Create a CompositeClassloader and set is as Camel's ApplicationClassloader

camel-k-loader-java/src/main/java/org/apache/camel/k/loader/java/JavaSourceLoader.java

@@ -22,6 +22,7 @@
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
+import org.apache.camel.k.CompositeClassloader;
 import org.apache.camel.k.Runtime;
 import org.apache.camel.k.Source;
 import org.apache.camel.k.SourceLoader;
@@ -47,6 +48,14 @@ public Result load(Runtime runtime, Source source) throws Exception {
             final Reflect compiled = Reflect.compile(name, content);
             final Object instance = compiled.create().get();
 
+            // The given source may contains additional nested classes which are unknown to Camel
+            // as they are associated to the ClassLoader used to compile the source thus we need
+            // to add it to the ApplicationContextClassLoader.
+            final ClassLoader loader = runtime.getCamelContext().getApplicationContextClassLoader();
+            if (loader instanceof CompositeClassloader) {
+                ((CompositeClassloader) loader).addClassLoader(instance.getClass().getClassLoader());
+            }
+
             return Result.on(instance);
         }
     }

camel-k-loader-java/src/test/java/org/apache/camel/k/loader/java/RoutesLoaderTest.java

@@ -25,6 +25,7 @@
 import org.apache.camel.RoutesBuilder;
 import org.apache.camel.builder.RouteBuilder;
 import org.apache.camel.impl.DefaultCamelContext;
+import org.apache.camel.k.CompositeClassloader;
 import org.apache.camel.k.Runtime;
 import org.apache.camel.k.Source;
 import org.apache.camel.k.SourceLoader;
@@ -109,6 +110,20 @@ public void testLoadJavaWithModel() throws Exception {
         });
     }
 
+    @Test
+    public void testLoadJavaWithNestedType() throws Exception {
+        TestRuntime runtime = new TestRuntime();
+        Source source = Sources.fromURI("classpath:MyRoutesWithNestedTypes.java");
+        SourceLoader loader = RoutesConfigurer.load(runtime, source);
+
+        assertThat(loader).isInstanceOf(JavaSourceLoader.class);
+        assertThat(runtime.builders).hasSize(1);
+        assertThat(runtime.builders).first().isInstanceOf(RouteBuilder.class);
+
+        runtime.getCamelContext().addRoutes(runtime.builders.get(0));
+        runtime.getCamelContext().getApplicationContextClassLoader().loadClass("MyRoutesWithNestedTypes$MyModel");
+    }
+
     @ParameterizedTest
     @MethodSource("parameters")
     public void testLoaders(String location, Class<? extends SourceLoader> type) throws Exception {
@@ -148,6 +163,7 @@ static class TestRuntime implements Runtime {
 
         public TestRuntime() {
             this.camelContext = new DefaultCamelContext();
+            this.camelContext.setApplicationContextClassLoader(new CompositeClassloader());
             this.builders = new ArrayList<>();
             this.configurations = new ArrayList<>();
         }

camel-k-loader-java/src/test/resources/MyRoutesWithNestedTypes.java

@@ -0,0 +1,28 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import org.apache.camel.Exchange;
+import org.apache.camel.Processor;
+import org.apache.camel.builder.RouteBuilder;
+
+public class MyRoutesWithNestedTypes extends RouteBuilder {
+    @Override
+    public void configure() throws Exception {
+    }
+
+    public static class MyModel {
+    }
+}

camel-k-main/camel-k-runtime-main/src/main/java/org/apache/camel/k/main/ApplicationRuntime.java

@@ -28,6 +28,7 @@
 import org.apache.camel.RoutesBuilder;
 import org.apache.camel.RuntimeCamelException;
 import org.apache.camel.impl.DefaultCamelContext;
+import org.apache.camel.k.CompositeClassloader;
 import org.apache.camel.k.Runtime;
 import org.apache.camel.k.support.PropertiesSupport;
 import org.apache.camel.main.BaseMainSupport;
@@ -52,6 +53,7 @@ public ApplicationRuntime() {
 
         this.context = new DefaultCamelContext();
         this.context.setName("camel-k");
+        this.context.setApplicationContextClassLoader(new CompositeClassloader());
 
         this.main = new MainAdapter();
         this.main.configure().setXmlRoutes("false");

camel-k-quarkus/camel-k-quarkus-core/deployment/src/main/java/org/apache/camel/k/core/quarkus/deployment/DeploymentProcessor.java

@@ -30,6 +30,7 @@
 import org.apache.camel.k.Constants;
 import org.apache.camel.k.Runtime;
 import org.apache.camel.k.core.quarkus.RuntimeRecorder;
+import org.apache.camel.quarkus.core.deployment.spi.CamelContextCustomizerBuildItem;
 import org.apache.camel.quarkus.core.deployment.spi.CamelMainListenerBuildItem;
 import org.apache.camel.quarkus.core.deployment.spi.CamelServicePatternBuildItem;
 import org.apache.camel.spi.HasId;
@@ -133,4 +134,10 @@ CamelMainListenerBuildItem registerListener(RuntimeRecorder recorder) {
 
         return new CamelMainListenerBuildItem(recorder.createMainListener(listeners));
     }
+
+    @Record(ExecutionTime.STATIC_INIT)
+    @BuildStep
+    void customizeContext(RuntimeRecorder recorder, BuildProducer<CamelContextCustomizerBuildItem> customizers) {
+        customizers.produce(new CamelContextCustomizerBuildItem(recorder.registerCompositeClassLoader()));
+    }
 }

camel-k-quarkus/camel-k-quarkus-core/runtime/src/main/java/org/apache/camel/k/core/quarkus/RuntimeRecorder.java

