Adding a FileDownload Control by library control - jsf

Question

I am trying to build an JSF library control for XPages based on the examples by Keith Strickland.
http://xprentice.gbs.com/A55BAC/keithstric.nsf/default.xsp?documentId=82770C11FA7B9B21852579C100581766
I'm having a little bit trouble in building a FileDownloadControl
Here is the code I've built:
public class Libcontrol extends UIComponentBase implements FacesComponent {
private static final String RENDERER_TYPE = "de.chris.Libcontrol ";
private static final String COMPONENT_FAMILY = "de.chris";
public Libcontrol() {
setRendererType(RENDERER_TYPE);
}
#Override
public String getFamily() {
return COMPONENT_FAMILY;
}
#SuppressWarnings("unchecked")
public void initBeforeContents(FacesContext arg0) throws FacesException {
FacesContext context;
ExpressionEvaluatorImpl evaluator;
context = FacesContext.getCurrentInstance();
evaluator = new ExpressionEvaluatorImpl(context);
XspFileDownload result = new XspFileDownload();
String sourceId = "fileDownload1/#value";
String valueExpr = "#{document1.FileField}";
ValueBinding value = evaluator.createValueBinding(result, valueExpr, sourceId,Object.class);
result.setValueBinding("value", value);
result.setDisplayLastModified(true);
result.setAllowDelete(true);
result.setTitle("filedown");
result.setRows(30);
result.setId("fileDownload1");
this.getChildren().add(result);
}
public void buildContents(FacesContext arg0, FacesComponentBuilder arg1) throws FacesException {
// Do Nothing
}
public void initAfterContents(FacesContext arg0) throws FacesException {
// Do nothing
}
}
Why is the control not completely rendered? When I look to the HTML Code I see a starttag from the control but no Files to download
and yes I've uploaded files to the corresponding NotesDocument.
Here is the renderer I have implmented respectively copied:
public class MainLibcontrolRenderer extends Renderer {
#Override
public void encodeBegin(FacesContext context, UIComponent component) {
try {
super.encodeBegin(context, component);
context = FacesContext.getCurrentInstance();
UIViewRootEx rootEx = (UIViewRootEx) context.getViewRoot();
/*rootEx.setDojoParseOnLoad(true);
rootEx.setDojoTheme(true);*/
ResponseWriter writer = context.getResponseWriter();
writer.startElement("fieldset", component);
} catch (Exception e) {
e.printStackTrace();
}
}
#Override
public void encodeChildren(FacesContext context, UIComponent component) {
try {
super.encodeChildren(context, component);
} catch (Exception e) {
e.printStackTrace();
}
}
#Override
public void encodeEnd(FacesContext context, UIComponent component) {
try {
super.encodeEnd(context, component);
ResponseWriter writer = context.getResponseWriter();
writer.endElement("fieldset");
} catch (Exception e) {
e.printStackTrace();
}
}
}

Answer 1

Stephan is right: the reason the contents do not render is that you're not building them. When implementing FacesComponent, the buildContents method typically should instruct the FacesComponentBuilder to initiate the build process; e.g.:
arg1.buildAll(arg0, this, true);
NOTE: I'm using the argument names from your example; ideally, you should use meaningful argument names like "context" and "builder".
The buildAll method referred to above causes the component tree to properly reflect any changes made to the structure during the init methods. If you skip this step, the subsequent JSF phases (including RENDER_RESPONSE) are unaware of any components you injected.
By the way, Keith also makes a valid point: hardcoding the value binding and other properties - at least, in the example you provided - tends to defeat the purpose of defining a reusable control. I'd echo Keith's advice to take a closer look at what you're trying to accomplish to determine whether a custom component is really the appropriate implementation. And one final caution: use extreme care when programmatically setting the id property on injected components... you could end up with a name collision that cannot be detected during compilation. In other words, Designer can't warn you... it will just break at runtime and the reason for failure will probably not be obvious.