org.apache.polygene.api.common

Annotation Type UseDefaults

@Retention(value=RUNTIME)
 @Target(value={METHOD,FIELD})
 @Documented
public @interface UseDefaults

Annotation to denote that the initial value of a Property will be the default value for the type if none is specified during construction.

These are the default values used for various types:

 Byte: 0
 Short: 0
 Character: 0
 Integer: 0
 Long: 0L
 Double: 0.0d
 Float: 0.0f
 Boolean: false
 String: ""
 List: empty java.util.ArrayList
 Set: empty java.util.HashSet
 Collection: empty java.util.ArrayList
 enum: first declared value
 

If this annotation is not used, the property will be set to null, and unless @Optional is declared is not allowed.

The @UseDefaults annotation can also have a value in its declaration. This value is used, unless it is overridden in the assembly (see below). Java does not support generic types of annotation values, so it accepts String values, which are deserialized from JSON using the Serialization SPI. This allows for (albeit somewhat tedious) any object type to have a default value declared on it. If the property type is String, then no value deserialization is done.

It is also possible to change the default values for Composites during the assembly. This is done by calling the org.apache.polygene.bootstrap.ModuleAssembly#forMixin(Class) method.

Example; Let's assume that we have the following mixin type;

 public interface SomeType
 {
     @UseDefaults
     Property<String> someValue();
 }
 

And that we want to have someValue() to be initialized to "<unknown>" instead of the empty string. Then we need to declare the default for that with the following in the assembler.

 public void assemble( ModuleAssembly module )
 {
     module.forMixin( SomeType.class ).declareDefaults().someValue().set( "<unknown>" );
 }
 }
 

Optional Element Summary

Optional Elements

Modifier and Type	Optional Element and Description
String	value

Element Detail

value

public abstract String value

Default:

""