JPA Attribute Converter: Difference between revisions

From NovaOrdis Knowledge Base
Jump to navigation Jump to search
Line 33: Line 33:
==The Converter Class==
==The Converter Class==


Provide a converter class, which must implement AttributeConverter<''Entity-Field-Type'', ''Database-Type''> and be annotated with @javax.persistence.Converter:
Provide a converter class, which must implement AttributeConverter<''Entity-Field-Type'', ''Database-Type''> and be annotated with [[@Converter|@javax.persistence.Converter]]:


<syntaxhighlight lang='java'>
<syntaxhighlight lang='java'>

Revision as of 20:32, 31 October 2018

External

Internal

Overview

An attribute converter allows the developer to specify methods to convert between the database and the Java representation of an attribute. Attribute conversion was introduced in JPA 2.1. All entity class. mapped superclass or embeddable class attributes can be type-converted, with the following exceptions:

  • identity attributes
  • version attributes
  • relationship attributes
  • attributes annotated as @Temporal or @Enumerated.

Playground Example

https://github.com/ovidiuf/playground/tree/master/spring/jpa/attribute-converter

Programming Model

@Convert Annotation

Annotate the entity fields to be converter with @javax.persistence.Convert:

@Convert(converter = PayloadConverter.class)
private Payload payload;

The Converter Class

Provide a converter class, which must implement AttributeConverter<Entity-Field-Type, Database-Type> and be annotated with @javax.persistence.Converter:

@Converter
public class PayloadConverter implements AttributeConverter<Payload, String> {

  @Override
  public String convertToDatabaseColumn(Payload attribute) {
     ...
  }

  @Override
  public Payload convertToEntityAttribute(String dbData) {
     ...
  }
}