fix StringHttpMessageConverter

Author: jihoon.son

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/http/HttpMessageConverters.java

@@ -26,6 +26,7 @@
 import java.util.Map;
 
 import org.springframework.http.converter.HttpMessageConverter;
+import org.springframework.http.converter.StringHttpMessageConverter;
 import org.springframework.http.converter.support.AllEncompassingFormHttpMessageConverter;
 import org.springframework.http.converter.xml.AbstractXmlHttpMessageConverter;
 import org.springframework.http.converter.xml.MappingJackson2XmlHttpMessageConverter;
@@ -121,14 +122,24 @@ private List<HttpMessageConverter<?>> getCombinedConverters(Collection<HttpMessa
 		List<HttpMessageConverter<?>> processing = new ArrayList<>(converters);
 		for (HttpMessageConverter<?> defaultConverter : defaultConverters) {
 			Iterator<HttpMessageConverter<?>> iterator = processing.iterator();
+			boolean skipDefault = false;
 			while (iterator.hasNext()) {
 				HttpMessageConverter<?> candidate = iterator.next();
 				if (isReplacement(defaultConverter, candidate)) {
 					combined.add(candidate);
 					iterator.remove();
+
+					if (defaultConverter instanceof StringHttpMessageConverter
+							&& defaultConverter.getSupportedMediaTypes().equals(candidate.getSupportedMediaTypes())) {
+						skipDefault = true;
+					}
 				}
 			}
-			combined.add(defaultConverter);
+
+			if (!skipDefault) {
+				combined.add(defaultConverter);
+			}
+
 			if (defaultConverter instanceof AllEncompassingFormHttpMessageConverter allEncompassingConverter) {
 				configurePartConverters(allEncompassingConverter, converters);
 			}

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/http/HttpMessageConvertersTests.java

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.autoconfigure.http;
 
+import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
@@ -163,4 +164,19 @@ private AllEncompassingFormHttpMessageConverter findFormConverter(Collection<Htt
 		return null;
 	}
 
+	@Test
+	void replaceDefaultStringHttpConverter() {
+		StringHttpMessageConverter converter = new StringHttpMessageConverter(StandardCharsets.UTF_8);
+		HttpMessageConverters converters = new HttpMessageConverters(converter);
+		assertThat(converters.getConverters()).contains(converter);
+		List<StringHttpMessageConverter> httpConverters = new ArrayList<>();
+		for (HttpMessageConverter<?> candidate : converters) {
+			if (candidate instanceof StringHttpMessageConverter) {
+				httpConverters.add((StringHttpMessageConverter) candidate);
+			}
+		}
+
+		assertThat(httpConverters).hasSize(1);
+		assertThat(httpConverters.get(0)).isEqualTo(converter);
+	}
 }