SQL解析

     private static String getCountSql(String sql) {
         return "select count(*) from "+cutOrderByOrGroupBy(getFromHql(sql));
     }

     private static String cutOrderByOrGroupBy(String hql) {
         int lastFromIndex = hql.lastIndexOf(" from ");
         int lastOG = hql.lastIndexOf(" order by ");
         if (lastOG < 0) {
             lastOG = hql.lastIndexOf(" group by ");
         }
         if (lastFromIndex < lastOG) {
             return hql.substring(0, lastOG);
         }
         return hql;
     }

     private static String getFromHql(String sql) {
         String tmpSql = sql;
         int fIndex = tmpSql.indexOf(" from ");
         tmpSql = tmpSql.substring(fIndex+5);
         //确保from没被( 和 )包裹起来，即为该语句主from
         if (!equalOpenAndCloseParenthesis(tmpSql)) {
             tmpSql = getFromHql(tmpSql);
         }
         return tmpSql;
     }

     private static Boolean equalOpenAndCloseParenthesis(String subSql) {
         final Pattern opPattern = Pattern.compile("\\(");
         final Matcher opMatch = opPattern.matcher(subSql);
         final List<String> opMatches = new ArrayList<String>();
         while (opMatch.find()) {
             opMatches.add(opMatch.group(0));
         }
         final Pattern cpPattern = Pattern.compile("\\)");
         final Matcher cpMatch = cpPattern.matcher(subSql);
         final List<String> cpMatches = new ArrayList<String>();
         while (cpMatch.find()) {
             cpMatches.add(cpMatch.group(0));
         }
         return opMatches.size() == cpMatches.size();
     }

根据from左右两侧括号情况判断某个from是否是主sql的from关键字。