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/*
* Copyright (C) 2007 The Guava Authors
*
* Licensed 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 com.google.common.eventbus;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.base.Preconditions;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import javax.annotation.Nullable;
/**
* Wraps a single-argument 'handler' method on a specific object.
*
* <p>This class only verifies the suitability of the method and event type if
* something fails. Callers are expected to verify their uses of this class.
*
* <p>Two EventHandlers are equivalent when they refer to the same method on the
* same object (not class). This property is used to ensure that no handler
* method is registered more than once.
*
* @author Cliff Biffle
*/
class EventHandler {
/** Object sporting the handler method. */
private final Object target;
/** Handler method. */
private final Method method;
/**
* Creates a new EventHandler to wrap {@code method} on @{code target}.
*
* @param target object to which the method applies.
* @param method handler method.
*/
EventHandler(Object target, Method method) {
Preconditions.checkNotNull(target,
"EventHandler target cannot be null.");
Preconditions.checkNotNull(method, "EventHandler method cannot be null.");
this.target = target;
this.method = method;
method.setAccessible(true);
}
/**
* Invokes the wrapped handler method to handle {@code event}.
*
* @param event event to handle
* @throws InvocationTargetException if the wrapped method throws any
* {@link Throwable} that is not an {@link Error} ({@code Error} instances are
* propagated as-is).
*/
public void handleEvent(Object event) throws InvocationTargetException {
checkNotNull(event);
try {
method.invoke(target, new Object[] { event });
} catch (IllegalArgumentException e) {
throw new Error("Method rejected target/argument: " + event, e);
} catch (IllegalAccessException e) {
throw new Error("Method became inaccessible: " + event, e);
} catch (InvocationTargetException e) {
if (e.getCause() instanceof Error) {
throw (Error) e.getCause();
}
throw e;
}
}
@Override public String toString() {
return "[wrapper " + method + "]";
}
@Override public int hashCode() {
final int PRIME = 31;
return (PRIME + method.hashCode()) * PRIME
+ System.identityHashCode(target);
}
@Override public boolean equals(@Nullable Object obj) {
if (obj instanceof EventHandler) {
EventHandler that = (EventHandler) obj;
// Use == so that different equal instances will still receive events.
// We only guard against the case that the same object is registered
// multiple times
return target == that.target && method.equals(that.method);
}
return false;
}
}
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