通过反射使用java 中不对外公开的类：

 

/***      * encode by Base64      */      public static String encodeBase64(byte[]input) throws Exception{          Class clazz=Class.forName("com.sun.org.apache.xerces.internal.impl.dv.util.Base64");          Method mainMethod= clazz.getMethod("encode", byte[].class);          mainMethod.setAccessible(true);           Object retObj=mainMethod.invoke(null, new Object[]{input});           return (String)retObj;      }      /***      * decode by Base64      */      public static byte[] decodeBase64(String input) throws Exception{          Class clazz=Class.forName("com.sun.org.apache.xerces.internal.impl.dv.util.Base64");          Method mainMethod= clazz.getMethod("decode", String.class);          mainMethod.setAccessible(true);           Object retObj=mainMethod.invoke(null, input);           return (byte[])retObj;      }