api/src/main/java/javax/faces/convert/EnumConverter.java

/*
 * 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 javax.faces.convert;

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

import org.apache.myfaces.buildtools.maven2.plugin.builder.annotation.JSFConverter;

/**
 * see Javadoc of <a href="http://java.sun.com/j2ee/javaserverfaces/1.2/docs/api/index.html">JSF Specification</a>
 *
 * @author Stan Silvert
 */
@JSFConverter
public class EnumConverter implements Converter, StateHolder {
    
    public static final String CONVERTER_ID = "javax.faces.Enum";
    public static final String ENUM_ID = "javax.faces.converter.EnumConverter.ENUM";
    public static final String ENUM_NO_CLASS_ID = "javax.faces.converter.EnumConverter.ENUM_NO_CLASS";
    
    private Class targetClass;
    
    private boolean isTransient = false;
    
    /** Creates a new instance of EnumConverter */
    public EnumConverter() {
    }
    
    public EnumConverter(Class targetClass) {
        if (!targetClass.isEnum()) throw new IllegalArgumentException("targetClass for EnumConverter must be an Enum");
        this.targetClass = targetClass;
    }

    public String getAsString(FacesContext facesContext, UIComponent uiComponent, Object value) throws ConverterException {
        if (facesContext == null) throw new NullPointerException("facesContext can not be null");
        if (uiComponent == null) throw new NullPointerException("uiComponent can not be null");
        if (value == null) return "";
        checkTargetClass(facesContext, uiComponent, value);
        
        for (Object enumConstant : targetClass.getEnumConstants()) {
            if (enumConstant == value) return enumConstant.toString();
        }

        return value.toString();
    }

    public Object getAsObject(FacesContext facesContext, UIComponent uiComponent, String value) throws ConverterException {
        if (facesContext == null) throw new NullPointerException("facesContext");
        if (uiComponent == null) throw new NullPointerException("uiComponent");
        if (value == null)  return null;
        value = value.trim();
        if (value.length() == 0)  return null;
        checkTargetClass(facesContext, uiComponent, value);
        
        // we know targetClass and value can't be null, so we can use Enum.valueOf
        // instead of the hokey looping called for in the javadoc
        try {
           return Enum.valueOf(targetClass, value);    
        } catch (IllegalArgumentException e) {
            Object[] params = new Object[]{value, 
                                           firstConstantOfEnum(), 
                                           _MessageUtils.getLabel(facesContext, uiComponent)};
            
            throw new ConverterException(_MessageUtils.getErrorMessage(facesContext,
                                                                       ENUM_ID,
                                                                       params));
        }
    }

    private void checkTargetClass(FacesContext facesContext, UIComponent uiComponent, Object value) {
        if (targetClass == null) {
            Object[] params = new Object[]{value, _MessageUtils.getLabel(facesContext, uiComponent)};
            throw new ConverterException(_MessageUtils.getErrorMessage(facesContext, 
                                                                       ENUM_NO_CLASS_ID, 
                                                                       params));
        }
    }

    // find the first constant value of the targetClass and return as a String
    private String firstConstantOfEnum() {
        Object[] enumConstants= targetClass.getEnumConstants();

        if (enumConstants.length != 0 ) return enumConstants[0].toString();
        
        return ""; // if empty Enum
    }

    public void restoreState(FacesContext context, Object state) {
        targetClass = (Class)state;
    }

    public Object saveState(FacesContext context) {
        return targetClass;
    }

    public void setTransient(boolean newTransientValue) {
        isTransient = newTransientValue;
    }

    public boolean isTransient() {
        return isTransient;
    }
    
}