Efficient STOMP content-length header check

Issue: SPR-14747
(cherry picked from commit f2e1e1b)

Author: jhoeller

spring-messaging/src/main/java/org/springframework/messaging/simp/stomp/BufferingStompDecoder.java

@@ -102,7 +102,7 @@ public List<Message<byte[]>> decode(ByteBuffer newBuffer) {
 		this.chunks.add(newBuffer);
 		checkBufferLimits();
 
-		if (getExpectedContentLength() != null && getBufferSize() < this.expectedContentLength) {
+		if (this.expectedContentLength != null && getBufferSize() < this.expectedContentLength) {
 			return Collections.<Message<byte[]>>emptyList();
 		}
 
@@ -139,12 +139,12 @@ private void checkBufferLimits() {
 		if (this.expectedContentLength != null) {
 			if (this.expectedContentLength > this.bufferSizeLimit) {
 				throw new StompConversionException(
-						"'content-length' header value " + this.expectedContentLength +
-						"  exceeds configured message buffer size limit " + this.bufferSizeLimit);
+						"STOMP 'content-length' header value " + this.expectedContentLength +
+						"  exceeds configured buffer size limit " + this.bufferSizeLimit);
 			}
 		}
 		if (getBufferSize() > this.bufferSizeLimit) {
-			throw new StompConversionException("The configured stomp frame buffer size limit of " +
+			throw new StompConversionException("The configured STOMP buffer size limit of " +
 					this.bufferSizeLimit + " bytes has been exceeded");
 		}
 	}

spring-messaging/src/main/java/org/springframework/messaging/simp/stomp/StompHeaderAccessor.java

@@ -29,21 +29,21 @@
 import org.springframework.messaging.simp.SimpMessageType;
 import org.springframework.messaging.support.MessageHeaderAccessor;
 import org.springframework.util.ClassUtils;
+import org.springframework.util.CollectionUtils;
 import org.springframework.util.MimeType;
 import org.springframework.util.MimeTypeUtils;
 import org.springframework.util.StringUtils;
 
 /**
- * A {@code MessageHeaderAccessor} to use when creating a {@code Message} from a
- * decoded STOMP frame, or when encoding a {@code Message} to a STOMP frame.
+ * A {@code MessageHeaderAccessor} to use when creating a {@code Message} from
+ * a decoded STOMP frame, or when encoding a {@code Message} to a STOMP frame.
  *
- * <p>When created from STOMP frame content, the actual STOMP headers are stored
- * in the native header sub-map managed by the parent class
+ * <p>When created from STOMP frame content, the actual STOMP headers are
+ * stored in the native header sub-map managed by the parent class
  * {@link org.springframework.messaging.support.NativeMessageHeaderAccessor}
- * while the parent class
- * {@link org.springframework.messaging.simp.SimpMessageHeaderAccessor} manages
- * common processing headers some of which are based on STOMP headers (e.g.
- * destination, content-type, etc).
+ * while the parent class {@link SimpMessageHeaderAccessor} manages common
+ * processing headers some of which are based on STOMP headers
+ * (e.g. destination, content-type, etc).
  *
  * <p>An instance of this class can also be created by wrapping an existing
  * {@code Message}. That message may have been created with the more generic
@@ -502,12 +502,8 @@ public static String getPasscode(Map<String, Object> headers) {
 	}
 
 	public static Integer getContentLength(Map<String, List<String>> nativeHeaders) {
-		if (nativeHeaders.containsKey(STOMP_CONTENT_LENGTH_HEADER)) {
-			List<String> values = nativeHeaders.get(STOMP_CONTENT_LENGTH_HEADER);
-			String value = (values != null ? values.get(0) : null);
-			return Integer.valueOf(value);
-		}
-		return null;
+		List<String> values = nativeHeaders.get(STOMP_CONTENT_LENGTH_HEADER);
+		return (!CollectionUtils.isEmpty(values) ? Integer.valueOf(values.get(0)) : null);
 	}