com.epam.deltix.util.lang.FileSystemClassLoader Maven / Gradle / Ivy

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/*
 * Copyright 2021 EPAM Systems, Inc
 *
 * See the NOTICE file distributed with this work for additional information
 * regarding copyright ownership. 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 com.epam.deltix.util.lang;

import java.io.*;

import com.epam.deltix.util.io.IOUtil;
import com.epam.deltix.util.io.RegexFilenameFilter;

import java.net.URL;
import java.util.*;

/**
 *  {@link ClassLoader} implementation, which loads definitions of classes from the specified directory and implements
 * {@link ClassDirectory} interface.
 */
public final class FileSystemClassLoader 
    extends AbstractClassLoader 
    implements ClassDirectory 
{
    private final File mClassDir;
    
    public FileSystemClassLoader (File rootDir, boolean searchParentFirst) {
        this (rootDir, FileSystemClassLoader.class.getClassLoader (), searchParentFirst);
    }

    public FileSystemClassLoader (File rootDir, ClassLoader parent, boolean searchParentFirst) {
        super (parent, searchParentFirst);
        mClassDir = rootDir;        
        map (mClassDir, null);
    }

    private void            map (File dir, String packPath) {
        File []     files = dir.listFiles ();
        
        if (files == null)
            return;
        
        for (File f : files) {
            String          name = f.getName ();
            
            if (f.isDirectory ())
                map (f, packPath == null ? name : packPath + '.' + name);
            else if (name.equals ("package-info.class"))
                definePackage (packPath, null, null, null, null, null, null, null);
        }
    }
    
    @Override
    public URL              findResource (String name) {
        File        f = new File (mClassDir, name);
        return (f.exists () ? IOUtil.createFileUrl (f) : null);
    }
    
    @Override
    protected InputStream   findResourceAsStream (String name) {
        try {
            return (new FileInputStream (new File (mClassDir, name)));
        } catch (FileNotFoundException x) {
            return (null);
        }
    }

    private final static FilenameFilter CLASS_FILE_FILTER = new RegexFilenameFilter(".*\\.class");

    @Override
    public Collection > listClassesForPackage(final String packageName) {
        final String                subfolder = packageName.replace('.', File.separatorChar);
        final StringBuilder         sb = new StringBuilder();
        final ArrayList > ret = new ArrayList > ();        
        final File                  folder = new File (mClassDir, subfolder);

        final File[] files = folder.listFiles (CLASS_FILE_FILTER);
        if(files != null) {
            for (File classf : files) {
                final String            fileName = classf.getName();

                sb.setLength(0);
                sb.append(packageName);
                sb.append ('.');
                sb.append (fileName, 0, fileName.length() - 6);

                try {
                    ret.add (loadClass (sb.toString ()));
                } catch (ClassNotFoundException e) {
                    throw new RuntimeException(e);
                }
            }
        }
        
        return (ret);
    }                  
}