將Java異常信息保存到字符串中

/**
 * 將異常信息轉化成字符串
 * @param t
 * @return
 * @throws IOException 
 */
private static String exception(Throwable t) throws IOException{
	if(t == null)
		return null;
	ByteArrayOutputStream baos = new ByteArrayOutputStream();
	try{
		t.printStackTrace(new PrintStream(baos));
	}finally{
		baos.close();
	}
	return baos.toString();
}