org.fcrepo.indexer.JcrXmlRetriever.java Source code

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Here is the source code for org.fcrepo.indexer.JcrXmlRetriever.java

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/**
 * Copyright 2015 DuraSpace, Inc.
 *
 * 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.fcrepo.indexer;

import static com.google.common.base.Throwables.propagate;
import static org.apache.http.HttpStatus.SC_OK;
import static org.slf4j.LoggerFactory.getLogger;

import java.io.IOException;
import java.io.InputStream;
import java.net.URI;

import org.apache.http.Header;
import org.apache.http.HttpException;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpHead;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.util.EntityUtils;
import org.slf4j.Logger;

import com.google.common.base.Supplier;

import javax.ws.rs.core.Link;

/**
 * Retrieves Modeshape jcr/xml for file system persistence
 * @author lsitu
 */
public class JcrXmlRetriever implements Supplier<InputStream> {

    private final URI identifier;

    private final HttpClient httpClient;

    private static final Logger LOGGER = getLogger(JcrXmlRetriever.class);

    /**
     * Constructor
     * @param identifier the URI identifier
     * @param client the http client
     */
    public JcrXmlRetriever(final URI identifier, final HttpClient client) {
        this.identifier = identifier;
        this.httpClient = client;
    }

    @Override
    /**
     * Retrieve jcr/xml with no binary contents from the repository
     */
    public InputStream get() {

        try {
            // make an initial HEAD request and check Link headers for descriptions located elsewhere
            final HttpHead headRequest = new HttpHead(identifier);
            final HttpResponse headResponse = httpClient.execute(headRequest);
            URI descriptionURI = null;
            final Header[] links = headResponse.getHeaders("Link");
            if (links != null) {
                for (Header h : headResponse.getHeaders("Link")) {
                    final Link link = Link.valueOf(h.getValue());
                    if (link.getRel().equals("describedby")) {
                        descriptionURI = link.getUri();
                        LOGGER.debug("Using URI from Link header: {}", descriptionURI);
                    }
                }
            }
            if (descriptionURI == null) {
                descriptionURI = identifier;
            }

            final HttpUriRequest request = new HttpGet(descriptionURI.toString() + "/fcr:export?skipBinary=true");
            LOGGER.debug("Retrieving jcr/xml content from: {}...", request.getURI());
            final HttpResponse response = httpClient.execute(request);
            if (response.getStatusLine().getStatusCode() == SC_OK) {
                return response.getEntity().getContent();
            } else {
                throw new HttpException(response.getStatusLine().getStatusCode() + " : "
                        + EntityUtils.toString(response.getEntity()));
            }
        } catch (IOException | HttpException e) {
            throw propagate(e);
        }
    }

}