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 request attribute. 029 * 030 * <p>The main motivation is to provide convenient access to request attributes 031 * from a controller method with an optional/required check and a cast to the 032 * target method parameter type. 033 * 034 * @author Rossen Stoyanchev 035 * @since 4.3 036 * @see RequestMapping 037 * @see SessionAttribute 038 */ 039@Target(ElementType.PARAMETER) 040@Retention(RetentionPolicy.RUNTIME) 041@Documented 042public @interface RequestAttribute { 043 044 /** 045 * Alias for {@link #name}. 046 */ 047 @AliasFor("name") 048 String value() default ""; 049 050 /** 051 * The name of the request attribute to bind to. 052 * <p>The default name is inferred from the method parameter name. 053 */ 054 @AliasFor("value") 055 String name() default ""; 056 057 /** 058 * Whether the request attribute is required. 059 * <p>Defaults to {@code true}, leading to an exception being thrown if 060 * the attribute is missing. Switch this to {@code false} if you prefer 061 * a {@code null} or Java 8 {@code java.util.Optional} if the attribute 062 * doesn't exist. 063 */ 064 boolean required() default true; 065 066}