com.esri.gpt.control.webharvest.client.dcat.DCATQueryBuilder.java Source code

Introduction

Here is the source code for com.esri.gpt.control.webharvest.client.dcat.DCATQueryBuilder.java

Source

/*
 * Copyright 2013 Esri.
 *
 * 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 com.esri.gpt.control.webharvest.client.dcat;

import com.esri.gpt.catalog.harvest.protocols.HarvestProtocolDCAT;
import com.esri.gpt.control.webharvest.IterationContext;
import com.esri.gpt.control.webharvest.common.CommonCapabilities;
import com.esri.gpt.framework.dcat.DcatParser;
import com.esri.gpt.framework.dcat.DcatParserAdaptor;
import com.esri.gpt.framework.dcat.DcatVersion;
import com.esri.gpt.framework.resource.api.Native;
import com.esri.gpt.framework.resource.api.Publishable;
import com.esri.gpt.framework.resource.api.SourceUri;
import com.esri.gpt.framework.resource.common.CommonPublishable;
import com.esri.gpt.framework.resource.common.UrlUri;
import com.esri.gpt.framework.resource.query.Capabilities;
import com.esri.gpt.framework.resource.query.Criteria;
import com.esri.gpt.framework.resource.query.Query;
import com.esri.gpt.framework.resource.query.QueryBuilder;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.util.Iterator;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.xml.transform.TransformerException;
import org.apache.commons.io.IOUtils;

/**
 * DCAT query builder.
 */
public class DCATQueryBuilder implements QueryBuilder {

    /** logger */
    private static final Logger LOGGER = Logger.getLogger(DCATQuery.class.getCanonicalName());
    /** capabilities */
    private static final Capabilities capabilities = new DCATCommonCapabilities();
    /** iteration context */
    private IterationContext context;
    /** service info */
    private DCATInfo info;

    /**
     * Creates instance of the builder.
     * @param context iteration context
     * @param protocol protocol
     * @param url URL
     */
    public DCATQueryBuilder(IterationContext context, HarvestProtocolDCAT protocol, String url) {
        if (context == null) {
            throw new IllegalArgumentException("No context provided.");
        }
        this.context = context;
        this.info = new DCATInfo(url, protocol.getFormat());
    }

    @Override
    public Capabilities getCapabilities() {
        return capabilities;
    }

    @Override
    public Query newQuery(Criteria crt) {
        Query q = new DCATQuery(context, info, crt);
        LOGGER.log(Level.FINER, "Query created: {0}", q);
        return q;
    }

    /**
     * Open stream.
     * @return stream
     * @throws IOException if opening stream fails
     */
    private InputStream openStream(URL url) throws IOException {

        // create temporary file
        final File tempFile = File.createTempFile("dcat_", Long.toString(System.nanoTime()));

        InputStream in = null;
        OutputStream out = null;

        try {

            // copy URL stream into temporary file
            in = url.openStream();
            out = new FileOutputStream(tempFile);
            IOUtils.copy(in, out);

        } catch (IOException ex) {

            // close temporary file stream and delete file
            IOUtils.closeQuietly(out);
            out = null;
            tempFile.delete();

            // rethrow exception
            throw ex;

        } catch (RuntimeException ex) {

            // close temporary file stream and delete file
            IOUtils.closeQuietly(out);
            out = null;
            tempFile.delete();

            // rethrow exception
            throw ex;

        } finally {

            // close all quietly
            IOUtils.closeQuietly(out);
            IOUtils.closeQuietly(in);

        }

        return new FileInputStream(tempFile) {
            @Override
            public void close() throws IOException {
                super.close();
                // delete temporary file
                tempFile.delete();
            }
        };
    }

    @Override
    public Native getNativeResource() {
        DCATIteratorAdaptor adaptor = null;
        try {
            URL url = new URL(info.getUrl());
            adaptor = new DCATIteratorAdaptor(info.getFormat(),
                    new DcatParserAdaptor(new DcatParser(openStream(url))));
            Iterator<Publishable> iterator = adaptor.iterator();
            if (iterator.hasNext() && adaptor.getDcatVersion().compareTo(DcatVersion.DV10) == 0) {
                return new NativeImpl(iterator.next().getContent());
            }
        } catch (Exception ex) {
            LOGGER.log(Level.WARNING, "Error reading native resource.", ex);
        } finally {
            if (adaptor != null) {
                adaptor.close();
            }
        }
        return null;
    }

    /**
     * Native implementation.
     */
    private class NativeImpl extends CommonPublishable implements Native {
        private String content;

        public NativeImpl(String content) {
            this.content = content;
        }

        @Override
        public SourceUri getSourceUri() {
            return new UrlUri(info.getUrl());
        }

        @Override
        public String getContent() throws IOException {
            return content;
        }
    }

    /**
     * DCAT capabilities.
     */
    private static class DCATCommonCapabilities extends CommonCapabilities {

        @Override
        public boolean canQueryFromDate() {
            return true;
        }

        @Override
        public boolean canQueryToDate() {
            return true;
        }
    }

}