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The Camel API
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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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
 *
 *      http://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.apache.camel;

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;

/**
 * An annotation used to mark classes and methods to indicate code capable of converting from a type to another type
 * which are then auto-discovered using the Type Conversion
 * Support
 */
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Target({ ElementType.TYPE, ElementType.METHOD })
public @interface Converter {

    /**
     * Whether or not returning null is a valid response.
     */
    boolean allowNull() default false;

    /**
     * Whether this converter is a regular converter or a fallback converter.
     *
     * The difference between a regular converter and a fallback-converter is that the fallback is resolved at last if
     * no regular converter could be found. Also the method signature is scoped to be generic to allow handling a
     * broader range of types trying to be converted. The fallback converter can just return null if it can not
     * handle the types to convert from/to.
     */
    boolean fallback() default false;

    /**
     * Whether or not this fallback converter can be promoted to a first class type converter.
     */
    boolean fallbackCanPromote() default false;

    /**
     * Whether to ignore the type converter if it cannot be loaded for some reason.
     * 
     * This can be used if a Camel component provides multiple components where the end user can opt-out some of these
     * components by excluding dependencies on the classpath, meaning the type converter would not be able to load due
     * class not found errors. But in those cases its okay as the component is opted-out.
     * 

     * Important this configuration must be set on the class-level, not on the method.
     */
    boolean ignoreOnLoadError() default false;

    /**
     * Whether to let the Camel compiler plugin to generate java source code for fast loading of the type converters.
     * 

     * Important this configuration must be set on the class-level, not on the method.
     */
    boolean generateLoader() default false;

    /**
     * Whether to let the Camel compiler plugin to generate java source code for fast loading of the type converters,
     * bulked together into a single class for optimal performance.
     * 

     * This can be done for almost all regular type converters, and not for fallback converters.
     * 
     * Important this configuration must be set on the class-level, not on the method.
     */
    boolean generateBulkLoader() default false;

    /**
     * To be used for ordering converter methods when source code generating bulk loaders. The order is lowest to
     * highest, eg 1, 2, 3.
     */
    int order() default 0;

}