HHH-17644 Add test for issue

Author: dreab8

hibernate-core/src/test/java/org/hibernate/orm/test/inheritance/discriminator/SingleTableAndGenericsTest.java

@@ -0,0 +1,95 @@
+package org.hibernate.orm.test.inheritance.discriminator;
+
+import org.hibernate.annotations.JdbcTypeCode;
+
+import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.JiraKey;
+import org.hibernate.testing.orm.junit.SessionFactory;
+import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.junit.jupiter.api.Test;
+
+import jakarta.persistence.Column;
+import jakarta.persistence.DiscriminatorColumn;
+import jakarta.persistence.DiscriminatorValue;
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import jakarta.persistence.Inheritance;
+import jakarta.persistence.Table;
+
+import static jakarta.persistence.InheritanceType.SINGLE_TABLE;
+import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
+import static org.hibernate.type.SqlTypes.JSON;
+
+@DomainModel(
+		annotatedClasses = {
+				// the order is important to reproduce the issue
+				SingleTableAndGenericsTest.B.class,
+				SingleTableAndGenericsTest.A.class,
+		}
+)
+@SessionFactory
+@JiraKey("HHH-17644")
+public class SingleTableAndGenericsTest {
+
+	@Test
+	public void testIt(SessionFactoryScope scope) {
+		String payload = "{\"book\": \"1\"}";
+		String aId = "1";
+
+		scope.inTransaction(
+				session -> {
+					A a = new A();
+					a.setId( aId );
+					session.persist( a );
+					a.setPayload( payload );
+				}
+		);
+
+		scope.inTransaction(
+				session -> {
+					A a = session.find( A.class, aId );
+					assertThat( a ).isNotNull();
+					String payload1 = a.getPayload();
+					assertThat( payload1 ).isNotNull();
+					assertThat( payload1 ).contains( "book" );
+				}
+		);
+	}
+
+	@Entity(name = "B")
+	@Table(name = "table_b")
+	@Inheritance(strategy = SINGLE_TABLE)
+	@DiscriminatorColumn(name = "demo_type")
+	public static abstract class B<T> {
+
+		@Id
+		@Column(name = "id", nullable = false)
+		private String id;
+
+		@Column(name = "payload")
+		@JdbcTypeCode(JSON)
+		private T payload;
+
+		public String getId() {
+			return id;
+		}
+
+		public void setId(String id) {
+			this.id = id;
+		}
+
+		public T getPayload() {
+			return payload;
+		}
+
+		public void setPayload(T payload) {
+			this.payload = payload;
+		}
+	}
+
+	@Entity(name = "C")
+	@DiscriminatorValue("child")
+	public static class A extends B<String> {
+	}
+}
+