You are viewing a plain text version of this content. The canonical link for it is here.
Posted to dev@cocoon.apache.org by Marcus Crafter <cr...@dresdnerbank.de> on 2000/11/30 11:14:32 UTC
[C2/Patch] Selector Heaven :-)
Hi All,
Hope all is going well across the Cocoon globe!
Attached is a set of files to add initial support for the following
selectors to Cocoon 2:
o ParamSelectorFactory
Used for testing values from request parameters.
o SessionSelectorFactory
Used for testing values from session attributes.
o ContextSelectorFactory
Used for testing values from context attributes.
o RequestHeaderSelectorFactory
Used for testing values from request headers.
Each of the selectors use an underlying boolean engine which can
parse and evaluate strings for truthness. The boolean engine uses JLex
and CUP to scan and parse strings according to a defined (and
extensible) grammar.
Currently, the following operators (programmer-style and
english-style) are supported:
=, !=, <, >, <=, >=, &&, || , !, (, )
eq, ne lt, gt, le, ge, and, or
The operators also automatically select string, or integer based
arithmetic depending on the arguments given (eg. when given an integer,
= performs integer comparison, when given a string, = performs string
comparison).
Using these operators one can create simple to quite powerful and
useful tests.
Examples:
<!-- test whether myparameter equals the integer 5 -->
<when test="myparameter=5">
<!-- test whether myparameter is lexographically greater than
the string 'abcde' -->
<when test="myparameter>'abcde'">
<!-- test whether myparameter is less than 10 or greater than
20 -->
<when test="myparameter < 10 or myparameter > 20">
<!-- test whether myparmeter simply exists -->
<when test="myparameter">
(more examples are in the Test directory)
Technically, the selectors simply pass the string to the boolean
engine for evaluation with a 'context' the engine can use to retrieve
values of variables.
In effect, a boolean style selector can now be made out of any class
that provides a way to map variables to values - the
ParamSelectorFactory, etc, selectors only differ by the way they
provide a context for the boolean engine to operate in.
I've tested the code in our environment here, but what it needs now is
much more rigorous testing. I'm building a test rig for the engine to
automate much of the testing and will send the rest of it in over the
next days (the file Tester.java is the start of it, but it needs a bit
more work). If you see some strange behaviour or think that something
is wrong, please send me the string you used to evaluate, and the
values of the variables you used (if any). I'll look in to it.
What is not yet implemented includes support for floating point
numbers in the scanner (the parser and logic supports them), more
rigorous error handling, a complete test rig, and other operators not
listed above. I'm going to be looking into these next.
I'm also looking into optimising the code a some more to reduce the
number of objects created each test. The addition of some flyweights,
and mutator methods should help here.
I've also noticed that my coding style is a slightly different from
Apache's. Is there a code formatter one can use to automatically
format code according to Apache's guidelines ? (where are the
guidelines ?). Something like indent for C ?
If the Cocoon developers are OK with it, I'm happy for this to
be included in the general Cocoon 2 distribution. The files are ready
to be dropped into CVS as is, except for the parser and scanner java
files which must be generated (I didn't touch the build.xml, perhaps
one of the other more 'ant' familiar developers might be able to help
me out there), but what should happen before the build starts (perhaps
in the prepare rule) is the following:
java -classpath jlex.jar JLex.Main Scanner.jlex
mv Scanner.jlex.java Yylex.java
to generate the scanner (yes, unfortunately the move is necessary),
and then:
java -classpath cup.jar java_cup.Main < Parser.cup
to generate the parser.
These two steps generate the files Yylex.java, parser.java and
sym.java, which should be moved/copy into the
cocoon/selection/helpers/bool directory and then compiled (I've
included pregenerated versions of these files in the attachment above
for those who want to see what the generated scanner/parser code looks
like).
I haven't included JLex or CUP in the attachments above to keep the
size down. JLex is available from
http://www.cs.princeton.edu/~appel/modern/java/JLex/ (version 1.2.5),
and CUP is available from
http://www.cs.princeton.edu/~appel/modern/java/CUP/ (version 0.10j).
They need to be downloaded and added to the lib directory.
The only other change is to add the selectors to your sitemap
configuration:
<map:selector name="parameter" factory="org.apache.cocoon.selection.ParamSelectorFactory"/>
<map:selector name="session" factory="org.apache.cocoon.selection.SessionSelectorFactory"/>
<map:selector name="context" factory="org.apache.cocoon.selection.ContextSelectorFactory"/>
<map:selector name="header" factory="org.apache.cocoon.selection.RequestHeaderSelectorFactory"/>
and everything should be fine! Various logging is also written to the
WEB-INF/logs/cocoon.log file, using the org.apache.log.* classes
recently added to Cocoon.
