java - Unmarshal NullPointerException (with JAXB reference implementation) -

i'm trying unmarshall xml file, strange npe depths of jaxb library. you, please, me solve problem?

here's exception stacktrace's top:

java.lang.nullpointerexception @ com.sun.xml.bind.v2.runtime.unmarshaller.loader.reporterror(loader.java:258) @ com.sun.xml.bind.v2.runtime.unmarshaller.loader.handlegenericexception(loader.java:245) @ com.sun.xml.bind.v2.runtime.unmarshaller.scope.add(scope.java:123) @ com.sun.xml.bind.v2.runtime.property.arrayerproperty$receiverimpl.receive(arrayerproperty.java:213) @ com.sun.xml.bind.v2.runtime.unmarshaller.unmarshallingcontext.endelement(unmarshallingcontext.java:538) 

here's xml classes code:

public class base {     public base() {     } }  public class  extends base {     public a() {     } }  public class b extends base{     public b() {     } }   @xmlrootelement(name = "test") @xmlaccessortype public class testxml {     @xmlelementwrapper(name = "list")     @xmlanyelement     @xmljavatypeadapter(adapter.class)     public list<base> list = new arraylist<>(); } 

here's adapter's unmarshal() method, taken here , modified.

@suppresswarnings({ "unchecked", "rawtypes" }) @override public t unmarshal(element element) throws exception {     if (null == element) {         return null;     }      // 1. determine values type type attribute.     class<?> clazz = classloader.loadclass(element.getattribute("class"));      // 2. unmarshal element based on value's type.     domsource source = new domsource(element);     unmarshaller unmarshaller = getjaxbcontext(clazz).createunmarshaller();     jaxbelement jaxbelement = unmarshaller.unmarshal(source, clazz);      return (t) jaxbelement.getvalue();       } 

here's test code:

jaxbcontext jaxbcontext = jaxbcontext.newinstance(testxml.class); unmarshaller unmarshaller = jaxbcontext.createunmarshaller();         testxml auth = (testxml) unmarshaller.unmarshal(new file("testdata/test.xml")); 

and finally, here's xml file, try unmarshall:

<test>     <list>         <item class="my.package.a" />         <item class="my.package.b" />     </list> </test> 

while debugging found out adapter works well, i.e. unmarshall() method returns instance of right class, bad happens after it.

the next thing found out adapter's code

jaxbelement jaxbelement = unmarshaller.unmarshal(source, clazz); 

causes npe. when remove line of code , replace unmarshall()'s return statement

return new a(); //for example 

no npe occurs.

try changing line,

// 1. determine values type type attribute.     class<?> clazz = classloader.loadclass(element.getattribute("class")); 

to,

// 1. determine values type type attribute.     class<?> clazz = classloader.loadclass(element.getattribute("class")); 

reason being clazz variable null.