Spring Boot HTTP Interface Client

Spring Boot 3.2+ ile Java veya Kotlin arayüzleri üzerinden deklaratif ve tip güvenli HTTP istemcileri tanımlayabilirsiniz. Bu makalede JSONPlaceholder API örneği ile baştan sona nasıl yapılandıracağınızı öğreneceksiniz.

🌟 Neden HTTP Arayüz İstemcisi?

Deklaratif: Bir arayüz tanımlayıp HTTP çağrılarını yöntem anotasyonlarıyla eşleyin.
Tip güvenli: Yanlış imzalar veya hatalı yol konfigürasyonları derleme zamanında yakalanır.
Azaltılmış tekrar eden kod: Tek bir bean tanımı, manuel proxy veya template koduna gerek yok.
Spring Dostu: Spring Framework 6.2’nin @HttpExchange, @GetExchange ve WebClientAdapter bileşenlerini kullanır.

🌟 Ön Koşullar

☕ Java Development Kit (JDK) 21 veya üstü
📦 Spring Boot 3.2+
🔤 IDE (IntelliJ IDEA, Eclipse vb.)

🛠️ Adım 1: Bağımlılıkları Ekle

Projenizin yapı dosyasına Web starter’ı ekleyin:

Maven:

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-web</artifactId>
</dependency>

Gradle:

implementation 'org.springframework.boot:spring-boot-starter-web'

📝 Adım 2: Temel URL Ayarı

application.yml veya application.properties dosyanıza ekleyin:

jsonplaceholder:
  base-url: https://jsonplaceholder.typicode.com

jsonplaceholder.base-url=https://jsonplaceholder.typicode.com

🛠️ Adım 3: DTO ve İstemci Arayüzü Tanımla

// src/main/java/com/example/client/dto/PostDTO.java
package com.example.client.dto;

public record PostDTO(
    Integer userId,
    Integer id,
    String title,
    String body
) {}

// src/main/java/com/example/client/JsonPlaceholderClient.java
package com.example.client;

import com.example.client.dto.PostDTO;
import org.springframework.web.service.annotation.GetExchange;
import org.springframework.web.service.annotation.HttpExchange;
import org.springframework.web.bind.annotation.PathVariable;
import java.util.List;

@HttpExchange(url = "${jsonplaceholder.base-url}", accept = "application/json")
public interface JsonPlaceholderClient {

    @GetExchange("/posts")
    List<PostDTO> getPosts();

    @GetExchange("/posts/{id}")
    PostDTO getPost(@PathVariable("id") Integer id);
}

// src/main/kotlin/com/example/client/dto/PostDTO.kt
package com.example.client.dto

data class PostDTO(
    val userId: Int,
    val id: Int,
    val title: String,
    val body: String
)

// src/main/kotlin/com/example/client/JsonPlaceholderClient.kt
package com.example.client

import com.example.client.dto.PostDTO
import org.springframework.web.service.annotation.GetExchange
import org.springframework.web.service.annotation.HttpExchange
import org.springframework.web.bind.annotation.PathVariable

@HttpExchange(url = "${jsonplaceholder.base-url}", accept = "application/json")
interface JsonPlaceholderClient {

    @GetExchange("/posts")
    fun getPosts(): List<PostDTO>

    @GetExchange("/posts/{id}")
    fun getPost(@PathVariable("id") id: Int): PostDTO
}

🛠️ Adım 4: İstemci Bean’ini Yapılandır

// src/main/java/com/example/config/HttpClientConfig.java
package com.example.config;

import com.example.client.JsonPlaceholderClient;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.support.RestClientAdapter;
import org.springframework.web.service.invoker.HttpServiceProxyFactory;
import org.springframework.web.service.invoker.RestClient;

