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JTransfo core
There is a newer version: 2.10
/*
 * This file is part of jTransfo, a library for converting to and from transfer objects.
 * Copyright (c) PROGS bvba, Belgium
 *
 * The program is available in open source according to the Apache License, Version 2.0.
 * For full licensing details, see LICENSE.txt in the project root.
 */

package org.jtransfo;

/**
 * Interceptor which allows additional work to be done just before jTransfo converts between objects.
 * 
 * This is called at the end of the interceptor pipeline, before convertion of the individual fields.
 * The preconverter is only used when it is declared on the transfer object using {@link PreConvert}.
 * 

 * The preconverter should be re-entrant. A singleton is used for all convert invocations.
 * 
 *
 * @param  type of the transfer object
 * @param  type of the domain object
 */
public interface PreConverter {

    /**
     * Possible results of the preconverter.
     */
    enum Result {
        /** Continue conversion. */
        CONTINUE,
        /** Skip converting the object. */
        SKIP
    }

    /**
     * Do some work just before doing the actual conversion from domain to transfer object.
     * 
     * You can prevent the conversion of the actual object to happen by returning {@link Result#SKIP}.
     * 
     *
     * @param source source object. Should not be null.
     * @param target target object. Should not be null.
     * @param tags tags which indicate which fields can be converted based on {@link MapOnly} annotations.
     *      Tags are processed from left to right.
     * @return flag indicating whether the conversion should continue for the object
     */
    default Result preConvertToTo(D source, T target, String... tags) {
        return Result.CONTINUE;
    }

    /**
     * Do some work just before doing the actual conversion from transfer to domain object.
     * 
     * You can prevent the conversion of the actual object to happen by returning {@link Result#SKIP}.
     * 
     *
     * @param source source object. Should not be null.
     * @param target target object. Should not be null.
     * @param tags tags which indicate which fields can be converted based on {@link MapOnly} annotations.
     *      Tags are processed from left to right.
     * @return flag indicating whether the conversion should continue for the object
     */
    default Result preConvertToDomain(T source, D target, String... tags) {
        return Result.CONTINUE;
    }

}