Writing mTLS/Two-Way SSL/Client Certificate Authentication with Spring Boot 4 and HTTP Service Clients

Introduction

In my previous I setup client certification authentication with RestClient https://magnus-k-karlsson.blogspot.com/2026/04/writing-mtlstwo-way-sslclient.html

Here I will use new Spring Boot 4 Rest Client: HTTP Service Clients

Configuration

The configuration of the RestClient is the same.

Java Interface

package se.magnuskkarlsson.clientcert;

import org.springframework.web.service.annotation.GetExchange;

public interface HelloService {

    @GetExchange("/hello")
    public String hello();
}

Use It

    @Autowired
    RestClient restClient;

    private HelloService service;

    // https://docs.spring.io/spring-framework/reference/integration/rest-clients.html#rest-http-service-client
    @BeforeEach
    void setUp() throws Exception {
        // Using RestClient...
        RestClientAdapter adapter = RestClientAdapter.create(restClient);
        HttpServiceProxyFactory factory = HttpServiceProxyFactory.builderFor(adapter).build();
        service = factory.createClient(HelloService.class);
    }

    @Test
    void hello() throws Exception {
        System.out.println(service.hello());
    }