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/*
 * Copyright (c) 2011, 2024 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0,
 * or the Eclipse Distribution License v. 1.0 which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 */

// Contributors:
//     Oracle = 2.2 - Initial contribution
package org.eclipse.persistence.oxm.annotations;

import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

/**
 * XmlReadTransformer is used to allow the user direct access to the XML in order to populate their
 * object model. XmlReadTransformer is used in conjunction with {@linkplain XmlWriteTransformers}/{@linkplain XmlWriteTransformer} to create a customised
 * mapping for a specific attribute. XmlReadTransformer specifies the transformer to be invoked on the
 * unmarshal.
 *
 * Mapping a transformation: A transformer can be configured to perform both the
 * XML instance-to-Java attribute transformation at unmarshall time (via attribute transformer) and
 * the Java attribute-to-XML instance transformation at marshal time (via field transformer).
 * 
Example:
 * 

 * XML Schema
 * {@snippet lang="XML":
 *  
 *  
 *    
 *    
 *      
 *        
 *        
 *      
 *    
 *    
 *      
 *        
 *        
 *      
 *    
 *  
 * }
 * Employee Class
 * {@snippet :
 *  @XmlRootElement(name="employee")
 *  public class Employee {
 *      public String name;
 *
 *      @XmlReadTransformer(transformerClass = NormalHoursTransformer.class)
 *      @XmlWriteTransformers({
 *          @XmlWriteTransformer(transformerClass = StartTimeTransformer.class, xmlPath= "normal-hours/start-time/text()"),
 *          @XmlWriteTransformer(transformerClass = EndTimeTransformer.class, xmlPath="normal-hours/end-time/text()")
 *      })
 *      public String[] normalHours;
 *  }
 * }
 * Normal Hours Transformer
 * {@snippet :
 *  public class NormalHoursTransformer implements org.eclipse.persistence.mappings.transformers.AttributeTransformer {
 *
 *      @Override
 *      public String[] buildAttributeValue(DataRecord dRecord, Object o, Session s) {
 *          String startTime = (String) dRecord.get("normal-hours/start-time/text()");
 *          String endTime = (String) dRecord.get("normal-hours/end-time/text()");
 *          return new String[] {startTime, endTime};
 *      }
 *
 *      @Override
 *      public void initialize(AbstractTransformationMapping mapping) {
 *      }
 *   }
 * }
 *
 * @see org.eclipse.persistence.mappings.transformers.AttributeTransformer
 * @see XmlWriteTransformer
 * @see XmlWriteTransformers
 */
@Target({METHOD, FIELD})
@Retention(RUNTIME)
public @interface XmlReadTransformer {

    /**
     * User-defined class that must implement the
     * {@linkplain org.eclipse.persistence.mappings.transformers.AttributeTransformer}
     * interface. The class will be instantiated, its
     * {@linkplain org.eclipse.persistence.mappings.transformers.AttributeTransformer#buildAttributeValue(org.eclipse.persistence.sessions.DataRecord, Object, org.eclipse.persistence.sessions.Session) buildAttributeValue}
     * will be used to create the value to be assigned to the attribute.
     * 

     * Either transformerClass or {@linkplain #method()} must be specified, but not both.
     */
    Class transformerClass() default void.class;

    /**
     * The mapped class must have a method with this name which returns a value
     * to be assigned to the attribute (not assigns the value to the attribute).
     * 
     * Either {@linkplain #transformerClass()} or method must be specified, but not both.
     */
    String method() default "";

}