Switch Logback's file logging charset to UTF-8

This commit aligns the file charset between Log4j2 and Logback.

Prior to this commit, there was an inconsistency between the two: Log4j2
used UTF-8, while Logback used Charset.defaultCharset(), which is
platform-dependent.

See gh-46846

Signed-off-by: Dmytro Nosan <dimanosan@gmail.com>

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

@@ -16,7 +16,9 @@
 
 package org.springframework.boot.logging.logback;
 
+import java.io.Console;
 import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
 
 import ch.qos.logback.classic.Level;
 import ch.qos.logback.classic.encoder.PatternLayoutEncoder;
@@ -55,7 +57,7 @@ import org.springframework.util.StringUtils;
  */
 class DefaultLogbackConfiguration {
 
-	private static final String DEFAULT_CHARSET = Charset.defaultCharset().name();
+	private static final String DEFAULT_CHARSET = StandardCharsets.UTF_8.name();
 
 	private static final String NAME_AND_GROUP = "%esb(){APPLICATION_NAME}%esb{APPLICATION_GROUP}";
 
@@ -106,7 +108,7 @@ class DefaultLogbackConfiguration {
 		config.conversionRule("wEx", ExtendedWhitespaceThrowableProxyConverter.class,
 				ExtendedWhitespaceThrowableProxyConverter::new);
 		putProperty(config, "CONSOLE_LOG_PATTERN", CONSOLE_LOG_PATTERN);
-		putProperty(config, "CONSOLE_LOG_CHARSET", "${CONSOLE_LOG_CHARSET:-" + DEFAULT_CHARSET + "}");
+		putProperty(config, "CONSOLE_LOG_CHARSET", "${CONSOLE_LOG_CHARSET:-" + getConsoleCharset() + "}");
 		putProperty(config, "CONSOLE_LOG_THRESHOLD", "${CONSOLE_LOG_THRESHOLD:-TRACE}");
 		putProperty(config, "CONSOLE_LOG_STRUCTURED_FORMAT", "${CONSOLE_LOG_STRUCTURED_FORMAT:-}");
 		putProperty(config, "FILE_LOG_PATTERN", FILE_LOG_PATTERN);
@@ -123,6 +125,15 @@ class DefaultLogbackConfiguration {
 		config.logger("org.springframework.boot.actuate.endpoint.jmx", Level.WARN);
 	}
 
+	private String getConsoleCharset() {
+		Console console = getConsole();
+		return (console != null) ? console.charset().name() : DEFAULT_CHARSET;
+	}
+
+	@Nullable Console getConsole() {
+		return System.console();
+	}
+
 	void putProperty(LogbackConfigurator config, String name, String val) {
 		config.getContext().putProperty(name, resolve(config, val));
 	}

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

@@ -17,7 +17,6 @@
 package org.springframework.boot.logging.logback;
 
 import java.io.Console;
-import java.nio.charset.Charset;
 import java.util.function.BiConsumer;
 import java.util.function.Function;
 
@@ -78,11 +77,6 @@ public class LogbackLoggingSystemProperties extends LoggingSystemProperties {
 		return super.getConsole();
 	}
 
-	@Override
-	protected Charset getDefaultFileCharset() {
-		return Charset.defaultCharset();
-	}
-
 	@Override
 	protected void apply(@Nullable LogFile logFile, PropertyResolver resolver) {
 		super.apply(logFile, resolver);

core/spring-boot/src/test/java/org/springframework/boot/logging/logback/DefaultLogbackConfigurationTests.java

@@ -16,14 +16,19 @@
 
 package org.springframework.boot.logging.logback;
 
+import java.io.Console;
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 
+import ch.qos.logback.classic.LoggerContext;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.util.StreamUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.spy;
 
 /**
  * Tests for {@link DefaultLogbackConfiguration}
@@ -32,6 +37,10 @@ import static org.assertj.core.api.Assertions.assertThat;
  */
 class DefaultLogbackConfigurationTests {
 
+	private final LoggerContext loggerContext = new LoggerContext();
+
+	private final LogbackConfigurator logbackConfigurator = new LogbackConfigurator(this.loggerContext);
+
 	@Test
 	void defaultLogbackXmlContainsConsoleLogPattern() throws Exception {
 		assertThatDefaultXmlContains("CONSOLE_LOG_PATTERN", DefaultLogbackConfiguration.CONSOLE_LOG_PATTERN);
@@ -42,6 +51,48 @@ class DefaultLogbackConfigurationTests {
 		assertThatDefaultXmlContains("FILE_LOG_PATTERN", DefaultLogbackConfiguration.FILE_LOG_PATTERN);
 	}
 
