java - How to read objects (Polymorphic) of the chosen class, from the XML using JAX-B -

i created list of polymorphic objects. can convert them xml , vice versa (marshall , unmarshal using jaxb.) read objects chosen class.

i used few tutorials converting object lists jaxb, example one: http://memorynotfound.com/convert-xml-to-polymorphic-object-using-jax-b/ or one: http://bdoughan.blogspot.com/2010/11/jaxb-and-inheritance-using-substitution.html have got animal list, , 2 classes extends abstract animal class, dog, cat , bird. saved list(containing dogs , cats) xml, , xml file cats. possible make?

using code tutorial -> http://memorynotfound.com/convert-xml-to-polymorphic-object-using-jax-b/

    jaxbcontext jaxbcontext = jaxbcontext.newinstance(root.class);     unmarshaller unmarshaller = jaxbcontext.createunmarshaller();      root root = (root)unmarshaller.unmarshal(new stringreader(xml)); 

i ouptut:

root{animals=[com.memorynotfound.xml.jaxb.dog@520a3426, com.memorynotfound.xml.jaxb.cat@18eed359,com.memorynotfound.xml.jaxb.bird@643bd123]}

what try achieve is:

root{animals=[ com.memorynotfound.xml.jaxb.cat@18eed359]}

in 1 of answers got idea of xmlevent. fine idea, every tutorial says filtering. want achieve rid of other classes. tried change code:

public xmlevent nextevent() throws xmlstreamexception {     // read next event     xmlevent e = super.nextevent();     // if it's start element dog     if (e.geteventtype() == xmlevent.start_element &&  ("cat".equals(e.asstartelement().getname().getlocalpart()) ||             "bird".equals(e.asstartelement().getname().getlocalpart()))     )     {          // run through events until closing dog event         {             e = super.nextevent();         } while (e.geteventtype() != xmlevent.end_element || ! ("cat".equals(e.asstartelement().getname().getlocalpart()) ||                 "bird".equals(e.asstartelement().getname().getlocalpart()))          );         // read next event after  ends         e = super.nextevent();     }     return e; } 

but not working, not sure if understand solution.

you can create custom javax.xml.stream.xmleventreader , filter events. here silly - working - example:

public final class filteredxmleventreader extends eventreaderdelegate {      final set<string> filteredelements;      filteredxmleventreader(xmleventreader delegate, string... filteredelements) {         super(delegate);         this.filteredelements = new hashset<string>(arrays.aslist(filteredelements));     }      public xmlevent nextevent() throws xmlstreamexception {         // read next event          xmlevent e = super.nextevent();         // if it's start element filtered         if (e.geteventtype() == xmlevent.start_element && filteredelements.contains(e.asstartelement().getname().getlocalpart())) {             string element = e.asstartelement().getname().getlocalpart();             // run through events until closing similar element             {                 e = super.nextevent();             } while (e.geteventtype() != xmlevent.end_element || !element.equals(e.asendelement().getname().getlocalpart()));             // read next tag after closing element             e = super.nextevent();         }         return e;     } } 

then unmarshall content using xmleventreader:

jaxbcontext jaxbcontext = jaxbcontext.newinstance(root.class); xmleventreader xmlreader = xmlinputfactory.newfactory().createxmleventreader(new stringreader(xml)); unmarshaller unmarshaller = jaxbcontext.createunmarshaller(); root root = (root) unmarshaller.unmarshal(new filteredxmleventreader(xmlreader, "dog", "bird")); 

then dog , birds elements not read.

note there can issues if multiple filtered elements nested implementation.

edit: edited code above support multiple filtered elements.