Override StringHttpMessageConverter with UTF-8

Override the default StringHttpMessageConverter provided by the standard
Spring MVC configuration so that is uses UTF-8 instead of the aging
default of the servlet spec (that is ISO-8859-1)

Fixes gh-1800

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/HttpMessageConvertersAutoConfiguration.java

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.autoconfigure.web;
 
+import java.nio.charset.Charset;
 import java.util.Collections;
 import java.util.List;
 
@@ -28,6 +29,7 @@ import org.springframework.boot.context.properties.EnableConfigurationProperties
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.http.converter.HttpMessageConverter;
+import org.springframework.http.converter.StringHttpMessageConverter;
 import org.springframework.http.converter.json.GsonHttpMessageConverter;
 import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
 import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
@@ -47,11 +49,14 @@ import com.google.gson.Gson;
  * @author David Liu
  * @author Andy Wilkinson
  * @author Sebastien Deleuze
+ * @author Stephane Nicoll
  */
 @Configuration
 @ConditionalOnClass(HttpMessageConverter.class)
 public class HttpMessageConvertersAutoConfiguration {
 
+	private static final Charset UTF_8 = Charset.forName("UTF-8");
+
 	@Autowired(required = false)
 	private final List<HttpMessageConverter<?>> converters = Collections.emptyList();
 
@@ -118,4 +123,16 @@ public class HttpMessageConvertersAutoConfiguration {
 
 	}
 
+	@Configuration
+	@ConditionalOnClass(StringHttpMessageConverter.class)
+	protected static class StringHttpMessageConverterConfiguration {
+
+		@Bean
+		@ConditionalOnMissingBean
+		public StringHttpMessageConverter stringHttpMessageConverter() {
+			return new StringHttpMessageConverter(UTF_8);
+		}
+
+	}
+
 }

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/HttpMessageConvertersAutoConfigurationTests.java

@@ -24,6 +24,7 @@ import org.junit.Test;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.http.converter.StringHttpMessageConverter;
 import org.springframework.http.converter.json.GsonHttpMessageConverter;
 import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
 import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
@@ -46,7 +47,7 @@ import static org.junit.Assert.assertTrue;
  */
 public class HttpMessageConvertersAutoConfigurationTests {
 
-	private AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();;
+	private AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
 
 	@After
 	public void close() {
@@ -134,6 +135,26 @@ public class HttpMessageConvertersAutoConfigurationTests {
 		assertConverterBeanRegisteredWithHttpMessageConverters(GsonHttpMessageConverter.class);
 	}
 
+	@Test
+	public void defaultStringConverter() throws Exception {
+		this.context.register(HttpMessageConvertersAutoConfiguration.class);
+		this.context.refresh();
+		assertConverterBeanExists(StringHttpMessageConverter.class,
+				"stringHttpMessageConverter");
+		assertConverterBeanRegisteredWithHttpMessageConverters(StringHttpMessageConverter.class);
+	}
+
+	@Test
+	public void customStringConverter() throws Exception {
+		this.context.register(StringConverterConfig.class,
+				HttpMessageConvertersAutoConfiguration.class);
+		this.context.refresh();
+		assertConverterBeanExists(StringHttpMessageConverter.class,
+				"customStringMessageConverter");
+
+		assertConverterBeanRegisteredWithHttpMessageConverters(StringHttpMessageConverter.class);
+	}
+
 	private void assertConverterBeanExists(Class<?> type, String beanName) {
 		assertEquals(1, this.context.getBeansOfType(type).size());
 		List<String> beanNames = Arrays.asList(this.context.getBeanDefinitionNames());
@@ -202,4 +223,13 @@ public class HttpMessageConvertersAutoConfigurationTests {
 		}
 	}
 
+	@Configuration
+	protected static class StringConverterConfig {
+
+		@Bean
+		public StringHttpMessageConverter customStringMessageConverter() {
+			return new StringHttpMessageConverter();
+		}
+	}
+
 }

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -886,7 +886,8 @@ formatters, view controllers etc.) you can add your own `@Bean` of type
 Spring MVC uses the `HttpMessageConverter` interface to convert HTTP requests and
 responses. Sensible defaults are included out of the box, for example Objects can be
 automatically converted to JSON (using the Jackson library) or XML (using the Jackson
-XML extension if available, else using JAXB).
+XML extension if available, else using JAXB). Strings are encoded using `UTF-8` by
+default.
 
 If you need to add or customize converters you can use Spring Boot's
 `HttpMessageConverters` class:
@@ -909,6 +910,9 @@ If you need to add or customize converters you can use Spring Boot's
 	}
 ----
 
+Any `HttpMessageConverter` bean that is present in the context will be added to the list of
+converters. You can also override default converters that way.
+
 [[boot-features-spring-message-codes]]
 ==== MessageCodesResolver
 Spring MVC has a strategy for generating error codes for rendering error messages