Modernizing Java Server Pages By Transformation. S h a n n o n X u T h o m a s D e a n Q u e e n s U n i v e r s i t y

Transcription

1 Modernizing Java Server Pages By Transformation S h a n n o n X u T h o m a s D e a n Q u e e n s U n i v e r s i t y

2 Background CSER - Consortium for Software Engineering Research Dynamic Web Pages Multiple Technologies - CGI, shtml, JSP, ASP,.NET Mixing Code and Data Ok for small projects, seems to be proving a detriment to larger projects Separate Concerns: Application Code and Graphics Design Abstract User Interface [Schneider 2001] Custom Tags (JSP) replaces code with abstract tags

3 JSP Basics Mix Java and Template Text Template Text is sent to browser modified by inline Java HTML, Javascript, Applet Tags, CSS Java Code + standard Actions <% for (int i = 0; i < bean.titles.length; i++) { %> <jsp:usebean> forward pages, import classes, declare fields and methods

4 Custom Tags <%taglib uri= xxx prefix= mylib %> <mylib:cdtitle/> CdTitle.class <taglib> <uri>xxx</uri> <tag> <name>cdtitle</name/> <tag_class>cdtitle</tag_class> </tag> </taglib>

5 Custom Tags <%taglib uri= xxx prefix= mylib %> <mylib:cdtitle/> CdTitle.class <taglib> <uri>xxx</uri> <tag> <name>cdtitle</name/> <tag_class>cdtitle</tag_class> </tag> </taglib>

6 Custom Tags <%taglib uri= xxx prefix= mylib %> <mylib:cdtitle/> CdTitle.class <taglib> <uri>xxx</uri> <tag> <name>cdtitle</name/> <tag_class>cdtitle</tag_class> </tag> </taglib>

7 Custom Tags <%taglib uri= xxx prefix= mylib %> <mylib:cdtitle/> CdTitle.class <taglib> <uri>xxx</uri> <tag> <name>cdtitle</name/> <tag_class>cdtitle</tag_class> </tag> </taglib>

8 Custom Tags <%taglib uri= xxx prefix= mylib %> <mylib:cdtitle/> CdTitle.class <taglib> <uri>xxx</uri> <tag> <name>cdtitle</name/> <tag_class>cdtitle</tag_class> </tag> </taglib>

9 Custom Tags <%taglib uri= xxx prefix= mylib %> <mylib:cdtitle/> CdTitle.class <taglib> <uri>xxx</uri> <tag> <name>cdtitle</name/> <tag_class>cdtitle</tag_class> </tag> </taglib>

10 Requirements No Change to Functionality Identical Behaviour No change to Appearance Same HTML / Javascript is generated to browser Same web site structure (paths to pages) Keep Code Comments Maintenance Issue

11 MuiltiLingual Grammar [Synytskyy03] ASP Grammar HTML Base Grammar

12 MuiltiLingual Grammar [Synytskyy03] JSP Grammar [Li 2004] HTML Base Grammar

13 MuiltiLingual Grammar [Synytskyy03] JSP Grammar [Li 2004] Custom Tag Grammar HTML Base Grammar TLD XML Grammar [Xu 2005]

14 Parsing JSP <table> <%for(i=1;i<10;i++){%> <th><td><%=i%></td></th> <%}%> </table> Interesting <table> Interesting <%for(i=1;i<10;i++){%> Interesting Interesting Interesting <%=i%> <%}%> </table>

15 Parsing JSP <table> <%for(i=1;i<10;i++){%> <th><td><%=i%></td></th> <%}%> </table> Interesting <table> Interesting <%for(i=1;i<10;i++){%> Interesting Interesting Interesting <%=i%> <%}%> </table>

16 Parsing JSP <table> <%for(i=1;i<10;i++){%> <th><td><%=i%></td></th> <%}%> </table> Interesting <table> <% for_statement %> </table> for(i=1;i<10;i++){ %> } Interesting <%=i%> <%

17 Parsing JSP <table> <%for(i=1;i<10;i++){%> <th><td><%=i%></td></th> <%}%> </table> Interesting <table> <% for_statement %> </table> for(i=1;i<10;i++){ %> } Interesting <%=i%> <%

18 Parsing JSP <table> <%for(i=1;i<10;i++){%> <th><td><%=i%></td></th> <%}%> </table> Interesting <table> <% for_statement %> </table> for(i=1;i<10;i++){ %> } Interesting <%=i%> <%

