ban-maven-plugin/src/main/java/com/inteligr8/maven/ban/BanConfigurationDownloader.java

/*
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or (at your
 * option) any later version.
 * 
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 * 
 * You should have received a copy of the GNU General Public License along
 * with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
package com.inteligr8.maven.ban;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;

import org.apache.maven.execution.MavenSession;
import org.apache.maven.plugin.MojoFailureException;
import org.codehaus.plexus.util.xml.Xpp3Dom;
import org.codehaus.plexus.util.xml.Xpp3DomBuilder;
import org.codehaus.plexus.util.xml.pull.XmlPullParserException;
import org.eclipse.aether.impl.ArtifactResolver;
import org.eclipse.aether.impl.VersionRangeResolver;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * This class parses the a configuration file that conforms with the
 * specification defined by this plugin.
 */
public class BanConfigurationDownloader extends AbstractBanConfiguration {
    
    private final Logger logger = LoggerFactory.getLogger(this.getClass());
    
    /**
     * This constructs the downloader based on an accessible URL.
     * 
     * @param session A Maven session object.
     * @param artifactResolver A Maven Aether artifact resolver service.
     * @param versionRangeResolver A Maven Aether version range resolver service.
     * @param url The URL of a ban configuration file.
     * @throws IOException The file could not be downloaded for any number of reasons.
     * @throws MojoFailureException The file could not be parsed due to bad formatting or unexpected response.
     */
    public BanConfigurationDownloader(MavenSession session, ArtifactResolver artifactResolver, VersionRangeResolver versionRangeResolver, String url) throws IOException, MojoFailureException {
        super(session, artifactResolver, versionRangeResolver);
        
        try {
            Xpp3Dom rootDom = this.load(new URL(url));
            this.init(rootDom);
        } catch (XmlPullParserException xppe) {
            throw new MojoFailureException(xppe.getMessage(), xppe);
        }
    }

    /**
     * This constructs the downloader based on a file object.
     * 
     * @param session A Maven session object.
     * @param artifactResolver A Maven Aether artifact resolver service.
     * @param versionRangeResolver A Maven Aether version range resolver service.
     * @param file A file, typically local, though technically may be remote.
     * @throws IOException The file could not be read for any number of reasons.
     * @throws MojoFailureException The file could not be parsed due to bad formatting.
     */
    public BanConfigurationDownloader(MavenSession session, ArtifactResolver artifactResolver, VersionRangeResolver versionRangeResolver, File file) throws IOException, MojoFailureException {
        super(session, artifactResolver, versionRangeResolver);
        
        try {
            Xpp3Dom rootDom = this.load(file);
            this.init(rootDom);
        } catch (XmlPullParserException xppe) {
            throw new MojoFailureException(xppe.getMessage(), xppe);
        }
    }
    
    /**
     * This method loads the configuration from the specified URL.
     * 
     * @param url A URL of a ban configuration file.
     * @return A Maven Plexus XML DOM object.
     * @throws IOException The file could not be downloaded for any number of reasons.
     * @throws MojoFailureException The file could not be parsed due to bad formatting or unexpected response.
     */
    private Xpp3Dom load(URL url) throws IOException, XmlPullParserException {
        InputStream istream = url.openStream();
        BufferedInputStream bistream = new BufferedInputStream(istream, 16384);
        try {
            this.logger.debug("Downloading configuration: {}", url);
            return Xpp3DomBuilder.build(bistream, "utf-8");
        } finally {
            bistream.close();
        }
    }

    /**
     * This method loads the configuration from the specified file.
     * 
     * @param file A file, typically local, though technically may be remote.
     * @return A Maven Plexus XML DOM object.
     * @throws IOException The file could not be read for any number of reasons.
     * @throws MojoFailureException The file could not be parsed due to bad formatting.
     */
    private Xpp3Dom load(File file) throws IOException, XmlPullParserException {
        FileInputStream fistream = new FileInputStream(file);
        BufferedInputStream bistream = new BufferedInputStream(fistream, 16384);
        try {
            this.logger.debug("Downloading configuration: {}", file);
            return Xpp3DomBuilder.build(bistream, "utf-8");
        } finally {
            bistream.close();
        }
    }
    
}