Transformers.java

/**
 * Copyright 2010 Marko Lavikainen
 *
 * 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 net.contextfw.web.application.internal;

import java.io.StringReader;

import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.stream.StreamSource;

import net.contextfw.web.application.WebApplicationException;

import org.dom4j.Document;
import org.dom4j.io.DocumentResult;
import org.dom4j.io.DocumentSource;

public class Transformers {

    private static final TransformerFactory FACTORY =
            TransformerFactory.newInstance();

    private boolean initialized = false;

    private TransformersThreadLocal transformers;

    public Transformers() {
    }

    public void initialize(Document xsltDocument) {
        try {
            transformers = new TransformersThreadLocal(
                    FACTORY.newTemplates(new StreamSource(
                                    new StringReader(xsltDocument.asXML()))));
            initialized = true;
        } catch (TransformerConfigurationException e) {
            throw new WebApplicationException(
                    "Could not get transformer", e);
        }
    }

    public void invalidate() {
        initialized = false;
        transformers = null;
    }

    public boolean isInitialized() {
        return initialized;
    }

    public Document transform(Document document) {
        if (initialized) {
            DocumentSource source = new DocumentSource(document);
            DocumentResult result = new DocumentResult();
            Transformer tr = transformers.get();
            String lang = document.getRootElement()
                        .attributeValue("xml:lang");
            if (lang != null) {
                tr.setParameter("xml:lang", lang);
            }
            try {
                tr.transform(source, result);
            } catch (TransformerException e) {
                throw new WebApplicationException(e);
            }
            return result.getDocument();
        } else {
            throw new WebApplicationException("Transformers are not initialized");
        }
    }
}