用于服务器端图像生成的JavaFX [英] JavaFX for server-side image generation

问题描述

这听起来很奇怪，但我想使用JavaFX在服务器端生成我的图表图像。因为JavaFX具有很好的canvas API来执行图像转换连接和定位。

This could sound strange but I want to generate my chart images on server side using JavaFX. Because JavaFX has nice canvas API to perform image transformations joins and positioning.

特别是我有一个spring MVC服务来生成我的图表作为图像。
主要问题是如何从方便的Spring bean调用javaFX API。
如果我尝试从java应用程序运行javafx代码（不扩展javaFX Application类），我得到

In particular I have a spring MVC service to generate my charts as images. The main problem is how to invoke javaFX API from a convenient Spring bean. If I try to just run javafx code from java application (not extending javaFX Application class) I get

java.lang.IllegalStateException: Toolkit not initialized

您对如何解决此问题有任何建议/想法吗？

Do you have any suggestions/ideas how to solve this issue?

推荐答案

经过一些研究后，我用JavaFX实现了画布绘制，这是一个简化的例子：

So after some research I've implemented canvas draw with JavaFX and here is a simplified example:

首先，我创建了在单独的线程中启动的JavaFX应用程序（我使用Spring taskExecutor，但可以使用普通的java线程）。

First I made the JavaFX application which is being launched in a separate thread (I use Spring taskExecutor but a plain java thread can be used).

public class ChartGenerator extends Application {

    private static Canvas canvas;

    private static volatile byte[] result;

    public static void initialize(TaskExecutor taskExecutor) {
        taskExecutor.execute(new Runnable() {
            @Override
            public void run() {
                launch(ChartGenerator.class);
            }
        });
    }

    public static synchronized byte[] generateChart(final Object... params) {
        Platform.runLater(new Runnable() {
            @Override
            public void run() {
                ByteArrayOutputStream baos = null;
                try {
                    GraphicsContext gc = canvas.getGraphicsContext2D();
                    gc.clearRect(0, 0, canvas.getWidth(), canvas.getHeight());
                    /**
                     * Do the work with canvas
                     **/
                    final SnapshotParameters snapshotParameters = new SnapshotParameters();
                    snapshotParameters.setFill(Color.TRANSPARENT);
                    WritableImage image = canvas.snapshot(snapshotParameters, null);
                    BufferedImage bImage = SwingFXUtils.fromFXImage(image, null);
                    baos = new ByteArrayOutputStream();
                    ImageIO.write(bImage, chartType.outputFormat, baos);
                    result = baos.toByteArray();
                } catch (InstantiationException e) {
                    throw new ChartGenerationException(e);
                } catch (IllegalAccessException e) {
                    throw new ChartGenerationException(e);
                } catch (NoSuchMethodException e) {
                    throw new ChartGenerationException(e);
                } catch (InvocationTargetException e) {
                    throw new ChartGenerationException(e);
                } catch (IOException e) {
                    throw new ChartGenerationException(e);
                } finally {
                    IOUtils.closeQuietly(baos);
                }
            }
        });
        while (result == null) {
            //wait
        }
        byte[] ret = result;
        result = null;
        return ret;
    }


    @Override
    public void start(Stage stage) {
        canvas = new Canvas();
    }

    public static class ChartGenerationException extends RuntimeException {
        public ChartGenerationException(String message) {
            super(message);
        }
        public ChartGenerationException(Throwable cause) {
            super(cause);
        }
    }

}

然后我在Spring应用程序启动时调用initialize（）方法：

Then I call the initialize() method when the Spring application is started:

@Autowired private TaskExecutor taskExecutor;

@PostConstruct private void initChartGenerator() {
    ChartGenerator.initialize(taskExecutor);
}

这个cource解决方案可以移植到非Spring应用程序。

This solution of cource can be ported to a non-Spring application.

这是一个单线程解决方案（在我的情况下已经足够了）但我认为它可以用于多线程使用（可能使用RMI来调用draw方法）。

This is a single-threaded solution (in my case it's enough) but I think it could be adopted to multithreaded usage (maybe use RMI to invoke draw method).

此解决方案在我的Windows工作站上按原样工作，但在Linux服务器环境中应该调用一些额外的操作：

Also this solution works "as is" on my windows workstation but on linux server environment some additional actions should be invoked:

1. 您无法在OpenJDK上使用JavaFX（截至2013年8月） - 必须切换到Oracle JDK


2. Java版本必须不低于Java 7u6



3. 最复杂的 - 您必须使用虚拟显示来使JavaFX在无头环境中运行：

1. You cannot use JavaFX on OpenJDK (as of Aug 2013) - have to switch to Oracle JDK
2. Java version must be no less than Java 7u6

3. The most complex - you have to use virtual display to make JavaFX run on headless environments:

apt-get install xvfb

apt-get install xvfb

//然后在应用程序服务器上启动：

// then on application server start:

export DISPLAY =：99

export DISPLAY=":99"

start-stop-daemon --start --background --user jetty --exec/ usr / bin / sudo - -u jetty / usr / bin / Xvfb：99 -screen 0 1024x768x24

start-stop-daemon --start --background --user jetty --exec "/usr/bin/sudo" -- -u jetty /usr/bin/Xvfb :99 -screen 0 1024x768x24

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P.S。您还可以在服务器端使用其他JavaFX功能（例如，将html导出到图像）。

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P.S. You can also use other JavaFX capabilities on server side (e.g. export html to image) with this solution.

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