Hibernate jpa java.lang.ClassCastException: model.Dog cannot be cast to model.Dog
I have a weird exception and I can't figure out why. I have a list in memory from a database, but when I try to access getters or store an object in a variable, it throws an exception.
Here is the gist:
package model;
import java.io.Serializable;
import javax.persistence.*;
@Entity
@NamedQuery(name="Dog.findAll", query="SELECT d FROM Dog d")
public class Dog implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int id;
private String name;
public Dog() {
}
public int getId() {
return this.id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
}
this is my session bean implementation:
@Stateless(name = "mytable")
public class TableBean implements TableLocal {
@PersistenceContext(unitName = "sample")
private EntityManager manager;
@Override
public Dog getAll() {
Dog h = manager.find(Dog.class, 1);
Hibernate.initialize(h);
return h;
}
@Override
@SuppressWarnings("unchecked")
public List<Dog> findAll() {
Query query = manager.createQuery("SELECT h FROM Dog h",Dog.class);
List<Dog> col = query.getResultList();
Hibernate.initialize(col);
return col;
}
@Override
public void addDog() {
Dog d = new Dog();
//d.setId(2);
d.setName("chappy");
manager.persist(d);
}
}
I also have a bean service but it is pointless
@Stateless(name = "service")
public class ServiceBean implements ServiceLocal {
@EJB(beanName = "mytable")
TableLocal table;
@Override
public Dog getAll() {
return table.getAll();
}
@Override
public List<Dog> findAll() {
return table.findAll();
}
@Override
public void addDog() {
table.addDog();
}
}
and my servlet:
public class HelloServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
@EJB(beanName = "service")
ServiceLocal table;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
List<Dog> tables = table.findAll();
Iterator<Dog> it = tables.iterator();
while (it.hasNext()) {
Dog t = it.next();
resp.getWriter().println(t.getName());
}
/*Dog h = table.getAll();
resp.getWriter().println(h.getId() + " " + h.getName());*/
/*table.addDog();
resp.getWriter().println("Added!");*/
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
and erro:
2015-07-28T13:38:17.385+0300|Warning: StandardWrapperValve[HelloServlet]: Servlet.service() for servlet HelloServlet threw exception
java.lang.ClassCastException: model.Dog cannot be cast to model.Dog
at HelloServlet.doGet(HelloServlet.java:26)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:687)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:415)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:282)
at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:201)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:175)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:284)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:201)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:133)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:112)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:561)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:565)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:545)
at java.lang.Thread.run(Thread.java:745)
and my persistence.xml:
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1"
xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence
http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
<persistence-unit name="sample">
<provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
<jta-data-source>MySQL</jta-data-source>
<class>model.Dog</class>
<properties>
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect" />
<property name="hibernate.hbm2ddl" value="update" />
<property name="hibernate.transaction.jta.platform"
value="org.hibernate.service.jta.platform.internal.SunOneJtaPlatform" />
<property name="hibernate.show_sql" value="true"/>
<property name="hibernate.format_sql" value="true"/>
</properties>
</persistence-unit>
</persistence>
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2 answers
You most likely have two jars:
- one for the web
- one for core services (like EJB)
Both flags enable the class model.Dog
, and the application server loads two versions of the same class from two different sources. When the main tier sends a response model.Dog
to the web tier, the response has the version of the class loaded into the base tier, while the web tier already has a different execution version of that class, so you get the exception.
To fix this, you only need to include objects in the base tier, and the web tier should have a dependency on the base tier artifact and not include the entities themselves.
Update
Also remove this:
Hibernate.initialize(h);
Because it doesn't add any value in your particular use case.
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findAll()
Use QueryQuery instead of Query in your method . The reason is that TypedQuery getResultList()
returns a list of typed lists. i.e. in your case List<Dog>
, but Query getResultList returns RawList
You can try using the code below: -
@Override
@SuppressWarnings("unchecked")
public List<Dog> findAll() {
TypedQuery<Dog> query = manager.createQuery("SELECT h FROM Dog h",Dog.class);
List<Dog> col = query.getResultList();
Hibernate.initialize(col);
return col;
}
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