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How to override a gRPC list method for implementation in a Java service

I have the following schema in my messages.proto file:
message Person {
string id = 1;
string first_name = 2;
string last_name = 3;
string email = 4;
string alias = 5;
}
//CREATE, DELETE, UPDATE RESPONSES AND REQUESTS Messages
message ListPersonsRequest {
ListOptions options = 1;
}
message ListPersonsResponse {
repeated Person person = 1;
string total_count = 2;
string total_pages = 3;
string next_page_token = 4;
}
I have the following schema in my services.proto file:
service PersonService {
//rpc methods to create, update, delete...
rpc ListPersons (ListPersonsRequest) returns (ListPersonsResponse) {
option (google.api.http) = {
get: "/person"
};
}
}
In my class 'ServiceImp':
#GrpcService
#AllArgsConstructor(onConstructor = #__(#Autowired))
public class PersonServiceImpl extends PersonServiceImplBase
{
private PersonRepository personRepository;
#Override
public void getPerson(GetPersonRequest request, StreamObserver<GetPersonResponse> responseObserver)
{
try
{
Person person = personRepository.findById(UUID.fromString(request.getId())).orElseThrow(() -> new EntityNotFoundException());
Person personProto = Person
.newBuilder()
.setId(person.getId().toString())
.setFirstName(person.getFirstName())
.setLastName(person.getLastName())
.setEmail(person.getEmail())
.setAlias(person.getAlias()).build();
GetPersonResponse response = GetPersonResponse.newBuilder().setPerson(personProto).build();
responseObserver.onNext(response);
responseObserver.onCompleted();
}
catch (EntityNotFoundException e)
{
responseObserver.onError(Status.NOT_FOUND.withCause(e).asException());
}
}
#Override
public void createPerson(CreatePersonRequest request, StreamObserver<CreatePersonResponse> responseObserver)
{
Person person = Person.builder().firstName(request.getPerson().getFirstName()).lastName(request.getPerson().getLastName()).email(request.getPerson().getEmail()).alias(request.getPerson().getAlias())
.build();
person = personRepository.save(person); // probably should handle errors
Person personProto = Person.newBuilder().setId(person.getId().toString()).setFirstName(person.getFirstName())
.setLastName(person.getLastName()).setEmail(person.getEmail()).setAlias(person.getAlias()).build();
CreatePersonResponse response = CreatePersonResponse.newBuilder().setPerson(personProto).build();
responseObserver.onNext(response);
responseObserver.onCompleted();
}
#Override
public void listPersons(ListPersonsRequest request, StreamObserver<ListPersonsResponse> responseObserver){
}
}
I'm trying to response a object which contains a list of all the created items, but I'm confused with how to implement it in my listPerson method, that I'm overriding from the created serviceGRPC
private static volatile io.grpc.MethodDescriptor<grpc.generated.ListPersonsRequest,
grpc.generated.ListPersonsResponse> getListPersonsMethod;
#io.grpc.stub.annotations.RpcMethod(
fullMethodName = SERVICE_NAME + '/' + "ListPersons",
requestType = grpc.generated.ListPersonsRequest.class,
responseType = grpc.generated.ListPersonsResponse.class,
methodType = io.grpc.MethodDescriptor.MethodType.UNARY)
public static io.grpc.MethodDescriptor<grpc.generated.ListPersonsRequest,
grpc.generated.ListPersonsResponse> getListPersonsMethod() {
io.grpc.MethodDescriptor<grpc.generated.ListPersonsRequest, grpc.generated.ListPersonsResponse> getListPersonsMethod;
if ((getListPersonsMethod = PersonServiceGrpc.getListPersonsMethod) == null) {
synchronized (PersonServiceGrpc.class) {
if ((getListPersonsMethod = PersonServiceGrpc.getListPersonsMethod) == null) {
PersonServiceGrpc.getListPersonsMethod = getListPersonsMethod =
io.grpc.MethodDescriptor.<grpc.generated.ListPersonsRequest, grpc.generated.ListPersonsResponse>newBuilder()
.setType(io.grpc.MethodDescriptor.MethodType.UNARY)
.setFullMethodName(generateFullMethodName(SERVICE_NAME, "ListPersons"))
.setSampledToLocalTracing(true)
.setRequestMarshaller(io.grpc.protobuf.ProtoUtils.marshaller(
grpc.generated.ListPersonsRequest.getDefaultInstance()))
.setResponseMarshaller(io.grpc.protobuf.ProtoUtils.marshaller(
grpc.generated.ListPersonsResponse.getDefaultInstance()))
.setSchemaDescriptor(new PersonServiceMethodDescriptorSupplier("ListPersons"))
.build();
}
}
}
return getListPersonsMethod;
}
#Override
public void listPersons(ListPersonsRequest request, StreamObserver<ListPersonsResponse> responseObserver){
//Heres were implement is cofused
}
I know that using a stream you are returning an iterator and that means you can start processing the Items on client even before the server has finished the gRPC response, but I'm using the entire object. Is there a way to return it with the stored values? How?

