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package com.github.binarywang.wxpay.util;

import jodd.util.ClassUtil;
import lombok.val;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;

/**
 * 基于jodd.util.ResourcesUtil改造实现
 *
 * @author jodd
 */
public class ResourcesUtils {
  /**
   * Retrieves given resource as URL. Resource is always absolute and may
   * starts with a slash character.
   * 
   * Resource will be loaded using class loaders in the following order:
   * 

   * {@link Thread#getContextClassLoader() Thread.currentThread().getContextClassLoader()}
   * {@link Class#getClassLoader() ClassLoaderUtil.class.getClassLoader()}
   * if callingClass is provided: {@link Class#getClassLoader() callingClass.getClassLoader()}
   * 
   */
  public static URL getResourceUrl(String resourceName, final ClassLoader classLoader) {

    if (resourceName.startsWith("/")) {
      resourceName = resourceName.substring(1);
    }

    URL resourceUrl;

    // try #1 - using provided class loader
    if (classLoader != null) {
      resourceUrl = classLoader.getResource(resourceName);
      if (resourceUrl != null) {
        return resourceUrl;
      }
    }

    // try #2 - using thread class loader
    final ClassLoader currentThreadClassLoader = Thread.currentThread().getContextClassLoader();
    if ((currentThreadClassLoader != null) && (currentThreadClassLoader != classLoader)) {
      resourceUrl = currentThreadClassLoader.getResource(resourceName);
      if (resourceUrl != null) {
        return resourceUrl;
      }
    }

    // try #3 - using caller classloader, similar as Class.forName()
    val callerClass = ClassUtil.getCallerClass(2);
    val callerClassLoader = callerClass.getClassLoader();

    if ((callerClassLoader != classLoader) && (callerClassLoader != currentThreadClassLoader)) {
      resourceUrl = callerClassLoader.getResource(resourceName);
      return resourceUrl;
    }

    return null;
  }

  /**
   * Opens a resource of the specified name for reading.
   *
   * @see #getResourceAsStream(String, ClassLoader)
   */
  public static InputStream getResourceAsStream(final String resourceName) throws IOException {
    return getResourceAsStream(resourceName, null);
  }

  /**
   * Opens a resource of the specified name for reading.
   *
   * @see #getResourceUrl(String, ClassLoader)
   */
  public static InputStream getResourceAsStream(final String resourceName, final ClassLoader callingClass) throws IOException {
    final URL url = getResourceUrl(resourceName, callingClass);
    if (url != null) {
      return url.openStream();
    }
    return null;
  }

}