integrations/rest-management/rest-management/src/main/java/org/apache/aries/jax/rs/rest/management/handler/XMLSerializer.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.aries.jax.rs.rest.management.handler;

import java.io.IOException;
import java.io.OutputStream;
import java.util.function.BiConsumer;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;
import org.w3c.dom.Node;

class XMLSerializer {

    private final DocumentBuilder db;

    public XMLSerializer() {
        try {
            DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
            db = dbf.newDocumentBuilder();
        }
        catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    public void serialize(
            String rootElement, BiConsumer<Document, Node> consumer,
            OutputStream entityStream)
        throws Exception {

        try {
            Document dom = db.newDocument();
            Node parentNode = dom;
            if (rootElement != null) {
                parentNode = dom.createElement(rootElement);
                dom.appendChild(parentNode);
            }

            consumer.accept(dom, parentNode);

            Transformer tr = TransformerFactory.newInstance().newTransformer();
            tr.setOutputProperty(OutputKeys.STANDALONE, "yes");
            tr.setOutputProperty(OutputKeys.INDENT, "yes");
            tr.setOutputProperty(OutputKeys.METHOD, "xml");
            tr.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
            tr.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "4");

            tr.transform(
                new DOMSource(dom),
                new StreamResult(entityStream)
            );
        }
        catch (Exception e) {
            throw new IOException(e);
        }
    }

}