org.apache.solr.core.SolrResourceLoader.java Source code

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/*
 * 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.solr.core;

import org.apache.lucene.analysis.util.CharFilterFactory;
import org.apache.lucene.analysis.util.ResourceLoader;
import org.apache.lucene.analysis.util.ResourceLoaderAware;
import org.apache.lucene.analysis.util.TokenFilterFactory;
import org.apache.lucene.analysis.util.TokenizerFactory;
import org.apache.lucene.analysis.util.WordlistLoader;
import org.apache.lucene.codecs.Codec;
import org.apache.lucene.codecs.DocValuesFormat;
import org.apache.lucene.codecs.PostingsFormat;
import org.apache.lucene.util.IOUtils;
import org.apache.solr.common.SolrException;
import org.apache.solr.handler.admin.CoreAdminHandler;
import org.apache.solr.handler.component.SearchComponent;
import org.apache.solr.handler.component.ShardHandlerFactory;
import org.apache.solr.request.SolrRequestHandler;
import org.apache.solr.response.QueryResponseWriter;
import org.apache.solr.rest.RestManager;
import org.apache.solr.schema.FieldType;
import org.apache.solr.schema.ManagedIndexSchemaFactory;
import org.apache.solr.schema.SimilarityFactory;
import org.apache.solr.search.QParserPlugin;
import org.apache.solr.update.processor.UpdateRequestProcessorFactory;
import org.apache.solr.util.FileUtils;
import org.apache.solr.util.plugin.SolrCoreAware;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.naming.NoInitialContextException;
import java.io.Closeable;
import java.io.File;
import java.io.FileFilter;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStreamWriter;
import java.lang.reflect.Constructor;
import java.net.MalformedURLException;
import java.net.URI;
import java.net.URL;
import java.net.URLClassLoader;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.ConcurrentHashMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * @since solr 1.3
 */
public class SolrResourceLoader implements ResourceLoader, Closeable {
    public static final Logger log = LoggerFactory.getLogger(SolrResourceLoader.class);

    static final String project = "solr";
    static final String base = "org.apache" + "." + project;
    static final String[] packages = { "", "analysis.", "schema.", "handler.", "search.", "update.", "core.",
            "response.", "request.", "update.processor.", "util.", "spelling.", "handler.component.",
            "handler.dataimport.", "spelling.suggest.", "spelling.suggest.fst.", "rest.schema.analysis." };

    protected URLClassLoader classLoader;
    private final String instanceDir;
    private String dataDir;

    private final List<SolrCoreAware> waitingForCore = Collections.synchronizedList(new ArrayList<SolrCoreAware>());
    private final List<SolrInfoMBean> infoMBeans = Collections.synchronizedList(new ArrayList<SolrInfoMBean>());
    private final List<ResourceLoaderAware> waitingForResources = Collections
            .synchronizedList(new ArrayList<ResourceLoaderAware>());
    private static final Charset UTF_8 = StandardCharsets.UTF_8;

    //TODO: Solr5. Remove this completely when you obsolete putting <core> tags in solr.xml (See Solr-4196)
    private final Properties coreProperties;

    private volatile boolean live;

    // Provide a registry so that managed resources can register themselves while the XML configuration
    // documents are being parsed ... after all are registered, they are asked by the RestManager to
    // initialize themselves. This two-step process is required because not all resources are available
    // (such as the SolrZkClient) when XML docs are being parsed.    
    private RestManager.Registry managedResourceRegistry;

    public synchronized RestManager.Registry getManagedResourceRegistry() {
        if (managedResourceRegistry == null) {
            managedResourceRegistry = new RestManager.Registry();
        }
        return managedResourceRegistry;
    }

