ImageIO.getImageWriter(reader) not working inside tomcat

Hello Harald,

I wrote a basic test code that does work in a standalone test class:

public class Test {

public static void main(String[] arg)
{
    try
    {
        ImageInputStream iis = ImageIO.createImageInputStream(new FileInputStream(arg[0]));
        Iterator<ImageReader> readers = ImageIO.getImageReaders(iis);
        if (!readers.hasNext())
            throw new IOException("can't decode this image inputstream");

        ImageReader reader = readers.next();
        ImageReadParam param = reader.getDefaultReadParam();
        reader.setInput(iis, true, true);
        BufferedImage img = reader.read(0, param);

        ImageWriter writer = ImageIO.getImageWriter(reader);

        if (writer == null)
            throw new IOException("can't find writer, reader provider: " + reader.getOriginatingProvider());

        System.out.println("Writer: " + writer.getClass());
    }
    catch (Throwable t)
    {
        t.printStackTrace();
    }
}

}

The same code doesn’t work inside a tomcat webapp, writer is null so an exception is thrown.

I have:

• added the listener as described in the guide
• fixed class name typos inside JPEGImageWriterSpi (class names were not starting with “com”

I have verified with a test loop that the ImageWriter is loaded:

static
{
    System.out.println("ImageIO, looking for writers");

    Iterator<ImageWriter> ite = ImageIO.getImageWritersByFormatName("jpeg");

    while (ite.hasNext())
        System.out.println("ImageIO writer: " + ite.next().getClass());
}

And the result:

logs/catalina.out:ImageIO, looking for writers logs/catalina.out:ImageIO writer: class com.twelvemonkeys.imageio.plugins.jpeg.JPEGImageWriter logs/catalina.out:ImageIO writer: class com.sun.imageio.plugins.jpeg.JPEGImageWriter

Any idea about why is not working just inside tomcat? How to debug further?

Thanks,

Daniele.

[kkofler]

If, like me, you are still stumbling upon this old issue, and wonder what the best fix/workaround is these days:

• You want to use the com.twelvemonkeys.servlet.image.IIOProviderContextListener (that is documented on the https://haraldk.github.io/TwelveMonkeys/ front page under “Deploying the plugins in a web app”).
• To use this in a Maven project, you need this additional dependency:

    <dependency>
      <groupId>com.twelvemonkeys.servlet</groupId>
      <artifactId>servlet</artifactId>
      <version>3.3.2</version>
    </dependency>

• To use it in a Spring Boot project without a web.xml file, you want to add the following line to the onStartup method in your SpringBootServletInitializer subclass:

servletContext.addListener(IIOProviderContextListener.class);

of course with the following import:

import com.twelvemonkeys.servlet.image.IIOProviderContextListener;

With this, the standard ImageIO classes just work and you do not have to manually load any classes.

I hope this helps.

[stephanie-dm]

It would be great if @kkofler 's solution could be added to the documentation, because I think it costs people some time to find this…