Java.lang.Class cannot is cast to Java.lang.reflect.ParameterizedType

There are many operations in the DAO layer that can be implemented with paradigm and reflection, so I began to conceive my balm Basedao.

Basehibernatedaoadvance.java

 Public classBasehibernatedaoadvance<textendsModifyinfoentity, PKextendsSerializable, DTOextendsBasedto>extendsHibernatedaosupportImplementsBasedaoadvance<t, PK, dto> {        Private FinalLogger Logger =Loggerfactory.getlogger (GetClass ()); @AutowiredPrivate voidgetsessionfactory (sessionfactory sessionfactory) {Super. Setsessionfactory (sessionfactory); }        //entity class type (automatically assigned by construction method)    PrivateClass<t>Entityclass; PrivateClass<dto>Dtoclass; //constructor method, automatically gets the entity class type according to the instance class     Publicbasehibernatedaoadvance () {System.out.println ("-------------->in basehibernatedaoadvance");  This. Entityclass =NULL; Class C=getclass ();        System.out.println (c); Type T=C.getgenericsuperclass ();        System.out.println (t); if(tinstanceofParameterizedtype) {System.out.println ("In If"); Type[] P=( (Parameterizedtype) t). Getactualtypearguments ();            System.out.println (Arrays.tostring (p));  This. Entityclass = (class<t>) p[0];  This. Dtoclass = (class<dto>) p[2]; }    }}

Write and prepare some test classes.

@RunWith (Springjunit4classrunner.class) @ContextConfiguration (Locations= {"Classpath:/config/applicationcontext.xml","Classpath:/config/service.xml", "Classpath:/config/dao.xml" }) Public classBasedaoimpladvancetest {PrivateBasedaoadvance<course, Serializable, coursedto>Basedaoimpl;  PublicBasedaoadvance<course, Serializable, coursedto>Getbasedaoimpl () {returnBasedaoimpl; } @Autowired Public voidSetbasedaoimpl (basedaoadvance<course, Serializable, coursedto>Basedaoimpl) {         This. Basedaoimpl =Basedaoimpl; } @Test Public voidquerylist () {coursedto dto=Newcoursedto ();        Basedaoimpl.querylist (DTO); System.out.println ("Here-------------------->"); }}

But prompt error java.lang.NullPointerException

Look at the code and find out that this section of judgment doesn't pass.

        if (t instanceof Parameterizedtype) {            System.out.println ("in If");            Type[] p = ((Parameterizedtype) t). Getactualtypearguments ();            System.out.println (Arrays.tostring (P));            This.entityclass = (class<t>) p[0];            This.dtoclass = (class<dto>) p[2];        }

Remove if test, or error,Java.lang.ClassCastException:java.lang.Class cannot is cast to Java.lang.reflect.ParameterizedType

~ ~ ~ (>_<) ~ ~ ~

The reason is because the paradigm is not used in the right way.

Added specific DAO and implementation

 Public Interface extends Basedaoadvance<course, serializable,coursedto> {}

@Repository  Public class extends Implements Coursedao {}

Test class

@RunWith (Springjunit4classrunner.class) @ContextConfiguration (Locations= {"Classpath:/config/applicationcontext.xml","Classpath:/config/service.xml", "Classpath:/config/dao.xml" }) Public classCoursedaoimpltest {//private Basedaoadvance<course, Serializable, coursedto> Basedaoimpl;@AutowiredPrivateCoursedao Coursedao; @Test Public voidquerylist () {coursedto dto=Newcoursedto ();        Coursedao.querylist (DTO); System.out.println ("Here-------------------->"); }}

OK, Success!

The paradigm should be specified at compile time, not at runtime.

Java.lang.Class cannot is cast to Java.lang.reflect.ParameterizedType