# Persist dynamically typed entity properties with Hibernate and PostgreSQL

**URL:** <https://discourse.hibernate.org/t/persist-dynamically-typed-entity-properties-with-hibernate-and-postgresql/589>\
**Category:** Hibernate ORM\
**Created:** [April 20, 2018, 9:46am UTC](https://discourse.hibernate.org/t/persist-dynamically-typed-entity-properties-with-hibernate-and-postgresql/589 "2018-04-20T09:46:26Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![braniak94](https://avatars.discourse-cdn.com/v4/letter/b/f0a364/32.png) [@braniak94](https://discourse.hibernate.org/u/braniak94)\
**Post date:** [April 20, 2018, 9:46am UTC](https://discourse.hibernate.org/t/persist-dynamically-typed-entity-properties-with-hibernate-and-postgresql/589/1 "2018-04-20T09:46:26Z")

</div>

I would like to build field which can be String, Boolean or Long. In this case I tried use generics type and inheratiance. All code compiles correctly but when I want to get some parameters from database I got a error like:

> Object [id=1] was not of the specified subclass [unity.app.domain.Parameter] : Discriminator: 1",

What is more if I want to use post method to adding parameter to DB I got error like this:

> “Type definition error: [simple type, class unity.app.domain.Parameter]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of unity.app.domain.Parameter (no Creators, like default construct, exist): abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information\n at [Source: (PushbackInputStream); line: 1, column: 1]”,

I don’t have any ideas how to resolve this problem ☹

```auto
@Data
@Entity
@Table(name = "parameter")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "parameter", discriminatorType = DiscriminatorType.STRING)
public abstract class Parameter<T> {

    @Id
    @GeneratedValue(strategy = GenerationType.TABLE)
    @Column(name = "id", nullable = false)
    private Long id;

    @Column(name = "code")
    private String code;

    private T value;

    @Transient
    public abstract T getValue();

    public abstract void setValue(T value);
}

@Entity
@DiscriminatorValue(value = "boolean")
public class BooleanValue extends Parameter<Boolean> {

    @Column(name = "bool_value")
    private Boolean booleanValue;

    getValue()/setValue()[...]
}

@Entity
@DiscriminatorValue(value = "long")
public class LongValue extends Parameter<Long> {}

@Entity
@DiscriminatorValue(value = "string")
public class StringValue extends Parameter<String> {}

```

I am using postgresql and this is my table “parameter”:

```auto
  id BIGINT,
  code VARCHAR,
  name VARCHAR,
  description VARCHAR,
  bool_value BOOLEAN,
  string_value VARCHAR,
  long_value BIGINT

```

---

<div class="post-metadata">

**Author:** ![vlad](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.hibernate.org/vlad/32/658_2.png) [@vlad](https://discourse.hibernate.org/u/vlad)\
**Post date:** [April 20, 2018, 9:50am UTC](https://discourse.hibernate.org/t/persist-dynamically-typed-entity-properties-with-hibernate-and-postgresql/589/2 "2018-04-20T09:50:55Z")

</div>

1. There is no `parameter` column in your table and you told Hibernate that the discriminator should be found in the `parameter` column.
2. The table you have there is not what Hibernate expects for SINGLE\_TABLE inheritance. Just activate the `hbm2ddl` schema generatrion to see what tables Hibernate expects.
3. Since you use PostgreSQL, you don-t need this inheritance-based design to handle your requirement. Just use a [JSON property](https://github.com/vladmihalcea/hibernate-types) and store whatever you want in it.
4. The exception `Cannot construct instance of unity.app.domain.Parameter (no Creators, like default construct, exist)` is because you fetch entities as abstract class references and try to serialize to Jackson. Once you remove the inheritance model as suggested above, you will no longer have this problem.