juneau-core/juneau-marshall/src/main/java/org/apache/juneau/http/annotation/Response.java

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package org.apache.juneau.http.annotation;

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

import java.lang.annotation.*;

import org.apache.juneau.jsonschema.annotation.Schema;
import org.apache.juneau.*;
import org.apache.juneau.annotation.*;
import org.apache.juneau.httppart.*;
import org.apache.juneau.json.*;
import org.apache.juneau.jsonschema.*;
import org.apache.juneau.oapi.*;

/**
 * REST response annotation.
 *
 * <p>
 * Identifies an interface to use to interact with HTTP parts of an HTTP response through a bean.
 *
 * <p>
 * Can be used in the following locations:
 *  <ul>
 * 	<li>Exception classes thrown from server-side <ja>@RestMethod</ja>-annotated methods.
 * 	<li>Return type classes of server-side <ja>@RestMethod</ja>-annotated methods.
 * 	<li>Arguments and argument-types of server-side <ja>@RestMethod</ja>-annotated methods.
 * 	<li>Return type classes of server-side <ja>@RemoteMethod</ja>-annotated methods.
 * 	<li>Client-side <ja>@RemoteMethod</ja>-annotated methods.
 * 	<li>Return type interfaces of client-side <ja>@RemoteMethod</ja>-annotated methods.
 * </ul>
 *
 * <ul class='seealso'>
 * 	<li class='link'>{@doc juneau-rest-server.HttpPartAnnotations.Response}
 * 	<li class='link'>{@doc juneau-rest-client.RestProxies.Response}
 * 	<li class='link'>{@doc juneau-rest-server.Swagger}
 * 	<li class='extlink'>{@doc SwaggerResponseObject}
 * </ul>
 */
@Documented
@Target({PARAMETER,TYPE,METHOD})
@Retention(RUNTIME)
@Inherited
public @interface Response {

	/**
	 * Specifies the {@link HttpPartParser} class used for parsing strings to values.
	 *
	 * <p>
	 * Overrides for this part the part parser defined on the REST resource which by default is {@link OpenApiParser}.
	 */
	Class<? extends HttpPartParser> partParser() default HttpPartParser.Null.class;

	/**
	 * Specifies the {@link HttpPartSerializer} class used for serializing values to strings.
	 *
	 * <p>
	 * Overrides for this part the part serializer defined on the REST resource which by default is {@link OpenApiSerializer}.
	 */
	Class<? extends HttpPartSerializer> partSerializer() default HttpPartSerializer.Null.class;

	/**
	 * The HTTP response code.
	 *
	 * The default value is <c>500</c> for exceptions and <c>200</c> for return types.
	 */
	int[] code() default {};

	/**
	 * A synonym for {@link #code()}.
	 *
	 * <p>
	 * Allows you to use shortened notation if you're only specifying the code.
	 *
	 * <p>
	 * The following are completely equivalent ways of defining the response code:
	 * <p class='bcode w800'>
	 * 	<ja>@Response</ja>(code=404)
	 * 	<jk>public class</jk> NotFound <jk>extends</jk> RestException {...}
	 * </p>
	 * <p class='bcode w800'>
	 * 	<ja>@Response</ja>(404)
	 * 	<jk>public class</jk> NotFound <jk>extends</jk> RestException {...}
	 * </p>
	 */
	int[] value() default {};

	/**
	 * <mk>description</mk> field of the {@doc SwaggerResponseObject}.
	 *
	 * <h5 class='section'>Used for:</h5>
	 * <ul class='spaced-list'>
	 * 	<li>
	 * 		Server-side generated Swagger documentation.
	 * </ul>
	 *
	 * <ul class='notes'>
	 * 	<li>
	 * 		The format is plain text.
	 * 		<br>Multiple lines are concatenated with newlines.
	 * 	<li>
	 * 		Supports {@doc DefaultRestSvlVariables}
	 * 		(e.g. <js>"$L{my.localized.variable}"</js>).
	 * </ul>
	 */
	String[] description() default {};

