关于JSONObject取值方法getString()与optString()

用JSON这么久，刚发现JSONObject的getString()暗藏炸弹！！！

public Map<String, Object> queryalmMonitorInfo(@RequestBody String jsonStr)
    {
        JSONObject json = JSONObject.fromObject(jsonStr);
        // 当前页码
        int currentPage = json.getInt(SysConstant.PAGE);
        // 每页条数
        int pageSize = json.getInt(SysConstant.ROWS);
        Map<String, Object> mape = new HashMap<String, Object>();
        String areaid = json.getString("areaids");
        JSONArray areaids = JSONArray.fromObject(areaid);
        @SuppressWarnings("unchecked")
        List<String> areaIdlist = (List<String>) JSONArray.toCollection(areaids,
                String.class);

        String sysAndeqp = json.getString("eqpLists");
        List<String> eqpLists;
        if ("".equals(sysAndeqp)) {
            eqpLists = null;
        }
        else {

            JSONArray eqpList = JSONArray.fromObject(sysAndeqp);
            eqpLists = (List<String>) JSONArray.toCollection(eqpList,
                    String.class);
        }
        String sysEmsId = json.getString("sysEmsId");
        String techType = json.getString("techType");
        List<String> sysEmsIds;
        if ("".equals(sysEmsId)) {
            sysEmsIds = null;
        }
        else {
            /*
             * JSONArray sysEmsIdList = JSONArray.fromObject(sysEmsId);
             * sysEmsIds = (List<String>) JSONArray.toCollection(sysEmsIdList,
             * String.class);
             */

            String[] arr = sysEmsId.split(",");
            sysEmsIds = Arrays.asList(arr);

        }
        List<String> techTypes;
        if ("".equals(techType)) {
            techTypes = null;
        }
        else {
            /*
             * JSONArray techTypeList = JSONArray.fromObject(techType);
             * techTypes = (List<String>) JSONArray.toCollection(techTypeList,
             * String.class);
             */
            String[] arr1 = techType.split(",");
            techTypes = Arrays.asList(arr1);
        }
        String keyword = json.getString("keyword");
        String alarmLevel = json.getString("alarmLevel");
        String neEmsId = json.getString("neEmsId");
        String shelfEmsId = json.getString("shelfEmsId");
        String slotEmsId = json.getString("slotEmsId");
        int cardEmsId = json.getInt("cardEmsId");
        String isConf = json.getString("isConf");
        String portEmsId = json.getString("portEmsId");
        PageVo pageVo = PageUtil.assemblePageVo(currentPage, pageSize);
        mape.put("keyword", keyword);
        mape.put("alarmLevel", alarmLevel);
        mape.put("techType", techTypes);
        mape.put("areaId", areaIdlist);
        mape.put("sysEmsId", sysEmsIds);
        mape.put("neEmsId", neEmsId);
        mape.put("shelfEmsId", shelfEmsId);
        mape.put("slotEmsId", slotEmsId);
        mape.put("cardEmsId", cardEmsId);
        mape.put("portEmsId", portEmsId);
        mape.put("sysAndeqp", eqpLists);
        mape.put("isConf", isConf);
        //新加条件20180628
        mape.put("isDamage", json.optString("isDamage"));
        mape.put("techTypeName", json.optString("techTypeName"));
        mape.put("sysName", json.optString("sysName"));
        mape.put("neTypeName", json.optString("neTypeName"));
        mape.put("alarmLevelOriginal", json.optString("alarmLevelOriginal"));
        mape.put("alarmNeTimeStar", json.optString("alarmNeTimeStar"));
        mape.put("alarmNeTimeEnd", json.optString("alarmNeTimeEnd"));
        mape.put("ruleDesc", json.optString("ruleDesc"));
        mape.put("projectName", json.optString("projectName"));
        PageVo resPageVo = almMonitorService.getNetworkScaleAnalysis(pageVo, mape);
        Map<String, Object> map = new HashMap<String, Object>();
        map.put(SysConstant.ROWS, resPageVo.getVoList());
        map.put(SysConstant.TOTAL, resPageVo.getRecordCount());
        return map;
    }

项目用的SpringMVC，前端报错经过调试为此方法没有返回值，由于这是别人写的代码并没有try catch（这里表示气愤！！！），经过一点一点debug发现getString()方法无缘无故抛异常了，问了下度娘发现这个方法有雷：当JSONObject中不存在某key的时候就抛异常，而optString()不会，前端写的是自定义条件查询，JSONObject中的key并不是固定不变的，所以这里改为用optString()方法，mybatis配置的sql中有判断，不会影响查询。