ReadTransformer (EclipseLink 4.0.2, API Reference)

```
@Target({METHOD,FIELD})
@Retention(RUNTIME)
public @interface ReadTransformer
```
Annotation for org.eclipse.persistence.mappings.TransformationMapping. Unless the TransformationMapping is write-only, it should have a ReadTransformer, it defines transformation of database column(s) value(s) into attribute value. Also unless it's a read-only mapping, either WriteTransformer annotation or WriteTransformers annotation should be specified. Each WriteTransformer defines transformation of the attribute value to a single database column value (column is specified in the WriteTransformer).

See Also:

Transformation, WriteTransformer, Transformation can be specified within an Entity, MappedSuperclass and Embeddable class.

Author:

Andrei Ilitchev

Optional Element Summary

Optional Elements
Modifier and Type	Optional Element	Description
`String`	`method`	The mapped class must have a method with this name which returns a value to be assigned to the attribute (not assigns the value to the attribute).
`Class<?>`	`transformerClass`	User-defined class that must implement the org.eclipse.persistence.mappings.transformers.AttributeTransformer interface.

- Element Detail
  - transformerClass
```
Class<?> transformerClass
```
    User-defined class that must implement the org.eclipse.persistence.mappings.transformers.AttributeTransformer interface. The class will be instantiated, its buildAttributeValue will be used to create the value to be assigned to the attribute. Either transformerClass or method must be specified, but not both.
    
    Default:
    
    void.class
- - method
```
String method
```
    The mapped class must have a method with this name which returns a value to be assigned to the attribute (not assigns the value to the attribute). Either transformerClass or method must be specified, but not both.
    
    Default:
    
    ""