feat!: refactor ApiClient constructors hierarchy to remove Optional parameters

core/src/main/java/com/google/adk/sessions/ApiClient.java

@@ -16,11 +16,11 @@
 
 package com.google.adk.sessions;
 
-import static com.google.common.base.Preconditions.checkNotNull;
 import static com.google.common.base.StandardSystemProperty.JAVA_VERSION;
 
 import com.google.auth.oauth2.GoogleCredentials;
 import com.google.common.base.Ascii;
+import com.google.common.base.Strings;
 import com.google.common.collect.ImmutableMap;
 import com.google.genai.errors.GenAiIOException;
 import com.google.genai.types.HttpOptions;
@@ -35,83 +35,69 @@
 abstract class ApiClient {
   OkHttpClient httpClient;
   // For Google AI APIs
-  final Optional<String> apiKey;
+  final @Nullable String apiKey;
   // For Vertex AI APIs
-  final Optional<String> project;
-  final Optional<String> location;
-  final Optional<GoogleCredentials> credentials;
+  final @Nullable String project;
+  final @Nullable String location;
+  final @Nullable GoogleCredentials credentials;
   HttpOptions httpOptions;
   final boolean vertexAI;
 
   /** Constructs an ApiClient for Google AI APIs. */
-  ApiClient(Optional<String> apiKey, Optional<HttpOptions> customHttpOptions) {
-    checkNotNull(apiKey, "API Key cannot be null");
-    checkNotNull(customHttpOptions, "customHttpOptions cannot be null");
+  ApiClient(@Nullable String apiKey, @Nullable HttpOptions customHttpOptions) {
 
-    try {
-      this.apiKey = Optional.of(apiKey.orElseGet(() -> System.getenv("GOOGLE_API_KEY")));
-    } catch (NullPointerException e) {
+    this.apiKey = apiKey != null ? apiKey : System.getenv("GOOGLE_API_KEY");
+
+    if (Strings.isNullOrEmpty(this.apiKey)) {
       throw new IllegalArgumentException(
-          "API key must either be provided or set in the environment variable" + " GOOGLE_API_KEY.",
-          e);
+          "API key must either be provided or set in the environment variable"
+              + " GOOGLE_API_KEY.");
     }
 
-    this.project = Optional.empty();
-    this.location = Optional.empty();
-    this.credentials = Optional.empty();
+    this.project = null;
+    this.location = null;
+    this.credentials = null;
     this.vertexAI = false;
 
     this.httpOptions = defaultHttpOptions(/* vertexAI= */ false, this.location);
 
-    if (customHttpOptions.isPresent()) {
-      applyHttpOptions(customHttpOptions.get());
+    if (customHttpOptions != null) {
+      applyHttpOptions(customHttpOptions);
     }
 
     this.httpClient = createHttpClient(httpOptions.timeout().orElse(null));
   }
 
   ApiClient(
-      Optional<String> project,
-      Optional<String> location,
-      Optional<GoogleCredentials> credentials,
-      Optional<HttpOptions> customHttpOptions) {
-    checkNotNull(project, "project cannot be null");
-    checkNotNull(location, "location cannot be null");
-    checkNotNull(credentials, "credentials cannot be null");
-    checkNotNull(customHttpOptions, "customHttpOptions cannot be null");
+      @Nullable String project,
+      @Nullable String location,
+      @Nullable GoogleCredentials credentials,
+      @Nullable HttpOptions customHttpOptions) {
 
-    try {
-      this.project = Optional.of(project.orElseGet(() -> System.getenv("GOOGLE_CLOUD_PROJECT")));
-    } catch (NullPointerException e) {
+    this.project = project != null ? project : System.getenv("GOOGLE_CLOUD_PROJECT");
+
+    if (Strings.isNullOrEmpty(this.project)) {
       throw new IllegalArgumentException(
           "Project must either be provided or set in the environment variable"
-              + " GOOGLE_CLOUD_PROJECT.",
-          e);
-    }
-    if (this.project.get().isEmpty()) {
-      throw new IllegalArgumentException("Project must not be empty.");
+              + " GOOGLE_CLOUD_PROJECT.");
     }
 
