feat: Add registerFiles for Java.

Register files is a GenAi Only feature (no Vertex).
GenAi Doesn't support GoogleCredentials.
The register files method needs a GoogleCredentials token, so the user has to pass GoogleCredentials to the `registerFiles` method.

PiperOrigin-RevId: 862884363

Author: MarkDaoust

examples/src/main/java/com/google/genai/examples/RegisterFiles.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.genai.examples;
+
+import com.google.auth.oauth2.GoogleCredentials;
+import com.google.genai.Client;
+import com.google.genai.types.Content;
+import com.google.genai.types.File;
+import com.google.genai.types.GenerateContentResponse;
+import com.google.genai.types.Part;
+import com.google.genai.types.RegisterFilesResponse;
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * An example of how to use the registerFiles method to register GCS files with the Gemini Developer
+ * API.
+ */
+public final class RegisterFiles {
+  public static void main(String[] args) throws IOException {
+    // Instantiate the client. The client by default uses the Gemini Developer API.
+    Client client = new Client();
+
+    if (client.vertexAI()) {
+      System.out.println("registerFiles is only supported in the Gemini Developer client.");
+      System.exit(0);
+    }
+
+    // GoogleCredentials.getApplicationDefault() will use application default credentials.
+    // Note: registerFiles is only supported by the Gemini Developer API (MLDev), not Vertex AI.
+    GoogleCredentials credentials =
+        GoogleCredentials.getApplicationDefault()
+            .createScoped(
+                Arrays.asList(
+                    "https://www.googleapis.com/auth/cloud-platform",
+                    "https://www.googleapis.com/auth/devstorage.read_only"));
+
+    List<String> uris = Arrays.asList("gs://tensorflow_docs/image.jpg");
+
+    RegisterFilesResponse response = client.files.registerFiles(credentials, uris, null);
+
+    List<File> files =
+        response.files().orElseThrow(() -> new RuntimeException("No files returned"));
+    File file = files.get(0);
+
+    System.out.println("Registered file: " + file.uri().get());
+
+    // Use the registered file in a generateContent call.
+    Content content =
+        Content.fromParts(
+            Part.fromText("can you summarize this file?"),
+            Part.fromUri(file.uri().get(), file.mimeType().get()));
+
+    GenerateContentResponse genResponse =
+        client.models.generateContent("gemini-2.5-flash", content, null);
+
+    System.out.println("Response: " + genResponse.text());
+  }
+
+  private RegisterFiles() {}
+}

src/main/java/com/google/genai/AsyncFiles.java

@@ -18,8 +18,11 @@
 
 package com.google.genai;
 
+import static com.google.common.base.Preconditions.checkNotNull;
+
 import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.node.ObjectNode;
+import com.google.auth.oauth2.GoogleCredentials;
 import com.google.genai.Common.BuiltRequest;
 import com.google.genai.errors.GenAiIOException;
 import com.google.genai.types.CreateFileConfig;
@@ -32,9 +35,12 @@
 import com.google.genai.types.GetFileConfig;
 import com.google.genai.types.ListFilesConfig;
 import com.google.genai.types.ListFilesResponse;
+import com.google.genai.types.RegisterFilesConfig;
+import com.google.genai.types.RegisterFilesResponse;
 import com.google.genai.types.UploadFileConfig;
 import com.google.genai.types.Video;
 import java.io.InputStream;
+import java.util.List;
 import java.util.concurrent.CompletableFuture;
 import java.util.function.Function;
 
@@ -116,6 +122,20 @@ public CompletableFuture<DeleteFileResponse> delete(String name, DeleteFileConfi
             });
   }
 
+  CompletableFuture<RegisterFilesResponse> privateRegisterFiles(
+      List<String> uris, RegisterFilesConfig config) {
+
+    BuiltRequest builtRequest = files.buildRequestForPrivateRegisterFiles(uris, config);
+    return this.apiClient
+        .asyncRequest("post", builtRequest.path(), builtRequest.body(), builtRequest.httpOptions())
+        .thenApplyAsync(
+            response -> {
+              try (ApiResponse res = response) {
+                return files.processResponseForPrivateRegisterFiles(res, config);
+              }
+            });
+  }
+
   /**
    * Asynchronously makes an API request to list the available files.
    *
@@ -149,6 +169,31 @@ public CompletableFuture<AsyncPager<File>> list(ListFilesConfig config) {
                 request.apply(finalConfig)));
   }
 
+  /**
+   * Asynchronously registers Google Cloud Storage files for use with the API.
+   *
+   * @param credentials The Google Cloud credentials to use for registering the files.
+   * @param uris The list of GCS URIs to register.
+   * @param config Optional configuration for the registration request.
+   * @return A future that resolves to the response containing the registered files.
+   */
+  public CompletableFuture<RegisterFilesResponse> registerFiles(
+      GoogleCredentials credentials, List<String> uris, RegisterFilesConfig config) {
+    if (this.apiClient.vertexAI()) {
+      CompletableFuture<RegisterFilesResponse> future = new CompletableFuture<>();
+      future.completeExceptionally(
+          new UnsupportedOperationException(
+              "This method is only supported in the Gemini Developer client."));
+      return future;
+    }
+    checkNotNull(credentials, "credentials cannot be null");
+    checkNotNull(uris, "uris cannot be null");
+
+    return CompletableFuture.supplyAsync(
+            () -> files.internalPrepareRegisterFilesConfig(credentials, config))
+        .thenCompose(updatedConfig -> privateRegisterFiles(uris, updatedConfig));
+  }
+
   /**
    * Asynchronously uploads a file to the GenAI API.
    *