FIX: NPE when fetching inherited beans from cache (#1373)

src/main/java/io/ebeaninternal/server/deploy/BeanDescriptor.java

@@ -71,6 +71,7 @@ import io.ebeaninternal.server.query.STreePropertyAssocMany;
 import io.ebeaninternal.server.query.STreePropertyAssocOne;
 import io.ebeaninternal.server.query.STreeType;
 import io.ebeaninternal.server.query.SqlBeanLoad;
+import io.ebeaninternal.server.querydefn.DefaultOrmQuery;
 import io.ebeaninternal.server.querydefn.OrmQueryDetail;
 import io.ebeaninternal.server.rawsql.SpiRawSql;
 import io.ebeaninternal.server.type.DataBind;
@@ -1878,6 +1879,9 @@ public class BeanDescriptor<T> implements BeanType<T>, STreeType {
    * on first access (lazy load) or immediately (eager load)
    */
   public EntityBean createEntityBean(boolean isNew) {
+    if (prototypeEntityBean == null) {
+      throw new UnsupportedOperationException("cannot create entity bean for abstract entity " + getName());
+    }
     try {
       EntityBean bean = (EntityBean) prototypeEntityBean._ebean_newInstance();
 
@@ -1969,6 +1973,13 @@ public class BeanDescriptor<T> implements BeanType<T>, STreeType {
   public T createReference(Object id, PersistenceContext pc) {
 
     try {
+      if (inheritInfo != null && !inheritInfo.isConcrete()) {
+        // we actually need to do a query because we don't know the type without the discriminator
+        // value, just select the id property and discriminator column (auto added)
+        DefaultOrmQuery<T> query = new DefaultOrmQuery<>(this, ebeanServer, ebeanServer.getExpressionFactory());
+        return query.select(getIdProperty().getName()).setId(id).findOne();
+      }
+
       EntityBean eb = createEntityBean();
       id = convertSetId(id, eb);
       EntityBeanIntercept ebi = eb._ebean_getIntercept();

src/test/java/org/tests/inheritance/cache/TestInheritanceRefCache.java

@@ -0,0 +1,64 @@
+package org.tests.inheritance.cache;
+
+import io.ebean.BaseTestCase;
+import io.ebean.Ebean;
+import org.tests.model.basic.cache.CInhOne;
+import org.tests.model.basic.cache.CInhRef;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.List;
+
+import org.ebeantest.LoggedSqlCollector;
+
+public class TestInheritanceRefCache extends BaseTestCase {
+
+  @Test
+  public void test() {
+
+    CInhOne one = new CInhOne();
+    one.setLicenseNumber("O12");
+    one.setDriver("Jimmy");
+    one.setNotes("Hello");
+
+    Ebean.save(one);
+
+    CInhRef ref = new CInhRef();
+    ref.setRef(one);
+
+    Ebean.save(ref);
+
+    Integer id = ref.getId();
+
+    LoggedSqlCollector.start();
+    CInhRef gotRef = Ebean.find(CInhRef.class).setId(id).findOne();
+
+    assertThat(gotRef).isInstanceOf(CInhRef.class);
+    assertThat(gotRef.getRef()).isInstanceOf(CInhOne.class);
+    List<String> sql = LoggedSqlCollector.stop();
+    assertThat(sql).hasSize(1);
+    assertThat(sql.get(0)).contains("from cinh_ref").contains("left join cinh_root");
+
+    // fetch again - from cache (but fetch second bean from cache)
+    LoggedSqlCollector.start();
+    gotRef = Ebean.find(CInhRef.class).setId(id).findOne();
+
+    assertThat(gotRef).isInstanceOf(CInhRef.class);
+    assertThat(gotRef.getRef()).isInstanceOf(CInhOne.class);
+    sql = LoggedSqlCollector.stop();
+    assertThat(sql).hasSize(1);
+    assertThat(sql.get(0)).contains("from cinh_root");
+
+
+    // fetch again - both from cache
+    LoggedSqlCollector.start();
+    gotRef = Ebean.find(CInhRef.class).setId(id).findOne();
+
+    assertThat(gotRef).isInstanceOf(CInhRef.class);
+    assertThat(gotRef.getRef()).isInstanceOf(CInhOne.class);
+    sql = LoggedSqlCollector.stop();
+    assertThat(sql).hasSize(0);
+
+  }
+}

src/test/java/org/tests/model/basic/cache/CInhRef.java

@@ -0,0 +1,25 @@
+package org.tests.model.basic.cache;
+
+import org.tests.model.basic.BasicDomain;
+
+import io.ebean.annotation.Cache;
+
+import javax.persistence.Entity;
+import javax.persistence.ManyToOne;
+
+@Entity
+@Cache(enableQueryCache = true)
+public class CInhRef extends BasicDomain {
+  private static final long serialVersionUID = -4673953370819311120L;
+
+  @ManyToOne(cascade = {})
+  private CInhRoot ref;
+
+  public CInhRoot getRef() {
+    return ref;
+  }
+
+  public void setRef(CInhRoot ref) {
+    this.ref = ref;
+  }
+}