org.opencredo.couchdb.inbound.CouchDbAllDocumentsMessageSource.java Source code

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Here is the source code for org.opencredo.couchdb.inbound.CouchDbAllDocumentsMessageSource.java

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/*
 * Copyright 2011 the original author or authors
 *
 * 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.opencredo.couchdb.inbound;

import java.net.URI;
import java.net.URISyntaxException;
import java.util.HashMap;
import java.util.Map;
import java.util.Queue;
import java.util.concurrent.ArrayBlockingQueue;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.ObjectNode;
import org.opencredo.couchdb.core.CouchDbDocumentOperations;
import org.opencredo.couchdb.core.CouchDbDocumentTemplate;
import org.springframework.messaging.Message;
import org.springframework.integration.context.IntegrationObjectSupport;
import org.springframework.integration.core.MessageSource;
import org.springframework.integration.support.MessageBuilder;
import org.springframework.util.Assert;
import org.springframework.web.util.UriComponentsBuilder;

/**
 * A MessageSource that takes the URI of a CouchDB view or database and receives all messages sequentially by using the skip and limit parameters
 * which are supported by CouchDB. The retrieval of the documents is performed through an instance of CouchDbDocumentOperations.
 * <p/>
 * Each request returns and stores internally a number of {@link JsonNode}s equal to the queue capacity; when the queue becomes empty, a new request
 * is made with limit and skip adjusted accordingly.
 * 
 * @author Kambiz Darabi
 * @since 2014-02-18
 */
public class CouchDbAllDocumentsMessageSource extends IntegrationObjectSupport implements MessageSource<URI> {

    private final int limit;

    /**
     * The number of documents which we already retrieved.
     */
    private int skip = 0;

    final CouchDbDocumentOperations couchDbDocumentOperations;

    private final Queue<URI> toBeReceived;

    /**
     * The base URI of the database or view to which <code>limit</code> and <code>skip</code> query parameters are added.
     */
    private final URI databaseUri;

    private String baseUri;

    /**
     * Creates an instance with a default database to connect to.
     * 
     * @throws URISyntaxException
     */
    public CouchDbAllDocumentsMessageSource(String databaseUrl, int limit) throws URISyntaxException {
        this.couchDbDocumentOperations = new CouchDbDocumentTemplate(databaseUrl);
        this.limit = limit;
        this.toBeReceived = new ArrayBlockingQueue<URI>(limit);
        this.databaseUri = new URI(databaseUrl);
        int ind = databaseUrl.indexOf("/_all_docs");
        if (ind != -1) {
            this.baseUri = databaseUrl.substring(0, ind);
        } else {
            ind = databaseUrl.indexOf("/_design/");
            if (ind != -1) {
                this.baseUri = databaseUrl.substring(0, ind);
            } else {
                throw new IllegalArgumentException(
                        "databaseUrl must be a /_design/../_view/... or a /_all_docs URL");
            }
        }
    }

    public Message<URI> receive() {
        if (toBeReceived.isEmpty()) {
            URI skipUri = UriComponentsBuilder.fromUri(databaseUri).replaceQueryParam("limit", limit)
                    .replaceQueryParam("skip", skip).build().toUri();
            ObjectNode response = couchDbDocumentOperations.readDocument(skipUri, ObjectNode.class);
            ArrayNode rows = (ArrayNode) response.get("rows");
            int size = rows.size();
            Assert.isTrue(size <= limit, "Retrieved more rows than limit");
            for (int i = 0; i < size; i++) {
                JsonNode node = rows.get(i);
                String id = node.get("id").textValue();
                try {
                    toBeReceived.add(new URI(baseUri + "/" + id));
                    skip++;
                } catch (URISyntaxException e) {
                    logger.error("Error creating the URI of document from baseUri and ID", e);
                    return null;
                }
            }
        }

        Map<String, String> headers = createHeaderMap(databaseUri, skip, limit);
        return prepareMessage(toBeReceived.poll(), headers);
    }

    Map<String, String> createHeaderMap(URI uri, int skip, int limit) {
        Map<String, String> headers = new HashMap<String, String>(4);
        headers.put("couchdb-uri", uri.toString());
        headers.put("couchdb-skip", String.valueOf(skip));
        headers.put("couchdb-limit", String.valueOf(limit));
        return headers;
    }

    private Message<URI> prepareMessage(URI uri, Map<String, String> headers) {
        Message<URI> message = null;
        if (uri != null) {
            message = MessageBuilder.withPayload(uri).copyHeaders(headers).build();
        }
        return message;
    }
}