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Struts 2 - Understanding the working between OGNL and params interceptor

 
Eshan Kapoor
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I am new to struts 2. I am studying it from the book Struts2 In Action. I am having difficulty in understanding some concepts in OGNL which are as follows-

1)We know that params interceptor moves the data from the request parameters to the action object in ValueStack. Now while reading, I came upon a line that says- "The tricky part of the job is mapping the name of the parameter to an actual property on the ValueStack. This is where OGNL comes in. The params interceptor interprets the request parameter name as an OGNL expression to locate the correct destination property on the ValueStack".

Ques1)Here, what does "interprets" mean? Is it that params interceptor translates the request parameter into some OGNL expression and then OGNL expression provides mapping to the properties in ValueStack OR does it mean something else?

2) When result start its rendering process, the Struts 2 tags retrieve data from the ValueStack by referencing specific values with OGNL expressions.

Ques 2)So the tags take OGNL expressions, but how is the data being moved? Earlier, params interceptor was the one that moved the data but now there is no params interceptor. So how is the data being moved?
 
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