Featured Image with Sidebar

How to implement a JPA Attribute Converter

By Thorben Janssen

JPA 2.1 brings several improvements. One of them is the Attribute Converter. It allows the developer to specify methods to convert between the database and the Java representation of an attribute.

What can be converted?

A Converter supports type conversion of all basic attributes defined by entity classes, mapped superclasses, or embeddable classes. The only exceptions are Id attributes, version attributes, relationship attributes and attributes annotated as Temporal or Enumerated.

How to implement a Converter?

A Converter must implement the javax.persistence.AttributeConverter<X, Y> interface, where X is the class of the entity representation and Y the class of the database representation of the attribute. Additionally a Converter has to be annotated with the javax.persistence.Converter annotation.
The following example shows a Converter implementation that can be used to store a java.awt.Color object as a String with the format red|green|blue|alpha in the database. When reading the entity from the database, the String will be used to instantiate a new Color object.

package blog.thoughts.on.java.jpa21.converter;

import java.awt.Color;

import javax.persistence.AttributeConverter;
import javax.persistence.Converter;

public class ColorConverter implements AttributeConverter<Color, String> {

 private static final String SEPARATOR = "\\|";

  * Convert Color object to a String 
  * with format red|green|blue|alpha
 public String convertToDatabaseColumn(Color color) {
  StringBuilder sb = new StringBuilder();
  return sb.toString();

  * Convert a String with format red|green|blue|alpha
  * to a Color object
 public Color convertToEntityAttribute(String colorString) {
  String[] rgb = colorString.split(SEPARATOR);
  return new Color(Integer.parseInt(rgb[0]), 


As you can see the implementation is simple and straight forward. You just need to implement one method for each conversion.

How to use a Converter?

There are two options to define the usage of a Converter. The first one is to set autoapply=true at the @Converter annotation of the Converter class. In this case the JPA provider will use this Converter to convert all entity attributes of the given type.
If autoapply is set to false, you need to add the javax.persistence.Convert annotation to all attributes that shall be converted and specify the Converter class. The following code snippet shows an example for this approach:

public class RectangleEntity

   @GeneratedValue(strategy = GenerationType.IDENTITY)
   private Integer id;

   private Integer x;

   private Integer y;

   @Convert(converter = ColorConverter.class)
   private Color color;


That is all that needs to be done to implement a simple Attribute Converter. Don’t forget to grab your free Cheat Sheet about Attribute Converter and all the other features introduced with JPA 2.1.

If you want to try it yourself, you can use Hibernate 4.3.0.Beta4 which is part of the new Wildfly 8.0.0.Beta1 release.

Looking for more information? Read JPA 2.1 – 12 features every developer should know to get an overview about the features introduced with JPA 2.1 or have a look at the other examples on how to use an Attribute Converter:

Please leave a comment with your idea on how to use an Attribute Converter.
If you enjoyed reading this article and like to learn more about other Java EE features, make sure to subscribe to below or follow me on twitter .


JPA 2.1 Specification
Java Doc javax.persistence

About the author

Thorben is an independent consultant, international speaker, and trainer specialized in solving Java persistence problems with JPA and Hibernate.
He is also the author of Amazonโ€™s bestselling book Hibernate Tips - More than 70 solutions to common Hibernate problems.

Books and Courses

Coaching and Consulting


Leave a Reply

Your email address will not be published. Required fields are marked

This site uses Akismet to reduce spam. Learn how your comment data is processed.

  1. Hi Thorben.

    You already wrote about the exceptions concerning converting an id Attribute. Are there workarounds or official ways
    to Convert e.g. an String to an UUID vice versa?
    We had to switch our underlaying database from postgres to db/2, which does not support UUIDs natively. So we have to convert these right now.

    Kind regards

  2. Will AttributeConverter will get invoked in case of
    1. Static(Named) Or Dynamic Queries using javax.persistence.Query interface and entiyManager
    2. Queries using javax.persistence.Query interface and entiyManager with POJO (Constructor) used to map query result.

    1. Hi Amit,

      yes the AttributeConverter gets applied in all these situations.
      The only situation in which it isn’t used is a native SQL query.


    1. The X and Y were mentioned in the reference to the AttributeConverter interface:

      A Converter must implement the javax.persistence.AttributeConverter interface, where X is the class of the entity representation and Y the class of the database representation of the attribute. Additionally a Converter has to be annotated with the javax.persistence.Converter annotation.

  3. Is there any reason why ID attributes can not be converted?
    Hibernate User Types can be used with IDs, though.

    1. Hi Stefan,

      that’s the way it’s defined in the JPA spec. To be honest, I don’t know why they excluded IDs. One reason might be, that the conversion has to be biuniquely and that there is no way the spec or persistence provider can assure that.


  4. Its not working even after changing hibernate-jpa 2.0 module of Jboss to hibernate-jpa-2.1-api-1.0.0.Final.jar… any idea? why its not being called?

    1. Hi Raghu,
      you need to update the used Hibernate module to a version >4.3.0 or switch to Wildfly 8. The hibernate-jpa-2.1-api-1.0.0.Final.jar provides only the JPA 2.1 APIs but not the implementation.

  5. I followed the same steps as above..
    But my Converter never being called.
    I am using hibernate-jpa-2.1-api-1.0.0.Final.jar
    on Jboss 7.1.1 server…

    PLs help me

  6. Hi Thorben and others,

    I have a project where I need to create many different (70+) enums and hence repeatedly define 70+ AttributeConverters. Even though using Java8, there is no neat way of doing things at compile time.

    Anyone knows if we could define those converters at runtime?


  7. Is there also a way to use the Converter implicitly with a javax.persistence.Query? When I add the Object as a query parameter then I get an Exception.

  8. Hi

    Thanks for the article.

    I am using JBoss AS 7.1. I set the “” in persistence.xml. But it looks like the converer is not getting called in my case. Could you please help for the same. If the request comes from tomcat, then the converter is being called but not if the request is from jboss.

    Your help would be highly appreciable


{"email":"Email address invalid","url":"Website address invalid","required":"Required field missing"}