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/*
* 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.qpid.disttest;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
/**
* A variation of the visitor pattern that uses reflection to call the correct
* visit method. By convention, subclasses should provide public
* <pre>visit(SpecificClass)</pre> methods.
*/
public abstract class Visitor
{
private static final String VISITOR_METHOD_NAME = "visit";
public void visit(Object targetObject)
{
Class<? extends Object> targetObjectClass = targetObject.getClass();
final Method method = findVisitMethodForTargetObjectClass(targetObjectClass);
invokeVisitMethod(targetObject, method);
}
private Method findVisitMethodForTargetObjectClass(
Class<? extends Object> targetObjectClass)
{
final Method method;
try
{
method = getClass().getDeclaredMethod(VISITOR_METHOD_NAME, targetObjectClass);
}
catch (Exception e)
{
throw new DistributedTestException("Failed to find method " + VISITOR_METHOD_NAME + " on object of class " + targetObjectClass, e);
}
return method;
}
private void invokeVisitMethod(Object targetObject, final Method method)
{
try
{
method.invoke(this, targetObject);
}
catch (IllegalArgumentException e)
{
throw new DistributedTestException(e);
}
catch (IllegalAccessException e)
{
throw new DistributedTestException(e);
}
catch (InvocationTargetException e)
{
throw new DistributedTestException(e.getCause());
}
}
}
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