Generate streaming text content with Generative Model

import (
	"context"
	"errors"
	"fmt"
	"io"

	"cloud.google.com/go/vertexai/genai"
	"google.golang.org/api/iterator"
)

// generateContent shows how to	send a basic streaming text prompt, writing
// the response to the provided io.Writer.
func generateContent(w io.Writer, projectID, modelName string) error {
	ctx := context.Background()

	client, err := genai.NewClient(ctx, projectID, "us-central1")
	if err != nil {
		return fmt.Errorf("unable to create client: %w", err)
	}
	defer client.Close()

	model := client.GenerativeModel(modelName)

	iter := model.GenerateContentStream(
		ctx,
		genai.Text("Write a story about a magic backpack."),
	)
	for {
		resp, err := iter.Next()
		if err == iterator.Done {
			return nil
		}
		if len(resp.Candidates) == 0 || len(resp.Candidates[0].Content.Parts) == 0 {
			return errors.New("empty response from model")
		}
		if err != nil {
			return err
		}
		fmt.Fprint(w, "generated response: ")
		for _, c := range resp.Candidates {
			for _, p := range c.Content.Parts {
				fmt.Fprintf(w, "%s ", p)
			}
		}
	}
}

import com.google.cloud.vertexai.VertexAI;
import com.google.cloud.vertexai.generativeai.GenerativeModel;

public class StreamingQuestionAnswer {

  public static void main(String[] args) throws Exception {
    // TODO(developer): Replace these variables before running the sample.
    String projectId = "your-google-cloud-project-id";
    String location = "us-central1";
    String modelName = "gemini-2.0-flash-001";

    streamingQuestion(projectId, location, modelName);
  }

  // Ask a simple question and get the response via streaming.
  public static void streamingQuestion(String projectId, String location, String modelName)
      throws Exception {
    // Initialize client that will be used to send requests.
    // This client only needs to be created once, and can be reused for multiple requests.
    try (VertexAI vertexAI = new VertexAI(projectId, location)) {
      GenerativeModel model = new GenerativeModel(modelName, vertexAI);

      // Stream the result.
      model.generateContentStream("Write a story about a magic backpack.")
          .stream()
          .forEach(System.out::println);

      System.out.println("Streaming complete.");
    }
  }
}

const {VertexAI} = require('@google-cloud/vertexai');

/**
 * TODO(developer): Update these variables before running the sample.
 */
const PROJECT_ID = process.env.CAIP_PROJECT_ID;
const LOCATION = process.env.LOCATION;
const MODEL = 'gemini-2.0-flash-001';

async function generateContent() {
  // Initialize Vertex with your Cloud project and location
  const vertexAI = new VertexAI({project: PROJECT_ID, location: LOCATION});

  // Instantiate the model
  const generativeModel = vertexAI.getGenerativeModel({
    model: MODEL,
  });

  const request = {
    contents: [
      {
        role: 'user',
        parts: [
          {
            text: 'Write a story about a magic backpack.',
          },
        ],
      },
    ],
  };

  console.log(JSON.stringify(request));

  const result = await generativeModel.generateContentStream(request);
  for await (const item of result.stream) {
    console.log(item.candidates[0].content.parts[0].text);
  }
}