判断JSONObject是否存在某个Key
JSONObject jsonObj = new JSONObject();
jsonObj.put("version", "1.0.0"); // 版本号
jsonObj.put("encoding", "UTF-8"); // 编码方式判断jsonObject是否存在vesion属性
jsonObj.has("version"); // 返回true检查json字符串中是否存在该key
初衷，是由于工作需要，两个单位需要接口数据对接，单位一需要发送json数据串到单位二，然而单位一发送的json数据中的字段不确定，听他们解释说，客户在系统上输那些字段，他们就会把那些字段带过来，然后那些客户不输入的字段，他们就会默认不带。单位一要求单位二，将这种检测出不带的字段默认值为空！
所以作为单位二，我们就需要想办法检测到单位一哪些字段没带过来。起初立马想到的办法就是用异常情况处理，因为程序本身测试的时候就报not found了，所以用异常处理情有可原吧。。。如果用异常的，想了一下只能捕捉到not found之后，在finally里将捕捉到的这个字段直接置空就ok了。
那么问题来了，对异常的情况试了一下，finally太多不好处理；所以就想了用另外一个方法，用json的一个containsKey()函数来判断json串中是否存在这个key，即是否存在这个字段；当然，还有其他函数也可以判断的，这个根据自己引入的json包了。
下面介绍我自己的情况
导入的jar包为：
首先我导入的json包：
import net.sf.json.JSONArray;
import net.sf.json.JSONObject;代码如下：
public String dateRepository(String jsonData) {
Log4jBean.logger.info("开始处理入库程序!");
ReadConfig.PullConfigXml(); //启动配置文件
DBUtils db = new DBUtils();
JSONObject json=new JSONObject();
String jsonStr=jsonData.substring(44, jsonData.length());
JSONObject jsonObject = JSONObject.fromObject(jsonStr);
JSONObject jsonCard=jsonObject.getJSONObject("cardid_info")
JSONObject jsonObu = jsonObject.getJSONObject("obu_info");
JSONObject jsonUser=jsonObject.getJSONObject("user_info");
JSONObject jsonCar = jsonObject.getJSONObject("car_info");
//准备将所有json数据信息入开卡集合表ETC_OPEN_CARD_COLLECTION
JSONObject jsonAccno = jsonObject.getJSONObject("accno_info");
String allSql = "insert into ETC_OPEN_CARD_COLLECTION(ACCOUNTID,LINKMOBILE,ACCNO_USERNAME,CERTSN,POSID,GENTIME,TRX_SERNO,EMPLOYEEID,ORG_TRX_SERNO,CARD_ID,CARDTYPE,CARD_BRAND,CARD_MODEL,AGENCYID,CARD_USERID,VEHICLEID,ENABLETIME,EXPIRETIME,ISSUEDTYPE,CHANNELID,ISSUEDTIME,CARD_STATUS,STATUSCHANGETIME,CARD_OPERATION,OBU_ID,OBU_BRAND,OBU_MODEL,OBU_USERID,OBU_VEHICLEID,OBU_ENABLETIME,OBU_EXPIRETIME,REGISTEREDTYPE,REGISTEREDCHANNELID,REGISTEREDTIME,INSTALLTYPE,INSTALLCHANNELID,INSTALLTIME,OBU_STATUS,OBU_STATUSCHANGETIME,OBU_OPERATION,USER_ID,USERTYPE,USER_NAME,USERIDTYPE,USERIDNUM,USER_TEL,USER_ADDRESS,USER_REGISTEREDTYPE,USER_CHANNELID,USER_REGISTEREDTIME,DEPARTMENT,AGENTNAME,AGENTIDTYPE,AGENTIDNUM,USER_STATUS,USER_STATUSCHANGETIME,USER_OPERATION,CAR_ID,CAR_TYPE,CAR_USERID,OWNERNAME,OWNERIDTYPE,OWNERIDNUM,OWNERTEL,CAR_ADDRESS,CAR_CONTACT,CAR_REGISTEREDTYPE,CAR_CHANNELID,CAR_REGISTEREDTIME,VEHICLETYPE,VEHICLEMODEL,USECHARACTER,VIN,ENGINENUM,REGISTERDATE,ISSUEDATE,FILENUM,APPROVEDCOUNT,TOTALMASS,MAINTENANCEMASS,PERMITTEDWEIGHT,OUTSIDEDIMENSIONS,PERMITTEDTOWWEIGHT,TESTRECORD,WHEELCOUNT,AXLECOUNT,AXLEDISTANCE,AXISTYPE,CAR_OPERATION) values('"
+ (jsonAccno.containsKey("accountid")?jsonAccno.getString("accountid"):"")
+ "','"
+ (jsonAccno.containsKey("linkmobile")?jsonAccno.getString("linkmobile"):"")
+ "','"
+ (jsonAccno.containsKey("username")?jsonAccno.getString("username"):"")
+ "','"
+ (jsonAccno.containsKey("certsn")?jsonAccno.getString("certsn"):"")
+ "','"
+ (jsonAccno.containsKey("posid")?jsonAccno.getString("posid"):"")
+ "','"
+ (jsonAccno.containsKey("gentime")?jsonAccno.getString("gentime"):"")
+ "','"
+ (jsonAccno.containsKey("trx_serno")?jsonAccno.getString("trx_serno"):"")
+ "','"
+ (jsonAccno.containsKey("employeeid")?jsonAccno.getString("employeeid"):"")
+ "','"
+ (jsonAccno.containsKey("org_trx_serno")?jsonAccno.getString("org_trx_serno"):"")
+ "','"
+ (jsonCard.containsKey("id")?jsonCard.getString("id"):"")
+ "','"
+ (jsonCard.containsKey("cardType")?jsonCard.getString("cardType"):"")
