.addStatusEvent(warn);
+		listener.addStatusEvent(error);
+		assertThat(this.delegate.getStatuses()).containsExactly(warn, error);
+	}
+
+	@Test
+	void shouldStartUnderlyingStatusListener() {
+		FilteringStatusListener listener = createListener(Status.INFO);
+		assertThat(this.delegate.isStarted()).isFalse();
+		listener.start();
+		assertThat(this.delegate.isStarted()).isTrue();
+	}
+
+	@Test
+	void shouldStopUnderlyingStatusListener() {
+		FilteringStatusListener listener = createListener();
+		this.delegate.start();
+		assertThat(this.delegate.isStarted()).isTrue();
+		listener.stop();
+		assertThat(this.delegate.isStarted()).isFalse();
+	}
+
+	@Test
+	void shouldUseResetResistantValueFromUnderlyingStatusListener() {
+		FilteringStatusListener listener = createListener();
+		assertThat(listener.isResetResistant()).isEqualTo(this.delegate.isResetResistant());
+	}
+
+	private FilteringStatusListener createListener() {
+		return new FilteringStatusListener(this.delegate, Status.INFO);
+	}
+
+	private FilteringStatusListener createListener(int levelThreshold) {
+		return new FilteringStatusListener(this.delegate, levelThreshold);
+	}
+
+	private static final class DelegateStatusListener implements StatusListener, LifeCycle {
+
+		private final List<Status> statuses = new ArrayList<>();
+
+		private boolean started = false;
+
+		@Override
+		public void addStatusEvent(Status status) {
+			this.statuses.add(status);
+		}
+
+		List<Status> getStatuses() {
+			return this.statuses;
+		}
+
+		@Override
+		public boolean isResetResistant() {
+			return true;
+		}
+
+		@Override
+		public void start() {
+			this.started = true;
+		}
+
+		@Override
+		public void stop() {
+			this.started = false;
+		}
+
+		@Override
+		public boolean isStarted() {
+			return this.started;
+		}
+
+	}
+
+}

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/logging/logback/LogbackLoggingSystemTests.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.
@@ -32,12 +32,18 @@ import java.util.stream.Stream;
 import ch.qos.logback.classic.Level;
 import ch.qos.logback.classic.Logger;
 import ch.qos.logback.classic.LoggerContext;
+import ch.qos.logback.classic.spi.ILoggingEvent;
 import ch.qos.logback.classic.spi.LoggerContextListener;
+import ch.qos.logback.core.AppenderBase;
 import ch.qos.logback.core.ConsoleAppender;
 import ch.qos.logback.core.encoder.LayoutWrappingEncoder;
 import ch.qos.logback.core.joran.spi.JoranException;
 import ch.qos.logback.core.rolling.RollingFileAppender;
 import ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy;
+import ch.qos.logback.core.status.OnConsoleStatusListener;
+import ch.qos.logback.core.status.OnErrorConsoleStatusListener;
+import ch.qos.logback.core.status.Status;
+import ch.qos.logback.core.status.StatusListener;
 import ch.qos.logback.core.util.DynamicClassLoadingException;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
@@ -649,12 +655,41 @@ class LogbackLoggingSystemTests extends AbstractLoggingSystemTests {
 			assertThat(output).contains("LevelChangePropagator")
 				.contains("SizeAndTimeBasedFileNamingAndTriggeringPolicy")
 				.contains("DebugLogbackConfigurator");
+			LoggerContext loggerContext = this.logger.getLoggerContext();
+			List<StatusListener> statusListeners = loggerContext.getStatusManager().getCopyOfStatusListenerList();
+			assertThat(statusListeners).hasSize(1);
+			StatusListener statusListener = statusListeners.get(0);
+			assertThat(statusListener).isInstanceOf(OnConsoleStatusListener.class);
 		}
 		finally {
 			System.clearProperty("logback.debug");
 		}
 	}
 
+	@Test
+	void logbackErrorStatusListenerShouldBeRegistered(CapturedOutput output) {
+		this.loggingSystem.beforeInitialize();
+		initialize(this.initializationContext, null, getLogFile(tmpDir() + "/tmp.log", null));
+		LoggerContext loggerContext = this.logger.getLoggerContext();
+		List<StatusListener> statusListeners = loggerContext.getStatusManager().getCopyOfStatusListenerList();
+		assertThat(statusListeners).hasSize(1);
+		StatusListener statusListener = statusListeners.get(0);
+		assertThat(statusListener).isInstanceOf(FilteringStatusListener.class);
+		assertThat(statusListener).hasFieldOrPropertyWithValue("levelThreshold", Status.ERROR);
+		assertThat(statusListener).extracting("delegate").isInstanceOf(OnErrorConsoleStatusListener.class);
+		AppenderBase<ILoggingEvent> appender = new AppenderBase<>() {
+			@Override
+			protected void append(ILoggingEvent eventObject) {
+				throw new IllegalStateException("Fail to append");
+			}
+		};
+		this.logger.addAppender(appender);
+		appender.setContext(loggerContext);
+		appender.start();
+		this.logger.info("Hello world");
+		assertThat(output).contains("Fail to append").contains("Hello world");
+	}
+
 	@Test
 	void testRollingFileNameProperty() {
 		String rollingFile = "my.log.%d{yyyyMMdd}.%i.gz";

spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-structured-logging/src/main/java/smoketest/structuredlogging/DuplicateJsonMembersCustomizer.java

@@ -0,0 +1,32 @@
+/*
+ * 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package smoketest.structuredlogging;
+
+import java.util.Objects;
+
+import org.springframework.boot.json.JsonWriter.Members;
+import org.springframework.boot.logging.structured.StructuredLoggingJsonMembersCustomizer;
+
+public class DuplicateJsonMembersCustomizer implements StructuredLoggingJsonMembersCustomizer<Object> {
+
+	@Override
+	public void customize(Members<Object> members) {
+		members.add("test").as(Objects::toString);
+		members.add("test").as(Objects::toString);
+	}
+
+}

spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-structured-logging/src/main/resources/application.properties

@@ -7,3 +7,6 @@ logging.structured.json.customizer=smoketest.structuredlogging.SampleJsonMembers
 #---
 spring.config.activate.on-profile=custom
 logging.structured.format.console=smoketest.structuredlogging.CustomStructuredLogFormatter
+#---
+spring.config.activate.on-profile=on-error
+logging.structured.json.customizer=smoketest.structuredlogging.DuplicateJsonMembersCustomizer

spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-structured-logging/src/test/java/smoketest/structuredlogging/SampleStructuredLoggingApplicationTests.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.
@@ -65,4 +65,10 @@ class SampleStructuredLoggingApplicationTests {
 		assertThat(output).contains("epoch=").contains("msg=\"Starting SampleStructuredLoggingApplication");
 	}
 
+	@Test
+	void shouldCaptureCustomizerError(CapturedOutput output) {
+		SampleStructuredLoggingApplication.main(new String[] { "--spring.profiles.active=on-error" });
+		assertThat(output).contains("The name 'test' has already been written");
+	}
+
 }