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luismrluismr
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🍮 Now Flight Tracker uses Command Query Segregation instead of Use Cases 🤭
1 parent e167e32 commit b328f88

23 files changed

Lines changed: 600 additions & 223 deletions

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‎src/main/java/dev/luismachadoreis/flighttracker/server/common/application/cqs/command/Command.java‎

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package dev.luismachadoreis.flighttracker.server.common.application.cqs.command;
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/*
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* This interface is a marker interface for commands that return a result of type R.
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*/
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public interface Command<R> {}

‎src/main/java/dev/luismachadoreis/flighttracker/server/common/application/cqs/command/CommandHandler.java‎

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package dev.luismachadoreis.flighttracker.server.common.application.cqs.command;
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/*
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* This interface is a marker interface for command handlers that return a result of type R.
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*/
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public interface CommandHandler<C extends Command<R>, R> {
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/*
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* This method handles a command and returns a result of type R.
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*/
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R handle(C command);
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}

‎src/main/java/dev/luismachadoreis/flighttracker/server/common/application/cqs/mediator/Mediator.java‎

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package dev.luismachadoreis.flighttracker.server.common.application.cqs.mediator;
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import dev.luismachadoreis.flighttracker.server.common.application.cqs.command.Command;
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import dev.luismachadoreis.flighttracker.server.common.application.cqs.query.Query;
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/*
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* This interface is a mediator that sends commands and queries to the application context.
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*/
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public interface Mediator {
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/*
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* This method sends a command to the application context and returns the result.
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*/
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<R> R send(Command<R> command);
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/*
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* This method sends a query to the application context and returns the result.
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*/
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<R> R send(Query<R> query);
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}

‎src/main/java/dev/luismachadoreis/flighttracker/server/common/application/cqs/mediator/SpringMediator.java‎

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package dev.luismachadoreis.flighttracker.server.common.application.cqs.mediator;
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import org.springframework.context.ApplicationContext;
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import org.springframework.core.GenericTypeResolver;
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import org.springframework.stereotype.Component;
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import dev.luismachadoreis.flighttracker.server.common.application.cqs.command.Command;
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import dev.luismachadoreis.flighttracker.server.common.application.cqs.command.CommandHandler;
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import dev.luismachadoreis.flighttracker.server.common.application.cqs.query.Query;
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import dev.luismachadoreis.flighttracker.server.common.application.cqs.query.QueryHandler;
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import java.util.Arrays;
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import java.util.Objects;
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/*
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* This class is a mediator that sends commands and queries to the application context.
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*/
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@Component
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public class SpringMediator implements Mediator {
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private final ApplicationContext applicationContext;
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/*
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* This constructor injects the application context into the mediator.
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*/
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public SpringMediator(ApplicationContext applicationContext) {
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this.applicationContext = applicationContext;
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}
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/*
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* This method sends a command to the application context and returns the result.
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*/
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@Override
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@SuppressWarnings("unchecked")
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public <R> R send(Command<R> command) {
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Objects.requireNonNull(command, "Command cannot be null");
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Class<?> commandClass = command.getClass();
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return Arrays.stream(applicationContext.getBeanNamesForType(CommandHandler.class))
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.map(applicationContext::getBean)
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.filter(handler -> {
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Class<?>[] generics = GenericTypeResolver.resolveTypeArguments(handler.getClass(), CommandHandler.class);
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return generics != null && generics[0].equals(commandClass);
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})
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.findFirst()
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.map(
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handler -> ((CommandHandler<Command<R>, R>) handler).handle(command)
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)
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.orElseThrow(
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() -> new IllegalStateException("No handler found for command: %s".formatted(commandClass.getName()))
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);
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}
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/*
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* This method sends a query to the application context and returns the result.
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*/
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@Override
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@SuppressWarnings("unchecked")
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public <R> R send(Query<R> query) {
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Objects.requireNonNull(query, "Query cannot be null");
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Class<?> queryClass = query.getClass();
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return Arrays.stream(applicationContext.getBeanNamesForType(QueryHandler.class))
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.map(applicationContext::getBean)
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.filter(handler -> {
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Class<?>[] generics = GenericTypeResolver.resolveTypeArguments(handler.getClass(), QueryHandler.class);
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return generics != null && generics[0].equals(queryClass);
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})
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.findFirst()
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.map(
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handler -> (
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(QueryHandler<Query<R>, R>) handler).handle(query)
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)
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.orElseThrow(
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() -> new IllegalStateException("No handler found for query: %s".formatted(queryClass.getName()))
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);
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}
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}

