org.directwebremoting.guice.util.OutermostCallInterceptor Maven / Gradle / Ivy

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DWR is easy Ajax for Java. It makes it simple to call Java code directly from Javascript. It gets rid of almost all the boiler plate code between the web browser and your Java code.

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/*
 * Copyright 2008 Tim Peierls
 *
 * 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 org.directwebremoting.guice.util;

import com.google.inject.Inject;
import com.google.inject.Injector;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;

/**
 * Provides static decorator method for restricting interception to
 * the outermost of several nested matching join points. Also provides
 * corresponding MethodInterceptor wrapper method.
 * @author Tim Peierls [tim at peierls dot net]
 */
public class OutermostCallInterceptor implements MethodInterceptor
{
    /**
     * For passing to bindInterceptor to wrap injected MethodInterceptors.
     */
    public static MethodInterceptorWrapper outermostCallWrapper()
    {
        return new MethodInterceptorWrapper()
        {
            public MethodInterceptor wrap(MethodInterceptor methodInterceptor)
            {
                return outermostCall(methodInterceptor);
            }
        };
    }

    /**
     * Decorates a MethodInterceptor so that only the outermost invocation
     * using that interceptor will be intercepted and nested invocations will
     * be ignored.
     */
    public static MethodInterceptor outermostCall(MethodInterceptor interceptor)
    {
        return new OutermostCallInterceptor(interceptor);
    }

    @Inject void injectInterceptor(Injector injector)
    {
        injector.injectMembers(interceptor);
    }

    public Object invoke(MethodInvocation invocation) throws Throwable
    {
        int savedCount = count.get();
        count.set(savedCount + 1);
        try
        {
            if (count.get() > 1)
            {
                return invocation.proceed();
            }
            else
            {
                return interceptor.invoke(invocation);
            }
        }
        finally
        {
            count.set(savedCount);
        }
    }

    private OutermostCallInterceptor(MethodInterceptor interceptor)
    {
        this.interceptor = interceptor;
    }

    private final MethodInterceptor interceptor;

    private final ThreadLocal count = new ThreadLocal()
    {
        @Override
        protected Integer initialValue()
        {
            return 0;
        }
    };
}