/*
 * Copyright 2002-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.bind.annotation;

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

import org.springframework.core.annotation.AliasFor;

Annotation to bind a method parameter to a session attribute.
The main motivation is to provide convenient access to existing, permanent
session attributes (e.g. user authentication object) with an optional/required
check and a cast to the target method parameter type.
For use cases that require adding or removing session attributes consider injecting org.springframework.web.context.request.WebRequest or javax.servlet.http.HttpSession into the controller method. 
For temporary storage of model attributes in the session as part of the workflow for a controller, consider using SessionAttributes instead. 
Author:
Rossen Stoyanchev
See Also:
RequestMapping
SessionAttributes
RequestAttribute
Since:
4.3/**
 * Annotation to bind a method parameter to a session attribute.
 *
 * <p>The main motivation is to provide convenient access to existing, permanent
 * session attributes (e.g. user authentication object) with an optional/required
 * check and a cast to the target method parameter type.
 *
 * <p>For use cases that require adding or removing session attributes consider
 * injecting {@code org.springframework.web.context.request.WebRequest} or
 * {@code javax.servlet.http.HttpSession} into the controller method.
 *
 * <p>For temporary storage of model attributes in the session as part of the
 * workflow for a controller, consider using {@link SessionAttributes} instead.
 *
 * @author Rossen Stoyanchev
 * @since 4.3
 * @see RequestMapping
 * @see SessionAttributes
 * @see RequestAttribute
 */
@Target(ElementType.PARAMETER)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface SessionAttribute {

	
Alias for name. /**
	 * Alias for {@link #name}.
	 */
	@AliasFor("name")
	String value() default "";

	
The name of the session attribute to bind to.
The default name is inferred from the method parameter name.
/**
	 * The name of the session attribute to bind to.
	 * <p>The default name is inferred from the method parameter name.
	 */
	@AliasFor("value")
	String name() default "";

	
Whether the session attribute is required.
Defaults to true, leading to an exception being thrown if the attribute is missing in the session or there is no session. Switch this to false if you prefer a null or Java 8 java.util.Optional if the attribute doesn't exist. /**
	 * Whether the session attribute is required.
	 * <p>Defaults to {@code true}, leading to an exception being thrown
	 * if the attribute is missing in the session or there is no session.
	 * Switch this to {@code false} if you prefer a {@code null} or Java 8
	 * {@code java.util.Optional} if the attribute doesn't exist.
	 */
	boolean required() default true;

}