Convert

Specifies the conversion of a Basic field or property. It is not necessary to use the Basic annotation or corresponding XML element to specify the Basic type.

The Convert annotation should not be used to specify conversion of the following: Id attributes, version attributes, relationship attributes, and attributes explicitly denoted as Enumerated or Temporal. Applications that specify such conversions will not be portable.

The Convert annotation may be applied to a basic attribute or to an element collection of basic type (in which case the converter is applied to the elements of the collection). In these cases, the attributeName element must not be specified.

The Convert annotation may be applied to an embedded attribute or to a map collection attribute whose key or value is of embeddable type (in which case the converter is applied to the specified attribute of the embeddable instances contained in the collection). In these cases, the attributeName element must be specified.

To override conversion mappings at multiple levels of embedding, a dot (".") notation form must be used in the attributeName element to indicate an attribute within an embedded attribute. The value of each identifier used with the dot notation is the name of the respective embedded field or property.

When the Convert annotation is applied to a map containing instances of embeddable classes, the attributeName element must be specified, and "key." or "value." must be used to prefix the name of the attribute that is to be converted in order to specify it as part of the map key or map value.

When the Convert annotation is applied to a map to specify conversion of a map key of basic type, "key" must be used as the value of the attributeName element to specify that it is the map key that is to be converted.

The Convert annotation may be applied to an entity class that extends a mapped superclass to specify or override a conversion mapping for an inherited basic or embedded attribute.

Example 1:

  Convert a basic attribute

     @Converter
     public class BooleanToIntegerConverter
        implements AttributeConverter<Boolean, Integer> {  ... }

     @Entity
     public class Employee {
         @Id long id;

         @Convert(converter=BooleanToIntegerConverter.class)
          boolean fullTime;
          ...
     }

Example 2:

  Auto-apply conversion of a basic attribute

     @Converter(autoApply=true)
     public class EmployeeDateConverter
        implements AttributeConverter<com.acme.EmployeeDate, java.sql.Date> {  ... }

     @Entity
     public class Employee {
         @Id long id;
         ...
         // EmployeeDateConverter is applied automatically
         EmployeeDate startDate;
     }

Example 3:

  Disable conversion in the presence of an autoapply converter

     @Convert(disableConversion=true)
     EmployeeDate lastReview;

Example 4:

  Apply a converter to an element collection of basic type

     @ElementCollection
     // applies to each element in the collection
     @Convert(converter=NameConverter.class)
     List<String> names;

Example 5:

  Apply a converter to an element collection that is a map or basic values.
                 The converter is applied to the map value.

     @ElementCollection
     @Convert(converter=EmployeeNameConverter.class)
     Map<String, String> responsibilities;

Example 6:

  Apply a converter to a map key of basic type

     @OneToMany
     @Convert(converter=ResponsibilityCodeConverter.class,
              attributeName="key")
     Map<String, Employee> responsibilities;

Example 7:

  Apply a converter to an embeddable attribute

     @Embedded
     @Convert(converter=CountryConverter.class,
              attributeName="country")
     Address address;

Example 8:

  Apply a converter to a nested embeddable attribute

     @Embedded
     @Convert(converter=CityConverter.class,
              attributeName="region.city")
     Address address;

Example 9:

  Apply a converter to a nested attribute of an embeddable that is a map key
                 of an element collection

     @Entity public class PropertyRecord {
          ...
         @Convert(attributeName="key.region.city",
                  converter=CityConverter.class)
         @ElementCollection
         Map<Address, PropertyInfo> parcels;
     }

Example 10:

 Apply a converter to an embeddable that is a map key for a relationship

     @OneToMany
     @Convert(attributeName="key.jobType",
              converter=ResponsibilityTypeConverter.class)
     Map<Responsibility, Employee> responsibilities;

Example 11:

 Override conversion mappings for attributes inherited from a mapped superclass

     @Entity
         @Converts({
            @Convert(attributeName="startDate",
                     converter=DateConverter.class),
            @Convert(attributeName="endDate",
                     converter=DateConverter.class)})
     public class FullTimeEmployee extends GenericEmployee { ... }