Message Headers Improvement

src/main/java/io/nats/client/api/MessageInfo.java

@@ -64,21 +64,21 @@ public MessageInfo(Message msg, String streamName, boolean direct) {
         this.direct = direct;
 
         if (direct) {
-            this.headers = msg.getHeaders();
-            this.subject = headers.getLast(NATS_SUBJECT);
+            Headers msgHeaders = msg.getHeaders();
+            this.subject = msgHeaders.getLast(NATS_SUBJECT);
             this.data = msg.getData();
-            seq = Long.parseLong(headers.getFirst(NATS_SEQUENCE));
-            time = DateTimeUtils.parseDateTime(headers.getFirst(NATS_TIMESTAMP));
-            stream = headers.getFirst(NATS_STREAM);
-            String temp = headers.getFirst(NATS_LAST_SEQUENCE);
+            seq = Long.parseLong(msgHeaders.getFirst(NATS_SEQUENCE));
+            time = DateTimeUtils.parseDateTime(msgHeaders.getFirst(NATS_TIMESTAMP));
+            stream = msgHeaders.getFirst(NATS_STREAM);
+            String temp = msgHeaders.getFirst(NATS_LAST_SEQUENCE);
             if (temp == null) {
                 lastSeq = -1;
             }
             else {
                 lastSeq = JsonUtils.safeParseLong(temp, -1);
             }
             // these are control headers, not real headers so don't give them to the user.
-            headers.remove(NATS_SUBJECT, NATS_SEQUENCE, NATS_TIMESTAMP, NATS_STREAM, NATS_LAST_SEQUENCE);
+            headers = new Headers(msgHeaders, true, MESSAGE_INFO_HEADERS);
         }
         else if (hasError()) {
             subject = null;

src/main/java/io/nats/client/impl/Headers.java

@@ -25,7 +25,7 @@
  * An object that represents a map of keys to a list of values. It does not accept
  * null or invalid keys. It ignores null values, accepts empty string as a value
  * and rejects invalid values.
- *
+ * !!!
  * THIS CLASS IS NOT THREAD SAFE
  */
 public class Headers {
@@ -36,21 +36,47 @@ public class Headers {
 
 	private final Map<String, List<String>> valuesMap;
 	private final Map<String, Integer> lengthMap;
+	private final boolean readOnly;
 	private byte[] serialized;
 	private int dataLength;
 
 	public Headers() {
-		valuesMap = new HashMap<>();
-		lengthMap = new HashMap<>();
+		this(null, false, null);
 	}
 
 	public Headers(Headers headers) {
-		this();
+		this(headers, false, null);
+	}
+
+	public Headers(Headers headers, boolean readOnly) {
+		this(headers, readOnly, null);
+	}
+
+	public Headers(Headers headers, boolean readOnly, String[] keysNotToCopy) {
+		Map<String, List<String>> tempValuesMap = new HashMap<>();
+		Map<String, Integer> tempLengthMap = new HashMap<>();
 		if (headers != null) {
-			valuesMap.putAll(headers.valuesMap);
-			lengthMap.putAll(headers.lengthMap);
+			tempValuesMap.putAll(headers.valuesMap);
+			tempLengthMap.putAll(headers.lengthMap);
 			dataLength = headers.dataLength;
-			serialized = null;
+			if (keysNotToCopy != null) {
+				for (String key : keysNotToCopy) {
+					if (key != null) {
+						if (tempValuesMap.remove(key) != null) {
+							dataLength -= tempLengthMap.remove(key);
+						}
+					}
+				}
+			}
+		}
+		this.readOnly = readOnly;
+		if (readOnly) {
+			valuesMap = Collections.unmodifiableMap(tempValuesMap);
+			lengthMap = Collections.unmodifiableMap(tempLengthMap);
+		}
+		else {
+			valuesMap = tempValuesMap;
+			lengthMap = tempLengthMap;
 		}
 	}
 
@@ -155,7 +181,7 @@ public Headers put(Map<String, List<String>> map) {
 
 	// the put delegate that all puts call
 	private void _put(String key, Collection<String> values) {
-		if (key == null || key.length() == 0) {
+		if (key == null || key.isEmpty()) {
 			throw new IllegalArgumentException("Key cannot be null or empty.");
 		}
 		if (values != null) {
@@ -203,7 +229,7 @@ private void _remove(String key) {
 	}
 
