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 classes and methods to indicate code capable of
027 * converting from a type to another type which are then auto-discovered using
028 * the <a href="http://camel.apache.org/type-converter.html">Type
029 * Conversion Support</a>
030 */
031@Retention(RetentionPolicy.RUNTIME)
032@Documented
033@Target({ElementType.TYPE, ElementType.METHOD })
034public @interface Converter {
035
036    /**
037     * Whether or not returning <tt>null</tt> is a valid response.
038     */
039    boolean allowNull() default false;
040
041    /**
042     * Whether this converter is a regular converter or a fallback converter.
043     *
044     * The difference between a regular converter and a fallback-converter
045     * is that the fallback is resolved at last if no regular converter could be found.
046     * Also the method signature is scoped to be generic to allow handling a broader range
047     * of types trying to be converted. The fallback converter can just return <tt>null</tt>
048     * if it can not handle the types to convert from/to.
049     */
050    boolean fallback() default false;
051
052    /**
053     * Whether or not this fallback converter can be promoted to a first class type converter.
054     */
055    boolean fallbackCanPromote() default false;
056
057    /**
058     * Whether to ignore the type converter if it cannot be loaded for some reason.
059     * <p/>
060     * This can be used if a Camel component provides multiple components
061     * where the end user can opt-out some of these components by excluding
062     * dependencies on the classpath, meaning the type converter would not
063     * be able to load due class not found errors. But in those cases its
064     * okay as the component is opted-out.
065     * <p/>
066     * Important this configuration must be set on the class-level, not on the method.
067     */
068    boolean ignoreOnLoadError() default false;
069
070    /**
071     * Whether to let the Camel compiler plugin to generate java source code
072     * for fast loading of the type converters.
073     * <p/>
074     * Important this configuration must be set on the class-level, not on the method.
075     */
076    boolean loader() default false;
077
078}