Struts example source code file (StrutsTypeConverter.java)

This example Struts source code file (StrutsTypeConverter.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Struts tags/keywords

class, class, defaulttypeconverter, defaulttypeconverter, object, object, string, string, strutstypeconverter, util

The Struts StrutsTypeConverter.java source code

/*
 * $Id: StrutsTypeConverter.java 651946 2008-04-27 13:41:38Z apetrelli $
 *
 * 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.struts2.util;

import java.util.Map;

import com.opensymphony.xwork2.conversion.impl.DefaultTypeConverter;

/**
 * <!-- START SNIPPET: javadoc -->
 *
 * Base class for type converters used in Struts. This class provides two abstract methods that are used to convert
 * both to and from strings -- the critical functionality that is core to Struts's type coversion system.
 *
 * <p/> Type converters do not have to use this class. It is merely a helper base class, although it is recommended that
 * you use this class as it provides the common type conversion contract required for all web-based type conversion.
 *
 * <p/> There's a hook (fall back method) called performFallbackConversion of which
 * could be used to perform some fallback conversion if <code>convertValue method of this
 * failed. By default it just ask its super class (Ognl's DefaultTypeConverter) to do the conversion.
 *
 * <p/> To allow the framework to recognize that a conversion error has occurred, throw an XWorkException or
 * preferable a TypeConversionException.
 *
 * <!-- END SNIPPET: javadoc -->
 *
 */
public abstract class StrutsTypeConverter extends DefaultTypeConverter {
    public Object convertValue(Map context, Object o, Class toClass) {
        if (toClass.equals(String.class)) {
            return convertToString(context, o);
        } else if (o instanceof String[]) {
            return convertFromString(context, (String[]) o, toClass);
        } else if (o instanceof String) {
            return convertFromString(context, new String[]{(String) o}, toClass);
        } else {
            return performFallbackConversion(context, o, toClass);
        }
    }

    /**
     * Hook to perform a fallback conversion if every default options failed. By default
     * this will ask Ognl's DefaultTypeConverter (of which this class extends) to
     * perform the conversion.
     *
     * @param context
     * @param o
     * @param toClass
     * @return The fallback conversion
     */
    protected Object performFallbackConversion(Map context, Object o, Class toClass) {
        return super.convertValue(context, o, toClass);
    }


    /**
     * Converts one or more String values to the specified class.
     *
     * @param context the action context
     * @param values  the String values to be converted, such as those submitted from an HTML form
     * @param toClass the class to convert to
     * @return the converted object
     */
    public abstract Object convertFromString(Map context, String[] values, Class toClass);

    /**
     * Converts the specified object to a String.
     *
     * @param context the action context
     * @param o       the object to be converted
     * @return the converted String
     */
    public abstract String convertToString(Map context, Object o);
}