	/**
	 * <mk>schema</mk> field of the {@doc SwaggerResponseObject}.
	 *
	 * <h5 class='section'>Used for:</h5>
	 * <ul class='spaced-list'>
	 * 	<li>
	 * 		Server-side schema-based serializing and serializing validation.
	 * 	<li>
	 * 		Server-side generated Swagger documentation.
	 * </ul>
	 */
	Schema schema() default @Schema;

	/**
	 * <mk>headers</mk> field of the {@doc SwaggerResponseObject}.
	 *
	 * <h5 class='section'>Used for:</h5>
	 * <ul class='spaced-list'>
	 * 	<li>
	 * 		Server-side generated Swagger documentation.
	 * </ul>
	 */
	ResponseHeader[] headers() default {};

	/**
	 * A serialized example of the body of a response.
	 *
	 * <p>
	 * This is the {@doc SimpleJson} of an example of the body.
	 *
	 * <p>
	 * This value is converted to a POJO and then serialized to all the registered serializers on the REST method to produce examples for all
	 * supported language types.
	 * <br>These values are then used to automatically populate the {@link #examples} field.
	 *
	 * <h5 class='section'>Example:</h5>
	 * <p class='bcode w800'>
	 * 	<jc>// A JSON representation of a PetCreate object.</jc>
	 * 	<ja>@Response</ja>(
	 * 		example=<js>"{name:'Doggie',price:9.99,species:'Dog',tags:['friendly','cute']}"</js>
	 * 	)
	 * </p>
	 *
	 * <p>
	 * There are several other options for defining this example:
	 * <ul class='spaced-list'>
	 * 	<li>
	 * 		Defining an <js>"x-example"</js> field in the inherited Swagger JSON response object (classpath file or <code><ja>@ResourceSwagger</ja>(value)</code>/<code><ja>@MethodSwagger</ja>(value)</code>).
	 * 	<li>
	 * 		Defining an <js>"x-example"</js> field in the Swagger Schema Object for the response object (including referenced <js>"$ref"</js> schemas).
	 * 	<li>
	 * 		Allowing Juneau to auto-generate a code example.
	 * </ul>
	 *
	 * <p>
	 * The latter is important because Juneau also supports auto-generation of JSON-Schema from POJO classes using {@link JsonSchemaSerializer} which has several of it's own
	 * options for auto-detecting and calculation POJO examples.
	 *
	 * <p>
	 * In particular, examples can be defined via static methods, fields, and annotations on the classes themselves.
	 *
	 * <p class='bcode w800'>
	 * 	<jc>// Annotation on class.</jc>
	 * 	<ja>@Example</ja>(<js>"{name:'Doggie',price:9.99,species:'Dog',tags:['friendly','cute']}"</js>)
	 * 	<jk>public class</jk> PetCreate {
	 * 		...
	 * 	}
	 * </p>
	 * <p class='bcode w800'>
	 * 	<jc>// Annotation on static method.</jc>
	 * 	<jk>public class</jk> PetCreate {
	 *
	 * 		<ja>@Example</ja>
	 * 		<jk>public static</jk> PetCreate <jsm>sample</jsm>() {
	 * 			<jk>return new</jk> PetCreate(<js>"Doggie"</js>, 9.99f, <js>"Dog"</js>, <jk>new</jk> String[] {<js>"friendly"</js>,<js>"cute"</js>});
	 * 		}
	 * 	}
	 * </p>
	 * <p class='bcode w800'>
	 * 	<jc>// Static method with specific name 'example'.</jc>
	 * 	<jk>public class</jk> PetCreate {
	 *
	 * 		<jk>public static</jk> PetCreate <jsm>example</jsm>() {
	 * 			<jk>return new</jk> PetCreate(<js>"Doggie"</js>, 9.99f, <js>"Dog"</js>, <jk>new</jk> String[] {<js>"friendly"</js>,<js>"cute"</js>});
	 * 		}
	 * 	}
	 * </p>
	 * <p class='bcode w800'>
	 * 	<jc>// Static field.</jc>
	 * 	<jk>public class</jk> PetCreate {
	 *
	 * 		<ja>@Example</ja>
	 * 		<jk>public static</jk> PetCreate <jsf>EXAMPLE</jsf> = <jk>new</jk> PetCreate(<js>"Doggie"</js>, 9.99f, <js>"Dog"</js>, <jk>new</jk> String[] {<js>"friendly"</js>,<js>"cute"</js>});
	 * 	}
	 * </p>
	 *
	 * <p>
	 * Examples can also be specified via generic properties as well using the {@link BeanContext#BEAN_examples} property at either the class or method level.
	 * <p class='bcode w800'>
	 * 	<jc>// Examples defined at class level.</jc>
	 * 	<ja>@RestResource</ja>(
	 * 		properties={
	 * 			<ja>@Property</ja>(
	 * 				name=<jsf>BEAN_examples</jsf>,
	 * 				value=<js>"{'org.apache.juneau.examples.rest.petstore.PetCreate': {name:'Doggie',price:9.99,species:'Dog',tags:['friendly','cute']}}"</js>
	 * 			)
	 * 		}
	 * 	)
	 * </p>
	 *
	 * <h5 class='section'>Used for:</h5>
	 * <ul class='spaced-list'>
	 * 	<li>
	 * 		Server-side generated Swagger documentation.
	 * </ul>
	 *
	 * <ul class='seealso'>
	 * 	<li class='ja'>{@link Example}
	 * 	<li class='jc'>{@link BeanContext}
	 * 	<ul>
	 * 		<li class='jf'>{@link BeanContext#BEAN_examples BEAN_examples}
	 * 	</ul>
	 * 	<li class='jc'>{@link JsonSchemaSerializer}
	 * 	<ul>
	 * 		<li class='jf'>{@link JsonSchemaGenerator#JSONSCHEMA_addExamplesTo JSONSCHEMA_addExamplesTo}
	 * 		<li class='jf'>{@link JsonSchemaGenerator#JSONSCHEMA_allowNestedExamples JSONSCHEMA_allowNestedExamples}
	 * 	</ul>
	 * </ul>
	 *
	 * <ul class='notes'>
	 * 	<li>
	 * 		The format is any {@doc SimpleJson} if the object can be converted to a POJO using {@link JsonParser#DEFAULT} or a simple String if the object
	 * 		has a schema associated with it meancan be converted from a String.
	 * 		<br>Multiple lines are concatenated with newlines.
	 * 	<li>
	 * 		The format of this object can also be a simple String if the body has a schema associated with it, meaning it's meant to be treated as an HTTP part.
	 * 	<li>
	 * 		Supports {@doc DefaultRestSvlVariables}
	 * 		(e.g. <js>"$L{my.localized.variable}"</js>).
	 * </ul>
	 */
	String[] example() default {};

