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// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
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package org.apache.juneau.annotation;

import static java.lang.annotation.ElementType.*;
import static java.lang.annotation.RetentionPolicy.*;

import java.lang.annotation.*;

import org.apache.juneau.swap.*;

/**
 * Associates {@link ObjectSwap} and {@link Surrogate} classes with POJOs and bean properties.
 *
 * <p>
 * Can be used in the following locations:
 * <ul>
 * 	<li>Classes.
 * 	<li>Bean getters/setters/fields.
 * 	<li><ja>@Rest</ja>-annotated classes and <ja>@RestOp</ja>-annotated methods when an {@link #on()} value is specified.
 * </ul>

 * <ul class='seealso'>
 * 	<li class='link'>{@doc jm.SwapAnnotation}
 * 	<li class='extlink'>{@source}
 * </ul>
 */
@Documented
@Target({TYPE,ANNOTATION_TYPE,FIELD,METHOD})
@Retention(RUNTIME)
@Inherited
@Repeatable(SwapAnnotation.Array.class)
@ContextApply(SwapAnnotation.Applier.class)
public @interface Swap {

	/**
	 * The {@link ObjectSwap} and {@link Surrogate} class.
	 *
	 * <p>
	 * A synonym for {@link #value()}.
	 *
	 * @return The annotation value.
	 */
	Class<?> impl() default void.class;

	/**
	 * Identifies the media types that this swap is applicable for.
	 *
	 * <p>
	 * In the following example, the swap is only invoked by the JSON serializer:
	 *
	 * <p class='bjava'>
	 * 	<ja>@Swap</ja>(impl=ToStringSwap.<jk>class</jk>, mediaTypes=<js>"&#42;/json"</js>)
	 * 	<jk>public class</jk> MyBean { ... }
	 *
	 * 	<jk>public class</jk> ToStringSwap <jk>extends</jk> ObjectSwap&lt;Object,String&gt; {
	 * 			<jk>public</jk> String swap(BeanSession <jv>session</jv>, Object <jv>value</jv>) <jk>throws</jk> Exception {
	 * 				<jk>return</jk> <jv>value</jv>.toString();
	 * 			}
	 * 		}
	 * </p>
	 *
	 * <ul class='seealso'>
	 * 	<li class='link'>{@doc jm.PerMediaTypeSwaps}
	 * </ul>
	 *
	 * @return The annotation value.
	 */
	String[] mediaTypes() default {};

	/**
	 * Dynamically apply this annotation to the specified classes/methods/fields.
	 *
	 * <p>
	 * Used in conjunction with {@link org.apache.juneau.BeanContext.Builder#applyAnnotations(Class...)} to dynamically apply an annotation to an existing class.
	 * It is ignored when the annotation is applied directly to classes.
	 *
	 * <h5 class='section'>Valid patterns:</h5>
	 * <ul class='spaced-list'>
	 *  <li>Classes:
	 * 		<ul>
	 * 			<li>Fully qualified:
	 * 				<ul>
	 * 					<li><js>"com.foo.MyClass"</js>
	 * 				</ul>
	 * 			<li>Fully qualified inner class:
	 * 				<ul>
	 * 					<li><js>"com.foo.MyClass$Inner1$Inner2"</js>
	 * 				</ul>
	 * 			<li>Simple:
	 * 				<ul>
	 * 					<li><js>"MyClass"</js>
	 * 				</ul>
	 * 			<li>Simple inner:
	 * 				<ul>
	 * 					<li><js>"MyClass$Inner1$Inner2"</js>
	 * 					<li><js>"Inner1$Inner2"</js>
	 * 					<li><js>"Inner2"</js>
	 * 				</ul>
	 * 		</ul>
	 * 	<li>Methods:
	 * 		<ul>
	 * 			<li>Fully qualified with args:
	 * 				<ul>
	 * 					<li><js>"com.foo.MyClass.myMethod(String,int)"</js>
	 * 					<li><js>"com.foo.MyClass.myMethod(java.lang.String,int)"</js>
	 * 					<li><js>"com.foo.MyClass.myMethod()"</js>
	 * 				</ul>
	 * 			<li>Fully qualified:
	 * 				<ul>
	 * 					<li><js>"com.foo.MyClass.myMethod"</js>
	 * 				</ul>
	 * 			<li>Simple with args:
	 * 				<ul>
	 * 					<li><js>"MyClass.myMethod(String,int)"</js>
	 * 					<li><js>"MyClass.myMethod(java.lang.String,int)"</js>
	 * 					<li><js>"MyClass.myMethod()"</js>
	 * 				</ul>
	 * 			<li>Simple:
	 * 				<ul>
	 * 					<li><js>"MyClass.myMethod"</js>
	 * 				</ul>
	 * 			<li>Simple inner class:
	 * 				<ul>
	 * 					<li><js>"MyClass$Inner1$Inner2.myMethod"</js>
	 * 					<li><js>"Inner1$Inner2.myMethod"</js>
	 * 					<li><js>"Inner2.myMethod"</js>
	 * 				</ul>
	 * 		</ul>
	 * 	<li>Fields:
	 * 		<ul>
	 * 			<li>Fully qualified:
	 * 				<ul>
	 * 					<li><js>"com.foo.MyClass.myField"</js>
	 * 				</ul>
	 * 			<li>Simple:
	 * 				<ul>
	 * 					<li><js>"MyClass.myField"</js>
	 * 				</ul>
	 * 			<li>Simple inner class:
	 * 				<ul>
	 * 					<li><js>"MyClass$Inner1$Inner2.myField"</js>
	 * 					<li><js>"Inner1$Inner2.myField"</js>
	 * 					<li><js>"Inner2.myField"</js>
	 * 				</ul>
	 * 		</ul>
	 * 	<li>A comma-delimited list of anything on this list.
	 * </ul>
	 *
	 * <ul class='seealso'>
	 * 	<li class='link'>{@doc jm.DynamicallyAppliedAnnotations}
	 * </ul>
	 *
	 * @return The annotation value.
	 */
	String[] on() default {};

