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/*
 * Copyright (c) 1997, 2018 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.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package javax.faces.convert;


import javax.faces.component.StateHolder;
import javax.faces.component.UIComponent;
import javax.faces.context.FacesContext;


/**
 * Converter is an
 * interface describing a Java class that can perform Object-to-String
 * and String-to-Object conversions between model data objects and a
 * String representation of those objects that is suitable for
 * rendering.
 * 
 * {@link Converter} implementations must have a zero-arguments public
 * constructor.  In addition, if the {@link Converter} class wishes to have
 * configuration property values saved and restored with the component tree,
 * the implementation must also implement {@link StateHolder}.
 * 
 * Starting with version 1.2 of the specification, an exception to the above
 * zero-arguments constructor requirement has been introduced.  If a converter has
 * a single argument constructor that takes a Class instance and
 * the Class of the data to be converted is
 * known at converter instantiation time, this constructor
 * must be used to instantiate the converter instead of the zero-argument
 * version.  This enables the per-class conversion
 * of Java enumerated types.
 * 
 * If any Converter implementation requires a
 * java.util.Locale to perform its job, it must obtain that
 * Locale from the {@link javax.faces.component.UIViewRoot}
 * of the current {@link FacesContext}, unless the
 * Converter maintains its own Locale as part
 * of its state.
 *
 * If the class implementing
 * Converter has a {@link
 * javax.faces.application.ResourceDependency} annotation, the action
 * described in ResourceDependency must be taken when
 * {@link javax.faces.component.ValueHolder#setConverter} is called.
 * If the class implementing Converter has a {@link
 * javax.faces.application.ResourceDependencies} annotation, the
 * action described in ResourceDependencies must be taken 
 * when {@link javax.faces.component.ValueHolder#setConverter} is called.
 * 
 * @param  The generic type of object value to convert.
 */

public interface Converter {


    /**
     * Convert the specified string value, which is associated with
     * the specified {@link UIComponent}, into a model data object that
     * is appropriate for being stored during the Process Validations 
     * phase of the request processing lifecycle.
     *
     * @param context   {@link FacesContext} for the request being processed
     * @param component {@link UIComponent} with which this model object
     *                  value is associated
     * @param value     String value to be converted (may be null)
     * @return null if the value to convert is null,
     *         otherwise the result of the conversion
     * @throws ConverterException   if conversion cannot be successfully
     *                              performed
     * @throws NullPointerException if context or
     *                              component is null
     */
    public T getAsObject(FacesContext context, UIComponent component,
                              String value);


    /**
     * Convert the specified model object value, which is associated with
     * the specified {@link UIComponent}, into a String that is suitable
     * for being included in the response generated during the
     * Render Response phase of the request processing
     * lifeycle.
     *
     * @param context   {@link FacesContext} for the request being processed
     * @param component {@link UIComponent} with which this model object
     *                  value is associated
     * @param value     Model object value to be converted
     *                  (may be null)
     * @return a zero-length String if value is null,
     *         otherwise the result of the conversion
     * @throws ConverterException   if conversion cannot be successfully
     *                              performed
     * @throws NullPointerException if context or
     *                              component is null
     */
    public String getAsString(FacesContext context, UIComponent component,
                              T value);


    /**
     * 
     * If this param is set, and calling toLowerCase().equals("true") on a
     * String representation of its value returns true,
     * Application.createConverter() must guarantee that the default for the
     * timezone of all javax.faces.convert.DateTimeConverter instances must
     * be equal to TimeZone.getDefault() instead of "GMT".
     * 
     * 
     * @since 2.0
     */
    public static final String DATETIMECONVERTER_DEFAULT_TIMEZONE_IS_SYSTEM_TIMEZONE_PARAM_NAME = 
            "javax.faces.DATETIMECONVERTER_DEFAULT_TIMEZONE_IS_SYSTEM_TIMEZONE";
    
}