Pattern pattern = Pattern.compile("开头.*?结束.*?结束|开头.*?结束", Pattern.DOTALL);
Pattern p = Pattern.compile("server_name.*?;"); //以server_name开始 ; 结束
Matcher m = p.matcher(ym);
List<String> result = new ArrayList<String>();
while (m.find()) {
result.add(m.group(0));
}