JSPick-a server pages design recovery tool

JSPick - A Server Pages Design Recovery Tool Dirk Draheim, Elfriede Fehr, and Gerald Weber Insitute for Computer Science Freie Universit¨at Berlin {draheim,fehr,weber}@inf.fu-berlin.de Abstract This paper presents the reverse engineering tool JSPick, which recovers page signatures and form types from server pages based presentation layers. A formal semantics of the tool is given in pseudo-evaluation style.

1 Introduction JSPick [13] is a reverse engineering tool for server pages based presentation layers. The formal semantics of the tool is independent of the scripting language used in the page. The system is implemented for Java Server Pages. JSPick generates a documentation of the whole system interface in an easy to read specification language. Beside that JSPick generates a GUI browser for each system. With that browser the developer can examine source code, abstract syntax trees, type information, warnings and the linkage structure of the system in quest under several different viewpoints. The presentation layer of web-based systems is built with one of the several common gateway interface (CGI) based technologies. It consists of a set of server side scripts. A script is a code unit that is called across the net by the user by submitting a form or selecting a link. On behalf of this the script eventually sends back to the web user agent a client page description, which may encompass forms and links. In our approach it is crucial that a form may be viewed as an editable method call, gathering actual parameters from the user. Furthermore links can be subsumed conceptually under forms as non-editable method calls having hidden parameters as constant actual parameters. We coin the two terms client page description safety and client page type safety for two desired properties of web applications. A web application has the property of client page description safety if its server scripts always only produce valid page descriptions with respect to a defined client page description language. A web application has the property of client page type safety if the client pages generated by the

server scripts always only contain such forms and links that provide exactly such actual parameters that are expected by the respective targeted server scripts. Listing 1 Example Page > > > TEXT , controltype = text > > > > > TEXTAREA , controltype = textarea > > > > > > >CHECKBOX , controltype = checkbox > > > > >RADIO , controltype = radiobutton > > > > >SELECT , controltype = select > > : SELECT [ ] , controltype = multipleselect [[if p ]] = [[switcharbitrary p ]] [[ifElse p1 p2 ]] = [[switchunique p1 p2 ]] arbitrary p . . . p ]] = [[switch n 1 8 > ⊥ , ∀ ([[pi ]]n) ↑ > > 1≤i≤n < λ n . t[ ] , ∀ (([[pi ]]n) ↑ ∨ ⇓ ([[pi ]]n) = t ∈ bt) > 1≤i≤n > > :VARIOUS[ ] , else unique p . . . p ]] = [[switch n 1 8 ⊥ , ∀ ([[pi ]]n) ↑ > > > 1≤i≤n > > > > t , ∀ ([[pi ]]n) = t ∈ bt > > 1≤i≤n < λ n . VARIOUS , ∀ ([[pi ]]n) ∈ bt > 1≤i≤n > > > > t[ ] , ∀ (([[pi ]]n) ↑ ∨ ⇓ ([[pi ]]n) = t ∈ bt) > > 1≤i≤n > > : VARIOUS[ ] , else

[[loop p ]] = λ n .

( ⊥
⇓ ([[p]]n) [ ]

, ([[p]]n) ↑ , else

[[p1 . . . pn ]] = 8 ⊥ , ∀ ([[pi ]]n) ↑ > > 1≤i≤n > > > > > [[pi ]]n , ∃ ! ([[pi ]]n) ↓ > > 1≤i≤n > > > > ∧ ∃ ([[pi ]]n) = radiobutton > > 1≤i≤n > > > > t[ ] , ∀ (([[pi ]]n) ↑ ∨ ⇓ ([[pi ]]n) = t ∈ bt) > > > 1≤i≤n > : VARIOUS[ ] , else

Figure 1. JSPick Pseudo-Evaluation.

6 Conclusion Web applications are ubiquitous. Ultra-thin client based tiered enterprise applications benefit from scalability and maintainability. Server pages technologies are widely used in the implementation of ultra-thin client applications. Unfortunately the low-level CGI programming model shines through in these technologies, especially user data is gathered in a completely untyped manner. In this paper a tool for code-structure sensitive recov-

Proceedings of the Seventh European Conference On Software Maintenance And Reengineering (CSMR’03) 0-7695-1902-4/03 $17.00 © 2003 IEEE

ery of page signatures and form types from server pages based presentation layers has been introduced. A formal semantics of this tool has been given as pseudo-evaluation. The findings are programming language independent and can be easily adapted to other server pages technologies [19][20][1].

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Proceedings of the Seventh European Conference On Software Maintenance And Reengineering (CSMR’03) 0-7695-1902-4/03 $17.00 © 2003 IEEE