tapestry/tapestry-framework/src/java/org/apache/tapestry/util/text/MarkupCharacterTranslator.java

// Copyright 2004, 2005 The Apache Software Foundation
//
// 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 org.apache.tapestry.util.text;

/**
 * An object that encodes a character according to rules of the HTML
 * specification, so that it will be properly parsed by a browser irrespectively
 * of the character encoding used in the HTML output.
 *
 * @author mb
 * @since 4.0
 */
public class MarkupCharacterTranslator implements ICharacterTranslator {

    private static final String SAFE_CHARACTERS = "01234567890"
                                                  + "abcdefghijklmnopqrstuvwxyz" + "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                                                  + "\t\n\r !#$%'()*+,-./:;=?@[\\]^_`{|}~";

    private static final String[][] ENTITIES = {
            {"\"", """},
            {"<", "&lt;"}, {">", "&gt;"}, {"&", "&amp;"}
    };

    private static final ICharacterMatcher SAFE_MATCHER = new AsciiCharacterMatcher(SAFE_CHARACTERS);
    private static final ICharacterTranslator ENTITY_TRANSLATOR = new AsciiCharacterTranslator(ENTITIES);

    private boolean _encodeNonAscii;
    private ICharacterMatcher _safeMatcher;
    private ICharacterTranslator _entityTranslator;

    public MarkupCharacterTranslator()
    {
        this(true);
    }

    public MarkupCharacterTranslator(boolean encodeNonAscii)
    {
        this(encodeNonAscii, SAFE_MATCHER, ENTITY_TRANSLATOR);
    }

    public MarkupCharacterTranslator(boolean encodeNonAscii,
                                     ICharacterMatcher safeMatcher, ICharacterTranslator entityTranslator)
    {
        _encodeNonAscii = encodeNonAscii;
        _safeMatcher = safeMatcher;
        _entityTranslator = entityTranslator;
    }

    public MarkupCharacterTranslator(boolean encodeNonAscii,
                                     String safeCharacters, String[][] entities)
    {
        _encodeNonAscii = encodeNonAscii;
        _safeMatcher = new AsciiCharacterMatcher(safeCharacters);
        _entityTranslator = new AsciiCharacterTranslator(entities);
    }

    /**
     * @see ICharacterTranslator#translate(char)
     */
    public String translate(char ch)
    {
        // IE and Firefox do not handle characters between 128 and 159 well,
        // so they have to be quoted as well
        if (ch >= 160 && !_encodeNonAscii)
            return null;

        if (_safeMatcher.matches(ch))
            return null;

        String entity = _entityTranslator.translate(ch);
        if (entity != null)
            return entity;

        // needs to use a NumberFormat here to be fully compliant,
        // but this is accepted fine by the browsers
        return "&#" + (int) ch + ";";
    }
}