‎src/main/java/dev/luismachadoreis/flighttracker/server/common/application/cqs/query/Query.java‎

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package dev.luismachadoreis.flighttracker.server.common.application.cqs.query;
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/*
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* This interface is a marker interface for queries that return a result of type R.
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*/
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public interface Query<R> {}

‎src/main/java/dev/luismachadoreis/flighttracker/server/common/application/cqs/query/QueryHandler.java‎

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package dev.luismachadoreis.flighttracker.server.common.application.cqs.query;
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/*
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* This interface is a marker interface for query handlers that return a result of type R.
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*/
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public interface QueryHandler<Q extends Query<R>, R> {
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/*
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* This method handles a query and returns a result of type R.
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*/
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R handle(Q query);
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}

src/main/java/dev/luismachadoreis/flighttracker/server/ping/infrastructure/kafka/FlightDataConsumerConfig.java renamed to src/main/java/dev/luismachadoreis/flighttracker/server/flightdata/infrastructure/kafka/FlightDataConsumerConfig.java

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package dev.luismachadoreis.flighttracker.server.ping.infrastructure.kafka;
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package dev.luismachadoreis.flighttracker.server.flightdata.infrastructure.kafka;
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import dev.luismachadoreis.flighttracker.server.ping.application.dto.FlightDataDTO;
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src/main/java/dev/luismachadoreis/flighttracker/server/ping/infrastructure/pubsub/flightdata/FlightDataSubscriber.java renamed to src/main/java/dev/luismachadoreis/flighttracker/server/flightdata/infrastructure/pubsub/FlightDataSubscriber.java

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package dev.luismachadoreis.flighttracker.server.ping.infrastructure.pubsub.flightdata;
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package dev.luismachadoreis.flighttracker.server.flightdata.infrastructure.pubsub;
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import dev.luismachadoreis.flighttracker.server.common.application.cqs.mediator.Mediator;
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import dev.luismachadoreis.flighttracker.server.ping.application.CreatePingCommand;
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import dev.luismachadoreis.flighttracker.server.ping.application.dto.FlightDataDTO;
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import dev.luismachadoreis.flighttracker.server.ping.application.dto.PingDTOMapper;
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import dev.luismachadoreis.flighttracker.server.ping.application.usecase.CreatePingUseCase;
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import lombok.RequiredArgsConstructor;
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import lombok.extern.slf4j.Slf4j;
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import org.springframework.kafka.annotation.KafkaListener;
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@RequiredArgsConstructor
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public class FlightDataSubscriber {
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private final CreatePingUseCase createPingUseCase;
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private final Mediator mediator;
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@KafkaListener(topics = "${spring.kafka.topic.flight-positions}", groupId = "${spring.kafka.consumer.group-id}")
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public void consumeFlightData(FlightDataDTO data) {
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log.debug("Received flight data: {}", data);
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createPingUseCase.execute(PingDTOMapper.fromFlightData(data));
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mediator.send(new CreatePingCommand(PingDTOMapper.fromFlightData(data)));
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}
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}

‎src/main/java/dev/luismachadoreis/flighttracker/server/ping/api/PingController.java‎