	/**
	 * Dynamically apply this annotation to the specified classes.
	 *
	 * <p>
	 * Identical to {@link #on()} except allows you to specify class objects instead of a strings.
	 *
	 * <ul class='seealso'>
	 * 	<li class='link'>{@doc jm.DynamicallyAppliedAnnotations}
	 * </ul>
	 *
	 * @return The annotation value.
	 */
	Class<?>[] onClass() default {};

	/**
	 * Identifies a template string along with this swap.
	 *
	 * <p>
	 * Template strings are arbitrary strings associated with swaps that help provide additional context information
	 * for the swap class.
	 * They're called 'templates' because their primary purpose is for providing template names, such as Apache FreeMarker
	 * template names.
	 *
	 * <p>
	 * The following is an example of a templated swap class used to serialize POJOs to HTML using FreeMarker:
	 *
	 * <p class='bjava'>
	 * 	<jc>// Our templated swap class.</jc>
	 * 	<jk>public class</jk> FreeMarkerSwap <jk>extends</jk> ObjectSwap&lt;Object,Reader&gt; {
	 *
	 * 		<jk>public</jk> MediaType[] forMediaTypes() {
	 * 			<jk>return</jk> MediaType.<jsm>forStrings</jsm>(<js>"&#42;/html"</js>);
	 * 		}
	 *
	 * 		<jk>public</jk> Reader swap(BeanSession <jv>session</jv>, Object <jv>value</jv>, String <jv>template</jv>) <jk>throws</jk> Exception {
	 * 			<jk>return</jk> <jsm>getFreeMarkerReader</jsm>(<jv>template</jv>, <jv>value</jv>);  <jc>// Some method that creates raw HTML.</jc>
	 * 		}
	 * 	}
	 * </p>
	 * <p class='bjava'>
	 * 	<ja>@Swap</ja>(impl=FreeMarkerSwap.<jk>class</jk>, template=<js>"MyPojo.div.ftl"</js>)
	 * 	<jk>public class</jk> MyPojo {}
	 * </p>
	 *
	 * <ul class='seealso'>
	 * 	<li class='link'>{@doc jm.TemplatedSwaps}
	 * </ul>
	 *
	 * @return The annotation value.
	 */
	String template() default "";

	/**
	 * The {@link ObjectSwap} and {@link Surrogate} class.
	 *
	 * <p>
	 * A synonym for {@link #impl()}.
	 *
	 * @return The annotation value.
	 */
	Class<?> value() default void.class;
}