SPR-8750 Refine 'Content-Type' update in MockHttpServletRequest/Response.

The initial solution kept these three in full sync at all times:
contentType field, characterEncoding field, 'Content-Type' header.
That is correct behavior, however it breaks existing tests that rely
on contentType and characterEncoding being equal to exactly what 
they were set to.

For example, consider:
response.setContentType("text/plain");
response.setCharacterEncoding("UTF-8");

Ideally both contentType and the 'Content-Type' header would now be
"text/plain;charset=UTF-8". However, existing tests would expect 
that contentType is equal to "text/plain".

To avoid breaking existing tests, contentType and characterEncoding
will continue to be equal to exactly what they were set to while
the 'Content-Type' header will always include both the content 
type and the charset.

The only exception to this rule is when a 'Content-Type' header
is set explicitly, the contentType and characterEncoding fields will 
be updated accordingly, possibly overriding the existing values.

org.springframework.orm/src/test/java/org/springframework/mock/web/MockHttpServletRequest.java

@@ -300,18 +300,17 @@ public class MockHttpServletRequest implements HttpServletRequest {
 
 	public void setCharacterEncoding(String characterEncoding) {
 		this.characterEncoding = characterEncoding;
-		if (this.contentType != null)  {
-			String type = removeCharset(this.contentType);
-			setContentType(type);
-		}
+		updateContentTypeHeader();
 	}
 	
-	private String removeCharset(String contentType) {
-		int index = contentType.toLowerCase().indexOf(CHARSET_PREFIX);
-		if (index != -1) {
-			contentType = contentType.substring(0, contentType.lastIndexOf(';', index));
+	private void updateContentTypeHeader() {
+		if (this.contentType != null) {
+			StringBuilder sb = new StringBuilder(this.contentType);
+			if (this.contentType.toLowerCase().indexOf(CHARSET_PREFIX) == -1 && this.characterEncoding != null) {
+				sb.append(";").append(CHARSET_PREFIX).append(this.characterEncoding);
+			}
+			doAddHeaderValue(CONTENT_TYPE_HEADER, sb.toString(), true);
 		}
-		return contentType;
 	}
 
 	public void setContent(byte[] content) {
@@ -330,10 +329,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 				String encoding = contentType.substring(charsetIndex + CHARSET_PREFIX.length());
 				this.characterEncoding = encoding;
 			}
-			else if (this.characterEncoding != null) {
-				this.contentType += ";" + CHARSET_PREFIX + this.characterEncoding;
-			}
-			doAddHeaderValue(CONTENT_TYPE_HEADER, this.contentType, true);
+			updateContentTypeHeader();
 		}
 	}
 

org.springframework.orm/src/test/java/org/springframework/mock/web/MockHttpServletResponse.java

@@ -140,18 +140,17 @@ public class MockHttpServletResponse implements HttpServletResponse {
 	public void setCharacterEncoding(String characterEncoding) {
 		this.characterEncoding = characterEncoding;
 		this.charset = true;
-		if (this.contentType != null)  {
-			String type = removeCharset(this.contentType);
-			setContentType(type);
-		}
+		updateContentTypeHeader();
 	}
 	
-	private String removeCharset(String contentType) {
-		int index = contentType.toLowerCase().indexOf(CHARSET_PREFIX);
-		if (index != -1) {
-			contentType = contentType.substring(0, contentType.lastIndexOf(';', index));
+	private void updateContentTypeHeader() {
+		if (this.contentType != null) {
+			StringBuilder sb = new StringBuilder(this.contentType);
+			if (this.contentType.toLowerCase().indexOf(CHARSET_PREFIX) == -1 && this.charset) {
+				sb.append(";").append(CHARSET_PREFIX).append(this.characterEncoding);
+			}
+			doAddHeaderValue(CONTENT_TYPE_HEADER, sb.toString(), true);
 		}
-		return contentType;
 	}
 
 	public String getCharacterEncoding() {
@@ -204,11 +203,9 @@ public class MockHttpServletResponse implements HttpServletResponse {
 			if (charsetIndex != -1) {
 				String encoding = contentType.substring(charsetIndex + CHARSET_PREFIX.length());
 				this.characterEncoding = encoding;
+				this.charset = true;
 			}
-			else if (this.charset) {
-				this.contentType += ";" + CHARSET_PREFIX + this.characterEncoding;
-			}
-			doAddHeaderValue(CONTENT_TYPE_HEADER, this.contentType, true);
+			updateContentTypeHeader();
 		}
 	}
 

org.springframework.test/src/main/java/org/springframework/mock/web/MockHttpServletRequest.java