19 Parsing JSP <table> <%for(i=1;i<10;i++){%> <th><td><%=i%></td></th> <%}%> </table> Interesting <table> <% for_statement %> </table> for(i=1;i<10;i++){ %> } Interesting <%=i%> <%

20 General Approach Java statements, expressions and declarations are moved to custom tag classes HTML code moved out of Java strings out.println( <TR><TD> ) %> <TR><TD> <%

21 General Approach Java Bean action elements translated to equivalent Java Code <jsp:usebean> <jsp:getproperty> <jsp:setproperty> JSP Page import directive generates an import statement in the resulting class import= java.sql.resultset %> <% import java.sql.resultset; %>

22 General Transformation Normalization 4 General Cases

23 Case 1 Simple Code <HTML><BODY> <% HttpSession s = request.getsession(true); String userid = ((String) s.getvalue( userid )).trim(); s.putvalue( username, userid); %> </BODY></HTML> <HTML><BODY> <mylib: usersession></mylib:usersession> </BODY></HTML>

24 Case 1b Simple Code <HTML><BODY> <% HttpSession s = request.getsession(true); String userid = ((String) s.getvalue( userid )).trim(); %> Welcome <% s.putvalue( username, userid); %> </BODY></HTML> <HTML><BODY> <mylib: usersession> Welcome </mylib:usersession> </BODY></HTML>

25 Case 2 - Nested Code <HTML><BODY> <% HttpSession s = request.getsession(true); String userid = ((String) s.getvalue( userid )).trim(); s.putvalue( username, userid); %> Welcome <%= username %> </BODY></HTML> <HTML><BODY> <mylib: usersession> Welcome <mylib:username/> </mylib:usersession> </BODY></HTML>

26 Case 3 Choice <HTML><BODY> <% if (condition) {%> HTML TEXT <% } else {%> }%> </BODY></HTML>

27 Case 3 Choice <HTML><BODY> <% bool choice = condition; if (choice) {%> HTML TEXT <% } if (!choice) {%> }%> </BODY></HTML>

28 Case 3 Choice <HTML><BODY> <mylib:checkcondition> <mylib:validcondition> HTML TEXT </mylib:validcondition> <mylib:invalidcondition> </mylib:invalidcondition> </mylib:checkcondition> </BODY></HTML>

29 CASE 4 - Iteration <HTML><BODY> <% while(condition){%> HTML TEXT <%}%> </BODY></HTML> <HTML><BODY> <mylib:whilecondition> HTML TEXT </mylib:whilecondition> </BODY></HTML>

30 Composing Cases The 4 cases compose to cover all code cases Case 2 provides basis for nesting tags are nested, classes are not classes find the class for the parent tag at runtime using JSP API Add get/set routines for variables

31 Nesting Cases 4,2 <HTML><BODY> <% while(condition){%> HTML <%= value %> TEXT <%}%> </BODY></HTML> <HTML><BODY> <mylib:whilecondition> HTML <mylib:getvalue/> TEXT </mylib:whilecondition> </BODY></HTML>

32 Implementation TXL Source Transformation Language Grammar + Transformation Rules Markup Approach Identify key statements of each case if statements, while statements (both with HTML text) propagate markups to include all statements

33 Implementation Original JSP Preprocessing Grouping Naming Class Gen Page and TLD TLD Pages Tag Classes Postprocesing

34 Implementation Original JSP Normalization & Lexical Issues Preprocessing Grouping Naming Class Gen Page and TLD TLD Pages Tag Classes Postprocesing

35 Implementation Original JSP Preprocessing Custom Tag Identification Grouping Naming Class Gen Page and TLD TLD Pages Tag Classes Postprocesing

36 Implementation Original JSP Preprocessing Names for Tags Grouping Naming Class Gen Page and TLD TLD Pages Tag Classes Postprocesing

37 Implementation

38 Implementation Original JSP Preprocessing Grouping Naming Class Gen Page and TLD TLD Pages Tag Classes Postprocesing Move to Java

39 Implementation Original JSP Preprocessing Grouping Remove Java Naming Class Gen Page and TLD TLD Pages Tag Classes Postprocesing

40 Implementation Original JSP Preprocessing Grouping Naming Class Gen Page and TLD Comments TLD Pages Tag Classes Postprocesing

41 Final Words Tested on 4 small systems (14 files) Each case generates separate custom tags Implementation is a greedy approach Better separation into tags Data and Control Flow Analys Clones E.g. Session management code

42 Questions?