[GitHub] jiangyunpeng opened a new issue #2507: Dubbo 's ExtensionLoader may be can't find custom Extension

[GitBox <gi...@apache.org>]

jiangyunpeng opened a new issue #2507: Dubbo 's ExtensionLoader may be can't find custom Extension  
URL: https://github.com/apache/incubator-dubbo/issues/2507
 
 
   
   ### Environment
   
   * Dubbo version: 2.6.3
   * Operating System version: mac OS
   * Java version: 1.8
   
   ### Steps to reproduce this issue
   
   Dubbo通过 ExtensionLoader 加载各种SPI的实现，但是findClassLoader可能无法发现自定义SPI扩展点。
   
   dubbo ExtensionLoader 代码：
   
       private void loadFile(Map<String, Class<?>> extensionClasses, String dir) {
           String fileName = dir + type.getName();
           try {
               Enumeration<java.net.URL> urls;
               ClassLoader classLoader = findClassLoader();
               if (classLoader != null) {
                   urls = classLoader.getResources(fileName);
               } else {
                   urls = ClassLoader.getSystemResources(fileName);
               }
             ......
        }
   
       private static ClassLoader findClassLoader() {
           return ExtensionLoader.class.getClassLoader();
       }
   
   
   可以看到 ExtensionLoader 使用的是本身class所在的ClassLoader load 文件，当我们自定义的SPI扩展点和dubbo不在同一个classloader就会导致无法被load。
   
   
   建议修改为  org.springframework.util.ClassUtils 中更合理的实现方式：
   
   	public static ClassLoader getDefaultClassLoader() {
   		ClassLoader cl = null;
   		try {
   			cl = Thread.currentThread().getContextClassLoader();
   		}
   		catch (Throwable ex) {
   			// Cannot access thread context ClassLoader - falling back...
   		}
   		if (cl == null) {
   			// No thread context class loader -> use class loader of this class.
   			cl = ClassUtils.class.getClassLoader();
   			if (cl == null) {
   				// getClassLoader() returning null indicates the bootstrap ClassLoader
   				try {
   					cl = ClassLoader.getSystemClassLoader();
   				}
   				catch (Throwable ex) {
   					// Cannot access system ClassLoader - oh well, maybe the caller can live with null...
   				}
   			}
   		}
   		return cl;
   

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