001/** 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.camel; 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; 024 025/** 026 * An annotation used to mark methods to indicate code capable of being a 027 * fallback converter which are then auto-discovered using 028 * the <a href="http://camel.apache.org/type-converter.html">Type 029 * Conversion Support</a>. 030 * <p/> 031 * The difference between a regular <tt>@Converter</tt> and a <tt>@FallbackConverter</tt> 032 * is that the fallback is resolved at last if no regular converter could be found. 033 * Also the method signature is scoped to be generic to allow handling a broader range 034 * of types trying to be converted. The fallback converter can just return <tt>null</tt> 035 * if it can not handle the types to convert from/to. 036 * 037 * @see org.apache.camel.component.file.GenericFileConverter GenericFileConverter for an example. 038 * 039 * @version 040 */ 041@Retention(RetentionPolicy.RUNTIME) 042@Documented 043@Target({ElementType.TYPE, ElementType.METHOD }) 044public @interface FallbackConverter { 045 046 /** 047 * Whether or not returning <tt>null</tt> is a valid response. 048 */ 049 boolean allowNull() default false; 050 051 /** 052 * Whether or not this fallback converter can be promoted to a first class type converter. 053 */ 054 boolean canPromote() default false; 055 056}