-    try {
-      this.location = Optional.of(location.orElse(System.getenv("GOOGLE_CLOUD_LOCATION")));
-    } catch (NullPointerException e) {
+    this.location = location != null ? location : System.getenv("GOOGLE_CLOUD_LOCATION");
+
+    if (Strings.isNullOrEmpty(this.location)) {
       throw new IllegalArgumentException(
           "Location must either be provided or set in the environment variable"
-              + " GOOGLE_CLOUD_LOCATION.",
-          e);
-    }
-    if (this.location.get().isEmpty()) {
-      throw new IllegalArgumentException("Location must not be empty.");
+              + " GOOGLE_CLOUD_LOCATION.");
     }
 
-    this.credentials = Optional.of(credentials.orElseGet(this::defaultCredentials));
+    this.credentials = credentials != null ? credentials : defaultCredentials();
 
     this.httpOptions = defaultHttpOptions(/* vertexAI= */ true, this.location);
 
-    if (customHttpOptions.isPresent()) {
-      applyHttpOptions(customHttpOptions.get());
+    if (customHttpOptions != null) {
+      applyHttpOptions(customHttpOptions);
     }
-    this.apiKey = Optional.empty();
+    this.apiKey = null;
     this.vertexAI = true;
     this.httpClient = createHttpClient(httpOptions.timeout().orElse(null));
   }
@@ -142,17 +128,17 @@ public boolean vertexAI() {
 
   /** Returns the project ID for Vertex AI APIs. */
   public @Nullable String project() {
-    return project.orElse(null);
+    return project;
   }
 
   /** Returns the location for Vertex AI APIs. */
   public @Nullable String location() {
-    return location.orElse(null);
+    return location;
   }
 
   /** Returns the API key for Google AI APIs. */
   public @Nullable String apiKey() {
-    return apiKey.orElse(null);
+    return apiKey;
   }
 
   /** Returns the HttpClient for API calls. */
@@ -192,7 +178,7 @@ private void applyHttpOptions(HttpOptions httpOptionsToApply) {
     this.httpOptions = mergedHttpOptionsBuilder.build();
   }
 
-  static HttpOptions defaultHttpOptions(boolean vertexAI, Optional<String> location) {
+  static HttpOptions defaultHttpOptions(boolean vertexAI, @Nullable String location) {
     ImmutableMap.Builder<String, String> defaultHeaders = ImmutableMap.builder();
     defaultHeaders
         .put("Content-Type", "application/json")
@@ -202,14 +188,14 @@ static HttpOptions defaultHttpOptions(boolean vertexAI, Optional<String> locatio
     HttpOptions.Builder defaultHttpOptionsBuilder =
         HttpOptions.builder().headers(defaultHeaders.buildOrThrow());
 
-    if (vertexAI && location.isPresent()) {
+    if (vertexAI && location != null) {
       defaultHttpOptionsBuilder
           .baseUrl(
-              Ascii.equalsIgnoreCase(location.get(), "global")
+              Ascii.equalsIgnoreCase(location, "global")
                   ? "https://aiplatform.googleapis.com"
-                  : String.format("https://%s-aiplatform.googleapis.com", location.get()))
+                  : String.format("https://%s-aiplatform.googleapis.com", location))
           .apiVersion("v1beta1");
-    } else if (vertexAI && location.isEmpty()) {
+    } else if (vertexAI && Strings.isNullOrEmpty(location)) {
       throw new IllegalArgumentException("Location must be provided for Vertex AI APIs.");
     } else {
       defaultHttpOptionsBuilder

core/src/main/java/com/google/adk/sessions/HttpApiClient.java

@@ -18,33 +18,34 @@
 
 import com.google.auth.oauth2.GoogleCredentials;
 import com.google.common.base.Ascii;
+import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableMap;
 import com.google.genai.errors.GenAiIOException;
 import com.google.genai.types.HttpOptions;
 import java.io.IOException;
 import java.util.Map;
-import java.util.Optional;
 import okhttp3.MediaType;
 import okhttp3.Request;
 import okhttp3.RequestBody;
 import okhttp3.Response;
+import org.jspecify.annotations.Nullable;
 