@@ -300,18 +300,17 @@ public class MockHttpServletRequest implements HttpServletRequest {
 
 	public void setCharacterEncoding(String characterEncoding) {
 		this.characterEncoding = characterEncoding;
-		if (this.contentType != null)  {
-			String type = removeCharset(this.contentType);
-			setContentType(type);
-		}
+		updateContentTypeHeader();
 	}
 	
-	private String removeCharset(String contentType) {
-		int index = contentType.toLowerCase().indexOf(CHARSET_PREFIX);
-		if (index != -1) {
-			contentType = contentType.substring(0, contentType.lastIndexOf(';', index));
+	private void updateContentTypeHeader() {
+		if (this.contentType != null) {
+			StringBuilder sb = new StringBuilder(this.contentType);
+			if (this.contentType.toLowerCase().indexOf(CHARSET_PREFIX) == -1 && this.characterEncoding != null) {
+				sb.append(";").append(CHARSET_PREFIX).append(this.characterEncoding);
+			}
+			doAddHeaderValue(CONTENT_TYPE_HEADER, sb.toString(), true);
 		}
-		return contentType;
 	}
 
 	public void setContent(byte[] content) {
@@ -330,10 +329,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 				String encoding = contentType.substring(charsetIndex + CHARSET_PREFIX.length());
 				this.characterEncoding = encoding;
 			}
-			else if (this.characterEncoding != null) {
-				this.contentType += ";" + CHARSET_PREFIX + this.characterEncoding;
-			}
-			doAddHeaderValue(CONTENT_TYPE_HEADER, this.contentType, true);
+			updateContentTypeHeader();
 		}
 	}
 

org.springframework.test/src/main/java/org/springframework/mock/web/MockHttpServletResponse.java

@@ -139,18 +139,17 @@ public class MockHttpServletResponse implements HttpServletResponse {
 	public void setCharacterEncoding(String characterEncoding) {
 		this.characterEncoding = characterEncoding;
 		this.charset = true;
-		if (this.contentType != null)  {
-			String type = removeCharset(this.contentType);
-			setContentType(type);
-		}
+		updateContentTypeHeader();
 	}
 	
-	private String removeCharset(String contentType) {
-		int index = contentType.toLowerCase().indexOf(CHARSET_PREFIX);
-		if (index != -1) {
-			contentType = contentType.substring(0, contentType.lastIndexOf(';', index));
+	private void updateContentTypeHeader() {
+		if (this.contentType != null) {
+			StringBuilder sb = new StringBuilder(this.contentType);
+			if (this.contentType.toLowerCase().indexOf(CHARSET_PREFIX) == -1 && this.charset) {
+				sb.append(";").append(CHARSET_PREFIX).append(this.characterEncoding);
+			}
+			doAddHeaderValue(CONTENT_TYPE_HEADER, sb.toString(), true);
 		}
-		return contentType;
 	}
 	
 	public String getCharacterEncoding() {
@@ -203,11 +202,9 @@ public class MockHttpServletResponse implements HttpServletResponse {
 			if (charsetIndex != -1) {
 				String encoding = contentType.substring(charsetIndex + CHARSET_PREFIX.length());
 				this.characterEncoding = encoding;
+				this.charset = true;
 			}
-			else if (this.charset) {
-				this.contentType += ";" + CHARSET_PREFIX + this.characterEncoding;
-			}
-			doAddHeaderValue(CONTENT_TYPE_HEADER, this.contentType, true);
+			updateContentTypeHeader();
 		}
 	}
 

org.springframework.test/src/test/java/org/springframework/mock/web/MockHttpServletRequestTests.java

@@ -47,7 +47,7 @@ public class MockHttpServletRequestTests extends TestCase {
 		assertEquals("UTF-8", request.getCharacterEncoding());
 	}
 
-	public void testSetContentTypeHeader() {
+	public void testContentTypeHeader() {
 		String contentType = "test/plain";
 		MockHttpServletRequest request = new MockHttpServletRequest();
 		request.addHeader("Content-Type", contentType);
@@ -56,7 +56,7 @@ public class MockHttpServletRequestTests extends TestCase {
 		assertNull(request.getCharacterEncoding());
 	}
 
