fi.semantum.strategia.custom.OnDemandFileDownloader.java Source code

Introduction

Here is the source code for fi.semantum.strategia.custom.OnDemandFileDownloader.java

Source

/*******************************************************************************
 * Copyright (c) 2014 Ministry of Transport and Communications (Finland).
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     Semantum Oy - initial API and implementation
 *******************************************************************************/
package fi.semantum.strategia.custom;

import java.io.IOException;

import com.vaadin.server.DownloadStream;
import com.vaadin.server.FileDownloader;
import com.vaadin.server.StreamResource;
import com.vaadin.server.StreamResource.StreamSource;
import com.vaadin.server.VaadinRequest;
import com.vaadin.server.VaadinResponse;
import com.vaadin.server.VaadinSession;

/**
 * Adapted from https://vaadin.com/wiki/-/wiki/Main/Letting+the+user+download+a+file
 * This version also sets the content length and handles session locking properly.
 * 
 * This specializes {@link FileDownloader} in a way, such that both the file name and content can be determined
 * on-demand, i.e. when the user has clicked the component.
 *
 */
public class OnDemandFileDownloader extends FileDownloader {

    /**
     * Provide both the {@link StreamSource} and the filename in an on-demand way.
     */
    public interface OnDemandStreamSource extends StreamSource {
        public String getFileName();

        public long getFileSize();

        public void onRequest();
    }

    private static final long serialVersionUID = 1L;
    private final OnDemandStreamSource onDemandStreamSource;

    public OnDemandFileDownloader(OnDemandStreamSource onDemandStreamSource) {
        super(new StreamResource(onDemandStreamSource, "") {
            private static final long serialVersionUID = -7386418918429322891L;

            // Inject the content length
            @Override
            public DownloadStream getStream() {
                DownloadStream ds = super.getStream();
                long size = ((OnDemandStreamSource) getStreamSource()).getFileSize();
                if (size > 0) {
                    ds.setParameter("Content-Length", String.valueOf(size));
                }
                return ds;
            }
        });
        this.onDemandStreamSource = onDemandStreamSource;
    }

    @Override
    public boolean handleConnectorRequest(VaadinRequest request, VaadinResponse response, String path)
            throws IOException {
        VaadinSession session = getSession();

        session.lock();
        try {
            onDemandStreamSource.onRequest();
            getResource().setFilename(onDemandStreamSource.getFileName());
        } finally {
            session.unlock();
        }
        return super.handleConnectorRequest(request, response, path);
    }

    public StreamResource getResource() {
        return (StreamResource) this.getResource("dl");
    }

}