Always specify charset for form data requests

Issue: SPR-16613

Author: rstoyanchev

spring-web/src/main/java/org/springframework/http/converter/FormHttpMessageConverter.java

@@ -93,6 +93,9 @@ public class FormHttpMessageConverter implements HttpMessageConverter<MultiValue
 
 	public static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");
 
+	private static final MediaType DEFAULT_FORM_DATA_MEDIA_TYPE =
+			new MediaType(MediaType.APPLICATION_FORM_URLENCODED, DEFAULT_CHARSET);
+
 
 	private List<MediaType> supportedMediaTypes = new ArrayList<MediaType>();
 
@@ -279,15 +282,14 @@ private boolean isMultipart(MultiValueMap<String, ?> map, MediaType contentType)
 	private void writeForm(MultiValueMap<String, String> form, MediaType contentType,
 			HttpOutputMessage outputMessage) throws IOException {
 
-		Charset charset;
-		if (contentType != null) {
-			outputMessage.getHeaders().setContentType(contentType);
-			charset = (contentType.getCharset() != null ? contentType.getCharset() : this.charset);
-		}
-		else {
-			outputMessage.getHeaders().setContentType(MediaType.APPLICATION_FORM_URLENCODED);
+		contentType = (contentType != null ? contentType : DEFAULT_FORM_DATA_MEDIA_TYPE);
+		Charset charset = contentType.getCharset();
+		if (charset == null) {
 			charset = this.charset;
+			contentType = new MediaType(contentType, charset);
 		}
+		outputMessage.getHeaders().setContentType(contentType);
+
 		StringBuilder builder = new StringBuilder();
 		for (Iterator<String> nameIterator = form.keySet().iterator(); nameIterator.hasNext();) {
 			String name = nameIterator.next();

spring-web/src/test/java/org/springframework/http/converter/FormHttpMessageConverterTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -22,7 +22,6 @@
 import java.io.StringReader;
 import java.nio.charset.Charset;
 import java.util.List;
-
 import javax.xml.transform.Source;
 import javax.xml.transform.stream.StreamSource;
 
@@ -31,7 +30,6 @@
 import org.apache.commons.fileupload.FileUpload;
 import org.apache.commons.fileupload.RequestContext;
 import org.apache.commons.fileupload.disk.DiskFileItemFactory;
-
 import org.junit.Before;
 import org.junit.Test;
 
@@ -47,14 +45,10 @@
 import org.springframework.util.MultiValueMap;
 
 import static org.hamcrest.CoreMatchers.*;
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertNotNull;
-import static org.junit.Assert.assertNull;
-import static org.junit.Assert.assertThat;
-import static org.junit.Assert.assertTrue;
-import static org.mockito.BDDMockito.never;
-import static org.mockito.BDDMockito.verify;
+import static org.hamcrest.CoreMatchers.endsWith;
+import static org.hamcrest.CoreMatchers.startsWith;
+import static org.junit.Assert.*;
+import static org.mockito.BDDMockito.*;
 
 /**
  * @author Arjen Poutsma
@@ -122,8 +116,8 @@ public void writeForm() throws IOException {
 
 		assertEquals("Invalid result", "name+1=value+1&name+2=value+2%2B1&name+2=value+2%2B2&name+3",
 				outputMessage.getBodyAsString(UTF_8));
-		assertEquals("Invalid content-type", new MediaType("application", "x-www-form-urlencoded"),
-				outputMessage.getHeaders().getContentType());
+		assertEquals("Invalid content-type", "application/x-www-form-urlencoded;charset=UTF-8",
+				outputMessage.getHeaders().getContentType().toString());
 		assertEquals("Invalid content-length", outputMessage.getBodyAsBytes().length,
 				outputMessage.getHeaders().getContentLength());
 	}

spring-web/src/test/java/org/springframework/web/client/AbstractMockWebServerTestCase.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -168,7 +168,7 @@ private void assertFilePart(Buffer buffer, String disposition, String boundary,
 	}
 
 	private MockResponse formRequest(RecordedRequest request) {
-		assertEquals("application/x-www-form-urlencoded", request.getHeader("Content-Type"));
+		assertEquals("application/x-www-form-urlencoded;charset=UTF-8", request.getHeader("Content-Type"));
 		String body = request.getBody().readUtf8();
 		assertThat(body, Matchers.containsString("name+1=value+1"));
 		assertThat(body, Matchers.containsString("name+2=value+2%2B1"));