 	/**
-	 * Returns the number of keys (case sensitive) in the header.
+	 * Returns the number of keys (case-sensitive) in the header.
 	 *
 	 * @return the number of keys
 	 */
@@ -221,7 +247,7 @@ public boolean isEmpty() {
 	}
 
 	/**
-	 * Removes all of the keys The object map will be empty after this call returns.
+	 * Removes all the keys The object map will be empty after this call returns.
 	 */
 	public void clear() {
 		valuesMap.clear();
@@ -231,20 +257,20 @@ public void clear() {
 	}
 
 	/**
-	 * Returns <tt>true</tt> if key (case sensitive) is present (has values)
+	 * Returns <tt>true</tt> if key (case-sensitive) is present (has values)
 	 *
 	 * @param key key whose presence is to be tested
-	 * @return <tt>true</tt> if the key (case sensitive) is present (has values)
+	 * @return <tt>true</tt> if the key (case-sensitive) is present (has values)
 	 */
 	public boolean containsKey(String key) {
 		return valuesMap.containsKey(key);
 	}
 
 	/**
-	 * Returns <tt>true</tt> if key (case insensitive) is present (has values)
+	 * Returns <tt>true</tt> if key (case-insensitive) is present (has values)
 	 *
 	 * @param key exact key whose presence is to be tested
-	 * @return <tt>true</tt> if the key (case insensitive) is present (has values)
+	 * @return <tt>true</tt> if the key (case-insensitive) is present (has values)
 	 */
 	public boolean containsKeyIgnoreCase(String key) {
 		for (String k : valuesMap.keySet()) {
@@ -256,7 +282,7 @@ public boolean containsKeyIgnoreCase(String key) {
 	}
 
 	/**
-	 * Returns a {@link Set} view of the keys (case sensitive) contained in the object.
+	 * Returns a {@link Set} view of the keys (case-sensitive) contained in the object.
 	 *
 	 * @return a read-only set the keys contained in this map
 	 */
@@ -265,7 +291,7 @@ public Set<String> keySet() {
 	}
 
 	/**
-	 * Returns a {@link Set} view of the keys (case insensitive) contained in the object.
+	 * Returns a {@link Set} view of the keys (case-insensitive) contained in the object.
 	 *
 	 * @return a read-only set of keys (in lowercase) contained in this map
 	 */
@@ -278,43 +304,43 @@ public Set<String> keySetIgnoreCase() {
 	}
 
 	/**
-	 * Returns a {@link List} view of the values for the specific (case sensitive) key.
+	 * Returns a {@link List} view of the values for the specific (case-sensitive) key.
 	 * Will be {@code null} if the key is not found.
 	 *
-	 * @return a read-only list of the values for the case sensitive key.
+	 * @return a read-only list of the values for the case-sensitive key.
 	 */
 	public List<String> get(String key) {
 		List<String> values = valuesMap.get(key);
 		return values == null ? null : Collections.unmodifiableList(values);
 	}
 
 	/**
-	 * Returns the first value for the specific (case sensitive) key.
+	 * Returns the first value for the specific (case-sensitive) key.
 	 * Will be {@code null} if the key is not found.
 	 *
-	 * @return the first value for the case sensitive key.
+	 * @return the first value for the case-sensitive key.
 	 */
 	public String getFirst(String key) {
 		List<String> values = valuesMap.get(key);
 		return values == null ? null : values.get(0);
 	}
 
 	/**
-	 * Returns the last value for the specific (case sensitive) key.
+	 * Returns the last value for the specific (case-sensitive) key.
 	 * Will be {@code null} if the key is not found.
 	 *
-	 * @return the last value for the case sensitive key.
+	 * @return the last value for the case-sensitive key.
 	 */
 	public String getLast(String key) {
 		List<String> values = valuesMap.get(key);
 		return values == null ? null : values.get(values.size() - 1);
 	}
 