    /**
     * <p>
     * This loader will delegate to the context classloader when possible,
     * otherwise it will attempt to resolve resources using any jar files
     * found in the "lib/" directory in the specified instance directory.
     * </p>
     *
     * @param instanceDir - base directory for this resource loader, if null locateSolrHome() will be used.
     * @see #locateSolrHome
     */
    public SolrResourceLoader(String instanceDir, ClassLoader parent, Properties coreProperties) {
        if (instanceDir == null) {
            this.instanceDir = SolrResourceLoader.locateSolrHome();
            log.info("new SolrResourceLoader for deduced Solr Home: '{}'", this.instanceDir);
        } else {
            this.instanceDir = normalizeDir(instanceDir);
            log.info("new SolrResourceLoader for directory: '{}'", this.instanceDir);
        }

        this.classLoader = createClassLoader(null, parent);
        addToClassLoader("./lib/", null, true);
        reloadLuceneSPI();
        this.coreProperties = coreProperties;
    }

    /**
     * <p>
     * This loader will delegate to the context classloader when possible,
     * otherwise it will attempt to resolve resources using any jar files
     * found in the "lib/" directory in the specified instance directory.
     * If the instance directory is not specified (=null), SolrResourceLoader#locateInstanceDir will provide one.
     * <p>
     */
    public SolrResourceLoader(String instanceDir, ClassLoader parent) {
        this(instanceDir, parent, null);
    }

    /**
     * Adds every file/dir found in the baseDir which passes the specified Filter
     * to the ClassLoader used by this ResourceLoader.  This method <b>MUST</b>
     * only be called prior to using this ResourceLoader to get any resources, otherwise
     * its behavior will be non-deterministic. You also have to {link @reloadLuceneSPI}
     * before using this ResourceLoader.
     * 
     * <p>This method will quietly ignore missing or non-directory <code>baseDir</code>
     *  folder. 
     *
     * @param baseDir base directory whose children (either jars or directories of
     *                classes) will be in the classpath, will be resolved relative
     *                the instance dir.
     * @param filter The filter files must satisfy, if null all files will be accepted.
     * @param quiet  Be quiet if baseDir does not point to a directory or if no file is 
     *               left after applying the filter. 
     */
    void addToClassLoader(final String baseDir, final FileFilter filter, boolean quiet) {
        File base = FileUtils.resolvePath(new File(getInstanceDir()), baseDir);
        if (base != null && base.exists() && base.isDirectory()) {
            File[] files = base.listFiles(filter);
            if (files == null || files.length == 0) {
                if (!quiet) {
                    log.warn("No files added to classloader from lib: " + baseDir + " (resolved as: "
                            + base.getAbsolutePath() + ").");
                }
            } else {
                this.classLoader = replaceClassLoader(classLoader, base, filter);
            }
        } else {
            if (!quiet) {
                log.warn("Can't find (or read) directory to add to classloader: " + baseDir + " (resolved as: "
                        + base.getAbsolutePath() + ").");
            }
        }
    }

    /**
     * Reloads all Lucene SPI implementations using the new classloader.
     * This method must be called after {@link #addToClassLoader(String, FileFilter, boolean)}
     * and {@link #addToClassLoader(String,FileFilter,boolean)} before using
     * this ResourceLoader.
     */
    void reloadLuceneSPI() {
        // Codecs:
        PostingsFormat.reloadPostingsFormats(this.classLoader);
        DocValuesFormat.reloadDocValuesFormats(this.classLoader);
        Codec.reloadCodecs(this.classLoader);
        // Analysis:
        CharFilterFactory.reloadCharFilters(this.classLoader);
        TokenFilterFactory.reloadTokenFilters(this.classLoader);
        TokenizerFactory.reloadTokenizers(this.classLoader);
    }

    private static URLClassLoader replaceClassLoader(final URLClassLoader oldLoader, final File base,
            final FileFilter filter) {
        if (null != base && base.canRead() && base.isDirectory()) {
            File[] files = base.listFiles(filter);

            if (null == files || 0 == files.length)
                return oldLoader;

            URL[] oldElements = oldLoader.getURLs();
            URL[] elements = new URL[oldElements.length + files.length];
            System.arraycopy(oldElements, 0, elements, 0, oldElements.length);

            for (int j = 0; j < files.length; j++) {
                try {
                    URL element = files[j].toURI().normalize().toURL();
                    log.info("Adding '" + element.toString() + "' to classloader");
                    elements[oldElements.length + j] = element;
                } catch (MalformedURLException e) {
                    SolrException.log(log, "Can't add element to classloader: " + files[j], e);
                }
            }
            ClassLoader oldParent = oldLoader.getParent();
            IOUtils.closeWhileHandlingException(oldLoader); // best effort
            return URLClassLoader.newInstance(elements, oldParent);
        }
        // are we still here?
        return oldLoader;
    }

