Enforce UTF-8 response encoding in SseEmitter

This commit sets the response content type to
"text/event-stream;charset=UTF-8". Even if the SSE spec says that the
encoding should always be UTF-8 and that specifying the charset is
optional, we're setting it in all cases, since some containers might use
the default encoding "ISO-8859-1" and confuse HTTP clients.

Issue: SPR-14407

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/SseEmitter.java

 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -38,6 +38,8 @@ public class SseEmitter extends ResponseBodyEmitter {
 
 	static final MediaType TEXT_PLAIN = new MediaType("text", "plain", Charset.forName("UTF-8"));
 
+	static final MediaType UTF8_TEXT_EVENTSTREAM = new MediaType("text", "event-stream", Charset.forName("UTF-8"));
+
 
 	/**
 	 * Create a new SseEmitter instance.
@@ -65,7 +67,7 @@ public class SseEmitter extends ResponseBodyEmitter {
 
 		HttpHeaders headers = outputMessage.getHeaders();
 		if (headers.getContentType() == null) {
-			headers.setContentType(new MediaType("text", "event-stream"));
+			headers.setContentType(UTF8_TEXT_EVENTSTREAM);
 		}
 	}
 

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/ResponseBodyEmitterReturnValueHandlerTests.java

@@ -148,7 +148,7 @@ public class ResponseBodyEmitterReturnValueHandlerTests {
 
 		assertTrue(this.request.isAsyncStarted());
 		assertEquals(200, this.response.getStatus());
-		assertEquals("text/event-stream", this.response.getContentType());
+		assertEquals("text/event-stream;charset=UTF-8", this.response.getContentType());
 
 		SimpleBean bean1 = new SimpleBean();
 		bean1.setId(1L);
@@ -178,7 +178,7 @@ public class ResponseBodyEmitterReturnValueHandlerTests {
 
 		assertTrue(this.request.isAsyncStarted());
 		assertEquals(200, this.response.getStatus());
-		assertEquals("text/event-stream", this.response.getContentType());
+		assertEquals("text/event-stream;charset=UTF-8", this.response.getContentType());
 		assertEquals("bar", this.response.getHeader("foo"));
 	}