You don't need to do any streaming here. All you need to do is return your result by calling responseObserver.onNext(myListPersonsResponse) after constructing the response object.

How to create a domain object from a Json element?

the external web service returns me a Json file of the form
{"forecasts":[{"period_end":"2021-01-15T01:00:00.0000000Z","period":"PT30M","ghi90":0,"ghi":0,"ghi10":0},{"period_end":"2021-01-15T01:30:00.0000000Z","period":"PT30M","ghi90":0,"ghi":0,"ghi10":0},{"period_end":"2021-01-15T02:00:00.0000000Z","period":"PT30M","ghi90":0,"ghi":0,"ghi10":0}]}
Using RestRespone a transform an json element
RestResponse resp = rest.get(url)
resp.json instanceof JsonElement
How can I create a domain object from the Json element variable, knowing that my wrapper class is
class ForecastGhi {
static constraints = {
}
private ArrayList<IrradianciaGlobalHorizontal> forecast
ArrayList<IrradianciaGlobalHorizontal> getForecast() {
return forecast
}
void setForecast(ArrayList<IrradianciaGlobalHorizontal> forecast) {
this.forecast = forecast
}
}
and de persist domain class is
class IrradianciaGlobalHorizontal {
static constraints = {
}
#JsonProperty("all")
private def period_end
private def period
private def ghi90
private def ghi
private def ghi10
def getGhi() {
this.ghi
}
void setGhi(int ghi) {
this.ghi = ghi
}
def getGhi90() {
this.ghi90
}
void setGhi90(int ghi90) {
this.ghi90 = ghi90
}
def getGhi10() {
this.ghi10
}
void setGhi10(int ghi10) {
this.ghi10 = ghi10
}
def getPeriod_end() {
this.period_end
}
void setPeriod_end(Date period_end) {
this.period_end = period_end
}
def getPeriod() {
this.period
}
void setPeriod(String period) {
this.period = period
}
}
Help please; thanks a lot

This is an issue with your API implementation; The endpoint changed the domain field names &/or domain name. This will cause issues with bringing said data back in.
Either that or front-end is not matching the API docs for the endpoint.
Field names/domain names should match the domain/resource unless you are going for a level of obfuscation and then accept that you are going to need a middle layer to act as a translater (ie EDI).
You want output to be able to be read as input by the same endpoint by merely changing the request method.
My suggestion (easiest solution): change original endpoint to match domain/resource field names