    /**
     * Convenience method for getting a new ClassLoader using all files found
     * in the specified lib directory.
     */
    static URLClassLoader createClassLoader(final File libDir, ClassLoader parent) {
        if (null == parent) {
            parent = Thread.currentThread().getContextClassLoader();
        }
        return replaceClassLoader(URLClassLoader.newInstance(new URL[0], parent), libDir, null);
    }

    public SolrResourceLoader(String instanceDir) {
        this(instanceDir, null, null);
    }

    /** Ensures a directory name always ends with a '/'. */
    public static String normalizeDir(String path) {
        return (path != null && (!(path.endsWith("/") || path.endsWith("\\")))) ? path + File.separator : path;
    }

    public String[] listConfigDir() {
        File configdir = new File(getConfigDir());
        if (configdir.exists() && configdir.isDirectory()) {
            return configdir.list();
        } else {
            return new String[0];
        }
    }

    public String getConfigDir() {
        return instanceDir + "conf" + File.separator;
    }

    public String getDataDir() {
        return dataDir;
    }

    public Properties getCoreProperties() {
        return coreProperties;
    }

    /**
     * EXPERT
     * <p/>
     * The underlying class loader.  Most applications will not need to use this.
     * @return The {@link ClassLoader}
     */
    public ClassLoader getClassLoader() {
        return classLoader;
    }

    /** Opens a schema resource by its name.
     * Override this method to customize loading schema resources.
     *@return the stream for the named schema
     */
    public InputStream openSchema(String name) throws IOException {
        return openResource(name);
    }

    /** Opens a config resource by its name.
     * Override this method to customize loading config resources.
     *@return the stream for the named configuration
     */
    public InputStream openConfig(String name) throws IOException {
        return openResource(name);
    }

    /** Opens any resource by its name.
     * By default, this will look in multiple locations to load the resource:
     * $configDir/$resource (if resource is not absolute)
     * $CWD/$resource
     * otherwise, it will look for it in any jar accessible through the class loader.
     * Override this method to customize loading resources.
     *@return the stream for the named resource
     */
    @Override
    public InputStream openResource(String resource) throws IOException {
        InputStream is = null;
        try {
            File f0 = new File(resource), f = f0;
            if (!f.isAbsolute()) {
                // try $CWD/$configDir/$resource
                f = new File(getConfigDir() + resource).getAbsoluteFile();
            }
            boolean found = f.isFile() && f.canRead();
            if (!found) { // no success with $CWD/$configDir/$resource
                f = f0.getAbsoluteFile();
                found = f.isFile() && f.canRead();
            }
            // check that we don't escape instance dir
            if (found) {
                if (!Boolean.parseBoolean(System.getProperty("solr.allow.unsafe.resourceloading", "false"))) {
                    final URI instanceURI = new File(getInstanceDir()).getAbsoluteFile().toURI().normalize();
                    final URI fileURI = f.toURI().normalize();
                    if (instanceURI.relativize(fileURI) == fileURI) {
                        // no URI relativize possible, so they don't share same base folder
                        throw new IOException(
                                "For security reasons, SolrResourceLoader cannot load files from outside the instance's directory: "
                                        + f
                                        + "; if you want to override this safety feature and you are sure about the consequences, you can pass the system property "
                                        + "-Dsolr.allow.unsafe.resourceloading=true to your JVM");
                    }
                }
                // relativize() returned a relative, new URI, so we are fine!
                return new FileInputStream(f);
            }
            // Delegate to the class loader (looking into $INSTANCE_DIR/lib jars).
            // We need a ClassLoader-compatible (forward-slashes) path here!
            is = classLoader.getResourceAsStream(resource.replace(File.separatorChar, '/'));
            // This is a hack just for tests (it is not done in ZKResourceLoader)!
            // -> the getConfigDir's path must not be absolute!
            if (is == null && System.getProperty("jetty.testMode") != null
                    && !new File(getConfigDir()).isAbsolute()) {
                is = classLoader.getResourceAsStream((getConfigDir() + resource).replace(File.separatorChar, '/'));
            }
        } catch (IOException ioe) {
            throw ioe;
        } catch (Exception e) {
            throw new IOException("Error opening " + resource, e);
        }
        if (is == null) {
            throw new IOException("Can't find resource '" + resource + "' in classpath or '"
                    + new File(getConfigDir()).getAbsolutePath() + "'");
        }
        return is;
    }

