How to use <p:graphicImage> with DefaultStreamedContent in an ui:repeat? - jsf

Question

I was trying to display a panel where user can see a list of items category(displayed as images) and on clicking they can view products within the category(images will be displayed)
For displaying the item category, i used the ui:repeat nad the supporting bean calss
Below is my xhtml code
<ui:repeat id="repeat" value="#{getData.images}" var="img" varStatus="loop">
<h:panelGroup>
<p:graphicImage id="img1" value="#{img}" alt="image not available" >
</p:graphicImage>
</h:panelGroup>
</ui:repeat>
And the Managed Bean Code parts
private ByteArrayOutputStream baos = new ByteArrayOutputStream();
private List<StreamedContent> imageList = new ArrayList<StreamedContent>();
public List<StreamedContent> getImages(){
for (int i = 0; i < sdh.getNumOfImages(); i++) {
imageID = imageIDArray.get(i);
ImageService imgSer = new ImageService();
imgList.add(imageID);
imgSer.setData(imageID);
baos = imgSer.getImage();
try {
imageList.add(new DefaultStreamedContent(new
ByteArrayInputStream(baos.toByteArray())));
} catch (Exception ex) {
ex.printStackTrace();
}
}
imageNum = 0;
return imageList;
}
public StreamedContent getData() {
baos = imageList.get(imageNum);
//imageList.add(baos);
imageNum++;
return new DefaultStreamedContent(new ByteArrayInputStream(baos.toByteArray()));
}
Now my problem if i don't uncomment the 'imageList.add(baos)' in 'getData', the images are not displayed.
Now i really wants to know how the 'ui:repeat' works, since the 'imageList' contains the images and i can save the same if required in either of the method. If i specify a fixed number (ex:'imageList.get(0)') in the 'getData' method then the same image is show multiple times. Where as if i put the 'imageNum' without the 'imageList.add(baos)' it throw error 'Error in streaming dynamic resource'
I tired Bjorn Pollex's suggestion and made the necessary changes but now images don't appear

Answer 1

It is not possible to use <p:graphicImage> this way. You should rather iterate over a collection of unique image identifiers, not over a collection of StreamedContent. Those unique image identifiers have then to be passed as a <f:param> to <p:graphicImage> which in turn will generate the right URLs for the browser.
<ui:repeat value="#{data.imageIds}" var="imageId">
<p:graphicImage value="#{imageStreamer.image}">
<f:param name="id" value="#{imageId}" />
</p:graphicImage>
</ui:repeat>
Your #{data} managed bean must just have a:
private List<Long> imageIds; // +getter
The #{imageStreamer} should be a separate application scoped managed bean which look basically like this:
#ManagedBean
#ApplicationScoped
public class ImageStreamer {
#EJB
private ImageService service;
public StreamedContent getImage() throws IOException {
FacesContext context = FacesContext.getCurrentInstance();
if (context.getCurrentPhaseId() == PhaseId.RENDER_RESPONSE) {
// So, we're rendering the view. Return a stub StreamedContent so that it will generate right URL.
return new DefaultStreamedContent();
}
else {
// So, browser is requesting the image. Get ID value from actual request param.
String id = context.getExternalContext().getRequestParameterMap().get("id");
Image image = service.find(Long.valueOf(id));
return new DefaultStreamedContent(new ByteArrayInputStream(image.getBytes()));
}
}
}

Answer 2

You used wrong ui:repeat tag. You have var attribute but you can't use this in p:graphicImage tag value attribute.Please see sample usage,
<ui:repeat value="#{yourBean.images}" var="img">
<p:graphicImage value="/images/#{img}" />
</ui:repeat>