FlowParser.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.nifi.authorization;

import org.apache.commons.io.IOUtils;
import org.apache.nifi.controller.serialization.FlowFromDOMFactory;
import org.apache.nifi.util.LoggingXmlParserErrorHandler;
import org.apache.nifi.web.api.dto.PortDTO;
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.XMLConstants;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.validation.Schema;
import javax.xml.validation.SchemaFactory;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
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;

/**
 * Parses a flow and returns the root group id and root group ports.
 */
public class FlowParser {

    private static final Logger logger = LoggerFactory.getLogger(FlowParser.class);

    private static final String FLOW_XSD = "/FlowConfiguration.xsd";

    private Schema flowSchema;
    private SchemaFactory schemaFactory;

    public FlowParser() throws SAXException {
        schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
        flowSchema = schemaFactory.newSchema(FileAuthorizer.class.getResource(FLOW_XSD));
    }

    /**
     * Extracts the root group id from the flow configuration file provided in nifi.properties, and extracts
     * the root group input ports and output ports, and their access controls.
     *
     */
    public FlowInfo 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;
            }

            // create validating document builder
            final DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
            docFactory.setNamespaceAware(true);
            docFactory.setSchema(flowSchema);

            // parse the flow
            final DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
            docBuilder.setErrorHandler(new LoggingXmlParserErrorHandler("Flow Configuration", logger));
            final Document document = docBuilder.parse(new ByteArrayInputStream(flowBytes));

            // extract the root group id
            final Element rootElement = document.getDocumentElement();

            final Element rootGroupElement = (Element) rootElement.getElementsByTagName("rootGroup").item(0);
            if (rootGroupElement == null) {
                logger.warn("rootGroup element not found in Flow Configuration file");
                return null;
            }

            final Element rootGroupIdElement = (Element) rootGroupElement.getElementsByTagName("id").item(0);
            if (rootGroupIdElement == null) {
                logger.warn("id element not found under rootGroup in Flow Configuration file");
                return null;
            }

            final String rootGroupId = rootGroupIdElement.getTextContent();

            final List<PortDTO> ports = new ArrayList<>();
            ports.addAll(getPorts(rootGroupElement, "inputPort"));
            ports.addAll(getPorts(rootGroupElement, "outputPort"));

            return new FlowInfo(rootGroupId, ports);

        } catch (final SAXException | ParserConfigurationException | IOException ex) {
            logger.error("Unable to parse flow {} due to {}", new Object[] { flowPath.toAbsolutePath(), ex });
            return null;
        }
    }

    /**
     * Gets the ports that are direct children of the given element.
     *
     * @param element the element containing ports
     * @param type the type of port to find (inputPort or outputPort)
     * @return a list of PortDTOs representing the found ports
     */
    private List<PortDTO> getPorts(final Element element, final String type) {
        final List<PortDTO> ports = new ArrayList<>();

        // add input ports
        final List<Element> portNodeList = getChildrenByTagName(element, type);
        for (final Element portElement : portNodeList) {
            final PortDTO portDTO = FlowFromDOMFactory.getPort(portElement);
            portDTO.setType(type);
            ports.add(portDTO);
        }

        return  ports;
    }

    /**
     * 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
     */
    private static List<Element> getChildrenByTagName(final Element element, final String tagName) {
        final List<Element> matches = new ArrayList<>();
        final NodeList nodeList = element.getChildNodes();
        for (int i = 0; i < nodeList.getLength(); i++) {
            final Node node = nodeList.item(i);
            if (!(node instanceof Element)) {
                continue;
            }

            final Element child = (Element) nodeList.item(i);
            if (child.getNodeName().equals(tagName)) {
                matches.add(child);
            }
        }

        return matches;
    }

}