+	@Test
+	void consoleLogCharsetShouldUseConsoleCharsetIfConsoleAvailable() {
+		DefaultLogbackConfiguration logbackConfiguration = spy(new DefaultLogbackConfiguration(null));
+		Console console = mock(Console.class);
+		given(console.charset()).willReturn(StandardCharsets.UTF_16);
+		given(logbackConfiguration.getConsole()).willReturn(console);
+		logbackConfiguration.apply(this.logbackConfigurator);
+		assertThat(this.loggerContext.getProperty("CONSOLE_LOG_CHARSET")).isEqualTo(StandardCharsets.UTF_16.name());
+	}
+
+	@Test
+	void consoleLogCharsetShouldDefaultToUtf8WhenConsoleIsNull() {
+		DefaultLogbackConfiguration logbackConfiguration = spy(new DefaultLogbackConfiguration(null));
+		given(logbackConfiguration.getConsole()).willReturn(null);
+		logbackConfiguration.apply(this.logbackConfigurator);
+		assertThat(this.loggerContext.getProperty("CONSOLE_LOG_CHARSET")).isEqualTo(StandardCharsets.UTF_8.name());
+	}
+
+	@Test
+	void consoleLogCharsetShouldUseSystemPropertyIfSet() {
+		withSystemProperty("CONSOLE_LOG_CHARSET", StandardCharsets.US_ASCII.name(), () -> {
+			new DefaultLogbackConfiguration(null).apply(this.logbackConfigurator);
+			assertThat(this.loggerContext.getProperty("CONSOLE_LOG_CHARSET"))
+				.isEqualTo(StandardCharsets.US_ASCII.name());
+		});
+	}
+
+	@Test
+	void fileLogCharsetShouldUseSystemPropertyIfSet() {
+		withSystemProperty("FILE_LOG_CHARSET", StandardCharsets.ISO_8859_1.name(), () -> {
+			new DefaultLogbackConfiguration(null).apply(this.logbackConfigurator);
+			assertThat(this.loggerContext.getProperty("FILE_LOG_CHARSET"))
+				.isEqualTo(StandardCharsets.ISO_8859_1.name());
+		});
+	}
+
+	@Test
+	void fileLogCharsetShouldDefaultToUtf8() {
+		new DefaultLogbackConfiguration(null).apply(this.logbackConfigurator);
+		assertThat(this.loggerContext.getProperty("FILE_LOG_CHARSET")).isEqualTo(StandardCharsets.UTF_8.name());
+	}
+
 	private void assertThatDefaultXmlContains(String name, String value) throws Exception {
 		String expected = "<property name=\"%s\" value=\"%s\"/>".formatted(name, value);
 		assertThat(defaultXmlContent()).contains(expected);
@@ -51,4 +102,21 @@ class DefaultLogbackConfigurationTests {
 		return StreamUtils.copyToString(getClass().getResourceAsStream("defaults.xml"), StandardCharsets.UTF_8);
 	}
 
+	private static void withSystemProperty(String name, String value, Runnable action) {
+		String previous = System.getProperty(name);
+		try {
+			System.setProperty(name, value);
+			action.run();
+		}
+		finally {
+			if (previous != null) {
+				System.setProperty(name, previous);
+			}
+			else {
+				System.clearProperty(name);
+			}
+		}
+
+	}
+
 }

core/spring-boot/src/test/java/org/springframework/boot/logging/logback/LogbackLoggingSystemPropertiesTests.java

@@ -131,10 +131,10 @@ class LogbackLoggingSystemPropertiesTests {
 	}
 
 	@Test
-	void fileCharsetWhenNoPropertyUsesDefault() {
+	void fileCharsetWhenNoPropertyUsesUtf8() {
 		new LoggingSystemProperties(new MockEnvironment()).apply(null);
 		assertThat(System.getProperty(LoggingSystemProperty.FILE_CHARSET.getEnvironmentVariableName()))
-			.isEqualTo(Charset.defaultCharset().name());
+			.isEqualTo(StandardCharsets.UTF_8.name());
 	}
 
 }