com.github.marschall.pathclassloader.PathClassLoader Maven / Gradle / Ivy

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package com.github.marschall.pathclassloader;

import java.io.IOException;
import java.net.URL;
import java.net.URLStreamHandler;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.List;

//TODO SecureClassLoader
public final class PathClassLoader extends ClassLoader {

  private static final URLStreamHandler HANDLER = new PathURLStreamHandler();

  private final Path path;

  static {
    registerAsParallelCapable();
  }

  public PathClassLoader(Path path) {
    this(path, null);
  }

  public PathClassLoader(Path path, ClassLoader parent) {
    super(parent);
    this.path = path;
  }

  @Override
  protected Class findClass(String name) throws ClassNotFoundException {
    // TODO path injection
    Path classPath = this.path.resolve(name.replace('.', '/').concat(".class"));
    if (Files.exists(classPath)) {
      try {
        byte[] byteCode = Files.readAllBytes(classPath);
        return this.defineClass(name, byteCode, 0, byteCode.length);
      } catch (IOException e) {
        throw new ClassNotFoundException(name, e);
      }
    } else {
      throw new ClassNotFoundException(name);
    }
  }

  @Override
  protected URL findResource(String name) {
    // TODO path injection
    Path resolved = this.path.resolve(name);
    if (Files.exists(resolved)) {
      try {
        return toURL(resolved);
      } catch (IOException e) {
        throw new RuntimeException("could not open " + resolved, e);
      }
    } else {
      return null;
    }
  }

  @Override
  protected Enumeration findResources(final String name) throws IOException {
    // TODO correct?
    final List resources = new ArrayList<>(1);

    Files.walkFileTree(path, new SimpleFileVisitor() {
      @Override
      public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
        if (!name.isEmpty()) {
          this.addIfMatches(resources, file);
        }
        return super.visitFile(file, attrs);
      }
      
      @Override
      public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
        if (!name.isEmpty() || path.equals(dir)) {
          this.addIfMatches(resources, dir);
        }
        return super.preVisitDirectory(dir, attrs);
      }

      void addIfMatches(List resources, Path file) throws IOException {
        if (path.relativize(file).toString().equals(name)) {
          resources.add(toURL(file));
        }
      }
      
    });
    return Collections.enumeration(resources);
  }

  private URL toURL(Path path) throws IOException {
    return new URL(null, path.toUri().toString(), HANDLER);
  }

}