001/* 002 * Copyright 2002-2016 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.web.bind.annotation; 018 019import java.lang.annotation.Documented; 020import java.lang.annotation.ElementType; 021import java.lang.annotation.Retention; 022import java.lang.annotation.RetentionPolicy; 023import java.lang.annotation.Target; 024 025import org.springframework.core.annotation.AliasFor; 026 027/** 028 * Annotation to bind a method parameter to a session attribute. 029 * 030 * <p>The main motivation is to provide convenient access to existing, permanent 031 * session attributes (e.g. user authentication object) with an optional/required 032 * check and a cast to the target method parameter type. 033 * 034 * <p>For use cases that require adding or removing session attributes consider 035 * injecting {@code org.springframework.web.context.request.WebRequest} or 036 * {@code javax.servlet.http.HttpSession} into the controller method. 037 * 038 * <p>For temporary storage of model attributes in the session as part of the 039 * workflow for a controller, consider using {@link SessionAttributes} instead. 040 * 041 * @author Rossen Stoyanchev 042 * @since 4.3 043 * @see RequestMapping 044 * @see SessionAttributes 045 * @see RequestAttribute 046 */ 047@Target(ElementType.PARAMETER) 048@Retention(RetentionPolicy.RUNTIME) 049@Documented 050public @interface SessionAttribute { 051 052 /** 053 * Alias for {@link #name}. 054 */ 055 @AliasFor("name") 056 String value() default ""; 057 058 /** 059 * The name of the session attribute to bind to. 060 * <p>The default name is inferred from the method parameter name. 061 */ 062 @AliasFor("value") 063 String name() default ""; 064 065 /** 066 * Whether the session attribute is required. 067 * <p>Defaults to {@code true}, leading to an exception being thrown 068 * if the attribute is missing in the session or there is no session. 069 * Switch this to {@code false} if you prefer a {@code null} or Java 8 070 * {@code java.util.Optional} if the attribute doesn't exist. 071 */ 072 boolean required() default true; 073 074}