CAMEL-20809: camel-core - Optimize hasHeaders to not create headers m…

components/camel-irc/src/main/java/org/apache/camel/component/irc/IrcMessage.java

@@ -131,6 +131,11 @@ public IrcMessage newInstance() {
         return new IrcMessage(getCamelContext());
     }
 
+    @Override
+    protected boolean isPopulateHeadersSupported() {
+        return true;
+    }
+
     @Override
     protected void populateInitialHeaders(Map<String, Object> map) {
         map.put(IrcConstants.IRC_MESSAGE_TYPE, messageType);

components/camel-jms/src/main/java/org/apache/camel/component/jms/JmsMessage.java

@@ -240,6 +240,11 @@ protected Object createBody() {
         return null;
     }
 
+    @Override
+    protected boolean isPopulateHeadersSupported() {
+        return true;
+    }
+
     @Override
     protected void populateInitialHeaders(Map<String, Object> map) {
         if (jmsMessage != null && map != null) {

components/camel-mail/src/main/java/org/apache/camel/component/mail/MailMessage.java

@@ -95,6 +95,11 @@ protected Object createBody() {
         return null;
     }
 
+    @Override
+    protected boolean isPopulateHeadersSupported() {
+        return true;
+    }
+
     @Override
     protected void populateInitialHeaders(Map<String, Object> map) {
         if (mailMessage != null) {

components/camel-quartz/src/main/java/org/apache/camel/component/quartz/QuartzMessage.java

@@ -27,6 +27,7 @@
  * A Camel message to be created upon each scheduled job execution.
  */
 public class QuartzMessage extends DefaultMessage {
+
     private final JobExecutionContext jobExecutionContext;
 
     public QuartzMessage(Exchange exchange, JobExecutionContext jobExecutionContext) {
@@ -40,6 +41,11 @@ public JobExecutionContext getJobExecutionContext() {
         return jobExecutionContext;
     }
 
+    @Override
+    protected boolean isPopulateHeadersSupported() {
+        return true;
+    }
+
     @Override
     protected void populateInitialHeaders(Map<String, Object> map) {
         super.populateInitialHeaders(map);

components/camel-sjms/src/main/java/org/apache/camel/component/sjms/SjmsMessage.java

@@ -262,6 +262,11 @@ protected Object createBody() {
         return null;
     }
 
+    @Override
+    protected boolean isPopulateHeadersSupported() {
+        return true;
+    }
+
     @Override
     protected void populateInitialHeaders(Map<String, Object> map) {
         if (jmsMessage != null && map != null) {

components/camel-xmpp/src/main/java/org/apache/camel/component/xmpp/XmppMessage.java

@@ -29,6 +29,7 @@
  * Represents a {@link org.apache.camel.Message} for working with XMPP
  */
 public class XmppMessage extends DefaultMessage {
+
     private Stanza xmppPacket;
 
     public XmppMessage(CamelContext camelContext) {
@@ -89,6 +90,11 @@ protected Object createBody() {
         return null;
     }
 
+    @Override
+    protected boolean isPopulateHeadersSupported() {
+        return true;
+    }
+
     @Override
     protected void populateInitialHeaders(Map<String, Object> map) {
         if (xmppPacket != null) {

core/camel-core/src/test/java/org/apache/camel/impl/DefaultMessageHeaderTest.java

@@ -35,6 +35,16 @@ protected void setUp() {
         camelContext.start();
     }
 
+    @Test
+    public void testHasHeaders() {
+        Message msg = new DefaultMessage(camelContext);
+        assertFalse(msg.hasHeaders());
+
+        msg.setHeader("foo", "cheese");
+        assertTrue(msg.hasHeaders());
+        assertEquals("cheese", msg.getHeader("foo"));
+    }
+
     @Test
     public void testLookupCaseAgnostic() {
         Message msg = new DefaultMessage(camelContext);

core/camel-core/src/test/java/org/apache/camel/issues/PopulateInitialHeadersFailedIssueTest.java

@@ -65,6 +65,11 @@ public MyFaultMessage(Exchange exchange) {
             super(exchange);
         }
 
+        @Override
+        protected boolean isPopulateHeadersSupported() {
+            return true;
+        }
+
         @Override
         protected void populateInitialHeaders(Map<String, Object> map) {
             throw new IllegalArgumentException("Forced headers error");

core/camel-support/src/main/java/org/apache/camel/support/DefaultMessage.java

@@ -287,11 +287,11 @@ public void setHeaders(Map<String, Object> headers) {
 
     @Override
     public boolean hasHeaders() {
-        if (headers == null) {
+        if (headers == null && isPopulateHeadersSupported()) {
             // force creating headers
             headers = createHeaders();
         }
-        return !headers.isEmpty();
+        return headers != null && !headers.isEmpty();
     }
 
     @Override
@@ -328,6 +328,13 @@ protected void populateInitialHeaders(Map<String, Object> map) {
         // do nothing by default
     }
 
+    /**
+     * Whether subclasses need to populate headers when creating message.
+     */
+    protected boolean isPopulateHeadersSupported() {
+        return false;
+    }
+
     /**
      * Returns true if the headers have been mutated in some way
      */

docs/user-manual/modules/ROOT/pages/camel-4x-upgrade-guide-4_17.adoc

@@ -36,6 +36,19 @@ from("direct:start")
     .to("mock:result");
 ----
 
+==== Custom Camel components
+
+Custom components which has a custom message implementation by extending `DefaultMessage`, which rely on the `populateInitialHeaders`
+to initialize headers must now add the following method:
+
+[source,java]
+----
+    @Override
+    protected boolean isPopulateHeadersSupported() {
+        return true;
+    }
+----
+
 === camel-jbang
 
 The `camel-kamelets-catalog` JAR is now downloaded on-demand.