无法访问实例化类的受保护方法

Question

I am trying to access this protected class: protected boolean canDraw() , and get its value placed into a variable. Two ways I'm trying to access it are not working:

    <%@ page import="com.day.cq.wcm.foundation.Image" %>
    <%@include file="/apps/tju/global.jsp"%>
    <% //..... 
       Image thisImage = new Image(resource); %>

boolean foo = thisImage.canDraw(); throws The method canDraw() from the type Image is not visible

and

boolean foo = super.canDraw(); throws The method canDraw() is undefined for the type HttpJspBase

Full javadoc of the class being used can be found here: http://dev.day.com/docs/en/cq/5-3/javadoc/com/day/cq/wcm/foundation/Image.html

Answer 1

The method is protected. Therefore, you cannot access it from outside of the package and the classes which inherit from the class.

You are trying to access a protected method from a JSP page. The JSP page is not a sub-class of Image and therefore cannot access the method.

If there is not a better way to do what you're trying to do, subclass Image and make a public accessor for the attribute you're trying to access.

Answer 2

Well, it is protected, and you are trying to access it from a Servlet subclass (JSPs are compiled into Servlets). You can not do that, by the java specification.

Make it public (if you have the source code), or extend the original class into a class that has a public method that provides the same data. Alternatively (not recommended), use reflection to change its accessibility.

Answer 3

As mentioned in the other answers you would have to extend Image, override canDraw and make the overridden method's visibility public.

What do you intend to do after checking canDraw()? I imagine it is protected for a reason. This is speculative but if all you are doing is checking canDraw() and then drawing if it returns true, you can actually just invoke draw() directly. The JavaDoc states it internally checks canDraw():

http://dev.day.com/docs/en/cq/current/javadoc/com/day/cq/commons/ImageResource.html#draw(java.io.Writer)