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package com.sun.xml.internal.bind.annotation;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElementRef;
import javax.xml.bind.annotation.XmlValue;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
/**
* Designates a boolean field/property as a flag to indicate
* whether another property is present or not.
*
* <p>
* Sometimes you'd want to map a Java primitive type to an
* optional element/attribute. Doing this makes it impossible
* to represent the absence of the property, thus you always
* end up producing the value when you marshal to XML.
*
* For example,
* <pre>
* {@link XmlElement}
* class Foo {
* {@link XmlElement}
* int x;
* }
*
* marshaller.marshal(new Foo());
* </pre>
* and you get:
* <pre><xmp>
* <foo><x>0</x></foo>
* </xmp></pre>
*
* <p>
* By creating a side boolean field/property that has this annotation,
* you can indicate the absence of the property by setting this boolean
* to false.
* <pre>
* {@link XmlElement}
* class Foo {
* {@link XmlElement}
* int x;
* {@link XmlIsSet}("x")
* boolean xIsPresent;
* }
*
* Foo f = new Foo();
* f.x = 5;
* f.xIsPresent = false;
*
* marshaller.marshal(f);
*
* <xmp>
* <foo/>
* </xmp>
*
* f.xIsPresent = true;
* <xmp>
* <foo><x>5</x></foo>
* </xmp>
* </pre>
*
* <p>
* A property/field annotated with {@link XmlIsSet} itself will not show up in XML.
* It is an error to use this annotation on the same property/field
* as {@link XmlElement}, {@link XmlAttribute}, {@link XmlValue}, or {@link XmlElementRef},
* ...<b>TBD</b>.
*
* @deprecated
* this hasn't been implemented in the RI, and this hasn't been speced yet.
* I believe Joe asked for this feature. I'd like to drop this.
*
* @author Kohsuke Kawaguchi
*/
@Retention(RUNTIME)
@Target({FIELD,METHOD})
public @interface XmlIsSet {
/**
* Specifies the name of the property to attach to.
*/
String value();
}