com.vaadin.data.util.converter.StringToEnumConverter Maven / Gradle / Ivy

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/*
 * Vaadin Framework 7
 *
 * Copyright (C) 2000-2024 Vaadin Ltd
 *
 * This program is available under Vaadin Commercial License and Service Terms.
 *
 * See  for the full
 * license.
 */
package com.vaadin.data.util.converter;

import java.util.EnumSet;
import java.util.Locale;

/**
 * A converter that converts from {@link String} to an {@link Enum} and back.
 * 
 * Designed to provide nice human readable strings for {@link Enum} classes
 * conforming to one of these patterns:
 * 

 * The constants are named SOME_UPPERCASE_WORDS and there's no toString
 * implementation.
 * toString() always returns the same human readable string that is not the
 * same as its name() value. Each constant in the enum type returns a distinct
 * toString() value.
 * 
 * Will not necessarily work correctly for other cases.
 * 
 *
 * @author Vaadin Ltd
 * @since 7.4
 */
public class StringToEnumConverter implements Converter {

    @Override
    public Enum convertToModel(String value, Class targetType,
            Locale locale) throws ConversionException {
        if (value == null || value.trim().equals("")) {
            return null;
        }

        return stringToEnum(value, targetType, locale);
    }

    /**
     * Converts the given string to the given enum type using the given locale
     * 
     * Compatible with {@link #enumToString(Enum, Locale)}
     *
     * @param value
     *            The string value to convert
     * @param enumType
     *            The type of enum to create
     * @param locale
     *            The locale to use for conversion. If null, the JVM default
     *            locale will be used
     * @return The enum which matches the given string
     * @throws ConversionException
     *             if the conversion fails
     */
    public static > T stringToEnum(String value,
            Class enumType, Locale locale) throws ConversionException {
        if (locale == null) {
            locale = Locale.getDefault();
        }

        if (!enumType.isEnum()) {
            throw new ConversionException(
                    enumType.getName() + " is not an enum type");
        }

        // First test for the human-readable value since that's the more likely
        // input
        String upperCaseValue = value.toUpperCase(locale);
        T match = null;
        for (T e : EnumSet.allOf(enumType)) {
            String upperCase = enumToString(e, locale).toUpperCase(locale);
            if (upperCase.equals(upperCaseValue)) {
                if (match != null) {
                    throw new ConversionException("Both " + match.name()
                            + " and " + e.name()
                            + " are matching the input string " + value);
                }
                match = e;
            }
        }

        if (match != null) {
            return match;
        }

        // Then fall back to using a strict match based on name()
        try {
            return Enum.valueOf(enumType, upperCaseValue);
        } catch (Exception ee) {
            throw new ConversionException(ee);
        }
    }

    /**
     * Converts the given enum to a human readable string using the given locale
     * 
     * Compatible with {@link #stringToEnum(String, Class, Locale)}
     *
     * @param value
     *            The enum value to convert
     * @param locale
     *            The locale to use for conversion. If null, the JVM default
     *            locale will be used
     * @return A human readable string based on the enum
     * @throws ConversionException
     *             if the conversion fails
     */
    public static String enumToString(Enum value, Locale locale) {
        if (locale == null) {
            locale = Locale.getDefault();
        }

        String enumString = value.toString();
        if (enumString.equals(value.name())) {
            // FOO -> Foo
            // FOO_BAR -> Foo bar
            // _FOO -> _foo
            String result = enumString.substring(0, 1).toUpperCase(locale);
            result += enumString.substring(1).toLowerCase(locale).replace('_',
                    ' ');
            return result;
        } else {
            return enumString;
        }
    }

    @Override
    public String convertToPresentation(Enum value,
            Class targetType, Locale locale)
            throws ConversionException {
        if (value == null) {
            return null;
        }

        return enumToString(value, locale);
    }

    @Override
    public Class getModelType() {
        return Enum.class;
    }

    @Override
    public Class getPresentationType() {
        return String.class;
    }

}