CAMEL-24360: camel-undertow - use UndertowHeaderFilterStrategy as the endpoint default

components/camel-undertow/src/main/java/org/apache/camel/component/undertow/UndertowEndpoint.java

@@ -37,7 +37,6 @@
 import org.apache.camel.component.undertow.UndertowConstants.EventType;
 import org.apache.camel.component.undertow.handlers.CamelWebSocketHandler;
 import org.apache.camel.component.undertow.spi.UndertowSecurityProvider;
-import org.apache.camel.http.base.HttpHeaderFilterStrategy;
 import org.apache.camel.http.base.OAuthHttpSecuritySupport;
 import org.apache.camel.http.base.OAuthProfileAwareHttpEndpoint;
 import org.apache.camel.http.base.cookie.CookieHandler;
@@ -85,7 +84,7 @@ public class UndertowEndpoint extends DefaultEndpoint
     @UriParam(label = "advanced")
     private AccessLogReceiver accessLogReceiver;
     @UriParam(label = "advanced")
-    private HeaderFilterStrategy headerFilterStrategy = new HttpHeaderFilterStrategy();
+    private HeaderFilterStrategy headerFilterStrategy = new UndertowHeaderFilterStrategy();
     @UriParam(label = "security")
     private SSLContextParameters sslContextParameters;
     @UriParam(label = "consumer")

components/camel-undertow/src/test/java/org/apache/camel/component/undertow/UndertowEndpointTest.java

@@ -18,10 +18,15 @@
 
 import java.net.URI;
 
+import org.apache.camel.http.base.HttpHeaderFilterStrategy;
+import org.apache.camel.spi.HeaderFilterStrategy;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertInstanceOf;
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 public class UndertowEndpointTest {
 
@@ -47,4 +52,35 @@ public void nonEmptyPathShouldBeKeptSame() {
         endpoint.setHttpURI(withSlash);
         assertEquals(withSlash, endpoint.getHttpURI());
     }
+
+    @Test
+    void defaultHeaderFilterStrategyIsUndertowSpecific() {
+        assertInstanceOf(UndertowHeaderFilterStrategy.class, endpoint.getHeaderFilterStrategy());
+    }
+
+    @Test
+    void defaultBindingKeepsUndertowHeaderFilterStrategy() {
+        // the endpoint pushes its own strategy into the lazily created binding, so the endpoint default
+        // decides which strategy the binding ends up running
+        DefaultUndertowHttpBinding binding
+                = assertInstanceOf(DefaultUndertowHttpBinding.class, endpoint.getUndertowHttpBinding());
+        HeaderFilterStrategy strategy = binding.getHeaderFilterStrategy();
+        assertInstanceOf(UndertowHeaderFilterStrategy.class, strategy);
+
+        // the undertow-specific prefixes added by CAMEL-23588 must therefore be in effect
+        assertTrue(strategy.applyFilterToExternalHeaders(UndertowConstants.CONNECTION_KEY, "aValue", null));
+        assertTrue(strategy.applyFilterToExternalHeaders(UndertowConstants.CONNECTION_KEY_LIST, "aValue", null));
+        assertTrue(strategy.applyFilterToExternalHeaders(UndertowConstants.SEND_TO_ALL, "aValue", null));
+        assertTrue(strategy.applyFilterToCamelHeaders(UndertowConstants.CONNECTION_KEY, "aValue", null));
+    }
+
+    @Test
+    void explicitHeaderFilterStrategyIsHandedToTheBinding() {
+        HeaderFilterStrategy custom = new HttpHeaderFilterStrategy();
+        endpoint.setHeaderFilterStrategy(custom);
+
+        DefaultUndertowHttpBinding binding
+                = assertInstanceOf(DefaultUndertowHttpBinding.class, endpoint.getUndertowHttpBinding());
+        assertSame(custom, binding.getHeaderFilterStrategy());
+    }
 }

docs/user-manual/modules/ROOT/pages/camel-4x-upgrade-guide-4_22.adoc

@@ -1619,3 +1619,35 @@ only once.
 In a Spring Boot application, Spring AI's auto-configured `ToolCallbackResolver` is built from the
 `ToolCallback` and `ToolCallbackProvider` beans in the context. A bare `@Bean Function<...>` is no
 longer resolvable by bean name; expose such tools as `ToolCallback` or `ToolCallbackProvider` beans.
+
+=== camel-undertow - UndertowHeaderFilterStrategy is now the endpoint default
+
+`UndertowEndpoint` defaulted its `headerFilterStrategy` to the base
+`HttpHeaderFilterStrategy`, and pushed that strategy into the `DefaultUndertowHttpBinding`
+it creates lazily, overwriting the `UndertowHeaderFilterStrategy` that the binding installs
+in its own constructor. The undertow-specific filtering was therefore not applied on
+endpoint-configured routes.
+
+The endpoint now defaults to `UndertowHeaderFilterStrategy`, which makes two already
+documented behaviours take effect:
+
+* The legacy `websocket.*` Exchange-header prefix, added to the in and out filters in
+  4.14.8 / 4.18.3 / 4.21.0 (see the 4.18 upgrade guide), is now filtered at the undertow
+  transport boundary as described there.
+* Header names that undertow does not accept (those for which
+  `io.undertow.util.HttpString.tryFromString` returns `null`) are skipped when mapping
+  external headers in, rather than being mapped onto the message.
+
+Ordinary application headers are unaffected, and Rest DSL consumers already used an
+undertow-specific strategy (`UndertowRestHeaderFilterStrategy`) so their behaviour does not
+change. Routes that relied on `websocket.*` headers crossing the undertow boundary in either
+direction, and routes that relied on undertow-invalid header names being mapped, can restore
+the previous behaviour by configuring `headerFilterStrategy` explicitly on the endpoint:
+
+[source,java]
+----
+from("undertow:http://0.0.0.0:8080/foo?headerFilterStrategy=#myStrategy")
+----
+
+Routes that already supply a custom `headerFilterStrategy` or a custom `undertowHttpBinding`
+are unaffected.