Use HTTP/1.1 unless HTTPS scheme is in URL

src/main/java/com/bisnode/opa/client/OpaClient.java

@@ -14,6 +14,7 @@
 import com.bisnode.opa.client.rest.OpaRestClient;
 
 import java.net.http.HttpClient;
+import java.util.Objects;
 
 /**
  * Opa client featuring {@link OpaDataApi}, {@link OpaQueryApi} and {@link OpaPolicyApi}
@@ -73,7 +74,10 @@ public Builder opaConfiguration(String url) {
         }
 
         public OpaClient build() {
-            HttpClient httpClient = HttpClient.newHttpClient();
+            Objects.requireNonNull(opaConfiguration, "build() called without opaConfiguration provided");
+            HttpClient httpClient = HttpClient.newBuilder()
+                    .version(opaConfiguration.getHttpVersion())
+                    .build();
             OpaRestClient opaRestClient = new OpaRestClient(opaConfiguration, httpClient, ObjectMapperFactory.getInstance().create());
             return new OpaClient(new OpaQueryClient(opaRestClient), new OpaDataClient(opaRestClient), new OpaPolicyClient(opaRestClient));
         }

src/main/java/com/bisnode/opa/client/OpaConfiguration.java

@@ -1,20 +1,36 @@
 package com.bisnode.opa.client;
 
 import java.beans.ConstructorProperties;
+import java.net.URI;
+import java.net.http.HttpClient;
 import java.util.Objects;
 
 /**
  * Contains all configuration needed to set up {@link OpaClient}
  */
 public final class OpaConfiguration {
     private final String url;
+    private final HttpClient.Version httpVersion;
 
     /**
      * @param url base URL to OPA server, containing protocol, and port (eg. http://localhost:8181)
      */
     @ConstructorProperties({"url"})
     public OpaConfiguration(String url) {
         this.url = url;
+        this.httpVersion = "https".equals(URI.create(url).getScheme()) ?
+                HttpClient.Version.HTTP_2 :
+                HttpClient.Version.HTTP_1_1;
+    }
+
+    /**
+     * @param url base URL to OPA server, containing protocol, and port (eg. http://localhost:8181)
+     * @param httpVersion preferred HTTP version to use for the client
+     */
+    @ConstructorProperties({"url", "httpVersion"})
+    public OpaConfiguration(String url, HttpClient.Version httpVersion) {
+        this.url = url;
+        this.httpVersion = httpVersion;
     }
 
     /**
@@ -24,6 +40,16 @@ public String getUrl() {
         return this.url;
     }
 
+    /**
+     * Get HTTP version configured for the client. If not configured will use HTTP2 for "https" scheme
+     * and HTTP1.1 for "http" scheme.
+     *
+     * @return httpVersion configured for use by the client
+     */
+    public HttpClient.Version getHttpVersion() {
+        return this.httpVersion;
+    }
+
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;