@Entity
@Table(name = "ObjectA", schema = "schemaA")

public class A {





     @JoinColumn(name = "schemaB_ID")

     public B getPropertyType() {

        return b;

     }

}

@Entity
@Table(name = "ObjectB", schema = "schemaB")

public class B {



}

package org.hibernate.bugs;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.util.Date;
import java.util.HashSet;
import java.util.Set;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;

/**
* This template demonstrates how to develop a test case for Hibernate ORM, using the Java Persistence API.
*/
public class JPAUnitTestCase {

   private EntityManagerFactory entityManagerFactory;
   private EntityManagerFactory entityManagerFactory2;

   @Before
   public void init() {

      entityManagerFactory = Persistence.createEntityManagerFactory( "templatePU" );
      entityManagerFactory2 = Persistence.createEntityManagerFactory( "templatePU2" );
   }

   @After
   public void destroy() {
      entityManagerFactory2.close();
      entityManagerFactory.close();
   }

   // Entities are auto-discovered, so just add them anywhere on class-path
   // Add your tests, using standard JUnit.
   @Test
   public void twoSchemaJoinTest() throws Exception {
      EntityManager entityManager = entityManagerFactory.createEntityManager();
      try {
         entityManager.getTransaction().begin();

         Location location1 = new Location("city1");
         Location location2 = new Location("city2");
         entityManager.persist(location1);
         entityManager.persist(location2);
         Set<Location> locations = new HashSet<>();
         locations.add(location1);
         locations.add(location2);
         Event event = new Event(new Date());
         event.setLocations(locations);
         entityManager.persist(event);
         entityManager.getTransaction().commit();

         entityManager.getTransaction().begin();
         String queryString = "Select distinct t from Event t join fetch t.locations";
         Query query = entityManager.createQuery(queryString);
         Event event1 = (Event) query.getSingleResult();
         System.out.println(event1.getId());

         //assertEquals(event.getCreatedOn(), dbEvent.getCreatedOn());
         entityManager.getTransaction().commit();
      }
      catch(Exception e){
         e.printStackTrace();
      }
      finally{
         entityManager.close();
      }

   }

   private void createLocations(){
      EntityManager entityManager2 = entityManagerFactory2.createEntityManager();
      entityManager2.getTransaction().begin();

      Location location1 = new Location("city1");
      Location location2 = new Location("city2");


      entityManager2.persist( location1 );
      entityManager2.persist( location2 );


      entityManager2.getTransaction().commit();
      entityManager2.close();
   }
}

package org.hibernate.bugs;

import java.util.Date;
import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

@Entity
@Table(name = "Event", schema = "db1")
public class Event {
    private Long id;
    @Temporal(TemporalType.TIMESTAMP )
    private Date createdOn;
    private Set<Location> locations;

    public Event() {
    }
    public Event(Date createdOn) {
        this.createdOn = createdOn;
    }


    @Id
    @GeneratedValue
    public Long getId() {
        return id;
    }

    @OneToMany(fetch = FetchType.EAGER, cascade = {CascadeType.REFRESH}, targetEntity = Location.class)
    public Set<Location> getLocations() {
        return locations;
    }

    public Date getCreatedOn() {
        return createdOn;
    }

    public void setLocations(Set<Location> locations) {
        this.locations=locations;
    }

    public void setCreatedOn(Date createdOn) {
        this.createdOn = createdOn;
    }

    public void setId(Long id) {

        this.id = id;
    }



}


package org.hibernate.bugs;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name = "Location", schema = "db2")
public class Location {
    private Long id;
    String name;

    public Location() {
    }

    public Location(String name) {
        this.name = name;
    }

    @Id
    @GeneratedValue
    public Long getId() {
        return id;
    }

    @Column(name = "NAME", unique = true, nullable = false, length = 128)
    public String getName(){
        return this.name;
    }


    public void setName(String name){
        this.name =  name;
    }

    public void setId(Long id) {
        this.id = id;
    }
}

<persistence 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"
             version="2.1">
<!--<persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"-->
             <!--version="2.0">-->

    <persistence-unit name="templatePU" transaction-type="RESOURCE_LOCAL">

        <description>Hibernate test case template Persistence Unit</description>
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
        <class>org.hibernate.bugs.Event</class>

        <exclude-unlisted-classes>false</exclude-unlisted-classes>


        <properties>
            <property name="hibernate.archive.autodetection" value="class, hbm"/>

            <property name="hibernate.dialect" value="org.hibernate.dialect.H2Dialect"/>
            <property name="hibernate.connection.driver_class" value="org.h2.Driver"/>
            <property name="hibernate.connection.url" value="jdbc:h2:mem:db1;DB_CLOSE_DELAY=-1"/>
            <property name="hibernate.connection.username" value="sa"/>

            <property name="hibernate.connection.pool_size" value="5"/>

            <property name="hibernate.show_sql" value="true"/>
            <property name="hibernate.format_sql" value="true"/>
            <property name="hibernate.hbm2ddl.auto" value="create-drop"/>

            <property name="hibernate.max_fetch_depth" value="5"/>

            <property name="hibernate.cache.region_prefix" value="hibernate.test"/>
            <property name="hibernate.cache.region.factory_class"
                      value="org.hibernate.testing.cache.CachingRegionFactory"/>

            <!--NOTE: hibernate.jdbc.batch_versioned_data should be set to false when testing with Oracle-->
            <property name="hibernate.jdbc.batch_versioned_data" value="true"/>

            <property name="javax.persistence.validation.mode" value="NONE"/>
            <property name="hibernate.service.allow_crawling" value="false"/>
            <property name="hibernate.session.events.log" value="true"/>
        </properties>

    </persistence-unit>
    <persistence-unit name="templatePU2" transaction-type="RESOURCE_LOCAL">

        <description>Hibernate test case template Persistence Unit</description>
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>

        <class>org.hibernate.bugs.Location</class>
        <exclude-unlisted-classes>false</exclude-unlisted-classes>

        <properties>
            <property name="hibernate.archive.autodetection" value="class, hbm"/>

            <property name="hibernate.dialect" value="org.hibernate.dialect.H2Dialect"/>
            <property name="hibernate.connection.driver_class" value="org.h2.Driver"/>
            <property name="hibernate.connection.url" value="jdbc:h2:mem:db2;DB_CLOSE_DELAY=-1"/>
            <property name="hibernate.connection.username" value="sa"/>

            <property name="hibernate.connection.pool_size" value="5"/>

            <property name="hibernate.show_sql" value="true"/>
            <property name="hibernate.format_sql" value="true"/>
            <property name="hibernate.hbm2ddl.auto" value="create-drop"/>

            <property name="hibernate.max_fetch_depth" value="5"/>

            <property name="hibernate.cache.region_prefix" value="hibernate.test"/>
            <property name="hibernate.cache.region.factory_class"
                      value="org.hibernate.testing.cache.CachingRegionFactory"/>

            <!--NOTE: hibernate.jdbc.batch_versioned_data should be set to false when testing with Oracle-->
            <property name="hibernate.jdbc.batch_versioned_data" value="true"/>

            <property name="javax.persistence.validation.mode" value="NONE"/>
            <property name="hibernate.service.allow_crawling" value="false"/>
            <property name="hibernate.session.events.log" value="true"/>
        </properties>

    </persistence-unit>
</persistence>