com.gistlabs.mechanize.filters.DefaultMechanizeChainFilter.java Source code

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Here is the source code for com.gistlabs.mechanize.filters.DefaultMechanizeChainFilter.java

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/**
 * Copyright (C) 2012-2014 Gist Labs, LLC. (http://gistlabs.com)
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */
package com.gistlabs.mechanize.filters;

import java.util.LinkedList;

import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.protocol.HttpContext;

/**
 * Inprired by Servlet Filters, this represents executing a request and getting a response.
 *
 * Each filter in turn is called, and eventually a terminal MechanizeFilter will be called last.
 *
 */
public class DefaultMechanizeChainFilter implements MechanizeFilter {
    final MechanizeFilter theEnd;
    final LinkedList<MechanizeChainFilter> filters = new LinkedList<MechanizeChainFilter>();

    public DefaultMechanizeChainFilter(final MechanizeFilter theEnd) {
        if (theEnd == null)
            throw new NullPointerException("The end of the processing chain can't be null!");
        this.theEnd = theEnd;
    }

    /**
     * Adds a filter, runs after those added before it
     *
     * @param filter
     * @return
     */
    public DefaultMechanizeChainFilter add(final MechanizeChainFilter filter) {
        filters.add(filter);
        return this;
    }

    /**
     * Adds a filter, to the front of the pipeline
     *
     * @param filter
     */
    public void prefix(final MechanizeChainFilter filter) {
        filters.addFirst(filter);
    }

    @Override
    public HttpResponse execute(final HttpUriRequest request, final HttpContext context) {
        return new ExecutionState().execute(request, context);
    }

    class ExecutionState implements MechanizeFilter {
        int index = 0;

        @Override
        public HttpResponse execute(final HttpUriRequest request, final HttpContext context) {
            if (moreFilters())
                return filters.get(index++).execute(request, context, this);
            else
                return theEnd.execute(request, context);
        }

        public boolean moreFilters() {
            return index < filters.size();
        }
    }
}