XPathExpression question
"Keeney, Wayne" <[email protected]> Fri, 7 Jun 2013 12:35:45 -0600
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Here's hoping this question gets to the right place.
We are using JDOM2 (2.0.3) and it's my understanding that instances of XPat=
hExpression are not thread safe. We were using clone as a (hopefully) more=
efficient method of getting our "own" instance of a pre compiled XPathExpr=
ession safe from other thread access. This is not my main question, but is=
it more efficient?
My main question has to do with setting variables on the XPathExpression. =
I could not get the variable setting to work on a cloned copy of an XPathEx=
pression, but it works if I set the variable before cloning. The problem w=
ith this, is of course, thread safety.
Is this a known bug, maybe fixed?
This works (but opens an opportunity for threading problems since we're usi=
ng precompiled static instances):
XPathExpression<Element> xPath =3D pathMap.get(meth=
od);
xPath.setVariable("variable", namespace, "fString")=
;
List<Element> elems =3D xPath.clone().evaluate(mode=
l.asDocument());
But this doesn't work, it doesn't seem to recognize the variable replacemen=
t:
XPathExpression<Element> xPath =3D pathMap.get(meth=
od).clone();
xPath.setVariable("variable", namespace, "fString")=
;
List<Element> elems =3D xPath.evaluate(model.asDocu=
ment());
pathmap is just a map of precompiled XPathExpressions.
Thanks,
Wayne Keeney
SAT Services
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</o:shapelayout></xml><![endif]--></head><body lang=3DEN-US link=3Dblue vli=
nk=3Dpurple><div class=3DWordSection1><p class=3DMsoNormal>Here’s hop=
ing this question gets to the right place. <o:p></o:p></p><p class=3D=
MsoNormal><o:p> </o:p></p><p class=3DMsoNormal>We are using JDOM2 (2.0=
.3) and it’s my understanding that instances of XPathExpression are n=
ot thread safe. We were using clone as a (hopefully) more efficient m=
ethod of getting our “own” instance of a pre compiled XPathExpr=
ession safe from other thread access. This is not my main question, b=
ut is it more efficient?<o:p></o:p></p><p class=3DMsoNormal><o:p> </o:=
p></p><p class=3DMsoNormal>My main question has to do with setting variable=
s on the XPathExpression. I could not get the variable setting to wor=
k on a cloned copy of an XPathExpression, but it works if I set the variabl=
e before cloning. The problem with this, is of course, thread safety.=
<o:p></o:p></p><p class=3DMsoNormal><o:p> </o:p></p><p class=3DMsoNorm=
al>Is this a known bug, maybe fixed? <o:p></o:p></p><p class=3DMsoNor=
mal><o:p> </o:p></p><p class=3DMsoNormal>This works (but opens an oppo=
rtunity for threading problems since we’re using precompiled static i=
nstances):<o:p></o:p></p><p class=3DMsoNormal style=3D'text-autospace:none'=
><span style=3D'font-size:10.0pt;font-family:Consolas;color:black'> &n=
bsp;  =
; XPathExpression<=
Element> xPath =3D </span><i><span style=3D'font-size:10.0pt;font-family=
:Consolas;color:#0000C0'>pathMap</span></i><span style=3D'font-size:10.0pt;=
font-family:Consolas;color:black'>.get(method);</span><span style=3D'font-s=
ize:10.0pt;font-family:Consolas'><o:p></o:p></span></p><p class=3DMsoNormal=
style=3D'text-autospace:none'><span style=3D'font-size:10.0pt;font-family:=
Consolas;color:black'>  =
; &n=
bsp; xPath.setVariable(</span><span style=3D'font-size:10.0pt;font-fa=
