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The system code for the caching AOP example
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/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) 2013-2015 Oracle and/or its affiliates. All rights reserved.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
 * obtain a copy of the License at
 * https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
 * or packager/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
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package org.glassfish.examples.caching.aop;

import java.lang.reflect.Method;
import java.util.HashMap;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;

/**
 * This is an interceptor that will implement caching
 * of method results.
 * 
 * This interceptor does not import any hk2 API and thus
 * is a pure AOP Alliance method interceptor that might be
 * used in any software that enabled AOP Alliance interceptors
 * 
 * @author jwells
 *
 */
public class CachingMethodInterceptor implements MethodInterceptor {
    private final HashMap cache = new HashMap();

    /* (non-Javadoc)
     * @see org.aopalliance.intercept.MethodInterceptor#invoke(org.aopalliance.intercept.MethodInvocation)
     */
    @Override
    public Object invoke(MethodInvocation invocation) throws Throwable {
        Object args[] = invocation.getArguments();
        if (args.length != 1) {
            return invocation.proceed();
        }
        
        Object arg = args[0];
        if (arg == null) {
            return invocation.proceed();
        }
        
        Method m = invocation.getMethod();
        CacheKey key = new CacheKey(m.getDeclaringClass().getName(), m.getName(), arg);
        
        if (!cache.containsKey(key)) {
            Object retVal = invocation.proceed();
            
            cache.put(key, retVal);
            
            return retVal;
        }
        
        // Found it in the cache!  Do not call the method
        return cache.get(key);
    }
}