-	public void testSetContentTypeHeaderUTF8() {
+	public void testContentTypeHeaderUTF8() {
 		String contentType = "test/plain;charset=UTF-8";
 		MockHttpServletRequest request = new MockHttpServletRequest();
 		request.addHeader("Content-Type", contentType);
@@ -65,31 +65,20 @@ public class MockHttpServletRequestTests extends TestCase {
 		assertEquals("UTF-8", request.getCharacterEncoding());
 	}
 
-	public void testSetCharacterEncoding() {
-		String contentType = "test/plain;charset=UTF-8";
+	public void testSetContentTypeThenCharacterEncoding() {
 		MockHttpServletRequest request = new MockHttpServletRequest();
 		request.setContentType("test/plain");
 		request.setCharacterEncoding("UTF-8");
-		assertEquals(contentType, request.getContentType());
-		assertEquals(contentType, request.getHeader("Content-Type"));
+		assertEquals("test/plain", request.getContentType());
+		assertEquals("test/plain;charset=UTF-8", request.getHeader("Content-Type"));
 		assertEquals("UTF-8", request.getCharacterEncoding());
 	}
 
-	public void testSetCharacterEncodingOppositeOrder() {
-		String contentType = "test/plain;charset=UTF-8";
+	public void testSetCharacterEncodingThenContentType() {
 		MockHttpServletRequest request = new MockHttpServletRequest();
 		request.setCharacterEncoding("UTF-8");
 		request.setContentType("test/plain");
-		assertEquals(contentType, request.getContentType());
-		assertEquals(contentType, request.getHeader("Content-Type"));
-		assertEquals("UTF-8", request.getCharacterEncoding());
-	}
-
-	public void testReplaceCharacterEncoding() {
-		MockHttpServletRequest request = new MockHttpServletRequest();
-		request.setContentType("test/plain;charset=ISO-8859-1");
-		request.setCharacterEncoding("UTF-8");
-		assertEquals("test/plain;charset=UTF-8", request.getContentType());
+		assertEquals("test/plain", request.getContentType());
 		assertEquals("test/plain;charset=UTF-8", request.getHeader("Content-Type"));
 		assertEquals("UTF-8", request.getCharacterEncoding());
 	}

org.springframework.test/src/test/java/org/springframework/mock/web/MockHttpServletResponseTests.java

@@ -32,88 +32,84 @@ import org.springframework.web.util.WebUtils;
  */
 public class MockHttpServletResponseTests extends TestCase {
 
-	public void testSetContentTypeWithNoEncoding() {
+	public void testSetContentType() {
 		String contentType = "test/plain";
 		MockHttpServletResponse response = new MockHttpServletResponse();
 		response.setContentType(contentType);
-		assertEquals("Character encoding should be the default", WebUtils.DEFAULT_CHARACTER_ENCODING,
-			response.getCharacterEncoding());
-		assertEquals("Content-Type header not set", contentType, response.getHeader("Content-Type"));
+		assertEquals(contentType, response.getContentType());
+		assertEquals(contentType, response.getHeader("Content-Type"));
+		assertEquals(WebUtils.DEFAULT_CHARACTER_ENCODING, response.getCharacterEncoding());
 	}
 
-	public void testSetContentTypeWithUTF8() {
-		String contentType = "test/plain; charset=UTF-8";
+	public void testSetContentTypeUTF8() {
+		String contentType = "test/plain;charset=UTF-8";
 		MockHttpServletResponse response = new MockHttpServletResponse();
 		response.setContentType(contentType);
-		assertEquals("Character encoding should be 'UTF-8'", "UTF-8", response.getCharacterEncoding());
-		assertEquals("Content-Type header not set", contentType, response.getHeader("Content-Type"));
+		assertEquals("UTF-8", response.getCharacterEncoding());
+		assertEquals(contentType, response.getContentType());
+		assertEquals(contentType, response.getHeader("Content-Type"));
 	}
 	
