Java Wicket resource issue

Question

Im working on a web app where we keep the code and web resources (such as css, image files etc) separated.

I have a file located here:

project root/src/main/webapp/images/icons/16/add.png

And in this location:

project root/src/main/java/se/su/dsv/scipro/icons

I have a class like so:

package se.su.dsv.scipro.icons;

import org.apache.wicket.ResourceReference;
import org.apache.wicket.behavior.AttributeAppender;
import org.apache.wicket.markup.html.image.Image;
import org.apache.wicket.model.Model;


public class ImageIcon extends Image {

    private static final long serialVersionUID = 1L;

    public static final String ICON_NEW_ADD = "../../../../../../webapp/images/icons/16/add.png";

    public ImageIcon(String id, String name, String size, String alt){
        super(id, new ResourceReference(ImageIcon.class, name));
        if(alt != null){
            add(new AttributeAppender("alt", true, new Model<String>(alt), " "));
        }
        else {
            add(new AttributeAppender("alt", true, new Model<String>(name), " "));
        }
    }

    public ImageIcon(String id, String name){
        this(id, name, "", null);
    }

    public ImageIcon(String id, String name, String alt){
        this(id, name, "", alt);
    }

    public static ResourceReference getImage(String imageName, String imageSize){
        return new ResourceReference(ImageIcon.class, imageName);
    }
}

But when I use this class somewhere in a panel or a page, e.g. like this:

add(new ImageIcon("new_add", ImageIcon.ICON_NEW_ADD));

I get the following exception:

2011 Oct 18 11:11:17,947[ERROR] - RequestCycle - Can't instantiate page using constructor public se.su.dsv.scipro.basepages.DemoPage(org.apache.wicket.PageParameters) and argument 
org.apache.wicket.WicketRuntimeException: Can't instantiate page using constructor public se.su.dsv.scipro.basepages.DemoPage(org.apache.wicket.PageParameters) and argument 
    at org.apache.wicket.session.DefaultPageFactory.createPage(DefaultPageFactory.java:212)
    at org.apache.wicket.session.DefaultPageFactory.newPage(DefaultPageFactory.java:65)
    at org.apache.wicket.request.target.component.BookmarkablePageRequestTarget.newPage(BookmarkablePageRequestTarget.java:298)
    at org.apache.wicket.request.target.component.BookmarkablePageRequestTarget.getPage(BookmarkablePageRequestTarget.java:320)
    at org.apache.wicket.request.target.component.BookmarkablePageRequestTarget.processEvents(BookmarkablePageRequestTarget.java:234)
    at org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents(AbstractRequestCycleProcessor.java:92)
        at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1250)
    at org.apache.wicket.RequestCycle.step(RequestCycle.java:1329)
    at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1436)
    at org.apache.wicket.RequestCycle.request(RequestCycle.java:545)
    at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:486)
    at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:319)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter.doFilterInternal(OpenEntityManagerInViewFilter.java:113)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
    at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    at org.apache.wicket.session.DefaultPageFactory.createPage(DefaultPageFactory.java:188)
    ... 27 more
Caused by: java.lang.IllegalArgumentException: Invalid path ../../../../../../webapp/images/icons/16/add.png
    at org.apache.wicket.util.lang.Packages.absolutePath(Packages.java:105)
    at org.apache.wicket.util.lang.Packages.absolutePath(Packages.java:44)
    at org.apache.wicket.markup.html.PackageResource.<init>(PackageResource.java:504)
    at org.apache.wicket.markup.html.PackageResource.newPackageResource(PackageResource.java:448)
    at org.apache.wicket.markup.html.PackageResource.get(PackageResource.java:424)
    at org.apache.wicket.ResourceReference.newResource(ResourceReference.java:304)
    at org.apache.wicket.ResourceReference.bind(ResourceReference.java:151)
    at org.apache.wicket.markup.html.image.resource.LocalizedImageResource.bind(LocalizedImageResource.java:180)
    at org.apache.wicket.markup.html.image.resource.LocalizedImageResource.setResourceReference(LocalizedImageResource.java:246)
    at org.apache.wicket.markup.html.image.Image.setImageResourceReference(Image.java:178)
    at org.apache.wicket.markup.html.image.Image.<init>(Image.java:101)
    at org.apache.wicket.markup.html.image.Image.<init>(Image.java:77)
    at se.su.dsv.scipro.icons.ImageIcon.<init>(ImageIcon.java:83)
    at se.su.dsv.scipro.icons.ImageIcon.<init>(ImageIcon.java:93)
    at se.su.dsv.scipro.basepages.DemoPage.<init>(DemoPage.java:16)
    ... 32 more

I guess it is because the image file resides outside any Java package? How can I address this?

Answer 1

Use a ContextRelativeResource. With it, the path to the image will be considered relative to the context root.

For instance, if you'd show this image with the following HTML:

<img src="images/icons/16/add.png">

Use the following:

new Image("add", new ContextRelativeResource("/images/icons/16/add.png")))

You might also find this blog post useful.

There's no ResourceReference version of this variant that I'm aware of, although you can try to integrate the one attached in this JIRA issue: WICKET-790