    /**
     * Accesses a resource by name and returns the (non comment) lines
     * containing data.
     *
     * <p>
     * A comment line is any line that starts with the character "#"
     * </p>
     *
     * @return a list of non-blank non-comment lines with whitespace trimmed
     * from front and back.
     * @throws IOException If there is a low-level I/O error.
     */
    public List<String> getLines(String resource) throws IOException {
        return getLines(resource, UTF_8);
    }

    /**
     * Accesses a resource by name and returns the (non comment) lines containing
     * data using the given character encoding.
     *
     * <p>
     * A comment line is any line that starts with the character "#"
     * </p>
     *
     * @param resource the file to be read
     * @return a list of non-blank non-comment lines with whitespace trimmed
     * @throws IOException If there is a low-level I/O error.
     */
    public List<String> getLines(String resource, String encoding) throws IOException {
        return getLines(resource, Charset.forName(encoding));
    }

    public List<String> getLines(String resource, Charset charset) throws IOException {
        try {
            return WordlistLoader.getLines(openResource(resource), charset);
        } catch (CharacterCodingException ex) {
            throw new SolrException(SolrException.ErrorCode.SERVER_ERROR,
                    "Error loading resource (wrong encoding?): " + resource, ex);
        }
    }

    /*
     * A static map of short class name to fully qualified class name 
     */
    private static final Map<String, String> classNameCache = new ConcurrentHashMap<>();

    // Using this pattern, legacy analysis components from previous Solr versions are identified and delegated to SPI loader:
    private static final Pattern legacyAnalysisPattern = Pattern.compile("((\\Q" + base + ".analysis.\\E)|(\\Q"
            + project + ".\\E))([\\p{L}_$][\\p{L}\\p{N}_$]+?)(TokenFilter|Filter|Tokenizer|CharFilter)Factory");

    @Override
    public <T> Class<? extends T> findClass(String cname, Class<T> expectedType) {
        return findClass(cname, expectedType, empty);
    }

    /**
     * This method loads a class either with its FQN or a short-name (solr.class-simplename or class-simplename).
     * It tries to load the class with the name that is given first and if it fails, it tries all the known
     * solr packages. This method caches the FQN of a short-name in a static map in-order to make subsequent lookups
     * for the same class faster. The caching is done only if the class is loaded by the webapp classloader and it
     * is loaded using a shortname.
     *
     * @param cname The name or the short name of the class.
     * @param subpackages the packages to be tried if the cname starts with solr.
     * @return the loaded class. An exception is thrown if it fails
     */
    public <T> Class<? extends T> findClass(String cname, Class<T> expectedType, String... subpackages) {
        if (subpackages == null || subpackages.length == 0 || subpackages == packages) {
            subpackages = packages;
            String c = classNameCache.get(cname);
            if (c != null) {
                try {
                    return Class.forName(c, true, classLoader).asSubclass(expectedType);
                } catch (ClassNotFoundException e) {
                    //this is unlikely
                    log.error("Unable to load cached class-name :  " + c + " for shortname : " + cname + e);
                }