Well, if there any questions, problems, suggestions, etc, please let
me know.
I have lots of questions though! - Are there other
operators/types people would like to use ? Are there any functions
people would like to use ? (eg. I thought about being able to test the
length of a request parameter in a selector ?), etc. Do people want to
compare floating point numbers internationally (ie. 0.00 in Australia,
and 0,00 in Germany ?). Are the chosen english style operator
names ok ? etc. What other kinds of selectors would be appropriate ?
And then comes the subject of documentation ?? :-)
Ok, Well I'll leave it there for the moment. Look forward to responses.
Cheers,
Marcus
--
.....
,,$$$$$$$$$, Marcus Crafter
;$' '$$$$: Computer Systems Engineer
$: $$$$: Open Software Associates GmbH
$ o_)$$$: 82-84 Mainzer Landstrasse
;$, _/\ &&:' 60327 Frankfurt Germany
' /( &&&
\_&&&&' Email : Marcus.Crafter@osa.de
&&&&. Business Hours : +49 69 9757 200
&&&&&&&: After Hours : +49 69 49086750
Re: [C2/Patch] Selector Heaven :-)
Posted by Marcus Crafter <cr...@dresdnerbank.de>.
Hi Stefan!
On 1 Dec 2000, Stefan Bodewig wrote:
> Marcus Crafter <cr...@dresdnerbank.de> wrote:
>
> > The files are ready to be dropped into CVS as is, except for
> > the parser and scanner java files which must be generated (I
> > didn't touch the build.xml, perhaps one of the other more
> > 'ant' familiar developers might be able to help me out there),
>
> Marcus, I'm not familiar with JLex or CUP, I have read some
> articles about them and thought, it might be interesting to take a
> look at them - unfortunately never found the time.
>
> I am quite familiar with Ant, though. If you are interested in
> creating <jlex> and <cup> tasks for Ant, I'd be happy to assist with
> the Ant specific part of it.
Sure, that would be great. What has to be done is as follows:
Before the source is compiled, the parser and scanner have to be
generated using JLex and CUP.
This line generates the scanner:
java -classpath jlex.jar JLex.Main Scanner.jlex
mv Scanner.jlex.java Yylex.java
and this line generates the parser:
java -classpath cup.jar java_cup.Main < Parser.cup
The move from Scanner.jlex.java to Yylex.java is currently required as
Yylex is a public class. (The scanner filename could be changed to
Yylex so that the move isn't necessary).
Something similar needs to be added to the build.xml. How it's done is
completely up to you! :-)
The cocoon build should then proceed as normal.
If there are any problems let me know.
Thanks again for your help. :-)
Cheers,
Marcus
--
.....
,,$$$$$$$$$, Marcus Crafter
;$' '$$$$: Computer Systems Engineer
$: $$$$: Open Software Associates GmbH
$ o_)$$$: 82-84 Mainzer Landstrasse
;$, _/\ &&:' 60327 Frankfurt Germany
' /( &&&
\_&&&&' Email : Marcus.Crafter@osa.de
&&&&. Business Hours : +49 69 9757 200
&&&&&&&: After Hours : +49 69 49086750
[ Part 2, "" Text/PLAIN (Name: "sitemap.xsl.diff") 57 lines. ]
[ Unable to print this part. ]
[ Part 3, "" Application/OCTET-STREAM (Name: "selectors.tar.gz") ]
[ 16KB. ]
[ Unable to print this part. ]
--
.....
,,$$$$$$$$$, Marcus Crafter
;$' '$$$$: Computer Systems Engineer
$: $$$$: Open Software Associates GmbH
$ o_)$$$: 82-84 Mainzer Landstrasse
;$, _/\ &&:' 60327 Frankfurt Germany
' /( &&&
\_&&&&' Email : Marcus.Crafter@osa.de
&&&&. Business Hours : +49 69 9757 200
&&&&&&&: After Hours : +49 69 49086750
Re: [C2/Patch] Selector Heaven :-)
Posted by Stefan Bodewig <bo...@apache.org>.
Marcus Crafter <cr...@dresdnerbank.de> wrote:
> The files are ready to be dropped into CVS as is, except for
> the parser and scanner java files which must be generated (I
> didn't touch the build.xml, perhaps one of the other more
> 'ant' familiar developers might be able to help me out there),
Marcus, I'm not familiar with JLex or CUP, I have read some
articles about them and thought, it might be interesting to take a
look at them - unfortunately never found the time.
I am quite familiar with Ant, though. If you are interested in
creating <jlex> and <cup> tasks for Ant, I'd be happy to assist with
the Ant specific part of it.
Cheers
Stefan