de.smartics.maven.plugin.jboss.modules.util.classpath.ClassPathContext.java Source code

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Here is the source code for de.smartics.maven.plugin.jboss.modules.util.classpath.ClassPathContext.java

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/*
 * Copyright 2013-2017 smartics, Kronseder & Reiner GmbH
 *
 * 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 de.smartics.maven.plugin.jboss.modules.util.classpath;

import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Enumeration;

import org.apache.commons.lang.ObjectUtils;

import de.smartics.maven.plugin.jboss.modules.util.Arg;

/**
 * A constraint on resources to be loaded from the class path.
 */
public final class ClassPathContext {
    // ********************************* Fields *********************************

    // --- constants ------------------------------------------------------------

    // --- members --------------------------------------------------------------

    /**
     * The class loader to load the directory listings.
     */
    private final ClassLoader classLoader;

    /**
     * Selects the archive root to load from.
     */
    private final String archiveRoot;

    // ****************************** Initializer *******************************

    // ****************************** Constructors ******************************

    /**
     * Default constructor.
     *
     * @param classLoader the class loader to load the directory listings.
     * @param archiveRoot the value for archiveRoot.
     * @throws NullPointerException if {@code classLoader} is <code>null</code>.
     */
    public ClassPathContext(final ClassLoader classLoader, final String archiveRoot) throws NullPointerException {
        Arg.checkNotNull("classLoader", classLoader);

        this.classLoader = classLoader;
        this.archiveRoot = archiveRoot;
    }

    // ****************************** Inner Classes *****************************

    // ********************************* Methods ********************************

    // --- init -----------------------------------------------------------------

    // --- get&set --------------------------------------------------------------

    // --- business -------------------------------------------------------------

    /**
     * Constructs the URL to the resource.
     *
     * @param resource the resource whose URL is requested.
     * @return the URL to the resource or <code>null</code> if the resource cannot
     *         be found on the class path.
     */
    public URL getResource(final String resource) {
        if (archiveRoot == null) {
            return classLoader.getResource(resource);
        }

        // TODO: maybe we should simply construct the URL?
        try {
            for (final Enumeration<URL> en = classLoader.getResources(resource); en.hasMoreElements();) {
                final URL current = en.nextElement();
                final String urlString = current.toExternalForm();
                if (urlString.startsWith(archiveRoot)) {
                    return current;
                }
            }
        } catch (final IOException e) {
            // return null
        }
        return null;
    }

    /**
     * Opens the stream to the resource.
     *
     * @param resource the resource whose stream is requested.
     * @return the stream to the resource or <code>null</code> if the resource
     *         cannot be found on the class path. If a stream is returned, the
     *         client is responsible to close that stream.
     */
    public InputStream getResourceAsStream(final String resource) {
        final URL url = getResource(resource);
        if (url != null) {
            try {
                return url.openStream();
            } catch (final IOException e) {
                // return null;
            }
        }
        return null;
    }

    /**
     * Constructs the URL to the resource.
     *
     * @param resource the resource whose URL is requested.
     * @return the constructed URL.
     * @throws IllegalArgumentException if the URL to the resource cannot be
     *           constructed.
     */
    public URL createUrl(final String resource) throws IllegalArgumentException {
        try {
            final String urlString = (archiveRoot != null ? archiveRoot : "") + resource;
            return new URL(urlString);
        } catch (final MalformedURLException e) {
            throw new IllegalArgumentException("Cannot construct URL with resource '" + resource + "'.", e);
        }
    }

    // --- object basics --------------------------------------------------------

    /**
     * Returns the hash code of the object.
     *
     * @return the hash code.
     */
    @Override
    public int hashCode() {
        return ObjectUtils.hashCode(archiveRoot);
    }

    /**
     * Returns <code>true</code> if the given object is semantically equal to the
     * given object, <code>false</code> otherwise.
     *
     * @param object the instance to compare to.
     * @return <code>true</code> if the given object is semantically equal to the
     *         given object, <code>false</code> otherwise.
     */
    @Override
    public boolean equals(final Object object) {
        if (this == object) {
            return true;
        } else if (object == null || getClass() != object.getClass()) {
            return false;
        }

        final ClassPathContext other = (ClassPathContext) object;

        return ObjectUtils.equals(archiveRoot, other.archiveRoot);
    }

    @Override
    public String toString() {
        return archiveRoot != null ? archiveRoot : "<unspecified archive root>";
    }
}