Re: [betwixt] info on .betwixt files, "add" methods, and CyclicReferenceExceptions

[robert burrell donkin]

many thanks for the patch.

i haven't used the code but it did prove very useful. the version i committed uses instance equality (==) rather than equals to determine whether a bean is it's own ancester. it also uses the stack implementation in jakarta-commons-collections for greater backwards compatibility. in addition, i've tried to protect the ways that subclasses can access the stack.

- robert

On Saturday, December 14, 2002, at 12:23 AM, Darren Scott wrote:

as i said, i had planned to take a look at creating a fix in
any case. if
you do make progress before then let me know so that i can
look at adding
some other features instead :)

- robert

I think I've got a fix for unexpected CyclicReferenceExceptions. Robert
asked me to provide a cvs diff -u for the fix - I've never used -u on
diff before and it seemed to produce a LOT of output, so here's output
from a regular diff between my working copy and the top of the source
tree (1.6):

RCS file:
/home/cvspublic/jakarta-commons/betwixt/src/java/org/apache/commons/betw
ixt/io/AbstractBeanWriter.java,v
retrieving revision 1.6
diff -w -r1.6 AbstractBeanWriter.java
71a72

import java.util.Stack;

106a108,109

    /** Stack containing ID attribute values for beans seen so far in

this graph */

    protected Stack idStack = new Stack();

183c186
<             log.trace( "Writing bean graph (qualified name '" +
qualifiedName + "'" );
---

            log.trace( "Writing bean graph (qualified name '" +

qualifiedName + "')" );
210c213
<                     if ( ref == null ) {
---

                    if ( idStack.search( bean ) == -1 ) {

216a220

                            idStack.push( bean );

249a254

                            idStack.push( bean );

256a262,264

                        // about to finish writing this bean - no need

to remember it any more

                        idStack.pop();

Basically, as well as recording bean IDs in a Hashmap, we now also
maintain a stack of beans currently being written. Each time we see a
new bean we add the bean to the stack before recursing further down the
graph by calling write(). When we leave the write() method, we pop the
bean off the stack as we are no longer interested in it (at least for
the purposes of checking for cycles). The decision as to whether a cycle
exists is then based on whether the bean is already in the stack - if it
is, we have already seen it as part of this graph and hence there is a
cycle. This means that multiple occurences that are not part of a cycle
no longer produce a CyclicReferenceException.

Give it a go and let me know if you think it works.

Regards,

Darren



--
To unsubscribe, e-mail:   <mailto:[EMAIL PROTECTED].
org>
For additional commands, e-mail: <mailto:[EMAIL PROTECTED].
org>

--
To unsubscribe, e-mail:   <mailto:[EMAIL PROTECTED]>
For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>