public Collection<RenderingResult> process(RenderingContext renderingCtx) throws RenderingException { List<RenderingResult> ret = new ArrayList<RenderingResult>(); for (RenderingEngine engine : engines.values()) { if (renderingCtx.accept(engine)) { RenderingResult result = engine.process(renderingCtx); if (result != null) { ret.add(result); } else if (log.isDebugEnabled()) { log.debug("rendering ignored by the engine " + engine.getFormatName()); } } } return ret; }