	/**
	 * Serialized examples of the body of a response.
	 *
	 * <p>
	 * This is a {@doc SimpleJson} object whose keys are media types and values are string representations of that value.
	 *
	 * <p>
	 * In general you won't need to populate this value directly since it will automatically be calculated based on the value provided in the {@link #example()} field.
	 * <br>However, this field allows you to override the behavior and show examples for only specified media types or different examples for different media types.
	 *
	 * <p class='bcode w800'>
	 * 	<jc>// A JSON representation of a PetCreate object.</jc>
	 * 	<ja>@Response</ja>(
	 * 		examples={
	 * 			<js>"'application/json':'{name:\\'Doggie\\',species:\\'Dog\\'}',"</js>,
	 * 			<js>"'text/uon':'(name:Doggie,species=Dog)'"</js>
	 * 		}
	 * 	)
	 * </p>
	 *
	 * <h5 class='section'>Used for:</h5>
	 * <ul class='spaced-list'>
	 * 	<li>
	 * 		Server-side generated Swagger documentation.
	 * </ul>
	 *
	 * <ul class='notes'>
	 * 	<li>
	 * 		The format is a {@doc SimpleJson} object with string keys (media type) and string values (example for that media type) .
	 * 	<li>
	 * 		The leading/trailing <c>{ }</c> characters are optional.
	 * 	<li>
	 * 		Multiple lines are concatenated with newlines so that you can format the value to be readable:
	 * 	<li>
	 * 		Supports {@doc DefaultRestSvlVariables}
	 * 		(e.g. <js>"$L{my.localized.variable}"</js>).
	 * 	<li>
	 * 		Resolution of variables is delayed until request time and occurs before parsing.
	 * 		<br>This allows you to, for example, pull in a JSON construct from a properties file based on the locale of the HTTP request.
	 * </ul>
	 */
	String[] examples() default {};

