Jpa: Could Not Determine Recommended Jdbctype For New update

The error message “Could not determine recommended JdbcType for <SomeCustomClass>” in JPA typically occurs when you try to persist an entity that includes a field or property of a custom class that is not supported by JPA out of the box.

To solve this error, you will need to explicitly specify how the custom class should be persisted to the database. There are two common ways to do this:

1. Use the @Convert annotation to specify a converter for the custom class. A converter is a class that tells JPA how to convert the custom class to a type that can be stored in the database. You can create your own converter by implementing the javax.persistence.AttributeConverter interface, or you can use a third-party converter library like Hibernate Types.

For example, if you have a custom class called “Address” that you want to persist as a VARCHAR in the database, you can create a converter like this:

java
@Converter(autoApply = true)
public class AddressConverter implements AttributeConverter<Address, String> {
    @Override
    public String convertToDatabaseColumn(Address address) {
        return address.toString();
    }
 
    @Override
    public Address convertToEntityAttribute(String dbData) {
        return Address.fromString(dbData);
    }
}

And then annotate the Address field in your entity with the @Convert annotation:

java
@Entity
public class Customer {
    @Id
    private Long id;
 
    private String name;
 
    @Convert(converter = AddressConverter.class)
    private Address address;
 
    // getters and setters
}

1. Implement the Serializable interface for the custom class. This approach tells JPA to serialize the object to a binary format that can be stored in a BLOB column in the database. Note that this approach is generally less efficient than using a converter, as it requires additional serialization and deserialization steps.

For example, if you have a custom class called “Color” that you want to persist as a BLOB in the database, you can make it Serializable:

java
public class Color implements Serializable {
    private int red;
    private int green;
    private int blue;
 
    // constructors, getters, and setters
}

And then include a Color field in your entity:

java
@Entity
public class Product {
    @Id
    private Long id;
 
    private String name;
 
    private Color color;
 
    // getters and setters
}