11d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert/*
21d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Copyright (C) 2007 The Guava Authors
31d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert *
41d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Licensed under the Apache License, Version 2.0 (the "License");
51d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * you may not use this file except in compliance with the License.
61d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * You may obtain a copy of the License at
71d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert *
81d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * http://www.apache.org/licenses/LICENSE-2.0
91d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert *
101d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Unless required by applicable law or agreed to in writing, software
111d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * distributed under the License is distributed on an "AS IS" BASIS,
121d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
131d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * See the License for the specific language governing permissions and
141d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * limitations under the License.
151d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */
161d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert
171d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertpackage com.google.common.eventbus;
181d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert
197dd252788645e940eada959bdde927426e2531c9Paul Duffinimport static com.google.common.base.Preconditions.checkNotNull;
207dd252788645e940eada959bdde927426e2531c9Paul Duffin
211d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport com.google.common.base.Preconditions;
227dd252788645e940eada959bdde927426e2531c9Paul Duffin
231d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport java.lang.reflect.InvocationTargetException;
241d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport java.lang.reflect.Method;
251d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert
267dd252788645e940eada959bdde927426e2531c9Paul Duffinimport javax.annotation.Nullable;
277dd252788645e940eada959bdde927426e2531c9Paul Duffin
281d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert/**
290888a09821a98ac0680fad765217302858e70fa4Paul Duffin * Wraps a single-argument subscriber method on a specific object.
301d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert *
311d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>This class only verifies the suitability of the method and event type if
321d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * something fails.  Callers are expected to verify their uses of this class.
331d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert *
340888a09821a98ac0680fad765217302858e70fa4Paul Duffin * <p>Two EventSubscribers are equivalent when they refer to the same method on the
350888a09821a98ac0680fad765217302858e70fa4Paul Duffin * same object (not class).   This property is used to ensure that no subscriber
361d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * method is registered more than once.
371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert *
381d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @author Cliff Biffle
391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */
400888a09821a98ac0680fad765217302858e70fa4Paul Duffinclass EventSubscriber {
411d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert
420888a09821a98ac0680fad765217302858e70fa4Paul Duffin  /** Object sporting the subscriber method. */
431d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert  private final Object target;
440888a09821a98ac0680fad765217302858e70fa4Paul Duffin  /** Subscriber method. */
451d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert  private final Method method;
461d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert
471d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert  /**
480888a09821a98ac0680fad765217302858e70fa4Paul Duffin   * Creates a new EventSubscriber to wrap {@code method} on @{code target}.
491d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert   *
501d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert   * @param target  object to which the method applies.
510888a09821a98ac0680fad765217302858e70fa4Paul Duffin   * @param method  subscriber method.
521d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert   */
530888a09821a98ac0680fad765217302858e70fa4Paul Duffin  EventSubscriber(Object target, Method method) {
540888a09821a98ac0680fad765217302858e70fa4Paul Duffin    Preconditions.checkNotNull(target,
550888a09821a98ac0680fad765217302858e70fa4Paul Duffin        "EventSubscriber target cannot be null.");
560888a09821a98ac0680fad765217302858e70fa4Paul Duffin    Preconditions.checkNotNull(method, "EventSubscriber method cannot be null.");
571d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert
581d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert    this.target = target;
591d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert    this.method = method;
601d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert    method.setAccessible(true);
611d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert  }
621d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert
631d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert  /**
640888a09821a98ac0680fad765217302858e70fa4Paul Duffin   * Invokes the wrapped subscriber method to handle {@code event}.
651d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert   *
661d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert   * @param event  event to handle
671d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert   * @throws InvocationTargetException  if the wrapped method throws any
687dd252788645e940eada959bdde927426e2531c9Paul Duffin   *     {@link Throwable} that is not an {@link Error} ({@code Error} instances are
691d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert   *     propagated as-is).
701d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert   */
711d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert  public void handleEvent(Object event) throws InvocationTargetException {
727dd252788645e940eada959bdde927426e2531c9Paul Duffin    checkNotNull(event);
731d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert    try {
741d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert      method.invoke(target, new Object[] { event });
751d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert    } catch (IllegalArgumentException e) {
761d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert      throw new Error("Method rejected target/argument: " + event, e);
771d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert    } catch (IllegalAccessException e) {
781d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert      throw new Error("Method became inaccessible: " + event, e);
791d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert    } catch (InvocationTargetException e) {
801d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert      if (e.getCause() instanceof Error) {
811d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert        throw (Error) e.getCause();
821d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert      }
831d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert      throw e;
841d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert    }
851d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert  }
861d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert
870888a09821a98ac0680fad765217302858e70fa4Paul Duffin  @Override public String toString() {
881d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert    return "[wrapper " + method + "]";
891d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert  }
901d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert
910888a09821a98ac0680fad765217302858e70fa4Paul Duffin  @Override public int hashCode() {
921d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert    final int PRIME = 31;
930888a09821a98ac0680fad765217302858e70fa4Paul Duffin    return (PRIME + method.hashCode()) * PRIME
940888a09821a98ac0680fad765217302858e70fa4Paul Duffin        + System.identityHashCode(target);
951d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert  }
961d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert
970888a09821a98ac0680fad765217302858e70fa4Paul Duffin  @Override public boolean equals(@Nullable Object obj) {
980888a09821a98ac0680fad765217302858e70fa4Paul Duffin    if (obj instanceof EventSubscriber) {
990888a09821a98ac0680fad765217302858e70fa4Paul Duffin      EventSubscriber that = (EventSubscriber) obj;
1007dd252788645e940eada959bdde927426e2531c9Paul Duffin      // Use == so that different equal instances will still receive events.
1017dd252788645e940eada959bdde927426e2531c9Paul Duffin      // We only guard against the case that the same object is registered
1027dd252788645e940eada959bdde927426e2531c9Paul Duffin      // multiple times
1037dd252788645e940eada959bdde927426e2531c9Paul Duffin      return target == that.target && method.equals(that.method);
1041d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert    }
1057dd252788645e940eada959bdde927426e2531c9Paul Duffin    return false;
1061d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert  }
1070888a09821a98ac0680fad765217302858e70fa4Paul Duffin
1080888a09821a98ac0680fad765217302858e70fa4Paul Duffin  public Object getSubscriber() {
1090888a09821a98ac0680fad765217302858e70fa4Paul Duffin    return target;
1100888a09821a98ac0680fad765217302858e70fa4Paul Duffin  }
1110888a09821a98ac0680fad765217302858e70fa4Paul Duffin
1120888a09821a98ac0680fad765217302858e70fa4Paul Duffin  public Method getMethod() {
1130888a09821a98ac0680fad765217302858e70fa4Paul Duffin    return method;
1140888a09821a98ac0680fad765217302858e70fa4Paul Duffin  }
1151d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert}
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