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

问题

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

回答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()));
        }
    }

}

回答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>

来源：https://stackoverflow.com/questions/10944673/how-to-use-pgraphicimage-with-defaultstreamedcontent-in-an-uirepeat