JPA / Hibernate：在复杂类上使用AttributeConverter时创建UserType是否明显？

Question

I'd like to map an arbitrary POJO class attribute as a String with an AttributeConverter<SomeClass, String> but I get this:

WARN: Could not find matching type descriptor for requested Java class [SomeClass]; using fallback

Does that mean AttributeConverter is not enough and I need to write a custom UserType for every complex class to be able transforming it into String and back?

Another solution requires @Embeddable . Is it more suitable here?

@Entity
public class SomePersistentClass {
    @Id
    int id;

    @Convert(converter = SomeClassConverter.class)
    public SomeClass attribute;

    //...
}

public class SomeClass {
    //...
}

Answer 1

Old question, but as of Hibernate 5.2.7 (Jan 24th, 2017) this warning changed to:

WARN org.hibernate.type.descriptor.java.JavaTypeDescriptorRegistry - HHH000481: Encountered Java type [class SomeClass] for which we could not locate a JavaTypeDescriptor and which does not appear to implement equals and/or hashCode. This can lead to significant performance problems when performing equality/dirty checking involving this Java type. Consider registering a custom JavaTypeDescriptor or at least implementing equals/hashCode. So, there are these solutions:

To solve this, simply make sure your type implements equals and hashcode, and also annotate it with Immutable.class in case it is immutable.

See: JavaTypeDescriptorRegistry - Could not find matching type descriptor for requested Java class

Answer 2

Define the pojo with

1. @Named

2. implements Converter

3. Override the getAsObject and getAsString method