View helper example

ApplicationHelper.java

public class ApplicationHelper implements ViewHelper {
  
	private final PrettyTimeFormatter formatter;

	public ApplicationHelper(PrettyTimeFormatter formatter) {
		this.formatter = formatter;
	}
	
	public String format(AbstractInstant instant) {
		return formatter.format(instant);
	}

	@Override
	public String getName() {
		return "app";
	}

}

HelpersInterceptor.java

@Intercepts(before=ForwardToDefaultViewInterceptor.class)
class HelpersInterceptor implements Interceptor{
  
	private final List<ViewHelper> helpers;
	private final Result result;

	public HelpersInterceptor(List<ViewHelper> helpers, Result result) {
		this.helpers = helpers;
		this.result = result;
	}

	@Override
	public boolean accepts(ResourceMethod method) {
		return true;
	}

	@Override
	public void intercept(InterceptorStack stack, ResourceMethod method,
			Object args) throws InterceptionException {
		for (ViewHelper helper : helpers) {
			result.include(helper.getClass().getSimpleName(), helper);
		}
		stack.next(method, args);
	}
	
}

old.tag

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>

<%@attribute name="time" required="true" type="org.joda.time.base.AbstractInstant"%>

<%
if (time != null) {
  org.joda.time.base.AbstractInstant time = (org.joda.time.base.AbstractInstant) jspContext.getAttribute("time");
	br.com.caelum.gnarus.utilMovePlease.PrettyTimeFormatter formatter = (br.com.caelum.gnarus.utilMovePlease.PrettyTimeFormatter) request.getAttribute("timeFormatter");

	out.write(formatter.format(time));
}
%>

usage.jsp

${app.format(usuario.createdAt)}

ViewHelper.java

interface ViewHelper {
  public String getName();
}