替换url 中的某个参数。

replaceUrlPara.java

	protected static String getRealPlayUrl(String playUrlWithTempSig, String sig) {
		// http://r13---sn-a5m7ln7r.googlevideo.com/videoplayback?
		// sparams=gcr%2Cid%2Cinitcwndbps%2Cip%2Cipbits%2Citag%2Cratebypass%2Csource%2Cupn%2Cexpire&source=youtube
		// &signature=74A5A84D017C326B86FBB2515BD6C00BCD85133A.E1CB6514CD41B99045FF236A3F7CF0F50F4AEC14&itag=22&key=yt5&mws=yes&gcr=cn&ms=au
		// &ipbits=0&ratebypass=yes&expire=1406281956&upn=raAqucAppMU&id=o-AP5UIALOxGG5ae6zN-JNagnKvRQa_WtGXk8czf3NgFuW&mv=u&sver=3&ip=199.245.60.115
		// &fexp=902408%2C924222%2C927622%2C934024%2C934030%2C941431%2C945066%2C946023&mt=1406260337&initcwndbps=1093375
		String realUrl = playUrlWithTempSig.replaceFirst("signature="+"[^&]*", "signature="+sig);
		System.out.println("======= realUrl ======="+realUrl);
		return realUrl;
	}