com.lyncode.xoai.serviceprovider.iterators.MetadataFormatIterator.java Source code

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Here is the source code for com.lyncode.xoai.serviceprovider.iterators.MetadataFormatIterator.java

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/**
 * Copyright 2012 Lyncode
 *
 * 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.
 *
 * @author Development @ Lyncode <development@lyncode.com>
 * @version 3.1.0
 */

package com.lyncode.xoai.serviceprovider.iterators;

import com.lyncode.xoai.serviceprovider.OAIServiceConfiguration;
import com.lyncode.xoai.serviceprovider.core.Parameters;
import com.lyncode.xoai.serviceprovider.exceptions.InternalHarvestException;
import com.lyncode.xoai.serviceprovider.exceptions.NoMetadataFormatsException;
import com.lyncode.xoai.serviceprovider.exceptions.ParseException;
import com.lyncode.xoai.serviceprovider.oaipmh.OAIPMHParser;
import com.lyncode.xoai.serviceprovider.oaipmh.spec.ListMetadataFormatsType;
import com.lyncode.xoai.serviceprovider.oaipmh.spec.MetadataFormatType;
import com.lyncode.xoai.serviceprovider.oaipmh.spec.OAIPMHtype;
import com.lyncode.xoai.serviceprovider.parser.AboutItemParser;
import com.lyncode.xoai.serviceprovider.parser.AboutSetParser;
import com.lyncode.xoai.serviceprovider.parser.MetadataParser;
import com.lyncode.xoai.serviceprovider.exceptions.IdDoesNotExistException;
import com.lyncode.xoai.serviceprovider.parser.DescriptionParser;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.StatusLine;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;

import java.io.IOException;
import java.io.InputStream;
import java.util.LinkedList;
import java.util.Queue;

/**
 * @author Development @ Lyncode <development@lyncode.com>
 * @version 3.1.0
 */
public class MetadataFormatIterator {
    private Parameters parameters;
    private OAIServiceConfiguration<MetadataParser, AboutItemParser, DescriptionParser, AboutSetParser> config;

    public MetadataFormatIterator(
            OAIServiceConfiguration<MetadataParser, AboutItemParser, DescriptionParser, AboutSetParser> config,
            Parameters parameters) {
        super();
        this.config = config;
        this.parameters = parameters;
    }

    private Queue<MetadataFormatType> _queue = null;

    private String makeUrl() {
        return this.parameters.toUrl();
    }

    public ListMetadataFormatsType harvest() throws InternalHarvestException {
        HttpClient httpclient = new DefaultHttpClient();
        String url = makeUrl();
        config.getLogger().info("Harvesting: " + url);
        HttpGet httpget = new HttpGet(url);
        httpget.addHeader("User-Agent", config.getServiceName() + " : XOAI Service Provider");
        httpget.addHeader("From", config.getServiceName());

        HttpResponse response = null;

        try {
            response = httpclient.execute(httpget);
            StatusLine status = response.getStatusLine();

            config.getLogger().debug(response.getStatusLine());

            if (status.getStatusCode() == 503) // 503 Status (must wait)
            {
                org.apache.http.Header[] headers = response.getAllHeaders();
                for (org.apache.http.Header h : headers) {
                    if (h.getName().equals("Retry-After")) {
                        String retry_time = h.getValue();
                        try {
                            Thread.sleep(Integer.parseInt(retry_time) * 1000);
                        } catch (NumberFormatException e) {
                            config.getLogger().warn("Cannot parse " + retry_time + " to Integer", e);
                        } catch (InterruptedException e) {
                            config.getLogger().debug(e.getMessage(), e);
                        }
                        httpclient.getConnectionManager().shutdown();
                        httpclient = new DefaultHttpClient();
                        response = httpclient.execute(httpget);
                    }
                }
            }

            HttpEntity entity = response.getEntity();
            InputStream instream = entity.getContent();

            OAIPMHtype res = OAIPMHParser.parse(instream, config);

            return res.getListMetadataFormats();
        } catch (IOException e) {
            throw new InternalHarvestException(e);
        } catch (ParseException e) {
            throw new InternalHarvestException(e);
        }

    }

    public boolean hasNext() throws NoMetadataFormatsException, IdDoesNotExistException, InternalHarvestException {
        if (_queue == null) {
            if (_queue == null)
                _queue = new LinkedList<MetadataFormatType>();
            this.harvest();
        }

        return (_queue.size() > 0);
    }

    public MetadataFormatType next() {
        return _queue.poll();
    }

}