fix(java-sdk): don't create a new HttpClient on every request (#287)

config/clients/java/config.overrides.json

@@ -175,6 +175,10 @@
       "destinationFilename": "src/test-integration/java/dev/openfga/sdk/api/client/OpenFgaClientIntegrationTest.java",
       "templateType": "SupportingFiles"
     },
+    "client-ApiClientTest.java.mustache" : {
+      "destinationFilename": "src/test/java/dev/openfga/sdk/api/client/ApiClientTest.java",
+      "templateType": "SupportingFiles"
+    },
     "creds-AccessToken.java.mustache" : {
       "destinationFilename": "src/main/java/dev/openfga/sdk/api/auth/AccessToken.java",
       "templateType": "SupportingFiles"

config/clients/java/template/client-ApiClientTest.java.mustache

@@ -0,0 +1,27 @@
+{{>licenseInfo}}
+package {{invokerPackage}};
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+
+import java.net.http.HttpClient;
+import org.junit.jupiter.api.Test;
+
+class ApiClientTest {
+
+    @Test
+    public void returnSameHttpClient() {
+        ApiClient apiClient = new ApiClient();
+        assertEquals(apiClient.getHttpClient(), apiClient.getHttpClient());
+    }
+
+    @Test
+    public void newHttpClientWhenBuilderModified() {
+        ApiClient apiClient = new ApiClient();
+
+        HttpClient client1 = apiClient.getHttpClient();
+        apiClient.setHttpClientBuilder(HttpClient.newBuilder());
+
+        assertNotEquals(client1, apiClient.getHttpClient());
+    }
+}

config/clients/java/template/libraries/native/ApiClient.mustache

@@ -48,6 +48,7 @@ import static java.nio.charset.StandardCharsets.UTF_8;
 public class ApiClient {
 
   private HttpClient.Builder builder;
+  private HttpClient client;
   private ObjectMapper mapper;
   private Consumer<HttpRequest.Builder> interceptor;
   private Consumer<HttpResponse<InputStream>> responseInterceptor;
@@ -59,6 +60,7 @@ public class ApiClient {
   public ApiClient() {
     this.builder = createDefaultHttpClientBuilder();
     this.mapper = createDefaultObjectMapper();
+    this.client = this.builder.build();
     interceptor = null;
     responseInterceptor = null;
     asyncResponseInterceptor = null;
@@ -77,6 +79,7 @@ public class ApiClient {
   public ApiClient(HttpClient.Builder builder, ObjectMapper mapper) {
     this.builder = builder;
     this.mapper = mapper;
+    this.client = this.builder.build();
     interceptor = null;
     responseInterceptor = null;
     asyncResponseInterceptor = null;
@@ -174,6 +177,7 @@ public class ApiClient {
    */
   public ApiClient setHttpClientBuilder(HttpClient.Builder builder) {
     this.builder = builder;
+    this.client = this.builder.build();
     return this;
   }
 
@@ -185,7 +189,7 @@ public class ApiClient {
    * @return The HTTP client.
    */
   public HttpClient getHttpClient() {
-    return builder.build();
+    return client;
   }
 
   /**