@Configuration
public class HttpClientConfig {

    @Bean
    public JsonPlaceholderClient jsonPlaceholderClient(RestClient.Builder restClientBuilder) {
        RestClient restClient = restClientBuilder
            .baseUrl("https://jsonplaceholder.typicode.com")
            .build();

        var factory = HttpServiceProxyFactory
            .builderFor(RestClientAdapter.create(restClient))
            .build();

        return factory.createClient(JsonPlaceholderClient.class);
    }
}

// src/main/kotlin/com/example/config/HttpClientConfig.kt
package com.example.config

import com.example.client.JsonPlaceholderClient
import org.springframework.context.annotation.Bean
import org.springframework.context.annotation.Configuration
import org.springframework.web.client.support.RestClientAdapter
import org.springframework.web.service.invoker.HttpServiceProxyFactory
import org.springframework.web.service.invoker.RestClient

@Configuration
class HttpClientConfig {

    @Bean
    fun jsonPlaceholderClient(restClientBuilder: RestClient.Builder): JsonPlaceholderClient {
        val restClient = restClientBuilder
            .baseUrl("https://jsonplaceholder.typicode.com")
            .build()

        val factory = HttpServiceProxyFactory
            .builderFor(RestClientAdapter.create(restClient))
            .build()

        return factory.createClient(JsonPlaceholderClient::class.java)
    }
}

🔄 Adım 5: Servis ve Controller Oluşturun

// src/main/java/com/example/service/PostService.java
package com.example.service;

import com.example.client.JsonPlaceholderClient;
import com.example.client.dto.PostDTO;
import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Service;
import java.util.List;

@Service
@RequiredArgsConstructor
public class PostService {
    private final JsonPlaceholderClient client;

    public List<PostDTO> getAllPosts() {
        return client.getPosts();
    }

    public PostDTO getPostById(Integer id) {
        return client.getPost(id);
    }
}

// src/main/java/com/example/controller/PostController.java
package com.example.controller;

import com.example.client.dto.PostDTO;
import com.example.service.PostService;
import lombok.RequiredArgsConstructor;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import java.util.List;

@RestController
@RequestMapping("/posts")
@RequiredArgsConstructor
public class PostController {
    private final PostService postService;

    @GetMapping
    public List<PostDTO> getAllPosts() {
        return postService.getAllPosts();
    }

    @GetMapping("/{id}")
    public ResponseEntity<PostDTO> getPostById(@PathVariable Integer id) {
        PostDTO post = postService.getPostById(id);
        return post != null ? ResponseEntity.ok(post) : ResponseEntity.notFound().build();
    }
}

// src/main/kotlin/com/example/service/PostService.kt
package com.example.service

import com.example.client.JsonPlaceholderClient
import com.example.client.dto.PostDTO
import org.springframework.stereotype.Service

@Service
class PostService(private val client: JsonPlaceholderClient) {
    fun getAllPosts(): List<PostDTO> = client.getPosts()
    fun getPostById(id: Int): PostDTO = client.getPost(id)
}

// src/main/kotlin/com/example/controller/PostController.kt
package com.example.controller

import com.example.client.dto.PostDTO
import com.example.service.PostService
import org.springframework.http.ResponseEntity
import org.springframework.web.bind.annotation.*

@RestController
@RequestMapping("/posts")
class PostController(private val postService: PostService) {
    @GetMapping
    fun getAllPosts(): List<PostDTO> = postService.getAllPosts()

    @GetMapping("/{id}")
    fun getPostById(@PathVariable id: Int): ResponseEntity<PostDTO> =
        ResponseEntity.ok(postService.getPostById(id))
}

▶️ Uygulamayı Çalıştır

./mvnw spring-boot:run
# veya
gradle bootRun

🧪 Endpointleri Test Et

curl http://localhost:8080/posts
curl http://localhost:8080/posts/1

Sonuç olarak, bu adımları takip ederek Spring Boot’un HTTP Interface Clienti deklaratif ve tip güvenli REST iletişimi için başarıyla yapılandırmış oldunuz. Bu yaklaşım, tekrar eden kodları azaltır ve güçlü Rest Client altyapısını kullanır.