NifiTemplateParser.java

package com.thinkbiganalytics.feedmgr.nifi;

/*-
 * #%L
 * thinkbig-feed-manager-controller
 * %%
 * Copyright (C) 2017 ThinkBig Analytics
 * %%
 * 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.
 * #L%
 */

import org.apache.commons.io.IOUtils;
import org.w3c.dom.Attr;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

import java.io.IOException;
import java.io.InputStream;
import java.io.StringReader;
import java.io.StringWriter;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
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 javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;

/**
 * Utility to get the name of a template for an xml string
 */
public class NifiTemplateParser {


    /**
     * @param nifiTemplate the nifi template xml string
     * @return the name of the template
     */
    public static String getTemplateName(String nifiTemplate) throws ParserConfigurationException, XPathExpressionException, IOException, SAXException {

        XPathFactory xpathFactory = XPathFactory.newInstance();
        XPath xpath = xpathFactory.newXPath();

        InputSource source = new InputSource(new StringReader(nifiTemplate));
        String name = (String) xpath.evaluate("/template/name", source, XPathConstants.STRING);
        return name;
    }

    public static String updateTemplateName(String nifiTemplate, String newName) throws Exception {

        XPathFactory xpathFactory = XPathFactory.newInstance();
        XPath xpath = xpathFactory.newXPath();
        Document doc = stringToDocument(nifiTemplate);

        InputSource source = new InputSource(new StringReader(nifiTemplate));

        Element element = (Element) xpath.compile("//template/name")
            .evaluate(doc, XPathConstants.NODE);

         element.setTextContent(newName);
        return documentToString(doc);
    }



    public static String documentToString(Document doc) throws Exception {

        TransformerFactory tf = TransformerFactory.newInstance();
        Transformer transformer = tf.newTransformer();
        transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no");
        StringWriter writer = new StringWriter();
        transformer.transform(new DOMSource(doc), new StreamResult(writer));
        String output = writer.getBuffer().toString();
        return output;
    }

    public static Document stringToDocument(String strXml) throws Exception {

        Document doc = null;
        try {
            DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
            DocumentBuilder builder = factory.newDocumentBuilder();
            StringReader strReader = new StringReader(strXml);
            InputSource is = new InputSource(strReader);
            doc = builder.parse(is);
        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        }

        return doc;
    }
}