我是 JAVA 新手，但我知道 Objective-C。我必须编写一个服务器端自定义代码，但下面的代码有问题：
/**
* This example will show a user how to write a custom code method
* with two parameters that updates the specified object in their schema
* when given a unique ID and a `year` field on which to update.
*/
public class UpdateObject implements CustomCodeMethod {
@Override
public String getMethodName() {
return "CRUD_Update";
}
@Override
public List<String> getParams() {
return Arrays.asList("car_ID","year");
}
@Override
public ResponseToProcess execute(ProcessedAPIRequest request, SDKServiceProvider serviceProvider) {
String carID = "";
String year = "";
LoggerService logger = serviceProvider.getLoggerService(UpdateObject.class);
logger.debug(request.getBody());
Map<String, String> errMap = new HashMap<String, String>();
/* The following try/catch block shows how to properly fetch parameters for PUT/POST operations
* from the JSON request body
*/
JSONParser parser = new JSONParser();
try {
Object obj = parser.parse(request.getBody());
JSONObject jsonObject = (JSONObject) obj;
// Fetch the values passed in by the user from the body of JSON
carID = (String) jsonObject.get("car_ID");
year = (String) jsonObject.get("year");
//Q1: This is assigning the values to fields in the fetched Object?
} catch (ParseException pe) {
logger.error(pe.getMessage(), pe);
return Util.badRequestResponse(errMap, pe.getMessage());
}
if (Util.hasNulls(year, carID)){
return Util.badRequestResponse(errMap);
}
//Q2: Is this creating a new HashMap? If so, why is there a need?
Map<String, SMValue> feedback = new HashMap<String, SMValue>();
//Q3: This is taking the key "updated year" and assigning a value (year)? Why?
feedback.put("updated year", new SMInt(Long.parseLong(year)));
DataService ds = serviceProvider.getDataService();
List<SMUpdate> update = new ArrayList<SMUpdate>();
/* Create the changes in the form of an Update that you'd like to apply to the object
* In this case I want to make changes to year by overriding existing values with user input
*/
update.add(new SMSet("year", new SMInt(Long.parseLong(year))));
SMObject result;
try {
// Remember that the primary key in this car schema is `car_id`
//Q4: If the Object is updated earlier with update.add... What is the code below doing?
result = ds.updateObject("car", new SMString(carID), update);
//Q5: What's the need for the code below?
feedback.put("updated object", result);
} catch (InvalidSchemaException ise) {
return Util.internalErrorResponse("invalid_schema", ise, errMap); // http 500 - internal server error
} catch (DatastoreException dse) {
return Util.internalErrorResponse("datastore_exception", dse, errMap); // http 500 - internal server error
}
return new ResponseToProcess(HttpURLConnection.HTTP_OK, feedback);
}
}
Q1：下面的代码是将值分配给获取的对象中的字段？
carID = (String) jsonObject.get("car_ID");
year = (String) jsonObject.get("year");
Q2：这是在创建一个新的HashMap吗？如果是这样，为什么需要？
Map<String, SMValue> feedback = new HashMap<String, SMValue>();
Q3：这是取键“更新年份”并赋值（年份）？为什么？
feedback.put("updated year", new SMInt(Long.parseLong(year)));
Q4：如果 Object 之前用 update.add 更新过……下面的代码是做什么的？
result = ds.updateObject("car", new SMString(carID), update);
Q5：下面的代码是做什么的？
feedback.put("updated object", result);