This quick start walks through using SC LoadBalancer OkHttpClient integration, load-balanced OkHttpClient-based Retrofit clients, and load-balanced WebClient-based Retrofit clients.
First, add the spring-cloud-square-okhttp dependency to your project:
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-square-okhttp</artifactId>
<version>0.4.0-M3</version>
</dependency>Then create a @LoadBalanced-annotated OkHttpClient.Builder bean:
@Configuration
class OkHttpClientConfig{
@Bean
@LoadBalanced
public OkHttpClient.Builder okHttpClientBuilder() {
return new OkHttpClient.Builder();
}
}Now you can use the serviceId or virtual hostname rather than an actual host:port in your requests — SC LoadBalancer resolves it by selecting one of the available service instances.
Request request = new Request.Builder()
.url("http://serviceId/hello").build();
Response response = builder.build().newCall(request).execute();First, add the spring-cloud-square-retrofit and spring-cloud-square-okhttp dependencies to your project:
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-square-retrofit</artifactId>
<version>0.4.0-M3</version>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-square-okhttp</artifactId>
<version>0.4.0-M3</version>
</dependency>
</dependencies>Use the @EnableRetrofitClients annotation to let us automatically instantiate and inject Retrofit clients for you. Then create a @LoadBalanced-annotated OkHttpClient.Builder bean to be used under the hood:
@Configuration
@EnableRetrofitClients
class OkHttpClientConfig {
@Bean
@LoadBalanced
public OkHttpClient.Builder okHttpClientBuilder() {
return new OkHttpClient.Builder();
}
}Create a Retrofit client and annotate it with @RetrofitClient, passing the serviceId of your service as argument (the annotation can also be used to pass a custom configuration that contains user-crated interceptors for the Retrofit client):
@RetrofitClient("serviceId")
interface HelloClient {
@GET("/")
Call<String> hello();
}Make sure to use Retrofit method annotations, such as @GET("/").
You can now inject the Retrofit client and use it to run load-balanced calls (by using serviceId instead of actual host:port):
class AService {
@Autowired
HelloClient client;
public String hello() throws IOException {
return client.hello().execute().body();
}
}We created a full sample for load-balanced-OkHttpClient-based Retrofit clients.
First, add the spring-cloud-square-retrofit and spring-boot-starter-webflux starter dependencies to your project:
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-square-retrofit</artifactId>
<version>0.4.0-M3</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-webflux</artifactId>
</dependency>
</dependencies>Use the @EnableRetrofitClients annotation to let us automatically instantiate and inject Retrofit clients for you. Then create a @LoadBalanced-annotated WebClient.Builder bean to be used under the hood:
@Configuration
@EnableRetrofitClients
class OkHttpClientConfig {
@Bean
@LoadBalanced
public WebClient.Builder webClientBuilder() {
return WebClient.builder();
}
}Create a Retrofit client and annotate it with @RetrofitClient, passing the serviceId of your service as argument:
@RetrofitClient("serviceId")
interface HelloClient {
@GET("/")
Mono<String> hello();
}Make sure to use Retrofit method annotations, such as @GET("/").
You can now inject the Retrofit client and use it to run load-balanced calls (by using serviceId instead of actual host:port):
class AService {
@Autowired
HelloClient client;
public String hello() throws IOException {
return client.hello();
}
}We created a full sample for load-balanced-WebClient-based Retrofit clients.
|
Tip
|
As the currently available release is a milestone, you need to add the Spring Milestone repository link to your projects for all the examples presented in this blog entry: |
<repositories>
<repository>
<id>spring-milestones</id>
<url>https://repo.spring.io/milestone</url>
</repository>
</repositories>We recommend using dependency management for other Spring Cloud dependencies:
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>${spring-cloud.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>This module supplies integration with Square’s [OkHttpClient](https://square.github.io/okhttp/) and [Spring Cloud LoadBalancer](https://github.com/spring-cloud/spring-cloud-commons/spring-cloud-loadbalancer).
An application interceptor is added to the OkHttpClient created by auto-configuration which resolves the scheme, host, and port from Spring Cloud LoadBalancer and rewrites the URL.
By supporting OkHttpClient, it enables Square’s [Retrofit](https://square.github.io/retrofit/) to use Spring Cloud LoadBalancer as well.
See [OkHttpLoadBalancerInterceptorTests](https://github.com/spring-cloud-incubator/spring-cloud-square/blob/main/spring-cloud-square-okhttp/src/test/java/org/springframework/cloud/square/okhttp/loadbalancer/OkHttpLoadBalancerInterceptorTests.java) for Spring Cloud LoadBalancer samples.
Support was also added for Spring WebClient. This implements an okhttp3.Call.Factory that uses WebClient under the covers. This provides a fully non-blocking shim instead of using okhttp3.
See [WebClientRetrofitTests](https://github.com/spring-cloud-incubator/spring-cloud-square/blob/main/spring-cloud-square-retrofit-webclient/src/test/java/org/springframework/cloud/square/retrofit/webclient/WebClientRetrofitTests.java) for WebClient samples.