If you have the opportunity to use Jackson library, you can do this:
ForecastGhi request = objectMapper.readValue(jsonAsText, ForecastGhi.class);
Create an objectMapper and configure to fail in case of unknown properties (just in case)
private String getJsonAsTextFromRest() {
String message = " {\"forecasts\":[{\"period_end\":\"2021-01-15T01:00:00.0000000Z\",\"period\":\"PT30M\",\"ghi90\":0,\"ghi\":0,\"ghi10\":0},{\"period_end\":\"2021-01-15T01:30:00.0000000Z\",\"period\":\"PT31M\",\"ghi90\":0,\"ghi\":0,\"ghi10\":0},{\"period_end\":\"2021-01-15T02:00:00.0000000Z\",\"period\":\"PT32M\",\"ghi90\":0,\"ghi\":0,\"ghi10\":0}]}";
return message;
}
#Override
public void run(String... arg0) throws Exception {
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, true);
objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
String jsonAsText = getJsonAsTextFromRest();
ForecastGhi request = objectMapper.readValue(jsonAsText, ForecastGhi.class);
request.getForecast().stream().forEach(it -> System.out.println(it.getPeriod() + " " + it.getGhi()));
}
public class IrradianciaGlobalHorizontal {
private Date period_end;
private String period;
private int ghi90;
private int ghi;
private int ghi10;
public int getGhi() {
return this.ghi;
}
public void setGhi(int ghi) {
this.ghi = ghi;
}
public int getGhi90() {
return this.ghi90;
}
public void setGhi90(int ghi90) {
this.ghi90 = ghi90;
}
public int getGhi10() {
return this.ghi10;
}
void setGhi10(int ghi10) {
this.ghi10 = ghi10;
}
public Date getPeriod_end() {
return this.period_end;
}
public void setPeriod_end(Date period_end) {
this.period_end = period_end;
}
public String getPeriod() {
return this.period;
}
public void setPeriod(String period) {
this.period = period;
}
}
ForecastGhi class.
import com.fasterxml.jackson.annotation.JsonProperty;
public class ForecastGhi {
private ArrayList<IrradianciaGlobalHorizontal> forecast;
#JsonProperty("forecasts")//It must be the same as the json property
public ArrayList<IrradianciaGlobalHorizontal> getForecast() {
return forecast;
}
#JsonProperty("forecasts")
public void setForecast(ArrayList<IrradianciaGlobalHorizontal> forecast) {
this.forecast = forecast;
}
}
Results:
PT30M 0
PT31M 0
PT32M 0
Dependencies Gradle:
compile group: 'com.fasterxml.jackson.core', name: 'jackson-core', version: '2.12.1'
Or
Dependencies Maven:
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>2.12.1</version>
</dependency>
Note: in your json example you use forecasts, but your java property name is forecast. In that case its necessary to decorate the property with #JsonProperty("forecasts"). If you dont do it, you get an error like this com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "forecasts"

how to use path variable in californium CoAP server?

Similar with Restful syntax in Jersey or other framework, I could fetch the variable in the Restful uri path like that:
#Path("/users/{username}")
public class UserResource {
#GET
#Produces("text/xml")
public String getUser(#PathParam("username") String userName) {
...
}
}
but in californium, the syntax is different, I try these codes but it is not correct:
class usersextends CoapResource {
public users() {
super("users/{username}");
}
#Override
public void handleGET(CoapExchange exchange) {
exchange.respond("The username is "+ ???????);
}
}
How could I use the same function as first piece of code did? Another thing is where I can find official document introduce the API? I just saw the source code and try to find the solution now.

Create your own MessageDeliverer and change findResource method:
public class MyMessageDeliverer implements MessageDeliverer {
private final Resource root;
public MyMessageDeliverer(Resource root) {
this.root = root;
}
/* You can use implementation of methods from ServerMessageDeliverer */
#Override
public void deliverRequest(Exchange exchange) {
}
#Override
public void deliverResponse(Exchange exchange, Response response) {
}
/* method returns last known Resource instead of null*/
private Resource findResource(List<String> list) {
LinkedList<String> path = new LinkedList<String>(list);
Resource current = root;
Resource last = null;
while (!path.isEmpty() && current != null) {
last = current;
String name = path.removeFirst();
current = current.getChild(name);
}
if (current == null) {
return last;
}
return current;
}
}
Use your MessageDeliverer:
server = new CoapServer();
server.setMessageDeliverer(new MyMessageDeliverer(server.getRoot()));
Add your Resource to server:
server.add(new Users());
Request /users/{username} will be delivered to your Users resource. Fetch the variable from request URI:
public class Users extends CoapResource {
public Users() {
super("users");
}
public void handleGet(CoapExchange exchange) {
List<String> uri = exchange.getRequestOptions().getUriPath();
uri.remove("users");
String username = uri.remove(0);
//for query params:
Map<String, String> params = new HashMap<String, String>();
for (String p : exchange.getRequestOptions().getUriQuery()) {
String[] parts = p.split("=");
params.put(parts[0], parts[1]);
}
String param = params.get("param");
}
}

