For the latest stable version, please use Spring Boot 3.4.0!

HTTP Clients

Spring Boot offers a number of starters that work with HTTP clients. This section answers questions related to using them.

Configure RestTemplate to Use a Proxy

As described in RestTemplate Customization, you can use a RestTemplateCustomizer with RestTemplateBuilder to build a customized RestTemplate. This is the recommended approach for creating a RestTemplate configured to use a proxy.

The exact details of the proxy configuration depend on the underlying client request factory that is being used.

Configure the TcpClient used by a Reactor Netty-based WebClient

When Reactor Netty is on the classpath a Reactor Netty-based WebClient is auto-configured. To customize the client’s handling of network connections, provide a ClientHttpConnector bean. The following example configures a 60 second connect timeout and adds a ReadTimeoutHandler:

Java
Kotlin

import io.netty.channel.ChannelOption;
import io.netty.handler.timeout.ReadTimeoutHandler;
import reactor.netty.http.client.HttpClient;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.client.ReactorResourceFactory;
import org.springframework.http.client.reactive.ClientHttpConnector;
import org.springframework.http.client.reactive.ReactorClientHttpConnector;

@Configuration(proxyBeanMethods = false)
public class MyReactorNettyClientConfiguration {

	@Bean
	ClientHttpConnector clientHttpConnector(ReactorResourceFactory resourceFactory) {
		HttpClient httpClient = HttpClient.create(resourceFactory.getConnectionProvider())
				.runOn(resourceFactory.getLoopResources())
				.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 60000)
				.doOnConnected((connection) -> connection.addHandlerLast(new ReadTimeoutHandler(60)));
		return new ReactorClientHttpConnector(httpClient);
	}

}

import io.netty.channel.ChannelOption
import io.netty.handler.timeout.ReadTimeoutHandler
import org.springframework.context.annotation.Bean
import org.springframework.context.annotation.Configuration
import org.springframework.http.client.reactive.ClientHttpConnector
import org.springframework.http.client.reactive.ReactorClientHttpConnector
import org.springframework.http.client.ReactorResourceFactory
import reactor.netty.http.client.HttpClient

@Configuration(proxyBeanMethods = false)
class MyReactorNettyClientConfiguration {

	@Bean
	fun clientHttpConnector(resourceFactory: ReactorResourceFactory): ClientHttpConnector {
		val httpClient = HttpClient.create(resourceFactory.connectionProvider)
			.runOn(resourceFactory.loopResources)
			.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 60000)
			.doOnConnected { connection ->
				connection.addHandlerLast(ReadTimeoutHandler(60))
			}
		return ReactorClientHttpConnector(httpClient)
	}

}

Note the use of ReactorResourceFactory for the connection provider and event loop resources. This ensures efficient sharing of resources for the server receiving requests and the client making requests.