Create the OKHttp client like this:

OkHttpClient client = new OkHttpClient();

Below shows how to create and send a request, with HTTP verb, body and headers set.

RequestBody body = RequestBody.create(MediaType.get("application/x-www-form-urlencoded; charset=UTF-8"), "http body");
Request req = new Request.Builder().url("https://localhost:8080/")
	.method("POST", body)
	.header("accept", "*/*")
	.build();
	
Response resp = client.newCall(req).execute();

OkhttpClient will default follow redirects (HTTP 302). If you wish to disable this, you can do this by using the Builer methods below with the parameter false

OkHttpClient client = new OkHttpClient.Builder()
  .followSslRedirects(false)
  .followRedirects(false)
  .build

HTTPS / TLS (SSL)

If you want to call an endpoint over TLS, you need to create the RestTemplate so that it accepts the server certificate. There are a number of ways to do this.

• The server certificate can be added as trusted by importing it into the Java cacerts. If the tests will execute at several machines, this may be an ardouous approach.

  $ keytool -import -trustcacerts -keystore $JAVA_HOME/jre/lib/security/cacerts -storepass changeit -alias ServerToBeTested -import -file servercert.cer

• You can create the OkHttpClient with a customized SSLContext and a HostnameVerifier. You can write your own logic which certificates to accept. Below example has a HostnameVerifier that always returns true, meaning that everything is accepted. Keep in mind that always accepting everything is less secure. Therefore, use this approach with caution.

  public OkHttpClient createClient() {
    try {
      X509TrustManager manager = getX509TrustManager();
     SSLContext sslContext = SSLContextBuilder
     .create().build();
     sslContext.init(null, new TrustManager[] { manager }, null);
     SSLSocketFactory sslSocketFactory = sslContext.getSocketFactory();
     
     OkHttpClient client = new OkHttpClient.Builder().sslSocketFactory(sslSocketFactory, manager)
         .hostnameVerifier((hostname, session)-> true)
         .build();
     return client;
    }catch(Exception e) {
      throw new RuntimeException(e);
    }
  }
  
  private X509TrustManager getX509TrustManager() {
    X509TrustManager manager = new X509TrustManager() {
      
      @Override
      public X509Certificate[] getAcceptedIssuers() {
        X509Certificate[] cArrr = new X509Certificate[0];
                return cArrr;
      }
      
      public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {}
      public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {}
    };
    return manager;
  }

Maven dependencies

Here are the Maven dependencies you need to use OKHttp as the client library for your load tests

<dependency>
  <groupId>com.squareup.okhttp3</groupId>
  <artifactId>okhttp-tls</artifactId>
  <version>4.2.2</version>
</dependency>