org.apache.commons.discovery.resource.names.DiscoverNamesInFile Maven / Gradle / Ivy

Show more of this group Show more artifacts with this name
Show all versions of commons-discovery Show documentation
Its an port to fix bugs in OSGi support. ... The Apache Commons Discovery 0.5 component is about discovering, or finding, implementations for pluggable interfaces.
The newest version!
/*
 * 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.commons.discovery.resource.names;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

import org.apache.commons.discovery.Resource;
import org.apache.commons.discovery.ResourceDiscover;
import org.apache.commons.discovery.ResourceIterator;
import org.apache.commons.discovery.ResourceNameDiscover;
import org.apache.commons.discovery.ResourceNameIterator;
import org.apache.commons.discovery.resource.ClassLoaders;
import org.apache.commons.discovery.resource.DiscoverResources;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/* 
 * Discover ALL files of a given name, and return resource names
 * contained within the set of files:
 * 
 *   one resource name per line,
 *   whitespace ignored,
 *   comments begin with '#'
 * 
 *
 * Default discoverer is DiscoverClassLoaderResources,
 * but it can be set to any other.
 */
public class DiscoverNamesInFile extends ResourceNameDiscoverImpl implements ResourceNameDiscover {

    private static Log log = LogFactory.getLog(DiscoverNamesInFile.class);

    /* 
     * Sets the {@code Log} for this class.
     *
     * @param _log This class {@code Log}
     * @deprecated This method is not thread-safe
     */
    @Deprecated
    public static void setLog(Log _log) {
        log = _log;
    }

    private ResourceDiscover _discoverResources;

    private final String _prefix;

    private final String _suffix;

    /* 
     * Construct a new resource discoverer.
     */
    public DiscoverNamesInFile() {
        _discoverResources = new DiscoverResources();
        _prefix = null;
        _suffix = null;
    }

    /* 
     * Construct a new resource discoverer.
     *
     * @param prefix The resource name prefix
     * @param suffix The resource name suffix
     */
    public DiscoverNamesInFile(String prefix, String suffix) {
        _discoverResources = new DiscoverResources();
        _prefix = prefix;
        _suffix = suffix;
    }

    /* 
     * Construct a new resource discoverer.
     *
     * @param loaders The class loaders holder
     */
    public DiscoverNamesInFile(ClassLoaders loaders) {
        _discoverResources = new DiscoverResources(loaders);
        _prefix = null;
        _suffix = null;
    }

    /* 
     * Construct a new resource discoverer.
     *
     * @param loaders The class loaders holder
     * @param prefix The resource name prefix
     * @param suffix The resource name suffix
     */
    public DiscoverNamesInFile(ClassLoaders loaders, String prefix, String suffix) {
        _discoverResources = new DiscoverResources(loaders);
        _prefix = prefix;
        _suffix = suffix;
    }

    /* 
     * Construct a new resource discoverer.
     *
     * @param discoverer The discoverer to resolve resources
     */
    public DiscoverNamesInFile(ResourceDiscover discoverer) {
        _discoverResources = discoverer;
        _prefix = null;
        _suffix = null;
    }

    /* 
     * Construct a new resource discoverer.
     *
     * @param discoverer The discoverer to resolve resources
     * @param prefix The resource name prefix
     * @param suffix The resource name suffix
     */
    public DiscoverNamesInFile(ResourceDiscover discoverer, String prefix, String suffix) {
        _discoverResources = discoverer;
        _prefix = prefix;
        _suffix = suffix;
    }

    /* 
     * Set the discoverer to resolve resources.
     *
     * @param discover The discoverer to resolve resources
     */
    public void setDiscoverer(ResourceDiscover discover) {
        _discoverResources = discover;
    }

    /* 
     * Return the discoverer to resolve resources.
     *
     * To be used by downstream elements...
     *
     * @return The discoverer to resolve resources
     */
    public ResourceDiscover getDiscover() {
        return _discoverResources;
    }

    /* 
     * {@inheritDoc}
     */
    @Override
    public ResourceNameIterator findResourceNames(final String serviceName) {
        String fileName;
        if (_prefix != null && _prefix.length() > 0) {
            fileName = _prefix + serviceName;
        } else {
            fileName = serviceName;
        }

        if (_suffix != null && _suffix.length() > 0) {
            fileName = fileName + _suffix;
        }

        if (log.isDebugEnabled()) {
            if (_prefix != null  &&  _suffix != null) {
                log.debug("find: serviceName='" + serviceName + "' as '" + fileName + "'");
            } else {
                log.debug("find: serviceName = '" + fileName + "'");
            }
        }


        final ResourceIterator files =
            getDiscover().findResources(fileName);

        return new ResourceNameIterator() {

            private int idx = 0;

            private List classNames = null;

            private String resource = null;

            public boolean hasNext() {
                if (resource == null) {
                    resource = getNextClassName();
                }
                return resource != null;
            }

            public String nextResourceName() {
                String element = resource;
                resource = null;
                return element;
            }

            private String getNextClassName() {
                if (classNames == null || idx >= classNames.size()) {
                    classNames = getNextClassNames();
                    idx = 0;
                    if (classNames == null) {
                        return null;
                    }
                }

                String className = classNames.get(idx++);

                if (log.isDebugEnabled()) {
                    log.debug("getNextClassResource: next class='" + className + "'");
                }

                return className;
            }

            private List getNextClassNames() {
                while (files.hasNext()) {
                    List results = readServices(files.nextResource());
                    if (results != null  &&  results.size() > 0) {
                        return results;
                    }
                }
                return null;
            }
        };
    }

    /* 
     * Parses the resource info file and store all the defined SPI implementation classes
     *
     * @param info The resource file
     * @return The list with all SPI implementation names
     */
    private List readServices(final Resource info) {
        List results = new ArrayList();

        InputStream is = info.getResourceAsStream();

        if (is != null) {
            try {
                try {
                    // This code is needed by EBCDIC and other
                    // strange systems.  It's a fix for bugs
                    // reported in xerces
                    BufferedReader rd;
                    try {
                        rd = new BufferedReader(new InputStreamReader(is, "UTF-8"));
                    } catch (java.io.UnsupportedEncodingException e) {
                        rd = new BufferedReader(new InputStreamReader(is));
                    }

                    try {
                        String serviceImplName;
                        while( (serviceImplName = rd.readLine()) != null) {
                            int idx = serviceImplName.indexOf('#');
                            if (idx >= 0) {
                                serviceImplName = serviceImplName.substring(0, idx);
                            }
                            serviceImplName = serviceImplName.trim();

                            if (serviceImplName.length() != 0) {
                                results.add(serviceImplName);
                            }
                        }
                    } finally {
                        rd.close();
                    }
                } finally {
                    is.close();
                }
            } catch (IOException e) {
                // ignore
            }
        }

        return results;
    }

}