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   *  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
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   *    https://www.apache.org/licenses/LICENSE-2.0
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  package org.apache.cayenne.di.spi;
  
  import java.lang.ref.WeakReference;
  import java.lang.reflect.Method;
  
  import org.apache.cayenne.di.DIRuntimeException;
  
  /**
   * A class that wraps an annotated method call of an object, passing it DI scope events.
   * 
   * @since 3.1
   */
  public class ScopeEventBinding {
  
      private WeakReference<Object> objectReference;
      private Method eventHandlerMethod;
      private int argWidth;
  
      public ScopeEventBinding(Object object, Method eventHandlerMethod) {
  
          // store weak references for objects to avoid retaining them when they go out of
          // scope
          this.objectReference = new WeakReference<Object>(object);
          this.eventHandlerMethod = eventHandlerMethod;
          this.argWidth = eventHandlerMethod.getParameterTypes().length;
  
          // allow public methods of non-public classes to be annotated
          eventHandlerMethod.setAccessible(true);
      }
  
      public Object getObject() {
          return objectReference.get();
      }
  
      public boolean onScopeEvent(Object... eventArgs) {
  
          Object object = objectReference.get();
          if (object == null) {
              return false;
          }
  
          try {
              eventHandlerMethod.invoke(object, invocationArguments(eventArgs));
          }
          catch (Exception e) {
              throw new DIRuntimeException(
                      "Error invoking event method %s",
                      e,
                      eventHandlerMethod.getName());
          }
  
          return true;
      }
  
      private Object[] invocationArguments(Object[] eventArgs) {
  
          int eventArgWidth = (eventArgs == null) ? 0 : eventArgs.length;
  
          if (argWidth != eventArgWidth) {
              throw new DIRuntimeException(
                      "Event argument list size (%d) is different "
                              + "from the handler method argument list size (%d)",
                      eventArgWidth,
                      argWidth);
          }
  
          return eventArgs;
      }
  }
  