mily:Consolas;color:#2A00FF'>"variable"</span><span style=3D'font=
-size:10.0pt;font-family:Consolas;color:black'>, </span><i><span style=3D'f=
ont-size:10.0pt;font-family:Consolas;color:#0000C0'>namespace</span></i><sp=
an style=3D'font-size:10.0pt;font-family:Consolas;color:black'>, </span><sp=
an style=3D'font-size:10.0pt;font-family:Consolas;color:#2A00FF'>"fStr=
ing"</span><span style=3D'font-size:10.0pt;font-family:Consolas;color:=
black'>);</span><span style=3D'font-size:10.0pt;font-family:Consolas'><o:p>=
</o:p></span></p><p class=3DMsoNormal><span style=3D'font-size:10.0pt;font-=
family:Consolas;color:black'> &nbs=
p; &=
nbsp; List<Element> elems =3D xPath.clone().evaluate(mode=
l.asDocument());<o:p></o:p></span></p><p class=3DMsoNormal><span style=3D'f=
ont-size:10.0pt;font-family:Consolas;color:black'><o:p> </o:p></span><=
/p><p class=3DMsoNormal><span style=3D'font-size:10.0pt;font-family:Consola=
s;color:black'>But this doesn’t work, it doesn’t seem to recogn=
ize the variable replacement:<o:p></o:p></span></p><p class=3DMsoNormal sty=
le=3D'text-autospace:none'><span style=3D'font-size:10.0pt;font-family:Cons=
olas;color:black'> &nb=
sp; =
XPathExpression<Element> xPath =3D </span><i><span style=3D'fo=
nt-size:10.0pt;font-family:Consolas;color:#0000C0'>pathMap</span></i><span =
style=3D'font-size:10.0pt;font-family:Consolas;color:black'>.get(method).cl=
one();</span><span style=3D'font-size:10.0pt;font-family:Consolas'><o:p></o=
:p></span></p><p class=3DMsoNormal style=3D'text-autospace:none'><span styl=
e=3D'font-size:10.0pt;font-family:Consolas;color:black'> &=
nbsp; &nbs=
p; xPath.setVariable(</span><span=
style=3D'font-size:10.0pt;font-family:Consolas;color:#2A00FF'>"variab=
le"</span><span style=3D'font-size:10.0pt;font-family:Consolas;color:b=
lack'>, </span><i><span style=3D'font-size:10.0pt;font-family:Consolas;colo=
r:#0000C0'>namespace</span></i><span style=3D'font-size:10.0pt;font-family:=
Consolas;color:black'>, </span><span style=3D'font-size:10.0pt;font-family:=
Consolas;color:#2A00FF'>"fString"</span><span style=3D'font-size:=
10.0pt;font-family:Consolas;color:black'>);</span><span style=3D'font-size:=
10.0pt;font-family:Consolas'><o:p></o:p></span></p><p class=3DMsoNormal><sp=
an style=3D'font-size:10.0pt;font-family:Consolas;color:black'> =
&nb=
sp; List<Element> ele=
ms =3D xPath.evaluate(model.asDocument());<o:p></o:p></span></p><p class=3D=
MsoNormal><span style=3D'font-size:10.0pt;font-family:Consolas;color:black'=
><o:p> </o:p></span></p><p class=3DMsoNormal><span style=3D'font-size:=
10.0pt;font-family:Consolas;color:black'>pathmap is just a map of precompil=
ed XPathExpressions.<o:p></o:p></span></p><p class=3DMsoNormal><span style=
=3D'font-size:10.0pt;font-family:Consolas;color:black'><o:p> </o:p></s=
pan></p><p class=3DMsoNormal><span style=3D'font-size:10.0pt;font-family:Co=
nsolas;color:black'>Thanks,<o:p></o:p></span></p><p class=3DMsoNormal><span=
style=3D'font-size:10.0pt;font-family:Consolas;color:black'><o:p> </o=
:p></span></p><p class=3DMsoNormal><span style=3D'font-size:10.0pt;font-fam=
ily:Consolas;color:black'>Wayne Keeney<o:p></o:p></span></p><p class=3DMsoN=
ormal><span style=3D'font-size:10.0pt;font-family:Consolas;color:black'>SAT=
Services</span><o:p></o:p></p><p class=3DMsoNormal><o:p> </o:p></p></=
div></body></html>=
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