code: /*
   * 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.skywalking.oap.server.core.oal.rt;
  
  import java.lang.reflect.Constructor;
  import java.util.HashSet;
  import java.util.Set;
  import lombok.RequiredArgsConstructor;
  import lombok.extern.slf4j.Slf4j;
  import org.apache.skywalking.oap.server.core.CoreModule;
  import org.apache.skywalking.oap.server.core.analysis.StreamAnnotationListener;
  import org.apache.skywalking.oap.server.core.source.SourceReceiver;
  import org.apache.skywalking.oap.server.core.storage.StorageBuilderFactory;
  import org.apache.skywalking.oap.server.core.storage.StorageModule;
  import org.apache.skywalking.oap.server.library.module.ModuleManager;
  import org.apache.skywalking.oap.server.library.module.ModuleProvider;
  import org.apache.skywalking.oap.server.library.module.ModuleStartException;
  import org.apache.skywalking.oap.server.library.module.Service;
  
  /**
   * Activate {@link OALEngine} according to {@link OALDefine}
   */
  @Slf4j
  @RequiredArgsConstructor
  public class OALEngineLoaderService implements Service {
  
      private final Set<OALDefine> oalDefineSet = new HashSet<>();
      private final ModuleManager moduleManager;
  
      /**
       * Normally it is invoked in the {@link ModuleProvider#start()} of the receiver-plugin module.
       */
      public void load(OALDefine define) throws ModuleStartException {
          if (oalDefineSet.contains(define)) {
              // each oal define will only be activated once
              return;
          }
          try {
              OALEngine engine = loadOALEngine(define);
              StreamAnnotationListener streamAnnotationListener = new StreamAnnotationListener(moduleManager);
              engine.setStreamListener(streamAnnotationListener);
              engine.setDispatcherListener(moduleManager.find(CoreModule.NAME)
                                                        .provider()
                                                        .getService(SourceReceiver.class)
                                                        .getDispatcherDetectorListener());
              engine.setStorageBuilderFactory(moduleManager.find(StorageModule.NAME)
                                                           .provider()
                                                           .getService(StorageBuilderFactory.class));
  
              engine.start(OALEngineLoaderService.class.getClassLoader());
              engine.notifyAllListeners();
  
              oalDefineSet.add(define);
          } catch (ReflectiveOperationException | OALCompileException e) {
              throw new ModuleStartException(e.getMessage(), e);
          }
      }
  
      /**
       * Load the OAL Engine runtime, because runtime module depends on core, so we have to use class::forname to locate
       * it.
       */
      private static OALEngine loadOALEngine(OALDefine define) throws ReflectiveOperationException {
          Class<?> engineRTClass = Class.forName("org.apache.skywalking.oal.rt.OALRuntime");
          Constructor<?> engineRTConstructor = engineRTClass.getConstructor(OALDefine.class);
          return (OALEngine) engineRTConstructor.newInstance(define);
      }
  }
  