+ "','"
+ (jsonCard.containsKey("brand")?jsonCard.getString("brand"):"")
+ "','"
+ (jsonCard.containsKey("model")?jsonCard.getString("model"):"")
+ "','"
+ (jsonCard.containsKey("agencyId")?jsonCard.getString("agencyId"):"")
+ "','"
+ (jsonCard.containsKey("userId")?jsonCard.getString("userId"):"")
+ "','"
+ (jsonCard.containsKey("vehicleId")?jsonCard.getString("vehicleId"):"")
+ "','"
+ (jsonCard.containsKey("enableTime")?jsonCard.getString("enableTime"):"")
+ "','"
+ (jsonCard.containsKey("expireTime")?jsonCard.getString("expireTime"):"")
+ "','"
+ (jsonCard.containsKey("issuedType")?jsonCard.getString("issuedType"):"")
+ "','"
+ (jsonCard.containsKey("channelId")?jsonCard.getString("channelId"):"")
+ "','"
+ (jsonCard.containsKey("issuedTime")?jsonCard.getString("issuedTime"):"")
+ "','"
+ (jsonCard.containsKey("status")?jsonCard.getString("status"):"")
+ "','"
+ (jsonCard.containsKey("statusChangeTime")?jsonCard.getString("statusChangeTime"):"")
+ "','"
+ (jsonCard.containsKey("operation")?jsonCard.getString("operation"):"")
+ "','"
+ (jsonObu.containsKey("id")?jsonObu.getString("id"):"")
+ "','"
+ (jsonObu.containsKey("brand")?jsonObu.getString("brand"):"")
+ "','"
+ (jsonObu.containsKey("model")?jsonObu.getString("model"):"")
+ "','"
+ (jsonObu.containsKey("userId")?jsonObu.getString("userId"):"")
+ "','"
+ (jsonObu.containsKey("vehicleId")?jsonObu.getString("vehicleId"):"")
+ "','"
+ (jsonObu.containsKey("enableTime")?jsonObu.getString("enableTime"):"")
+ "','"
+ (jsonObu.containsKey("expireTime")?jsonObu.getString("expireTime"):"")
+ "','"
+ (jsonObu.containsKey("registeredType")?jsonObu.getString("registeredType"):"")
+ "','"
+ (jsonObu.containsKey("registeredChannelId")?jsonObu.getString("registeredChannelId"):"")
+ "','"
+ (jsonObu.containsKey("registeredTime")?jsonObu.getString("registeredTime"):"")
+ "','"
+ (jsonObu.containsKey("installType")?jsonObu.getString("installType"):"")
+ "','"
+ (jsonObu.containsKey("installChannelId")?jsonObu.getString("installChannelId"):"")
+ "','"
+ (jsonObu.containsKey("installTime")?jsonObu.getString("installTime"):"")
+ "','"
+ (jsonObu.containsKey("status")?jsonObu.getString("status"):"")
+ "','"
+ (jsonObu.containsKey("statusChangeTime")?jsonObu.getString("statusChangeTime"):"")
+ "','"
+ (jsonObu.containsKey("operation")?jsonObu.getString("operation"):"")
+ "','"
+ (jsonUser.containsKey("id")?jsonUser.getString("id"):"")
+ "','"
+ (jsonUser.containsKey("userType")?jsonUser.getString("userType"):"")
+ "','"
+ (jsonUser.containsKey("userName")?jsonUser.getString("userName"):"")
+ "','"
+ (jsonUser.containsKey("userIdType")?jsonUser.getString("userIdType"):"")
+ "','"
+ (jsonUser.containsKey("userIdNum")?jsonUser.getString("userIdNum"):"")
+ "','"
+ (jsonUser.containsKey("tel")?jsonUser.getString("tel"):"")
+ "','"
+ (jsonUser.containsKey("address")?jsonUser.getString("address"):"")
+ "','"
+ (jsonUser.containsKey("registeredType")?jsonUser.getString("registeredType"):"")
+ "','"
+ (jsonUser.containsKey("channelId")?jsonUser.getString("channelId"):"")
+ "','"
+ (jsonUser.containsKey("registeredTime")?jsonUser.getString("registeredTime"):"")
+ "','"
+ (jsonUser.containsKey("department")?jsonUser.getString("department"):"")
+ "','"
+ (jsonUser.containsKey("agentName")?jsonUser.getString("agentName"):"")
+ "','"
