arrayconverter.java

APACHE 公司出的java bean 工具包

        if (onlyFirstToString) {
            size = 1;
        }

        // Create a StringBuffer containing a delimited list of the values
        StringBuffer buffer = new StringBuffer();
        for (int i = 0; i < size; i++) {
            if (i > 0) {
                buffer.append(delimiter);
            }
            Object element = iterator == null ? Array.get(value, i) : iterator.next();
            element = elementConverter.convert(String.class, element);
            if (element != null) {
                buffer.append(element);
            }
        }

        return buffer.toString();

    }

    /**
     * Handles conversion to an array of the specified type.
     *
     * @param type The type to which this value should be converted.
     * @param value The input value to be converted.
     * @return The converted value.
     * @throws Throwable if an error occurs converting to the specified type
     */
    protected Object convertToType(Class type, Object value) throws Throwable {

        if (!type.isArray()) {
            throw new ConversionException(toString(getClass())
                    + " cannot handle conversion to '"
                    + toString(type) + "' (not an array).");
        }

        // Handle the source
        int size = 0;
        Iterator iterator = null;
        if (value.getClass().isArray()) {
            size = Array.getLength(value);
        } else {
            Collection collection = convertToCollection(type, value);
            size = collection.size();
            iterator = collection.iterator();
        }

        // Allocate a new Array
        Class componentType = type.getComponentType();
        Object newArray = Array.newInstance(componentType, size);

        // Convert and set each element in the new Array
        for (int i = 0; i < size; i++) {
            Object element = iterator == null ? Array.get(value, i) : iterator.next();
            // TODO - probably should catch conversion errors and throw
            //        new exception providing better info back to the user
            element = elementConverter.convert(componentType, element);
            Array.set(newArray, i, element);
        }

        return newArray;
    }

    /**
     * Returns the value unchanged.
     *
     * @param value The value to convert
     * @return The value unchanged
     */
    protected Object convertArray(Object value) {
        return value;
    }

    /**
     * Converts non-array values to a Collection prior
     * to being converted either to an array or a String.
     * </p>
     * <ul>
     *   <li>{@link Collection} values are returned unchanged</li>
     *   <li>{@link Number}, {@link Boolean}  and {@link java.util.Date} 
     *       values returned as a the only element in a List.</li>
     *   <li>All other types are converted to a String and parsed
     *       as a delimited list.</li>
     * </ul>
     *
     * <strong>N.B.</strong> The method is called by both the
     * {@link ArrayConverter#convertToType(Class, Object)} and
     * {@link ArrayConverter#convertToString(Object)} methods for
     * <i>non-array</i> types.
     *
     * @param type The type to convert the value to
     * @param value value to be converted
     * @return Collection elements.
     */
    protected Collection convertToCollection(Class type, Object value) {
        if (value instanceof Collection) {
            return (Collection)value;
        }
        if (value instanceof Number ||
            value instanceof Boolean ||
            value instanceof java.util.Date) {
            List list = new ArrayList(1);
            list.add(value);
            return list;
        }
        
        return parseElements(type, value.toString());
    }

    /**
     * Return the default value for conversions to the specified
     * type.
     * @param type Data type to which this value should be converted.
     * @return The default value for the specified type.
     */
    protected Object getDefault(Class type) {
        if (type.equals(String.class)) {
            return null;
        }

        Object defaultValue = super.getDefault(type);
        if (defaultValue == null) {
            return null;
        }

        if (defaultValue.getClass().equals(type)) {
            return defaultValue;
        } else {
            return Array.newInstance(type.getComponentType(), defaultSize);
        }

    }

    /**
     * Provide a String representation of this array converter.
     *
     * @return A String representation of this array converter
     */
    public String toString() {
        StringBuffer buffer = new StringBuffer();
        buffer.append(toString(getClass()));
        buffer.append("[UseDefault=");
        buffer.append(isUseDefault());
        buffer.append(", ");
        buffer.append(elementConverter.toString());
        buffer.append(']');
        return buffer.toString();
    }

    /**
     * <p>Parse an incoming String of the form similar to an array initializer
     * in the Java language into a <code>List</code> individual Strings
     * for each element, according to the following rules.</p>
     * <ul>
     * <li>The string is expected to be a comma-separated list of values.</li>
     * <li>The string may optionally have matching '{' and '}' delimiters
     *   around the list.</li>
     * <li>Whitespace before and after each element is stripped.</li>
     * <li>Elements in the list may be delimited by single or double quotes.
     *  Within a quoted elements, the normal Java escape sequences are valid.</li>
     * </ul>
     *
     * @param type The type to convert the value to
     * @param value String value to be parsed
     * @return List of parsed elements.
     *
     * @throws ConversionException if the syntax of <code>svalue</code>
     *  is not syntactically valid
     * @throws NullPointerException if <code>svalue</code>
     *  is <code>null</code>
     */
    private List parseElements(Class type, String value) {

        if (log().isDebugEnabled()) {
            log().debug("Parsing elements, delimiter=[" + delimiter + "], value=[" + value + "]");
        }

        // Trim any matching '{' and '}' delimiters
        value = value.trim();
        if (value.startsWith("{") && value.endsWith("}")) {
            value = value.substring(1, value.length() - 1);
        }

        try {

            // Set up a StreamTokenizer on the characters in this String
            StreamTokenizer st = new StreamTokenizer(new StringReader(value));
            st.whitespaceChars(delimiter , delimiter); // Set the delimiters
            st.ordinaryChars('0', '9');  // Needed to turn off numeric flag
            st.wordChars('0', '9');      // Needed to make part of tokens
            for (int i = 0; i < allowedChars.length; i++) {
                st.ordinaryChars(allowedChars[i], allowedChars[i]);
                st.wordChars(allowedChars[i], allowedChars[i]);
            }

            // Split comma-delimited tokens into a List
            List list = null;
            while (true) {
                int ttype = st.nextToken();
                if ((ttype == StreamTokenizer.TT_WORD) || (ttype > 0)) {
                    if (list == null) {
                        list = new ArrayList();
                    }
                    list.add(st.sval.trim());
                } else if (ttype == StreamTokenizer.TT_EOF) {
                    break;
                } else {
                    throw new ConversionException("Encountered token of type "
                        + ttype + " parsing elements to '" + toString(type) + ".");
                }
            }

            if (list == null) {
                list = Collections.EMPTY_LIST;
            }
            if (log().isDebugEnabled()) {
                log().debug(list.size() + " elements parsed");
            }

            // Return the completed list
            return (list);

        } catch (IOException e) {

            throw new ConversionException("Error converting from String to '"
                    + toString(type) + "': " + e.getMessage(), e);

        }

    }

}