uitest/src/main/java/com/vaadin/tests/minitutorials/v7b6/LettingUserDownloadFile.java


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package com.vaadin.tests.minitutorials.v7b6;

import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

import javax.imageio.ImageIO;

import com.vaadin.server.FileDownloader;
import com.vaadin.server.StreamResource;
import com.vaadin.server.StreamResource.StreamSource;
import com.vaadin.server.VaadinRequest;
import com.vaadin.ui.Button;
import com.vaadin.ui.UI;

public class LettingUserDownloadFile extends UI {

    @Override
    protected void init(VaadinRequest request) {
        Button downloadButton = new Button("Download image");

        StreamResource myResource = createResource();
        FileDownloader fileDownloader = new FileDownloader(myResource);
        fileDownloader.extend(downloadButton);

        setContent(downloadButton);
    }

    private StreamResource createResource() {
        return new StreamResource(new StreamSource() {
            @Override
            public InputStream getStream() {
                String text = "My image";
                BufferedImage bi = new BufferedImage(100, 30,
                        BufferedImage.TYPE_3BYTE_BGR);
                bi.getGraphics().drawChars(text.toCharArray(), 0, text.length(),
                        10, 20);

                try {
                    ByteArrayOutputStream bos = new ByteArrayOutputStream();
                    ImageIO.write(bi, "png", bos);
                    return new ByteArrayInputStream(bos.toByteArray());
                } catch (IOException e) {
                    e.printStackTrace();
                    return null;
                }

            }
        }, "myImage.png");
    }

}