com.googlecode.objectify.annotation.AlsoLoad Maven / Gradle / Ivy

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*** THIS VERSION UPLOADED FOR USE WITH CEDAR-COMMON, TO AVOID DEPENDENCIES ON GOOGLE CODE-BASED MAVEN REPOSITORIES. *** The simplest convenient interface to the Google App Engine datastore

The newest version!

package com.googlecode.objectify.annotation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * Annotation which helps migrate schemas by loading one of several possible properties
 * in the entity into fields or methods.  This is typically used when a field is renamed,
 * allowing the field to be populated by both its current name and any prior names.
 * 
 * 
 * When placed on a field, the additional names (entity properties) will be checked
 * when this field is loaded.  If the entity contains data for more than one of the names,
 * an exception will be thrown. 
 * 
When placed on a parameter to a method that takes a single parameter, the method
 * will be called with the data value.  As with fields, any ambiguity in the data (multiple
 * properties that would cause the method to be called) will produce an exception.  However,
 * {@code @AlsoLoad} on a method parameter *can* be used to override field names and "steal" the
 * value that would otherwise have been set on a field.  This can be useful when changing the
 * type of a field.
 * 
 * 
 * @author Jeff Schnitzer 
 */
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD, ElementType.PARAMETER})
public @interface AlsoLoad
{
	String[] value();
}