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?
---
