未知属性错误struts2

Question

I am developing a struts2 application. I have a property in my jsp file, which need to refer to a property of an object that is in a list, but I run into unknown property error,

just to clarify: lets say my jsp property is called x my class is called a, it has a private String x and a set of getter and setters a is in ArrayList called b, and b is in the action class that jsp file is referring to (it is referring to the correct class as it can find the properties that are action's member but not the x which is in class a).

Answer 1

If I get your problem correctly (other people are right, it does read a bit like a Math problem) the problem is that Struts doesn't know to which element of the list to map the property in your JSP. Let me explain, suppose you have class A defined like this:

public class A {
    private String x;    
    //Getter and setter for x
}

and in your action class you have something like

public class MyAction extends ActionSupport {
    private A aProperty;
    //execute method and getter/setter for aProperty.
}

In this case you use aProperty.x to reference the x member of aProperty from your JSP. However, the moment your action class changes to

public class MyAction extends ActionSupport {
    private List<A> aList;
    //Execute method and getter/setter for aList.
}

you can no longer use aList.x since you need to tell Struts which item of the list to get in order to get/set x on this item. You can specify the item of the list you want to reference like this: aList[0].x

Let me know if this is not exactly what you were trying to ask in your question.