    001// Licensed under the Apache License, Version 2.0 (the "License");
    002// you may not use this file except in compliance with the License.
    003// You may obtain a copy of the License at
    004//
    005// http://www.apache.org/licenses/LICENSE-2.0
    006//
    007// Unless required by applicable law or agreed to in writing, software
    008// distributed under the License is distributed on an "AS IS" BASIS,
    009// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    010// See the License for the specific language governing permissions and
    011// limitations under the License.
    012
    013package org.apache.tapestry5.internal.util;
    014
    015import java.io.ByteArrayInputStream;
    016import java.io.IOException;
    017import java.io.InputStream;
    018import java.net.URL;
    019import java.nio.charset.Charset;
    020import java.util.Locale;
    021
    022import org.apache.tapestry5.commons.Resource;
    023
    024/**
    025 * Base class for virtual resources: resources that are not simply mapped to stored files, but are assembled, as necessary,
    026 * on the fly. This is used inside Tapestry to expose the application's localized message catalog as a module.
    027 * Subclasses should implement the {@link org.apache.tapestry5.commons.Resource#openStream()} method to return a stream of
    028 * the contents of the virtual resource.
    029 *
    030 * @see org.apache.tapestry5.services.javascript.ModuleManager
    031 * @see org.apache.tapestry5.internal.services.javascript.ModuleDispatcher
    032 * @since 5.4
    033 */
    034public abstract class VirtualResource implements Resource
    035{
    036    protected static final Charset UTF8 = Charset.forName("UTF-8");
    037
    038    private <T> T unsupported(String name)
    039    {
    040        throw new UnsupportedOperationException(String.format("Method %s() is not supported for a VirtualResource.", name));
    041    }
    042
    043    public boolean exists()
    044    {
    045
    046        return true;
    047    }
    048
    049    public URL toURL()
    050    {
    051        return unsupported("toURL");
    052    }
    053
    054    public Resource forLocale(Locale locale)
    055    {
    056        return unsupported("forLocale");
    057    }
    058
    059    public Resource forFile(String relativePath)
    060    {
    061        return this;
    062    }
    063
    064    public Resource withExtension(String extension)
    065    {
    066        return unsupported("withExtension");
    067    }
    068
    069    public String getFolder()
    070    {
    071        return unsupported("getFolder");
    072    }
    073
    074    public String getFile()
    075    {
    076        return unsupported("getFile");
    077    }
    078
    079    public String getPath()
    080    {
    081        return unsupported("getPath");
    082    }
    083
    084    protected InputStream toInputStream(String content) throws IOException
    085    {
    086        return toInputStream(content.getBytes(UTF8));
    087    }
    088
    089    protected InputStream toInputStream(byte[] content) throws IOException
    090    {
    091        return new ByteArrayInputStream(content);
    092    }
    093
    094    @Override
    095    public boolean isVirtual()
    096    {
    097        return true;
    098    }
    099}