-	public void testContentTypeHeaderWithNoEncoding() {
+	public void testContentTypeHeader() {
 		String contentType = "test/plain";
 		MockHttpServletResponse response = new MockHttpServletResponse();
 		response.addHeader("Content-Type", contentType);
-		assertEquals("contentType field not set", contentType, response.getContentType());
+		assertEquals(contentType, response.getContentType());
+		assertEquals(contentType, response.getHeader("Content-Type"));
+		assertEquals(WebUtils.DEFAULT_CHARACTER_ENCODING, response.getCharacterEncoding());
 
 		response = new MockHttpServletResponse();
 		response.setHeader("Content-Type", contentType);
-		assertEquals("contentType field not set", contentType, response.getContentType());
+		assertEquals(contentType, response.getContentType());
+		assertEquals(contentType, response.getHeader("Content-Type"));
+		assertEquals(WebUtils.DEFAULT_CHARACTER_ENCODING, response.getCharacterEncoding());
 	}
 
-	public void testContentTypeHeaderWithUTF8() {
-		String contentType = "test/plain; charset=UTF-8";
+	public void testContentTypeHeaderUTF8() {
+		String contentType = "test/plain;charset=UTF-8";
 		MockHttpServletResponse response = new MockHttpServletResponse();
-		response.addHeader("Content-Type", contentType);
-		assertEquals("contentType field not set", contentType, response.getContentType());
-		assertEquals("Character encoding should be 'UTF-8'", "UTF-8", response.getCharacterEncoding());
-		assertEquals("Content-Type header not set", contentType, response.getHeader("Content-Type"));
+		response.setHeader("Content-Type", contentType);
+		assertEquals(contentType, response.getContentType());
+		assertEquals(contentType, response.getHeader("Content-Type"));
+		assertEquals("UTF-8", response.getCharacterEncoding());
 
 		response = new MockHttpServletResponse();
-		response.setHeader("Content-Type", contentType);
-		assertEquals("contentType field not set", contentType, response.getContentType());
-		assertEquals("Character encoding should be 'UTF-8'", "UTF-8", response.getCharacterEncoding());
-		assertEquals("Content-Type header not set", contentType, response.getHeader("Content-Type"));
+		response.addHeader("Content-Type", contentType);
+		assertEquals(contentType, response.getContentType());
+		assertEquals(contentType, response.getHeader("Content-Type"));
+		assertEquals("UTF-8", response.getCharacterEncoding());
 	}
 
-	public void testSetCharacterEncoding() {
+	public void testSetContentTypeThenCharacterEncoding() {
 		MockHttpServletResponse response = new MockHttpServletResponse();
 		response.setContentType("test/plain");
 		response.setCharacterEncoding("UTF-8");
-		assertEquals("Character encoding not set", "UTF-8",	response.getCharacterEncoding());
-		assertEquals("contentType field not set", "test/plain;charset=UTF-8", response.getContentType());
-		assertEquals("Content-Type header not set", "test/plain;charset=UTF-8", response.getHeader("Content-Type"));
+		assertEquals("test/plain", response.getContentType());
+		assertEquals("test/plain;charset=UTF-8", response.getHeader("Content-Type"));
+		assertEquals("UTF-8", response.getCharacterEncoding());
 	}
 
-	public void testSetCharacterEncodingOppositeOrder() {
+	public void testSetCharacterEncodingThenContentType() {
 		MockHttpServletResponse response = new MockHttpServletResponse();
 		response.setCharacterEncoding("UTF-8");
 		response.setContentType("test/plain");
-		assertEquals("Character encoding not set", "UTF-8",	response.getCharacterEncoding());
-		assertEquals("contentType field not set", "test/plain;charset=UTF-8", response.getContentType());
-		assertEquals("Content-Type header not set", "test/plain;charset=UTF-8", response.getHeader("Content-Type"));
-	}
-	
-	public void testReplaceCharacterEncoding() {
-		MockHttpServletResponse response = new MockHttpServletResponse();
-		response.setContentType("test/plain;charset=ISO-8859-1");
-		response.setCharacterEncoding("UTF-8");
-		assertEquals("Character encoding not set", "UTF-8",	response.getCharacterEncoding());
-		assertEquals("contentType field not set", "test/plain;charset=UTF-8", response.getContentType());
-		assertEquals("Content-Type header not set", "test/plain;charset=UTF-8", response.getHeader("Content-Type"));
+		assertEquals("test/plain", response.getContentType());
+		assertEquals("test/plain;charset=UTF-8", response.getHeader("Content-Type"));
+		assertEquals("UTF-8", response.getCharacterEncoding());
 	}
-	
+
 	public void testContentLength() {
 		MockHttpServletResponse response = new MockHttpServletResponse();
 		response.setContentLength(66);
-		assertEquals("Content length field not set", 66,	response.getContentLength());
-		assertEquals("Content-Length header not set", "66", response.getHeader("Content-Length"));
+		assertEquals(66, response.getContentLength());
+		assertEquals("66", response.getHeader("Content-Length"));
 	}
 	
