java - ClassCastException with H2 -

i'm using h2 testing purposes, have problems when casting derived class. case is:

    @entity         @discriminatorcolumn(name = "dtype", discriminatortype = discriminatortype.string, length = 64)     public class {...}      @entity     @discriminatorcolumn(name = "dtype", discriminatortype = discriminatortype.string, length = 64)     public class b extends {...} 

my dataset looks like:

<a attr1=... attr2=... dtype="a"/> <b attr1=... attr2=... dtype="b"/> 

the problem when try query in jpa one:

query q = em.createquery("select a where..."); 

and try value this:

(b) q.getresultlist().get(0); 

i have following exception:

java.lang.classcastexception: mypackage.a cannot cast mypackage.b 

in mysql works fine, not in h2. h2 version: 1.3.171

assuming q.getresultlist() returns list of a objects,

b extends a , therefore, b can cast a. reverse not true. instance of a cannot cast b.