Java, Storing JSON Array to class and calling it from other class

I am trying to pull data from class in another class and populate a JPanel with the data, but it is not working for some reason.
Here is the full restConnector class where I pull the JSON data.
As far as I know this works fine.
public class restConnector {
private static final Logger LOGGER = LoggerFactory.getLogger(restConnector.class);
private static final restConnector INSTANCE = new restConnector();
public static restConnector getInstance() {
return restConnector.INSTANCE;
}
private restConnector(){
}
private static String user = "ss";
private static String pwd = "ee
public static String encode(String user, String pwd) {
final String credentials = user+":"+pwd;
BASE64Encoder encoder = new sun.misc.BASE64Encoder();
return encoder.encode(credentials.getBytes());
}
//Open REST connection
public static void init() {
restConnector.LOGGER.info("Starting REST connection...");
try {
Client client = Client.create();
client.addFilter(new LoggingFilter(System.out));
WebResource webResource = client.resource("https://somewebpage.com/
String url = "activepersonal";
ClientResponse response = webResource
.path("api/alerts/")
.queryParam("filter", ""+url)
.header("Authorization", "Basic "+encode(user, pwd))
.header("x-api-version", "1")
.accept("Application/json")
.get(ClientResponse.class);
if (response.getStatus() != 200) {
}else{
restConnector.LOGGER.info("REST connection STARTED.");
}
String output = response.getEntity(String.class);
ObjectMapper mapper = new ObjectMapper();
mapper.setPropertyNamingStrategy(new MyNameStrategy());
try {
List<Alert> alert = mapper.readValue(output, new TypeReference<List<Alert>>(){});
} catch (JsonGenerationException e) {
e.printStackTrace();
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
} catch (Exception e) {
e.printStackTrace();
}
}
public void close() {
}
}
However, when I try to pull the data in another class it gives me just null values from the system.out.print inside refreshData() method. Here is the code that is supposed to print the data
public class Application{
Alert alerts = new Alert();
public Application() {
refreshData();
}
private void initComponents() {
restConnector.init();
refreshData();
}
private void refreshData() {
System.out.println("appalertList: "+alerts.getComponentAt(0));
}
}
Here is my Alert class
#JsonIgnoreProperties(ignoreUnknown = true)
#JsonInclude(Include.NON_EMPTY)
public class Alert {
private int pasID;
private String status;
private boolean shared;
private String header;
private String desc;
public int getPasID() {
return pasID;
}
public void setPasID(int pasID) {
this.pasID = pasID;
}
public String getStatus() {
return status;
}
public void setStatus(String status) {
this.status = status;
}
public boolean isShared() {
return shared;
}
public void setShared(boolean shared) {
this.shared = shared;
}
public String getHeader() {
return header;
}
public void setHeader(String header) {
this.header = header;
}
public String getDesc() {
return desc;
}
public void setDesc(String desc) {
this.desc = desc;
}
#Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("\n***** Alert Details *****\n");
sb.append("PasID="+getPasID()+"\n");
sb.append("Status="+getStatus()+"\n");
sb.append("Shared="+isShared()+"\n");
sb.append("Header="+getHeader()+"\n");
sb.append("Description="+getDesc()+"\n");
sb.append("*****************************");
return sb.toString();
}
public String getComponentAt(int i) {
return toString();
}
}
I'm kind a lost with this and been stuck here for a couple of days already so all help would be really appreciated. Thanks for the help in advance.
Edit: Formatted the code a bit and removed the NullPointerException as it was not happening anymore.

As stated in comments:
Me: In your first bit of code you have this try { List<Alert> alert.., but you do absolutely nothing with the newly declared alert List<Alert>. It this where the data is supposed to be coming from?
OP: I'm under the impression that that bit of code is the one that pushes the JSON Array to the Alert.class. Is there something I'm missing there?
Me: And what makes you think it does that? All it does is read the json, and the Alert.class argument is the class type argument, so the mapper know the results should be mapped to the Alert attributes when it creates the Alert objects. That's how doing List<Alert> is possible, because passing Alert.class decribes T in List<T>. The List<Alert> is what's returned from the reading, but you have to determine what to actually do with the list. And currently, you do absolutely nothing with it
You maybe want to change the class just a bit.
Now this is in no way a good design, just an example of how you can get it to work. I would take some time to sit and think about how you want the restConnector to be fully utilized
That being said, you can have a List<Alert> alerts; class member in the restConnector class. And have a getter for it
public class restConnector {
private List<Alert> alerts;
public List<Alert> getAlerts() {
return alerts;
}
...
}
Then when deserializing with the mapper, assign the value to private List<Alert> alerts. What you are doing is declaring a new locally scoped list. So instead of
try {
List<Alert> alert = mapper.readValue...
do this instead
try {
alerts = mapper.readValue
Now the class member is assigned a value. So in the Application class you can do something like
public class Application {
List<Alert> alerts;
restConnector connect;
public Application() {
initComponents();
}
private void initComponents() {
connector = restConnector.getInstance();
connector.init();
alerts = connector.getAlerts();
refreshData();
}
private void refreshData() {
StringBuilder sb = new StringBuilder();
for (Alert alert : alerts) {
sb.append(alert.toString()).append("\n");
}
System.out.println("appalertList: "+ sb.toString());
}
}
Now you have access to the Alerts in the list.
But let me reiterate: THIS IS A HORRIBLE DESIGN. For one you are limiting the init method to one single call, in which it is only able to obtain one and only one resource. What if the rest service needs to access a different resource? You have made the request set in stone, so you cant.
Take some time to think of some good OOP designs where the class can be used for different scenarios.

