gsp, image from array byte

Question

I have a JDO class and a helper class Image to store images within a byte array

JDO class:

@PersistenceCapable
class Recipe{

    @PrimaryKey
        @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
        private Long key

        @Persistent
        private String description

        @Persistent(serialized = "true")
        private Image image;
}

Image class:

class Image implements Serializable {

    private byte[] content
    private String filename
    private String mimeType
}

In the gsp page I iterate through the recipes and want to show the images. I could do a controller like this to get the image src.

 def viewImage= {
    //retrieve photo code here
    response.setHeader("Content-disposition", "attachment; filename=${photo.name}")
    response.contentType = photo.fileType //'image/jpeg' will do too
    response.outputStream << photo.file //'myphoto.jpg' will do too
    response.outputStream.flush()
    return;
  }

But this way I have to send the key of the recipe to this controller and load the image again from the datastore. (I already have loaded it actually. But I think I can not send this data to the controller. Can I ?) Is there not a more convenient way to show the image from a byte array in gsp page ?

Answer 1

I have a similar usecase here, a File domain class holding a byte[] and meta information for uploaded files. To download the file, I'm using:

def fileDownload = {
    long id = params.id as long
    def file = File.get(id)
    assert file
    def fileName = URLEncoder.encode(file.name)
    response.addHeader("content-disposition", "attachment;filename=$fileName")
    response.contentType = file.contentType
    response.contentLength = file.data.size()
    response.outputStream << file.data
}

Regarding reloading the file over and over I would not care too much, Hibernate 2nd level caching cares about it. If you still have a good reason for not loading the file in the download request, you might store it into the http session in a previous call. The downside of storing this in the http session:

• in case of many concurrent sessions, high memory consumption
• you'll see weird exceptions from Hibernate (be sure for that!)
• everything stored in the http session must be serializable