--- Warren Liang <[EMAIL PROTECTED]> wrote:
> Hi all,
>
> How does JXPath handle circular object paths? My
> object graph is can
> have circular references to objects that are the
> same instance (i.e.
> obj1 == obj2), or are different instances but have
> equivalent values
> (i.e. obj1.equals(obj2))
>
> Right now, I'm evaluating JXPath expressions that do
> not match
> anything in the object graph and it seems like it's
> going through an
> infinite loop. Some of my expressions use the
> "match anywhere"
> operator (i.e. //).
If you are encountering behavior that feels wrong to
you, feel welcome to open an issue in JIRA, preferably
with some sample code that can easily be turned into a
standalone JUnit test.
>
> Does JXPath use a breadth first search or a depth
> first search through
> the object graph?
>
In my experience, not being the original author of the
code, JXPath determines matching nodes for a given
level, then applies subsequent levels in
recursive-descent fashion to each node selected at the
current level. So given:
<a>
<b>
<c /><c />
</b>
<b>
<c /><c />
</b>
<b>
<c /><c />
</b>
</a>
and path "/a/b/c", JXPath will determine that a[1]
matches the first step and apply the next step. Now
it determines that a[1]/b[1], a[1]/b[2] and a[1]/b[3]
match the second step. Then it applies the third step
to a[1]/b[1], a[1]/b[2], and a[1]/b[3] in succession.
I interpret this as being depth first.
> Ideally, I'd be able to tell JXPath to recurse a
> maximum depth, or to
> recognize that a node has already been traversed
> Are there hooks for
> me to do this?
>
I suppose nothing would ever stop you from
implementing a custom "I haven't seen this before"
function to guard each step, but it might get a little
heavy at RT depending on the size of your graph. Off
the top of my head I can't remember what, if any,
safeguards are built into JXPath to prevent infinite
recursion, hence my initial suggestion (and attempt to
put the onus onto you ;) ) that you submit reports for
problems encountered.
Is any of this helpful whatsoever?
-Matt
> Thanks,
>
> Warren Liang
>
>
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