/*
 * Copyright (c) 2010 Mysema Ltd.
 * All rights reserved.
 * 
 */
package com.mysema.rdfbean.annotations;

import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.PARAMETER;

import java.lang.annotation.Documented;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * Allows defining a default value for object/reference properties. For example
 * a default Role of a User:
 * 
 * <pre>
 * @ClassMapping(ns=TEST.NS)
 * public class User {
 * 
 *   @Default(ns=TEST.NS, "UserRole")
 *   @Predicate
 *   private Role role;
 *   ...
 * }
 * </pre>
 * 
 * @Default can also be used as such without @Predicate in order to
 * define non changeable references. This is particulary useful in conjunction
 * with @Inject for injecting named services to beans:
 * 
 * <pre>
 *   @Default(ns=TEST.SERVICES_NS, "userService")
 *   @Inject
 *   private UserService userService;
 * </pre>
 * 
 * @author sasa
 */
@Documented
@Target({ METHOD, FIELD, PARAMETER })
@Retention(RetentionPolicy.RUNTIME)
@Inherited
public @interface Default {

    /**
     * @return The local name of the resource URI. If namespace (ns) is not
     *         given, this is should be the full URI.
     */
    String ln() default "";

    /**
     * @return Namespace of the resource or empty string, if localName contains
     *         whole URI.
     */
    String ns();

}