@@ -20,12 +20,27 @@
 
 import io.quarkus.runtime.RuntimeValue;
 import io.quarkus.runtime.annotations.Recorder;
+import org.apache.camel.CamelContext;
+import org.apache.camel.k.CompositeClassloader;
 import org.apache.camel.k.Runtime;
 import org.apache.camel.main.MainListener;
+import org.apache.camel.quarkus.core.CamelContextCustomizer;
 
 @Recorder
 public class RuntimeRecorder {
     public RuntimeValue<MainListener> createMainListener(List<Runtime.Listener> listeners) {
         return new RuntimeValue<>(new RuntimeListenerAdapter(listeners));
     }
+
+    public RuntimeValue<CamelContextCustomizer> registerCompositeClassLoader() {
+        return new RuntimeValue<>(new CamelContextCustomizer() {
+            @Override
+            public void customize(CamelContext context) {
+                final ClassLoader oldLoader = context.getApplicationContextClassLoader();
+                final ClassLoader newLoader = CompositeClassloader.wrap(oldLoader);
+
+                context.setApplicationContextClassLoader(newLoader);
+            }
+        });
+    }
 }

camel-k-quarkus/camel-k-quarkus-itests/camel-k-quarkus-itests-core/src/main/java/org/apache/camel/k/core/quarkus/deployment/Application.java

@@ -19,6 +19,7 @@
 import java.util.ServiceLoader;
 
 import javax.enterprise.context.ApplicationScoped;
+import javax.inject.Inject;
 import javax.json.Json;
 import javax.json.JsonArrayBuilder;
 import javax.json.JsonObject;
@@ -27,11 +28,15 @@
 import javax.ws.rs.Produces;
 import javax.ws.rs.core.MediaType;
 
+import org.apache.camel.CamelContext;
 import org.apache.camel.k.Runtime;
 
 @Path("/test")
 @ApplicationScoped
 public class Application {
+    @Inject
+    CamelContext camelContext;
+
     @GET
     @Path("/services")
     @Produces(MediaType.APPLICATION_JSON)
@@ -46,4 +51,11 @@ public JsonObject getServices() {
             .add("services", builder)
             .build();
     }
+
+    @GET
+    @Path("/application-classloader")
+    @Produces(MediaType.TEXT_PLAIN)
+    public String getApplicationClassloader() {
+        return camelContext.getApplicationContextClassLoader().getClass().getName();
+    }
 }

camel-k-quarkus/camel-k-quarkus-itests/camel-k-quarkus-itests-core/src/test/java/org/apache/camel/k/core/quarkus/deployment/ExtensionTest.java

@@ -18,14 +18,17 @@
 
 import javax.ws.rs.core.MediaType;
 
+import io.quarkus.test.junit.DisabledOnNativeImage;
 import io.quarkus.test.junit.QuarkusTest;
 import io.restassured.RestAssured;
 import io.restassured.path.json.JsonPath;
+import org.apache.camel.k.CompositeClassloader;
 import org.apache.camel.k.listener.ContextConfigurer;
 import org.apache.camel.k.listener.RoutesConfigurer;
 import org.junit.jupiter.api.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.hamcrest.Matchers.is;
 
 @QuarkusTest
 public class ExtensionTest {
@@ -45,4 +48,15 @@ public void testServices() {
             RoutesConfigurer.class.getName()
         );
     }
+
+    @DisabledOnNativeImage
+    @Test
+    public void testClassLoader() {
+        RestAssured.given()
+            .accept(MediaType.TEXT_PLAIN)
+            .get("/test/application-classloader")
+            .then()
+            .statusCode(200)
+            .body(is(CompositeClassloader.class.getName()));
+    }
 }

camel-k-runtime-core/src/main/java/org/apache/camel/k/CompositeClassloader.java

@@ -0,0 +1,52 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.camel.k;
+
+import java.util.List;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+public class CompositeClassloader extends ClassLoader {
+    private final List<ClassLoader> loaders = new CopyOnWriteArrayList<>();
+
+    public CompositeClassloader() {
+    }
+
+    public CompositeClassloader(ClassLoader parent) {
+        super(parent);
+    }
+
+    public void addClassLoader(ClassLoader loader) {
+        loaders.add(loader);
+    }
+
+    @Override
+    public Class<?> loadClass(String name) throws ClassNotFoundException {
+        for (ClassLoader loader: loaders) {
+            try {
+                return loader.loadClass(name);
+            } catch (ClassNotFoundException e) {
+                // ignore
+            }
+        }
+
+        return super.loadClass(name);
+    }
+
+    public static CompositeClassloader wrap(ClassLoader parent) {
+        return parent != null ? new CompositeClassloader(parent) : new CompositeClassloader();
+    }
+}