SPR-8867 Fix issue with Content-Length header and UTF-8 charset.

The AbstractHttpMessageConverter was using the requested Content-Type
rather than the actual response Content-Type to determine the length
of the content. This can lead to a problem when a controller returns
a ResponseEntity with a Content-Type header that ignores (overrides)
the requested Content-Type. The fix ensures that actual response 
Content-Type is the one used both to write to the response and to 
determine the length of the content.

Author: rstoyanchev

build-spring-framework/resources/changelog.txt

@@ -23,10 +23,11 @@ Changes in version 3.1 RC2 (2011-11-15)
 * added ignoreDefaultModelOnRedirect attribute to <mvc:annotation-driven/>
 * added methods to UriComponentsBuilder for replacing the path or the query
 * added ServletUriComponentsBuilder to build a UriComponents instance starting with a ServletRequest
-* support UriComponentsBuilder as @Controller method argument
+* added support for UriComponentsBuilder as @Controller method argument
 * MockHttpServletRequest and MockHttpServletResponse now keep contentType field and Content-Type header in sync
 * fixed issue with cache ignoring prototype-scoped controllers in RequestMappingHandlerAdapter
-* update Spring MVC configuration section to include MVC Java config and the MVC namespace
+* updated Spring MVC configuration section to include MVC Java config and the MVC namespace
+* fixed issue with setting Content-Length header depending on the charset of the response
 
 Changes in version 3.1 RC1 (2011-10-11)
 ---------------------------------------

org.springframework.web/src/main/java/org/springframework/http/converter/AbstractHttpMessageConverter.java

@@ -173,7 +173,7 @@ public final void write(T t, MediaType contentType, HttpOutputMessage outputMess
 			}
 		}
 		if (headers.getContentLength() == -1) {
-			Long contentLength = getContentLength(t, contentType);
+			Long contentLength = getContentLength(t, headers.getContentType());
 			if (contentLength != null) {
 				headers.setContentLength(contentLength);
 			}

org.springframework.web/src/test/java/org/springframework/http/converter/StringHttpMessageConverterTests.java

@@ -85,4 +85,22 @@ public void writeUTF8() throws IOException {
 				outputMessage.getHeaders().getContentLength());
 		assertFalse("Invalid accept-charset", outputMessage.getHeaders().getAcceptCharset().isEmpty());
 	}
+
+	// SPR-8867
+	
+	@Test
+	public void writeOverrideRequestedContentType() throws IOException {
+		Charset utf8 = Charset.forName("UTF-8");
+		MediaType requestedContentType = new MediaType("text", "html");
+		MockHttpOutputMessage outputMessage = new MockHttpOutputMessage();
+		MediaType contentType = new MediaType("text", "plain", utf8);
+		outputMessage.getHeaders().setContentType(contentType);
+		String body = "H\u00e9llo W\u00f6rld";
+		converter.write(body, requestedContentType, outputMessage);
+		assertEquals("Invalid result", body, outputMessage.getBodyAsString(utf8));
+		assertEquals("Invalid content-type", contentType, outputMessage.getHeaders().getContentType());
+		assertEquals("Invalid content-length", body.getBytes(utf8).length,
+				outputMessage.getHeaders().getContentLength());
+		assertFalse("Invalid accept-charset", outputMessage.getHeaders().getAcceptCharset().isEmpty());
+	}
 }