serviceurlstreamhandlerfactory.java

来自「OSGI这是一个中间件,与UPNP齐名,是用于移植到嵌入式平台之上」· Java 代码 · 共 213 行

/*
 * Copyright (c) 2003-2004, KNOPFLERFISH project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials
 *   provided with the distribution.
 *
 * - Neither the name of the KNOPFLERFISH project nor the names of its
 *   contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.knopflerfish.framework;

import java.io.*;
import java.net.*;
import org.osgi.service.url.*;
import org.osgi.framework.*;
import org.osgi.util.tracker.*;
import java.util.Map;
import java.util.HashMap;

/**
 * Factory creating URLStreamHandlers from both built-in
 * handlers and OSGi-registered URLStreamHandlerServices.
 */
public class ServiceURLStreamHandlerFactory 
  implements URLStreamHandlerFactory
{
  Framework framework;

  //
  // Special framework handlers 
  //
  // String protocol -> URLStreamHandler
  Map handlers = new HashMap();

  // JVM classpath handlers. Initialized once at startup
  String[] jvmPkgs = null;

  //
  // OSGi URLStreamHandlerService wrappers
  // This map is not really necessary since the JVM
  // caches handlers anyway, but it just seems nice to have.
  // 
  // String (protocol) -> URLStreamHandlerWrapper
  Map wrapMap   = new HashMap();


  ServiceURLStreamHandlerFactory(Framework fw) {
    this.framework = fw;

    // Initialize JVM classpath packages
    String s = System.getProperty("java.protocol.handler.pkgs", "");
    
    jvmPkgs = Util.splitwords(s, "|", '\"');

    for(int i = 0; i < jvmPkgs.length; i++) {
      jvmPkgs[i] = jvmPkgs[i].trim();
      if(Debug.url) {
	Debug.println("JVMClassPath - URLHandler jvmPkgs[" + i + "]=" + jvmPkgs[i]);
      }
    }
  }

  public URLStreamHandler createURLStreamHandler(String protocol) {
    synchronized(handlers) {

      if(Debug.url) {
	Debug.println("createURLStreamHandler protocol=" + protocol);
      }

      // Check for
      // 1. JVM classpath handlers
      // 2. Framework built-in handlers
      // 2. OSGi-based handlers
      // 3. system handlers

      URLStreamHandler handler = getJVMClassPathHandler(protocol);
      if(handler != null) {
	if(Debug.url) {
	  Debug.println("using JVMClassPath handler for " + protocol);
	}
	return handler;
      }

	
      handler = (URLStreamHandler)handlers.get(protocol);
      if(handler != null) {
	if(Debug.url) {
	  Debug.println("using predefined handler for " + protocol);
	}
	return handler;
      }

      handler = getServiceHandler(protocol);
      if(handler != null) {
	if(Debug.url) {
	  Debug.println("Using service URLHandler for " + protocol);
	}
	return handler;
      }

      if(Debug.url) {
	Debug.println("Using default URLHandler for " + protocol);
      }
      return null;
    }
  }

  URLStreamHandler getServiceHandler(String protocol) {
    try {
      String filter = 
	"(" + 
	URLConstants.URL_HANDLER_PROTOCOL + 
	"=" + protocol + 
	")";
      
      ServiceReference[] srl = framework.services
	.get(URLStreamHandlerService.class.getName(), filter);
      
      if(srl != null && srl.length > 0) {
	URLStreamHandlerWrapper wrapper = (URLStreamHandlerWrapper)
	  wrapMap.get(protocol);
	
	if(wrapper == null) {
	  wrapper = new URLStreamHandlerWrapper(framework, protocol);
	  wrapMap.put(protocol, wrapper);
	}

	return wrapper;
      }
    } catch (InvalidSyntaxException e) {
      throw new RuntimeException("Failed to get service: " + e);
    }

    // no handler found
    return null;
  }


  /**
   * Check if there exists a JVM classpath handler for a protocol.
   */
  URLStreamHandler getJVMClassPathHandler(String protocol) {

    for(int i = 0; i < jvmPkgs.length; i++) {
      String className = jvmPkgs[i] + "." + protocol + ".Handler";
      try { 
	if(Debug.url) {
	  Debug.println("JVMClassPath - trying URLHandler class=" + className);
	}
	Class clazz = Class.forName(className);
	URLStreamHandler handler = (URLStreamHandler)clazz.newInstance();

	if(Debug.url) {
	  Debug.println("JVMClassPath - created URLHandler class=" + className);
	}

	return handler;
      } catch (Throwable t) {
	if(Debug.url) {
	  Debug.println("JVMClassPath - no URLHandler class " + className);
	}
      }
    }
    
    if(Debug.url) {
      Debug.println("JVMClassPath - no URLHandler for " + protocol);
    }
    
    return null;
  }


  /**
   * Sets the handler for a named protocol. 
   *
   * <p>
   * Any old handler for the specified protocol will be lost.
   * </p>
   *
   * @param protocol Protocol name.
   * @param handler Handler for the specified protocl name.
   */
  void setURLStreamHandler(String protocol, URLStreamHandler handler) {
    handlers.put(protocol, handler);
  }
}