chore: [vertexai] pass in immutable object in generateContent private method (googleapis#10494)

PiperOrigin-RevId: 613322025

Co-authored-by: Jaycee Li <[email protected]>

Author: copybara-service[bot]

java-vertexai/google-cloud-vertexai/src/main/java/com/google/cloud/vertexai/generativeai/GenerativeModel.java

@@ -551,7 +551,7 @@ public GenerateContentResponse generateContent(
   public GenerateContentResponse generateContent(
       List<Content> contents, GenerateContentConfig config) throws IOException {
     GenerateContentRequest.Builder requestBuilder =
-        GenerateContentRequest.newBuilder().addAllContents(contents);
+        GenerateContentRequest.newBuilder().setModel(this.resourceName).addAllContents(contents);
     if (config.getGenerationConfig() != null) {
       requestBuilder.setGenerationConfig(config.getGenerationConfig());
     } else if (this.generationConfig != null) {
@@ -568,7 +568,7 @@ public GenerateContentResponse generateContent(
       requestBuilder.addAllTools(this.tools);
     }
 
-    return generateContent(requestBuilder);
+    return generateContent(requestBuilder.build());
   }
 
   /**
@@ -592,7 +592,7 @@ public GenerateContentResponse generateContent(
       List<Content> contents, GenerationConfig generationConfig, List<SafetySetting> safetySettings)
       throws IOException {
     GenerateContentRequest.Builder requestBuilder =
-        GenerateContentRequest.newBuilder().addAllContents(contents);
+        GenerateContentRequest.newBuilder().setModel(this.resourceName).addAllContents(contents);
     if (generationConfig != null) {
       requestBuilder.setGenerationConfig(generationConfig);
     } else if (this.generationConfig != null) {
@@ -606,28 +606,24 @@ public GenerateContentResponse generateContent(
     if (this.tools != null) {
       requestBuilder.addAllTools(this.tools);
     }
-    return generateContent(requestBuilder);
+    return generateContent(requestBuilder.build());
   }
 
   /**
    * A base generateContent method that will be used internally.
    *
-   * @param requestBuilder a {@link com.google.cloud.vertexai.api.GenerateContentRequest.Builder}
-   *     instance
+   * @param request a {@link com.google.cloud.vertexai.api.GenerateContentRequest} instance
    * @return a {@link com.google.cloud.vertexai.api.GenerateContentResponse} instance that contains
    *     response contents and other metadata
    * @throws IOException if an I/O error occurs while making the API call
    */
-  private GenerateContentResponse generateContent(GenerateContentRequest.Builder requestBuilder)
+  private GenerateContentResponse generateContent(GenerateContentRequest request)
       throws IOException {
-    GenerateContentRequest request = requestBuilder.setModel(this.resourceName).build();
-    GenerateContentResponse response;
     if (this.transport == Transport.REST) {
-      response = vertexAi.getPredictionServiceRestClient().generateContentCallable().call(request);
+      return vertexAi.getPredictionServiceRestClient().generateContentCallable().call(request);
     } else {
-      response = vertexAi.getPredictionServiceClient().generateContentCallable().call(request);
+      return vertexAi.getPredictionServiceClient().generateContentCallable().call(request);
     }
-    return response;
   }
 
   /**