	/**
	 * Free-form value for the {@doc SwaggerResponseObject}.
	 *
	 * <p>
	 * This is a {@doc SimpleJson} object that makes up the swagger information for this field.
	 *
	 * <p>
	 * The following are completely equivalent ways of defining the swagger description of the Response object:
	 * <p class='bcode w800'>
	 * 	<jc>// Normal</jc>
	 * 	<ja>@Response</ja>(
	 * 		code=302,
	 * 		description=<js>"Redirect"</js>,
	 * 		headers={
	 * 			<ja>@ResponseHeader</ja>(
	 * 				name=<js>"Location"</js>,
	 * 				type=<js>"string"</js>,
	 * 				format=<js>"uri"</js>
	 * 			)
	 * 		}
	 * 	)
	 * </p>
	 * <p class='bcode w800'>
	 * 	<jc>// Free-form</jc>
	 * 	<ja>@Response</ja>(
	 * 		code=302,
	 * 		api={
	 * 			<js>"description: 'Redirect',"</js>,
	 * 			<js>"headers: {"</js>,
	 * 				<js>"Location: {"</js>,
	 * 					<js>"type: 'string',"</js>,
	 * 					<js>"format: 'uri'"</js>,
	 * 				<js>"}"</js>,
	 * 			<js>"}"</js>
	 * 		}
	 * 	)
	 * </p>
	 * <p class='bcode w800'>
	 * 	<jc>// Free-form using variables</jc>
	 * 	<ja>@Response</ja>(
	 * 		code=302,
	 * 		api=<js>"$L{redirectSwagger}"</js>
	 * 	)
	 * </p>
	 * <p class='bcode w800'>
	 * 	<mc>// Contents of MyResource.properties</mc>
	 * 	<mk>redirectSwagger</mk> = <mv>{ description: "Redirect", headers: { Location: { type: "string", format: "uri" } } }</mv>
	 * </p>
	 *
	 * <p>
	 * 	The reasons why you may want to use this field include:
	 * <ul>
	 * 	<li>You want to pull in the entire Swagger JSON definition for this field from an external source such as a properties file.
	 * 	<li>You want to add extra fields to the Swagger documentation that are not officially part of the Swagger specification.
	 * </ul>
	 *
	 * <h5 class='section'>Used for:</h5>
	 * <ul class='spaced-list'>
	 * 	<li>
	 * 		Server-side generated Swagger documentation.
	 * </ul>
	 *
	 * <ul class='notes'>
	 * 	<li>
	 * 		Note that the only swagger field you can't specify using this value is <js>"code"</js> whose value needs to be known during servlet initialization.
	 * 	<li>
	 * 		The format is a {@doc SimpleJson} object.
	 * 	<li>
	 * 		The leading/trailing <c>{ }</c> characters are optional.
	 * 		<br>The following two example are considered equivalent:
	 * 		<p class='bcode w800'>
	 * 	<ja>@Response</ja>(api=<js>"{description: 'Redirect'}"</js>)
	 * 		</p>
	 * 		<p class='bcode w800'>
	 * 	<ja>@Response</ja>(api=<js>"description: 'Redirect''"</js>)
	 * 		</p>
	 * 	<li>
	 * 		Multiple lines are concatenated with newlines so that you can format the value to be readable.
	 * 	<li>
	 * 		Supports {@doc DefaultRestSvlVariables}
	 * 		(e.g. <js>"$L{my.localized.variable}"</js>).
	 * 	<li>
	 * 		Values defined in this field supersede values pulled from the Swagger JSON file and are superseded by individual values defined on this annotation.
	 * </ul>
	 */
	String[] api() default {};
}