TypeConverter.java

/* Copyright 2005-2006 Tim Fennell
 *
 * Licensed 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 net.sourceforge.stripes.validation;

import java.util.Collection;
import java.util.Locale;

/**
 * Interface for all type converters in the validation system that provide facilities for
 * converting from String to a specific object type.
 *
 * @author Tim Fennell
 */
public interface TypeConverter<T> {

    /**
     * Sets the locale that the TypeConverter can expect incoming Strings to be in. This method will
     * only be called once during a TypeConverter's lifetime, and will be called prior to any
     * invocations of convert().
     *
     * @param locale the locale that the TypeConverter will be converting from.
     */
    void setLocale(Locale locale);

    /**
     * Convert a String to the target type supported by this converter.
     *
     * @param input the String being converted
     * @param targetType the Class representing the type of the property to which the return
     *        value of the conversion will be assigned.  In many cases this can be ignored as
     *        converters will return a single type more often than not.
     * @param errors an empty collection of validation errors that should be populated by the
     *        converter for any errors that occur during validation that are user input related.
     * @return T an instance of the converted type, or null if the input cannot be converted
     */
    T convert(String input, Class<? extends T> targetType, Collection<ValidationError> errors);
}