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package dev.luismachadoreis.flighttracker.server.ping.api;
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import dev.luismachadoreis.flighttracker.server.ping.application.CreatePingCommand;
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import dev.luismachadoreis.flighttracker.server.ping.application.GetRecentPingsQuery;
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import dev.luismachadoreis.flighttracker.server.ping.application.dto.PingDTO;
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import dev.luismachadoreis.flighttracker.server.ping.application.usecase.CreatePingUseCase;
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import dev.luismachadoreis.flighttracker.server.ping.application.usecase.GetPingsUseCase;
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import io.swagger.v3.oas.annotations.Operation;
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import io.swagger.v3.oas.annotations.Parameter;
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import io.swagger.v3.oas.annotations.media.Content;
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import io.swagger.v3.oas.annotations.media.Schema;
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import io.swagger.v3.oas.annotations.responses.ApiResponse;
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import io.swagger.v3.oas.annotations.tags.Tag;
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import org.springframework.beans.factory.annotation.Value;
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import dev.luismachadoreis.flighttracker.server.common.application.cqs.mediator.Mediator;
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import org.springframework.http.ResponseEntity;
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import org.springframework.web.bind.annotation.*;
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import org.springframework.web.servlet.support.ServletUriComponentsBuilder;
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import java.net.URI;
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import java.util.List;
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import java.util.UUID;
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import java.util.Optional;
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import lombok.extern.slf4j.Slf4j;
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import io.swagger.v3.oas.annotations.tags.Tag;
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import io.swagger.v3.oas.annotations.Operation;
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import io.swagger.v3.oas.annotations.responses.ApiResponse;
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import io.swagger.v3.oas.annotations.media.Content;
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import io.swagger.v3.oas.annotations.media.Schema;
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import org.springframework.beans.factory.annotation.Value;
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import org.springframework.web.bind.annotation.RequestMapping;
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import org.springframework.web.bind.annotation.RestController;
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@Tag(name = "Ping API", description = "API for managing flight position pings")
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@Slf4j
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@RestController
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@RequestMapping("/api/pings")
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@RequestMapping("/api/v2/pings")
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@Tag(name = "Ping API", description = "API for managing flight position pings")
2230
public class PingController {
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private final CreatePingUseCase createPingUseCase;
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private final GetPingsUseCase getPingsUseCase;
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private final int defaultRequestLimit;
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private final Mediator mediator;
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private final Integer defaultRequestLimit;
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public PingController(CreatePingUseCase createPingUseCase, GetPingsUseCase getPingsUseCase, @Value("${default.request.limit:50}") int defaultRequestLimit) {
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this.createPingUseCase = createPingUseCase;
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this.getPingsUseCase = getPingsUseCase;
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public PingController(Mediator mediator, @Value("${default.request.limit:50}") Integer defaultRequestLimit) {
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this.mediator = mediator;
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this.defaultRequestLimit = defaultRequestLimit;
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}
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}
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)
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@PostMapping
46-
public ResponseEntity<PingDTO> createPing(@RequestBody PingDTO pingDTO) {
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return ResponseEntity.ok(createPingUseCase.execute(pingDTO));
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public ResponseEntity<Void> createPing(@RequestBody PingDTO pingDTO) {
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UUID pingId = mediator.send(new CreatePingCommand(pingDTO));
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URI location = ServletUriComponentsBuilder
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.fromCurrentRequest()
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.path("/{id}")
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.buildAndExpand(pingId)
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.toUri();
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log.info("Ping created with id: {}", pingId);
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return ResponseEntity.created(location).build();
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}
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@Operation(
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}
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)
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@GetMapping
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public ResponseEntity<List<PingDTO>> getPings(
63-
@Parameter(
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description = "Maximum number of pings to retrieve",
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example = "50"
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)
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@RequestParam(required = false) Integer limit
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) {
69-
return ResponseEntity.ok(getPingsUseCase.execute(
70-
Optional.ofNullable(limit).orElse(defaultRequestLimit)
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));
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public ResponseEntity<List<PingDTO>> getRecentPings(@RequestParam(required = false) Integer limit) {
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List<PingDTO> pings = mediator.send(
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new GetRecentPingsQuery(
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Optional.ofNullable(limit).orElse(defaultRequestLimit)
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)
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);
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log.info("Recent pings retrieved: {}", pings);
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return ResponseEntity.ok(pings);
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}
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}

‎src/main/java/dev/luismachadoreis/flighttracker/server/ping/application/CreatePingCommand.java‎

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package dev.luismachadoreis.flighttracker.server.ping.application;
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import dev.luismachadoreis.flighttracker.server.common.application.cqs.command.Command;
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import dev.luismachadoreis.flighttracker.server.ping.application.dto.PingDTO;
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import java.util.UUID;
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/*
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* This record is a command that creates a ping.
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*/
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public record CreatePingCommand(PingDTO pingDTO) implements Command<UUID> {}

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