+ (jsonUser.containsKey("agentIdType")?jsonUser.getString("agentIdType"):"")
+ "','"
+ (jsonUser.containsKey("agentIdNum")?jsonUser.getString("agentIdNum"):"")
+ "','"
+ (jsonUser.containsKey("status")?jsonUser.getString("status"):"")
+ "','"
+ (jsonUser.containsKey("statusChangeTime")?jsonUser.getString("statusChangeTime"):"")
+ "','"
+ (jsonUser.containsKey("operation")?jsonUser.getString("operation"):"")
+ "','"
+ (jsonCar.containsKey("id")?jsonCar.getString("id"):"")
+ "','"
+ (jsonCar.containsKey("type")?jsonCar.getString("type"):"")
+ "','"
+ (jsonCar.containsKey("userId")?jsonCar.getString("userId"):"")
+ "','"+
(jsonCar.containsKey("ownerName")?jsonCar.getString("ownerName"):"")
+ "','"+
(jsonCar.containsKey("ownerIdType")?jsonCar.getString("ownerIdType"):"")
+ "','"+
(jsonCar.containsKey("ownerIdNum")?jsonCar.getString("ownerIdNum"):"")
+ "','"+
(jsonCar.containsKey("ownerTel")?jsonCar.getString("ownerTel"):"")
+ "','"+
(jsonCar.containsKey("address")?jsonCar.getString("address"):"")
+ "','"+
(jsonCar.containsKey("contact")?jsonCar.getString("contact"):"")
+ "','"+
(jsonCar.containsKey("registeredType")?jsonCar.getString("registeredType"):"")
+ "','"+
(jsonCar.containsKey("channelId")?jsonCar.getString("channelId"):"")
+ "','"+
(jsonCar.containsKey("registeredTime")?jsonCar.getString("registeredTime"):"")
+ "','"+
(jsonCar.containsKey("vehicleType")?jsonCar.getString("vehicleType"):"")
+ "','"+
(jsonCar.containsKey("vehicleModel")?jsonCar.getString("vehicleModel"):"")
+ "','"+
(jsonCar.containsKey("useCharacter")?jsonCar.getString("useCharacter"):"")
+ "','"+
(jsonCar.containsKey("VIN")?jsonCar.getString("VIN"):"")
+ "','"+
(jsonCar.containsKey("engineNum")?jsonCar.getString("engineNum"):"")
+ "','"+
(jsonCar.containsKey("registerDate")?jsonCar.getString("registerDate"):"")
+ "','"+
(jsonCar.containsKey("issueDate")?jsonCar.getString("issueDate"):"")
+ "','"+
(jsonCar.containsKey("fileNum")?jsonCar.getString("fileNum"):"")
+ "','"+
(jsonCar.containsKey("approvedCount")?jsonCar.getString("approvedCount"):"")
+ "','"+
(jsonCar.containsKey("totalMass")?jsonCar.getString("totalMass"):"")
+ "','"+
(jsonCar.containsKey("maintenanceMass")?jsonCar.getString("maintenanceMass"):"")
+ "','"+
(jsonCar.containsKey("permittedWeight")?jsonCar.getString("permittedWeight"):"")
+ "','"+
(jsonCar.containsKey("outsideDimensions")?jsonCar.getString("outsideDimensions"):"")
+ "','"+
(jsonCar.containsKey("permittedTowWeight")?jsonCar.getString("permittedTowWeight"):"")
+ "','"+
(jsonCar.containsKey("testRecord")?jsonCar.getString("testRecord"):"")
+ "','"+
(jsonCar.containsKey("wheelCount")?jsonCar.getString("wheelCount"):"")
+ "','"+
(jsonCar.containsKey("axleCount")?jsonCar.getString("axleCount"):"")
+ "','"+
(jsonCar.containsKey("axleDistance")?jsonCar.getString("axleDistance"):"")
+ "','"+
(jsonCar.containsKey("axisType")?jsonCar.getString("axisType"):"")
+ "','"+
(jsonCar.containsKey("operation")?jsonCar.getString("operation"):"")
+ "')";
int allParam = db.updateMethod(allSql, null);
if (allParam > 0) {
Log4jBean.logger.info("开卡集合数据写入开卡集合表成功!");
json.put("return_msg", "处理成功!");
json.put("return_code", "0");
} else {
Log4jBean.logger.error("开卡集合数据写入开卡集合表失败!");
json.put("return_msg", "处理失败!");
json.put("return_code", "-1");
}
return json.toString();
}通过代码可以看出，每个字段都用containsKey()函数做了处理，这样就不用害怕单位一发过来的j'son串中哪个字段找不到的情况了；
最后经测试已成功入库。。
以上为个人经验，希望能给大家一个参考，也希望大家多多支持编程网。
