RsdlIOManager.java

/*
Copyright (c) 2014-2015 Red Hat, Inc.

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.
*/

package org.ovirt.engine.api.rsdl;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;

import org.apache.commons.cli.CommandLine;
import org.apache.commons.cli.CommandLineParser;
import org.apache.commons.cli.DefaultParser;
import org.apache.commons.cli.HelpFormatter;
import org.apache.commons.cli.Option;
import org.apache.commons.cli.Options;
import org.apache.commons.cli.ParseException;
import org.apache.commons.io.FileUtils;

/**
 * This class is a simple utility that extracts the XML schema and the RSDL files from the engine artifacts and saves
 * it to a directory. It will be typically invoked using the {@code exec-maven-plugin} and with a command line like
 * this:
 *
 * <pre>
 * rsdl-io-manager --version=4 /tmp/myfiles
 * </pre>
 *
 * The {@code version} option is new in version 4 of the engine, so in order to preserve backwards compatibility when
 * it isn't given the default is 3.
 */
public class RsdlIOManager {
    // Names of the command line options:
    private static final String API_VERSION_OPTION = "api-version";

    // Default values of the command line options:
    private static final String API_VERSION_DEFAULT = "3";

    // The name of the files containing the names of the resources to copy:
    private static final String[] RESOURCE_NAMES = {
        "api.xsd",
        "rsdl.xml",
        "rsdl_gluster.xml",
    };

    public static void main(String[] args) throws IOException {
        // Create the command line options:
        Options options = new Options();

        // Option for the API version:
        options.addOption(Option.builder()
            .longOpt(API_VERSION_OPTION)
            .desc("The version number of the API, the default is version 3.")
            .required(false)
            .hasArg(true)
            .argName("VERSION")
            .build()
        );

        // Parse the command line:
        CommandLineParser parser = new DefaultParser();
        CommandLine line = null;
        try {
            line = parser.parse(options, args);
        }
        catch (ParseException exception) {
            System.err.println(exception.getMessage());
            HelpFormatter formatter = new HelpFormatter();
            formatter.setSyntaxPrefix("Usage: ");
            formatter.printHelp("rsdl-io-manager [OPTIONS] DIRECTORY", options);
            System.exit(1);
        }

        // Extract the API version:
        String apiVersion = line.getOptionValue(API_VERSION_OPTION);
        if (apiVersion == null || apiVersion.isEmpty()) {
            apiVersion = API_VERSION_DEFAULT;
        }

        // Check the arguments:
        args = line.getArgs();
        if (args.length != 1) {
            System.err.println("Exactly one argument containing the output directory is required.");
            System.exit(1);
        }

        // Make sure that the output directory exists:
        File outputDirectory = new File(args[0]);
        FileUtils.forceMkdir(outputDirectory);

        // Copy the resources to the output directory:
        for (String resourceName : RESOURCE_NAMES) {
            exportResource(apiVersion, resourceName, outputDirectory);
        }
    }

    private static void exportResource(String apiVersion, String resourceName, File outputDirectory) throws IOException {
        // Calculate the path of the resource:
        String resourcePath = String.format("/v%s/%s", apiVersion, resourceName);

        // Copy the resource to the output directory:
        InputStream inputResource = RsdlIOManager.class.getResourceAsStream(resourcePath);
        File outputFile = new File(outputDirectory, resourceName);
        System.out.printf("Copying resource \"%s\" to file \"%s\"%n", resourcePath, outputFile.getAbsolutePath());
        FileUtils.copyInputStreamToFile(inputResource, outputFile);
    }
}