            }
        }

        Class<? extends T> clazz = null;
        try {
            // first try legacy analysis patterns, now replaced by Lucene's Analysis package:
            final Matcher m = legacyAnalysisPattern.matcher(cname);
            if (m.matches()) {
                final String name = m.group(4);
                log.trace("Trying to load class from analysis SPI using name='{}'", name);
                try {
                    if (CharFilterFactory.class.isAssignableFrom(expectedType)) {
                        return clazz = CharFilterFactory.lookupClass(name).asSubclass(expectedType);
                    } else if (TokenizerFactory.class.isAssignableFrom(expectedType)) {
                        return clazz = TokenizerFactory.lookupClass(name).asSubclass(expectedType);
                    } else if (TokenFilterFactory.class.isAssignableFrom(expectedType)) {
                        return clazz = TokenFilterFactory.lookupClass(name).asSubclass(expectedType);
                    } else {
                        log.warn(
                                "'{}' looks like an analysis factory, but caller requested different class type: {}",
                                cname, expectedType.getName());
                    }
                } catch (IllegalArgumentException ex) {
                    // ok, we fall back to legacy loading
                }
            }

            // first try cname == full name
            try {
                return clazz = Class.forName(cname, true, classLoader).asSubclass(expectedType);
            } catch (ClassNotFoundException e) {
                String newName = cname;
                if (newName.startsWith(project)) {
                    newName = cname.substring(project.length() + 1);
                }
                for (String subpackage : subpackages) {
                    try {
                        String name = base + '.' + subpackage + newName;
                        log.trace("Trying class name " + name);
                        return clazz = Class.forName(name, true, classLoader).asSubclass(expectedType);
                    } catch (ClassNotFoundException e1) {
                        // ignore... assume first exception is best.
                    }
                }

                throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, "Error loading class '" + cname + "'",
                        e);
            }

        } finally {
            if (clazz != null) {
                //cache the shortname vs FQN if it is loaded by the webapp classloader  and it is loaded
                // using a shortname
                if (clazz.getClassLoader() == SolrResourceLoader.class.getClassLoader()
                        && !cname.equals(clazz.getName()) && (subpackages.length == 0 || subpackages == packages)) {
                    //store in the cache
                    classNameCache.put(cname, clazz.getName());
                }

                // print warning if class is deprecated
                if (clazz.isAnnotationPresent(Deprecated.class)) {
                    log.warn(
                            "Solr loaded a deprecated plugin/analysis class [{}]. Please consult documentation how to replace it accordingly.",
                            cname);
                }
            }
        }
    }

    static final String empty[] = new String[0];

    @Override
    public <T> T newInstance(String name, Class<T> expectedType) {
        return newInstance(name, expectedType, empty);
    }

    private static final Class[] NO_CLASSES = new Class[0];
    private static final Object[] NO_OBJECTS = new Object[0];

    public <T> T newInstance(String cname, Class<T> expectedType, String... subpackages) {
        return newInstance(cname, expectedType, subpackages, NO_CLASSES, NO_OBJECTS);
    }

    public CoreAdminHandler newAdminHandlerInstance(final CoreContainer coreContainer, String cname,
            String... subpackages) {
        Class<? extends CoreAdminHandler> clazz = findClass(cname, CoreAdminHandler.class, subpackages);
        if (clazz == null) {
            throw new SolrException(SolrException.ErrorCode.SERVER_ERROR,
                    "Can not find class: " + cname + " in " + classLoader);
        }

        CoreAdminHandler obj = null;
        try {
            Constructor<? extends CoreAdminHandler> ctor = clazz.getConstructor(CoreContainer.class);
            obj = ctor.newInstance(coreContainer);
        } catch (Exception e) {
            throw new SolrException(SolrException.ErrorCode.SERVER_ERROR,
                    "Error instantiating class: '" + clazz.getName() + "'", e);
        }

        if (!live) {
            //TODO: Does SolrCoreAware make sense here since in a multi-core context
            // which core are we talking about ?
            if (obj instanceof ResourceLoaderAware) {
                assertAwareCompatibility(ResourceLoaderAware.class, obj);
                waitingForResources.add((ResourceLoaderAware) obj);
            }
        }

        return obj;
    }

    public <T> T newInstance(String cName, Class<T> expectedType, String[] subPackages, Class[] params,
            Object[] args) {
        Class<? extends T> clazz = findClass(cName, expectedType, subPackages);
        if (clazz == null) {
            throw new SolrException(SolrException.ErrorCode.SERVER_ERROR,
                    "Can not find class: " + cName + " in " + classLoader);
        }

