Merge pull request #39601 from alvican

* pr/39601:
  Polish "Fix local dependent writing of banner into ByteArrayOutputStream"
  Fix local dependent writing of banner into ByteArrayOutputStream

Closes gh-39601

Author: mhalbritter

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/SpringApplicationBannerPrinter.java

@@ -20,6 +20,7 @@
 import java.io.IOException;
 import java.io.PrintStream;
 import java.io.UnsupportedEncodingException;
+import java.nio.charset.StandardCharsets;
 
 import org.apache.commons.logging.Log;
 
@@ -95,9 +96,11 @@ private Banner getTextBanner(Environment environment) {
 
 	private String createStringFromBanner(Banner banner, Environment environment, Class<?> mainApplicationClass)
 			throws UnsupportedEncodingException {
+		String charset = environment.getProperty("spring.banner.charset", StandardCharsets.UTF_8.name());
 		ByteArrayOutputStream baos = new ByteArrayOutputStream();
-		banner.printBanner(environment, mainApplicationClass, new PrintStream(baos));
-		String charset = environment.getProperty("spring.banner.charset", "UTF-8");
+		try (PrintStream printStream = new PrintStream(baos, false, charset)) {
+			banner.printBanner(environment, mainApplicationClass, printStream);
+		}
 		return baos.toString(charset);
 	}
 

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/SpringApplicationBannerPrinterTests.java

@@ -16,12 +16,19 @@
 
 package org.springframework.boot;
 
+import org.apache.commons.logging.Log;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.aot.hint.RuntimeHints;
 import org.springframework.aot.hint.predicate.RuntimeHintsPredicates;
+import org.springframework.context.support.GenericApplicationContext;
+import org.springframework.core.io.Resource;
+import org.springframework.core.io.ResourceLoader;
+import org.springframework.mock.env.MockEnvironment;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.BDDMockito.then;
+import static org.mockito.Mockito.mock;
 
 /**
  * Tests for {@link SpringApplicationBannerPrinter}.
@@ -38,4 +45,15 @@ void shouldRegisterRuntimeHints() {
 		assertThat(RuntimeHintsPredicates.resource().forResource("banner.txt")).accepts(runtimeHints);
 	}
 
+	@Test
+	void shouldUseUtf8() {
+		ResourceLoader resourceLoader = new GenericApplicationContext();
+		Resource resource = resourceLoader.getResource("classpath:/banner-utf8.txt");
+		SpringApplicationBannerPrinter printer = new SpringApplicationBannerPrinter(resourceLoader,
+				new ResourceBanner(resource));
+		Log log = mock(Log.class);
+		printer.print(new MockEnvironment(), SpringApplicationBannerPrinterTests.class, log);
+		then(log).should().info("\uD83D\uDE0D Spring Boot! \uD83D\uDE0D\n\n");
+	}
+
 }

spring-boot-project/spring-boot/src/test/resources/banner-utf8.txt

@@ -0,0 +1 @@
+😍 Spring Boot! 😍