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Dahua ICC Open API SDK for Java
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package com.dahuatech.hutool.core.lang;

import com.dahuatech.hutool.core.exceptions.UtilException;
import com.dahuatech.hutool.core.io.FileUtil;
import com.dahuatech.hutool.core.util.ClassUtil;
import com.dahuatech.hutool.core.util.ReflectUtil;
import com.dahuatech.hutool.core.util.URLUtil;

import java.io.File;
import java.io.FileFilter;
import java.io.IOException;
import java.lang.reflect.Method;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.List;

/**
 * 外部Jar的类加载器
 *
 * @author Looly
 */
public class JarClassLoader extends URLClassLoader {

  /** 构造 */
  public JarClassLoader() {
    this(new URL[] {});
  }

  /**
   * 构造
   *
   * @param urls 被加载的URL
   */
  public JarClassLoader(URL[] urls) {
    super(urls, ClassUtil.getClassLoader());
  }

  /**
   * 加载Jar到ClassPath
   *
   * @param dir jar文件或所在目录
   * @return JarClassLoader
   */
  public static JarClassLoader load(File dir) {
    final JarClassLoader loader = new JarClassLoader();
    loader.addJar(dir); // 查找加载所有jar
    loader.addURL(dir); // 查找加载所有class
    return loader;
  }

  /**
   * 加载Jar到ClassPath
   *
   * @param jarFile jar文件或所在目录
   * @return JarClassLoader
   */
  public static JarClassLoader loadJar(File jarFile) {
    final JarClassLoader loader = new JarClassLoader();
    loader.addJar(jarFile);
    return loader;
  }

  // ------------------------------------------------------------------- Constructor start

  /**
   * 加载Jar文件到指定loader中
   *
   * @param loader {@link URLClassLoader}
   * @param jarFile 被加载的jar
   * @throws UtilException IO异常包装和执行异常
   */
  public static void loadJar(URLClassLoader loader, File jarFile) throws UtilException {
    try {
      final Method method = ClassUtil.getDeclaredMethod(URLClassLoader.class, "addURL", URL.class);
      if (null != method) {
        method.setAccessible(true);
        final List jars = loopJar(jarFile);
        for (File jar : jars) {
          ReflectUtil.invoke(loader, method, new Object[] {jar.toURI().toURL()});
        }
      }
    } catch (IOException e) {
      throw new UtilException(e);
    }
  }

  /**
   * 加载Jar文件到System ClassLoader中
   *
   * @param jarFile 被加载的jar
   * @return System ClassLoader
   */
  public static URLClassLoader loadJarToSystemClassLoader(File jarFile) {
    URLClassLoader urlClassLoader = (URLClassLoader) ClassLoader.getSystemClassLoader();
    loadJar(urlClassLoader, jarFile);
    return urlClassLoader;
  }
  // ------------------------------------------------------------------- Constructor end

  /**
   * 递归获得Jar文件
   *
   * @param file jar文件或者包含jar文件的目录
   * @return jar文件列表
   */
  private static List loopJar(File file) {
    return FileUtil.loopFiles(
        file,
        new FileFilter() {
          @Override
          public boolean accept(File file) {
            return isJarFile(file);
          }
        });
  }

  /**
   * 是否为jar文件
   *
   * @param file 文件
   * @return 是否为jar文件
   * @since 4.4.2
   */
  private static boolean isJarFile(File file) {
    if (false == FileUtil.isFile(file)) {
      return false;
    }
    return file.getPath().toLowerCase().endsWith(".jar");
  }

  /**
   * 加载Jar文件，或者加载目录
   *
   * @param jarFileOrDir jar文件或者jar文件所在目录
   * @return this
   */
  public JarClassLoader addJar(File jarFileOrDir) {
    if (isJarFile(jarFileOrDir)) {
      return addURL(jarFileOrDir);
    }
    final List jars = loopJar(jarFileOrDir);
    for (File jar : jars) {
      addURL(jar);
    }
    return this;
  }

  // ------------------------------------------------------------------- Private method start

  @Override
  public void addURL(URL url) {
    super.addURL(url);
  }

  /**
   * 增加class所在目录或文件

   * 如果为目录，此目录用于搜索class文件，如果为文件，需为jar文件
   *
   * @param dir 目录
   * @return this
   * @since 4.4.2
   */
  public JarClassLoader addURL(File dir) {
    super.addURL(URLUtil.getURL(dir));
    return this;
  }
  // ------------------------------------------------------------------- Private method end
}