 /** Base client for the HTTP APIs. */
 public class HttpApiClient extends ApiClient {
   public static final MediaType MEDIA_TYPE_APPLICATION_JSON =
       MediaType.parse("application/json; charset=utf-8");
 
   /** Constructs an ApiClient for Google AI APIs. */
-  HttpApiClient(Optional<String> apiKey, Optional<HttpOptions> httpOptions) {
+  HttpApiClient(@Nullable String apiKey, @Nullable HttpOptions httpOptions) {
     super(apiKey, httpOptions);
   }
 
   /** Constructs an ApiClient for Vertex AI APIs. */
   HttpApiClient(
-      Optional<String> project,
-      Optional<String> location,
-      Optional<GoogleCredentials> credentials,
-      Optional<HttpOptions> httpOptions) {
+      @Nullable String project,
+      @Nullable String location,
+      @Nullable GoogleCredentials credentials,
+      @Nullable HttpOptions httpOptions) {
     super(project, location, credentials, httpOptions);
   }
 
@@ -54,9 +55,7 @@ public ApiResponse request(String httpMethod, String path, String requestJson) {
     boolean queryBaseModel =
         Ascii.equalsIgnoreCase(httpMethod, "GET") && path.startsWith("publishers/google/models/");
     if (this.vertexAI() && !path.startsWith("projects/") && !queryBaseModel) {
-      path =
-          String.format("projects/%s/locations/%s/", this.project.get(), this.location.get())
-              + path;
+      path = String.format("projects/%s/locations/%s/", this.project, this.location) + path;
     }
     String requestUrl =
         String.format(
@@ -85,11 +84,11 @@ private void setHeaders(Request.Builder requestBuilder) {
       requestBuilder.header(header.getKey(), header.getValue());
     }
 
-    if (apiKey.isPresent()) {
-      requestBuilder.header("x-goog-api-key", apiKey.get());
+    if (apiKey != null) {
+      requestBuilder.header("x-goog-api-key", apiKey);
     } else {
-      GoogleCredentials cred =
-          credentials.orElseThrow(() -> new IllegalStateException("credentials is required"));
+      Preconditions.checkState(credentials != null, "credentials is required");
+      GoogleCredentials cred = credentials;
       try {
         cred.refreshIfExpired();
       } catch (IOException e) {

core/src/main/java/com/google/adk/sessions/VertexAiClient.java

@@ -17,7 +17,6 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.Optional;
 import java.util.concurrent.TimeoutException;
 import javax.annotation.Nullable;
 import okhttp3.ResponseBody;
@@ -37,17 +36,15 @@ final class VertexAiClient {
   }
 
   VertexAiClient() {
-    this.apiClient =
-        new HttpApiClient(Optional.empty(), Optional.empty(), Optional.empty(), Optional.empty());
+    this.apiClient = new HttpApiClient((String) null, null, null, null);
   }
 
   VertexAiClient(
       String project,
       String location,
-      Optional<GoogleCredentials> credentials,
-      Optional<HttpOptions> httpOptions) {
-    this.apiClient =
-        new HttpApiClient(Optional.of(project), Optional.of(location), credentials, httpOptions);
+      @Nullable GoogleCredentials credentials,
+      @Nullable HttpOptions httpOptions) {
+    this.apiClient = new HttpApiClient(project, location, credentials, httpOptions);
   }
 
   Maybe<JsonNode> createSession(

core/src/main/java/com/google/adk/sessions/VertexAiSessionService.java

@@ -40,7 +40,7 @@
 import java.util.concurrent.ConcurrentMap;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
-import javax.annotation.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /** Connects to the managed Vertex AI Session Service. */
 // TODO: Use the genai HttpApiClient and ApiResponse methods once they are public.
@@ -65,8 +65,8 @@ public VertexAiSessionService() {
   public VertexAiSessionService(
       String project,
       String location,
-      Optional<GoogleCredentials> credentials,
-      Optional<HttpOptions> httpOptions) {
+      @Nullable GoogleCredentials credentials,
+      @Nullable HttpOptions httpOptions) {
     this.client = new VertexAiClient(project, location, credentials, httpOptions);
   }