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。