FallbackConverter.java

/**
 * 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 methods to indicate code capable of being a
 * fallback converter which are then auto-discovered using
 * the <a href="http://camel.apache.org/type-converter.html">Type
 * Conversion Support</a>.
 * <p/>
 * The difference between a regular <tt>@Converter</tt> and a <tt>@FallbackConverter</tt>
 * 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 <tt>null</tt>
 * if it can not handle the types to convert from/to.
 *
 * @see org.apache.camel.component.file.GenericFileConverter GenericFileConverter for an example.
 *
 * @version 
 */
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Target({ElementType.TYPE, ElementType.METHOD })
public @interface FallbackConverter {

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

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

}