 	/**
-	 * Returns a {@link List} view of the values for the specific (case insensitive) key.
+	 * Returns a {@link List} view of the values for the specific (case-insensitive) key.
 	 * Will be {@code null} if the key is not found.
 	 *
-	 * @return a read-only list of the values for the case insensitive key.
+	 * @return a read-only list of the values for the case-insensitive key.
 	 */
 	public List<String> getIgnoreCase(String key) {
 		List<String> values = new ArrayList<>();
@@ -323,11 +349,11 @@ public List<String> getIgnoreCase(String key) {
 				values.addAll(valuesMap.get(k));
 			}
 		}
-		return values.size() == 0 ? null : Collections.unmodifiableList(values);
+		return values.isEmpty() ? null : Collections.unmodifiableList(values);
 	}
 
 	/**
-	 * Performs the given action for each header entry (case sensitive keys) until all entries
+	 * Performs the given action for each header entry (case-sensitive keys) until all entries
 	 * have been processed or the action throws an exception.
 	 * Any attempt to modify the values will throw an exception.
 	 *
@@ -341,7 +367,7 @@ public void forEach(BiConsumer<String, List<String>> action) {
 	}
 
 	/**
-	 * Returns a {@link Set} read only view of the mappings contained in the header (case sensitive keys).
+	 * Returns a {@link Set} read only view of the mappings contained in the header (case-sensitive keys).
 	 * The set is not modifiable and any attempt to modify will throw an exception.
 	 *
 	 * @return a set view of the mappings contained in this map
@@ -447,7 +473,7 @@ public int serializeToArray(int destPosition, byte[] dest) {
 	 */
 	private void checkKey(String key) {
 		// key cannot be null or empty and contain only printable characters except colon
-		if (key == null || key.length() == 0) {
+		if (key == null || key.isEmpty()) {
 			throw new IllegalArgumentException(KEY_CANNOT_BE_EMPTY_OR_NULL);
 		}
 
@@ -500,10 +526,18 @@ private class Checker {
 		}
 
 		boolean hasValues() {
-			return list.size() > 0;
+			return !list.isEmpty();
 		}
 	}
 
+	/**
+	 * Whether the entire Headers is read only
+	 * @return the read only state
+	 */
+	public boolean isReadOnly() {
+		return readOnly;
+	}
+
 	@Override
 	public boolean equals(Object o) {
 		if (this == o) return true;

src/main/java/io/nats/client/impl/NatsMessage.java

@@ -90,7 +90,7 @@ public NatsMessage(String subject, String replyTo, Headers headers, byte[] data)
         this(data);
         this.subject = validateSubject(subject, true);
         this.replyTo = validateReplyTo(replyTo, false);
-        this.headers = headers;
+        this.headers = readOnlyOf(headers);
         this.utf8mode = false;
         finishConstruct();
     }
@@ -99,11 +99,18 @@ public NatsMessage(Message message) {
         this(message.getData());
         this.subject = message.getSubject();
         this.replyTo = message.getReplyTo();
-        this.headers = message.getHeaders();
+        this.headers = readOnlyOf(message.getHeaders());
         this.utf8mode = message.isUtf8mode();
         finishConstruct();
     }
 
+    private static Headers readOnlyOf(Headers headers) {
+        if (headers == null || headers.isReadOnly()) {
+            return headers;
+        }
+        return new Headers(headers, true, null);
+    }
+
     protected void finishConstruct() {
         int replyToLen = replyTo == null ? 0 : replyTo.length();
 
@@ -167,13 +174,6 @@ int getControlLineLength() {
         return controlLineLength;
     }
 
-    Headers getOrCreateHeaders() {
-        if (headers == null) {
-            headers = new Headers();
-        }
-        return headers;
-    }
-
     void setSubscription(NatsSubscription sub) {
         subscription = sub;
     }

src/main/java/io/nats/client/support/NatsJetStreamConstants.java

@@ -97,6 +97,7 @@ public interface NatsJetStreamConstants {
     String NATS_TIMESTAMP     = "Nats-Time-Stamp";
     String NATS_SUBJECT       = "Nats-Subject";
     String NATS_LAST_SEQUENCE = "Nats-Last-Sequence";
+    String[] MESSAGE_INFO_HEADERS = new String[]{NATS_SUBJECT, NATS_SEQUENCE, NATS_TIMESTAMP, NATS_STREAM, NATS_LAST_SEQUENCE};
 
     String NATS_PENDING_MESSAGES = "Nats-Pending-Messages";
     String NATS_PENDING_BYTES    = "Nats-Pending-Bytes";