Github user phrocker commented on a diff in the pull request: https://github.com/apache/nifi-minifi/pull/99#discussion_r150915720 --- Diff: minifi-nar-bundles/minifi-framework-bundle/minifi-framework/minifi-runtime/src/main/java/org/apache/nifi/minifi/FlowParser.java --- @@ -0,0 +1,154 @@ +/* + * 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.nifi.minifi; + +import org.apache.commons.io.IOUtils; +import org.apache.nifi.util.LoggingXmlParserErrorHandler; +import org.apache.nifi.util.file.FileUtils; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; +import org.w3c.dom.Document; +import org.w3c.dom.Element; +import org.w3c.dom.Node; +import org.w3c.dom.NodeList; +import org.xml.sax.SAXException; + +import javax.xml.parsers.DocumentBuilder; +import javax.xml.parsers.DocumentBuilderFactory; +import javax.xml.parsers.ParserConfigurationException; +import javax.xml.transform.Result; +import javax.xml.transform.Source; +import javax.xml.transform.TransformerException; +import javax.xml.transform.TransformerFactory; +import javax.xml.transform.dom.DOMSource; +import javax.xml.transform.stream.StreamResult; +import java.io.ByteArrayInputStream; +import java.io.ByteArrayOutputStream; +import java.io.File; +import java.io.IOException; +import java.io.InputStream; +import java.io.OutputStream; +import java.nio.file.Files; +import java.nio.file.Path; +import java.nio.file.StandardOpenOption; +import java.util.ArrayList; +import java.util.List; +import java.util.zip.GZIPInputStream; +import java.util.zip.GZIPOutputStream; + +/** + * Parses a flow from its xml.gz format into an XML {@link Document}. This class is primarily toward utilities for assisting + * with the handling of component bundles. + * <p> + * Provides auxiliary methods to aid in evaluating and manipulating the flow. + */ +public class FlowParser { + + private static final Logger logger = LoggerFactory.getLogger(FlowParser.class); + + /** + * Generates a {@link Document} from the flow configuration file provided + */ + public Document parse(final File flowConfigurationFile) { + if (flowConfigurationFile == null) { + logger.debug("Flow Configuration file was null"); + return null; + } + + // if the flow doesn't exist or is 0 bytes, then return null + final Path flowPath = flowConfigurationFile.toPath(); + try { + if (!Files.exists(flowPath) || Files.size(flowPath) == 0) { + logger.warn("Flow Configuration does not exist or was empty"); + return null; + } + } catch (IOException e) { + logger.error("An error occurred determining the size of the Flow Configuration file"); + return null; + } + + // otherwise create the appropriate input streams to read the file + try (final InputStream in = Files.newInputStream(flowPath, StandardOpenOption.READ); + final InputStream gzipIn = new GZIPInputStream(in)) { + + final byte[] flowBytes = IOUtils.toByteArray(gzipIn); + if (flowBytes == null || flowBytes.length == 0) { + logger.warn("Could not extract root group id because Flow Configuration File was empty"); + return null; + } + + final DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance(); + docFactory.setNamespaceAware(true); + + // parse the flow + final DocumentBuilder docBuilder = docFactory.newDocumentBuilder(); + docBuilder.setErrorHandler(new LoggingXmlParserErrorHandler("Flow Configuration", logger)); + final Document document = docBuilder.parse(new ByteArrayInputStream(flowBytes)); + return document; + + } catch (final SAXException | ParserConfigurationException | IOException ex) { + logger.error("Unable to parse flow {} due to {}", new Object[]{flowPath.toAbsolutePath(), ex}); + return null; + } + } + + + /** + * Writes a given XML Flow out to the specified path. + * + * @param flowDocument flowDocument of the associated XML content to write to disk + * @param flowXmlPath path on disk to write the flow + * @throws IOException if there are issues in accessing the target destination for the flow + * @throws TransformerException if there are issues in the xml transformation process + */ + public void writeFlow(final Document flowDocument, final Path flowXmlPath) throws IOException, TransformerException { + final ByteArrayOutputStream outputStream = new ByteArrayOutputStream(); + final Source xmlSource = new DOMSource(flowDocument); + final Result outputTarget = new StreamResult(outputStream); + TransformerFactory.newInstance().newTransformer().transform(xmlSource, outputTarget); + final InputStream is = new ByteArrayInputStream(outputStream.toByteArray()); + + try (final OutputStream output = Files.newOutputStream(flowXmlPath, StandardOpenOption.WRITE, StandardOpenOption.CREATE); + final OutputStream gzipOut = new GZIPOutputStream(output);) { + FileUtils.copy(is, gzipOut); + } + } + + /** + * Finds child elements with the given tagName. + * + * @param element the parent element + * @param tagName the child element name to find + * @return a list of matching child elements + */ + public static List<Element> getChildrenByTagName(final Element element, final String tagName) { + final List<Element> matches = new ArrayList<>(); --- End diff -- Could this be a little cleaner with IntStream, range, and filter?
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