Robospice + Retrofit + ORMLite

I'm using Robospice with Retrofit ans ORMLite modules. Retrofit part working good. I have City model for Retrofit:
City.java:
public class City {
public int city_id;
public String name;
#SuppressWarnings("serial")
public static class List extends ArrayList<City> {
}
}
I'm taking this model from server by GET-request:
MyApi.java
public interface MyAPI {
#GET("/cities")
City.List getCities();
}
This part works fine by calling this method:
getSpiceManager().execute(mRequestCity, "city", DurationInMillis.ONE_MINUTE, new ListCityRequestListener());
and listener:
public final class ListCityRequestListener implements RequestListener<City.List> {
#Override
public void onRequestFailure(SpiceException spiceException) {
Toast.makeText(RegisterActivity.this, "failure", Toast.LENGTH_SHORT).show();
}
#Override
public void onRequestSuccess(final City.List result) {
Toast.makeText(RegisterActivity.this, "success", Toast.LENGTH_SHORT).show();
updateCities(result);
}
}
At this time i want to download city list once from server and store this list into sqlitedb by ORMLite module. I've created ORMLite model:
City.java
#DatabaseTable(tableName = "city")
public class City {
public final static String DB_CITY_ID_FIELD_NAME = "id";
public final static String DB_CITY_NAME_FIELD_NAME = "name";
#DatabaseField(canBeNull = false, dataType = DataType.INTEGER, columnName = DB_CITY_ID_FIELD_NAME)
int id;
#DatabaseField(canBeNull = false, dataType = DataType.STRING, columnName = DB_CITY_NAME_FIELD_NAME)
private String name;
public City() {
}
#Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("id = ").append(id);
sb.append(", ").append("name = ").append(name);
return sb.toString();
}
}
My RetrofitSpiceService.java looks like this:
public class RetrofitSpiceService extends RetrofitGsonSpiceService {
private final static String BASE_URL = "http://example.com/api/v1";
private final static UserFunctions userFunctions = new UserFunctions();
#Override
public CacheManager createCacheManager(Application application) throws CacheCreationException {
CacheManager cacheManager = new CacheManager();
List< Class< ? >> classCollection = new ArrayList< Class< ? >>();
// add persisted classes to class collection
classCollection.add( City.class );
// init
RoboSpiceDatabaseHelper databaseHelper = new RoboSpiceDatabaseHelper( application, "sample_database.db", 1 );
InDatabaseObjectPersisterFactory inDatabaseObjectPersisterFactory = new InDatabaseObjectPersisterFactory( application, databaseHelper, classCollection );
cacheManager.addPersister( inDatabaseObjectPersisterFactory );
return cacheManager;
}
#Override
protected Builder createRestAdapterBuilder() {
Builder mBuilder = super.createRestAdapterBuilder();
mBuilder.setRequestInterceptor(new RequestInterceptor() {
#Override
public void intercept(RequestFacade request) {
if (userFunctions.isUserLoggedIn()) {
request.addHeader("Authorization", userFunctions.getToken());
}
}
});
return mBuilder;
}
#Override
public void onCreate() {
super.onCreate();
addRetrofitInterface(MyAPI.class);
}
#Override
protected String getServerUrl() {
return BASE_URL;
}
}
I can't understand how can i store and read data from my City database? How do i need to change RetrofitSpiceService? I want download data by Retrofit and store it to database by ORMLite. My CacheManager is correct, i.e. will work properly? Maybe I misunderstand how the module Robospice-ORMLite works?
Thanks a lot!

When you make execute() call with cache key and duration Robospice will store your response into database.
getSpiceManager().execute(mRequestCity, "city", DurationInMillis.ONE_MINUTE, new ListCityRequestListener());
All following requests during one minute will get data from this cache, and then it makes network call. If you want to get data only from cache take a look on getSpiceManager().getFromCache() method. I think it's what you are looking for.