ProtectionDomain 详细解释

对于很对方法，如何加载和寻找类，我做了一个小小的总结，这里用代码表示

A.java 和 B.java放在同一包下，再各种情况下，A如何寻找B,默认是在Eclipse编辑环境下

URL url = A.class.getProtectionDomain().getCodeSource()
    .getLocation();

System.out.println(url);

结果（未打成JAR时）:

file:/C:/Documents and Settings/Administrator.MICROSOF-B715C3/workspace/T/bin/

结果(打成JAR时)

file:/C:/Documents and Settings/Administrator.MICROSOF-B715C3/%e6%a1%8c%e9%9d%a2/1.jar

那么如何加载这个jar中的类呢

JarFile file = new JarFile(url.getFile());

接下来就是URLClassLoader得方法了，这部分参看我得另外一篇:http://blog.youkuaiyun.com/neusoftware_20063500/archive/2009/02/15/3894289.aspx

URL url = ClassLoader.getSystemResource("B.class");

System.out.println(url);

结果（未打成jar）

file:/C:/Documents and Settings/Administrator.MICROSOF-B715C3/workspace/T/bin/B.class

结果(打成jar)

jar:file:/C:/Documents and Settings/Administrator.MICROSOF-B715C3/%e6%a1%8c%e9%9d%a2/1.jar!/B.class

InputStream resourceAsStream = A.class.getResourceAsStream("B.class");
System.out.println(resourceAsStream);

结果(未打成jar)是class文件得流

结果(打成jar)是jar得输入流

http://hi.baidu.com/a26816523/item/5c9fce339035d4be623aff76