 	public void testContentLengthHeader() {
 		MockHttpServletResponse response = new MockHttpServletResponse();
 		response.addHeader("Content-Length", "66");
-		assertEquals("Content length field not set", 66,	response.getContentLength());
-		assertEquals("Content-Length header not set", "66", response.getHeader("Content-Length"));
+		assertEquals(66,response.getContentLength());
+		assertEquals("66", response.getHeader("Content-Length"));
 	}
 	
 	public void testHttpHeaderNameCasingIsPreserved() throws Exception {

org.springframework.web.servlet/src/test/java/org/springframework/mock/web/MockHttpServletRequest.java

@@ -310,18 +310,17 @@ public class MockHttpServletRequest implements HttpServletRequest {
 
 	public void setCharacterEncoding(String characterEncoding) {
 		this.characterEncoding = characterEncoding;
-		if (this.contentType != null)  {
-			String type = removeCharset(this.contentType);
-			setContentType(type);
-		}
+		updateContentTypeHeader();
 	}
 	
-	private String removeCharset(String contentType) {
-		int index = contentType.toLowerCase().indexOf(CHARSET_PREFIX);
-		if (index != -1) {
-			contentType = contentType.substring(0, contentType.lastIndexOf(';', index));
+	private void updateContentTypeHeader() {
+		if (this.contentType != null) {
+			StringBuilder sb = new StringBuilder(this.contentType);
+			if (this.contentType.toLowerCase().indexOf(CHARSET_PREFIX) == -1 && this.characterEncoding != null) {
+				sb.append(";").append(CHARSET_PREFIX).append(this.characterEncoding);
+			}
+			doAddHeaderValue(CONTENT_TYPE_HEADER, sb.toString(), true);
 		}
-		return contentType;
 	}
 
 	public void setContent(byte[] content) {
@@ -340,10 +339,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 				String encoding = contentType.substring(charsetIndex + CHARSET_PREFIX.length());
 				this.characterEncoding = encoding;
 			}
-			else if (this.characterEncoding != null) {
-				this.contentType += ";" + CHARSET_PREFIX + this.characterEncoding;
-			}
-			doAddHeaderValue(CONTENT_TYPE_HEADER, this.contentType, true);
+			updateContentTypeHeader();
 		}
 	}
 

org.springframework.web.servlet/src/test/java/org/springframework/mock/web/MockHttpServletResponse.java

@@ -145,18 +145,17 @@ public class MockHttpServletResponse implements HttpServletResponse {
 	public void setCharacterEncoding(String characterEncoding) {
 		this.characterEncoding = characterEncoding;
 		this.charset = true;
-		if (this.contentType != null)  {
-			String type = removeCharset(this.contentType);
-			setContentType(type);
-		}
+		updateContentTypeHeader();
 	}
 	
-	private String removeCharset(String contentType) {
-		int index = contentType.toLowerCase().indexOf(CHARSET_PREFIX);
-		if (index != -1) {
-			contentType = contentType.substring(0, contentType.lastIndexOf(';', index));
+	private void updateContentTypeHeader() {
+		if (this.contentType != null) {
+			StringBuilder sb = new StringBuilder(this.contentType);
+			if (this.contentType.toLowerCase().indexOf(CHARSET_PREFIX) == -1 && this.charset) {
+				sb.append(";").append(CHARSET_PREFIX).append(this.characterEncoding);
+			}
+			doAddHeaderValue(CONTENT_TYPE_HEADER, sb.toString(), true);
 		}
-		return contentType;
 	}
 
 	public String getCharacterEncoding() {
@@ -209,11 +208,9 @@ public class MockHttpServletResponse implements HttpServletResponse {
 			if (charsetIndex != -1) {
 				String encoding = contentType.substring(charsetIndex + CHARSET_PREFIX.length());
 				this.characterEncoding = encoding;
+				this.charset = true;
 			}
-			else if (this.charset) {
-				this.contentType += ";" + CHARSET_PREFIX + this.characterEncoding;
-			}
-			doAddHeaderValue(CONTENT_TYPE_HEADER, this.contentType, true);
+			updateContentTypeHeader();
 		}
 	}
 

org.springframework.web.servlet/src/test/java/org/springframework/web/servlet/view/json/MappingJacksonJsonViewTest.java