        T obj = null;
        try {

            Constructor<? extends T> constructor = clazz.getConstructor(params);
            obj = constructor.newInstance(args);

        } catch (Error err) {
            log.error("Loading Class " + cName + " (" + clazz.getName() + ") triggered serious java error: "
                    + err.getClass().getName(), err);
            throw err;

        } catch (Exception e) {
            throw new SolrException(SolrException.ErrorCode.SERVER_ERROR,
                    "Error instantiating class: '" + clazz.getName() + "'", e);
        }

        if (!live) {
            if (obj instanceof SolrCoreAware) {
                assertAwareCompatibility(SolrCoreAware.class, obj);
                waitingForCore.add((SolrCoreAware) obj);
            }
            if (obj instanceof ResourceLoaderAware) {
                assertAwareCompatibility(ResourceLoaderAware.class, obj);
                waitingForResources.add((ResourceLoaderAware) obj);
            }
            if (obj instanceof SolrInfoMBean) {
                //TODO: Assert here?
                infoMBeans.add((SolrInfoMBean) obj);
            }
        }

        return obj;
    }

    /**
     * Tell all {@link SolrCoreAware} instances about the SolrCore
     */
    public void inform(SolrCore core) {
        this.dataDir = core.getDataDir();

        // make a copy to avoid potential deadlock of a callback calling newInstance and trying to
        // add something to waitingForCore.
        SolrCoreAware[] arr;

        while (waitingForCore.size() > 0) {
            synchronized (waitingForCore) {
                arr = waitingForCore.toArray(new SolrCoreAware[waitingForCore.size()]);
                waitingForCore.clear();
            }

            for (SolrCoreAware aware : arr) {
                aware.inform(core);
            }
        }

        // this is the last method to be called in SolrCore before the latch is released.
        live = true;
    }

    /**
     * Tell all {@link ResourceLoaderAware} instances about the loader
     */
    public void inform(ResourceLoader loader) throws IOException {

        // make a copy to avoid potential deadlock of a callback adding to the list
        ResourceLoaderAware[] arr;

        while (waitingForResources.size() > 0) {
            synchronized (waitingForResources) {
                arr = waitingForResources.toArray(new ResourceLoaderAware[waitingForResources.size()]);
                waitingForResources.clear();
            }

            for (ResourceLoaderAware aware : arr) {
                aware.inform(loader);
            }
        }
    }

    /**
     * Register any {@link org.apache.solr.core.SolrInfoMBean}s
     * @param infoRegistry The Info Registry
     */
    public void inform(Map<String, SolrInfoMBean> infoRegistry) {
        // this can currently happen concurrently with requests starting and lazy components
        // loading.  Make sure infoMBeans doesn't change.

        SolrInfoMBean[] arr;
        synchronized (infoMBeans) {
            arr = infoMBeans.toArray(new SolrInfoMBean[infoMBeans.size()]);
            waitingForResources.clear();
        }

        for (SolrInfoMBean bean : arr) {
            // Too slow? I suspect not, but we may need
            // to start tracking this in a Set.
            if (!infoRegistry.containsValue(bean)) {
                try {
                    infoRegistry.put(bean.getName(), bean);
                } catch (Exception e) {
                    log.warn("could not register MBean '" + bean.getName() + "'.", e);
                }
            }
        }
    }

    /**
     * Determines the solrhome from the environment.
     * Tries JNDI (java:comp/env/solr/home) then system property (solr.solr.home);
     * if both fail, defaults to solr/
     * @return the instance directory name
     */
    /**
     * Finds the solrhome based on looking up the value in one of three places:
     * <ol>
     *  <li>JNDI: via java:comp/env/solr/home</li>
     *  <li>The system property solr.solr.home</li>
     *  <li>Look in the current working directory for a solr/ directory</li> 
     * </ol>
     *
     * The return value is normalized.  Normalization essentially means it ends in a trailing slash.
     * @return A normalized solrhome
     * @see #normalizeDir(String)
     */
    public static String locateSolrHome() {

