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From José Antonio Pérez Testa <>
Subject Re: [digester] how to use peek() to get object from top of stack ? bug??
Date Tue, 06 Jul 2004 08:38:00 GMT
Hi Marc,
The point is where are you calling peek(), I guess.
When you call addFactoryCreate() you are only setting the rules for 
The effective call to the FactoryCreateRule is made during the parsing 
of a XML. At that time, the only chance to call peek() is inside a 
method call or object constructor or any code the parsing triggers for 
Maybe I am pointing the obvious but you can not write :
digester.addObjectCreate("pattern", TemplateMappingEntity.class);
Object obj=digester.peek();

and expect peek() to be called between the instantiation of the two rules!

Marc Lustig wrote:

>Thanks Simon for reply. It's really weird because the log trace seems to 
>properly instantiate my class:
>74458 [main] DEBUG org.apache.commons.digester.Digester  -   New 
>74460 [main] DEBUG org.apache.commons.digester.Digester  -   Fire begin() for 
>FactoryCreateRule[className=null, attributeName=null, 
>74463 [main] DEBUG org.apache.commons.digester.Digester  - [FactoryCreateRule]
>{TemplateMappingProcessor/MappingEntity} New 
>but still when I call peek _immediately_ after the call to addFactoryCreate()
>I do get not this object , but the object that was formerly added to the stack 
>via push() method.
>Anymore hint ?
>Am Dienstag, 6. Juli 2004 00:54 schrieb Simon Kitching:
>>On Tue, 2004-07-06 at 04:50, Marc Lustig wrote:
>>>I'm having trouble to use peek() to get the object from top of the stack.
>>>I say
>>>Alright, peek() is returning the object from the stack properly.
>>>Now I add another object to the stack:
>>>digester.addObjectCreate("pattern", TemplateMappingEntity.class);
>>>... and now peek() is NOT giving me back an instance of
>>>WHY ?   (of course the pattern exists)
>>I don't know why you're not seeing the correct object. What you are
>>describing seems to be the correct way to use the digester. And peek
>>works fine - if it didn't, the Digester simply wouldn't work at all, and
>>quite a lot of people would notice that :-)
>>When exactly are you doing the peek? I hope you're aware that the object
>>will be on the stack only between the start tag of the element specified
>>by the pattern and the matching end tag.
>>eg for
>>  digester.addObjectCreate("foo/bar", MyClass.class);
>>and input
>>  <root>
>>    <foo>
>>      <bar>
>>        ...
>>      </bar>
>>    </foo>
>>  </root>
>>the MyClass instance is created and pushed on the stack when <bar> is
>>encountered in the input, and popped when </bar> is encountered. If you
>>need to refer to the object after its end tag, you need to use
>>SetNextRule to tell the parent object to store a reference to the
>>>I tried also using a factory to add an object to the stack:
>>>digester.addFactoryCreate("pattern", new MappingEntityFactory());
>>>In this case as well peek() is NOT returning the instance that is
>>>delivered by the createObject() method of my factory.
>>It should.
>>>What is wrong with the peek() method??
>>There definitely isn't anything wrong with the peek method. There must
>>be something odd in your code or environment, but I can't think what it
>>might be.
>>I suggest you enable debugging output for digester and have a look at
>>the generated information. The simplest way to enable logging is to run
>>java with:
>>  java \
>> -D org.apache.commons.logging.Log=\
>>     org.apache.commons.logging.impl.SimpleLog \
>> -D org.apache.commons.logging.simplelog.defaultlog=debug \
>> .....
>>Alternatives include putting log4j.jar in the classpath, and then also
>>putting a log4j.xml or file in the classpath.
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