@@ -92,7 +92,7 @@ public class MappingJacksonJsonViewTest {
 		assertEquals("no-cache, no-store, max-age=0", response.getHeader("Cache-Control"));
 		assertNotNull(response.getHeader("Expires"));
 
-		assertEquals(MappingJacksonJsonView.DEFAULT_CONTENT_TYPE + ";charset=UTF-8", response.getContentType());
+		assertEquals(MappingJacksonJsonView.DEFAULT_CONTENT_TYPE, response.getContentType());
 
 		String jsonResult = response.getContentAsString();
 		assertTrue(jsonResult.length() > 0);

org.springframework.web/src/test/java/org/springframework/mock/web/MockHttpServletRequest.java

@@ -310,18 +310,17 @@ public class MockHttpServletRequest implements HttpServletRequest {
 
 	public void setCharacterEncoding(String characterEncoding) {
 		this.characterEncoding = characterEncoding;
-		if (this.contentType != null)  {
-			String type = removeCharset(this.contentType);
-			setContentType(type);
-		}
+		updateContentTypeHeader();
 	}
 	
-	private String removeCharset(String contentType) {
-		int index = contentType.toLowerCase().indexOf(CHARSET_PREFIX);
-		if (index != -1) {
-			contentType = contentType.substring(0, contentType.lastIndexOf(';', index));
+	private void updateContentTypeHeader() {
+		if (this.contentType != null) {
+			StringBuilder sb = new StringBuilder(this.contentType);
+			if (this.contentType.toLowerCase().indexOf(CHARSET_PREFIX) == -1 && this.characterEncoding != null) {
+				sb.append(";").append(CHARSET_PREFIX).append(this.characterEncoding);
+			}
+			doAddHeaderValue(CONTENT_TYPE_HEADER, sb.toString(), true);
 		}
-		return contentType;
 	}
 
 	public void setContent(byte[] content) {
@@ -340,10 +339,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 				String encoding = contentType.substring(charsetIndex + CHARSET_PREFIX.length());
 				this.characterEncoding = encoding;
 			}
-			else if (this.characterEncoding != null) {
-				this.contentType += ";" + CHARSET_PREFIX + this.characterEncoding;
-			}
-			doAddHeaderValue(CONTENT_TYPE_HEADER, this.contentType, true);
+			updateContentTypeHeader();
 		}
 	}
 

org.springframework.web/src/test/java/org/springframework/mock/web/MockHttpServletResponse.java

@@ -144,18 +144,17 @@ public class MockHttpServletResponse implements HttpServletResponse {
 	public void setCharacterEncoding(String characterEncoding) {
 		this.characterEncoding = characterEncoding;
 		this.charset = true;
-		if (this.contentType != null)  {
-			String type = removeCharset(this.contentType);
-			setContentType(type);
-		}
+		updateContentTypeHeader();
 	}
 	
-	private String removeCharset(String contentType) {
-		int index = contentType.toLowerCase().indexOf(CHARSET_PREFIX);
-		if (index != -1) {
-			contentType = contentType.substring(0, contentType.lastIndexOf(';', index));
+	private void updateContentTypeHeader() {
+		if (this.contentType != null) {
+			StringBuilder sb = new StringBuilder(this.contentType);
+			if (this.contentType.toLowerCase().indexOf(CHARSET_PREFIX) == -1 && this.charset) {
+				sb.append(";").append(CHARSET_PREFIX).append(this.characterEncoding);
+			}
+			doAddHeaderValue(CONTENT_TYPE_HEADER, sb.toString(), true);
 		}
-		return contentType;
 	}
 
 	public String getCharacterEncoding() {
@@ -208,11 +207,9 @@ public class MockHttpServletResponse implements HttpServletResponse {
 			if (charsetIndex != -1) {
 				String encoding = contentType.substring(charsetIndex + CHARSET_PREFIX.length());
 				this.characterEncoding = encoding;
+				this.charset = true;
 			}
-			else if (this.charset) {
-				this.contentType += ";" + CHARSET_PREFIX + this.characterEncoding;
-			}
-			doAddHeaderValue(CONTENT_TYPE_HEADER, this.contentType, true);
+			updateContentTypeHeader();
 		}
 	}