        String home = null;
        // Try JNDI
        try {
            Context c = new InitialContext();
            home = (String) c.lookup("java:comp/env/" + project + "/home");
            log.info("Using JNDI solr.home: " + home);
        } catch (NoInitialContextException e) {
            log.info("JNDI not configured for " + project + " (NoInitialContextEx)");
        } catch (NamingException e) {
            log.info("No /" + project + "/home in JNDI");
        } catch (RuntimeException ex) {
            log.warn("Odd RuntimeException while testing for JNDI: " + ex.getMessage());
        }

        // Now try system property
        if (home == null) {
            String prop = project + ".solr.home";
            home = System.getProperty(prop);
            if (home != null) {
                log.info("using system property " + prop + ": " + home);
            }
        }

        // if all else fails, try 
        if (home == null) {
            home = project + '/';
            log.info(project + " home defaulted to '" + home + "' (could not find system property or JNDI)");
        }
        return normalizeDir(home);
    }

    public String getInstanceDir() {
        return instanceDir;
    }

    /**
     * Keep a list of classes that are allowed to implement each 'Aware' interface
     */
    private static final Map<Class, Class[]> awareCompatibility;
    static {
        awareCompatibility = new HashMap<>();
        awareCompatibility.put(SolrCoreAware.class,
                new Class[] { CodecFactory.class, ManagedIndexSchemaFactory.class, QueryResponseWriter.class,
                        SearchComponent.class, ShardHandlerFactory.class, SimilarityFactory.class,
                        SolrRequestHandler.class, UpdateRequestProcessorFactory.class });

        awareCompatibility.put(ResourceLoaderAware.class, new Class[] { CharFilterFactory.class,
                TokenFilterFactory.class, TokenizerFactory.class, QParserPlugin.class, FieldType.class });
    }

    /**
     * Utility function to throw an exception if the class is invalid
     */
    void assertAwareCompatibility(Class aware, Object obj) {
        Class[] valid = awareCompatibility.get(aware);
        if (valid == null) {
            throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, "Unknown Aware interface: " + aware);
        }
        for (Class v : valid) {
            if (v.isInstance(obj)) {
                return;
            }
        }
        StringBuilder builder = new StringBuilder();
        builder.append("Invalid 'Aware' object: ").append(obj);
        builder.append(" -- ").append(aware.getName());
        builder.append(" must be an instance of: ");
        for (Class v : valid) {
            builder.append("[").append(v.getName()).append("] ");
        }
        throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, builder.toString());
    }

    @Override
    public void close() throws IOException {
        IOUtils.close(classLoader);
    }

    public List<SolrInfoMBean> getInfoMBeans() {
        return Collections.unmodifiableList(infoMBeans);
    }

    public static void persistConfLocally(SolrResourceLoader loader, String resourceName, byte[] content) {
        // Persist locally
        File confFile = new File(loader.getConfigDir(), resourceName);
        OutputStreamWriter writer = null;
        try {
            File parentDir = confFile.getParentFile();
            if (!parentDir.isDirectory()) {
                if (!parentDir.mkdirs()) {
                    final String msg = "Can't create managed schema directory " + parentDir.getAbsolutePath();
                    log.error(msg);
                    throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, msg);
                }
            }
            final FileOutputStream out = new FileOutputStream(confFile);
            out.write(content);
            log.info("Written confile " + resourceName);
        } catch (IOException e) {
            final String msg = "Error persisting conf file " + resourceName;
            log.error(msg, e);
            throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, msg, e);
        } finally {
            org.apache.commons.io.IOUtils.closeQuietly(writer);
            try {
                FileUtils.sync(confFile);
            } catch (IOException e) {
                final String msg = "Error syncing conf file " + resourceName;
                log.error(msg, e);
            }
        }
    }

    public String resolve(String pathToResolve) {
        return Paths.get(instanceDir).resolve(pathToResolve).toString();
    }
}