VertexAI Gemini Chat

The Vertex AI Gemini API allows developers to build generative AI applications using the Gemini model. The Vertex AI Gemini API supports multimodal prompts as input and output text or code. A multimodal model is a model that is capable of processing information from multiple modalities, including images, videos, and text. For example, you can send the model a photo of a plate of cookies and ask it to give you a recipe for those cookies.

Gemini is a family of generative AI models developed by Google DeepMind that is designed for multimodal use cases. The Gemini API gives you access to the Gemini 1.0 Pro Vision and Gemini 1.0 Pro models. For specifications of the Vertex AI Gemini API models, see Model information.

Gemini API Reference

Prerequisites

Set up your Java Development Environment. Authenticate by running the following command. Replace PROJECT_ID with your Google Cloud project ID and ACCOUNT with your Google Cloud username.

gcloud config set project PROJECT_ID &&
gcloud auth application-default login ACCOUNT

Auto-configuration

Spring AI provides Spring Boot auto-configuration for the VertexAI Gemini Chat Client. To enable it add the following dependency to your project’s Maven pom.xml file:

<dependency>
    <groupId>org.springframework.ai</groupId>
    <artifactId>spring-ai-vertex-ai-gemini-spring-boot-starter</artifactId>
</dependency>

or to your Gradle build.gradle build file.

dependencies {
    implementation 'org.springframework.ai:spring-ai-vertex-ai-gemini-spring-boot-starter'
}
Refer to the Dependency Management section to add the Spring AI BOM to your build file.

Chat Properties

The prefix spring.ai.vertex.ai.gemini is used as the property prefix that lets you connect to VertexAI.

Property Description Default

spring.ai.vertex.ai.gemini.projectId

Google Cloud Platform project ID

-

spring.ai.vertex.ai.gemini.location

Region

-

spring.ai.vertex.ai.gemini.credentialsUri

URI to Vertex AI Gemini credentials. When provided it is used to create an a GoogleCredentials instance to authenticate the VertexAI.

-

The prefix spring.ai.vertex.ai.gemini.chat is the property prefix that lets you configure the chat client implementation for VertexAI Gemini Chat.

Property Description Default

spring.ai.vertex.ai.gemini.chat.options.model

This is the Vertex AI Gemini Chat model to use

gemini-pro-vision

spring.ai.vertex.ai.gemini.chat.options.temperature

Controls the randomness of the output. Values can range over [0.0,1.0], inclusive. A value closer to 1.0 will produce responses that are more varied, while a value closer to 0.0 will typically result in less surprising responses from the generative. This value specifies default to be used by the backend while making the call to the generative.

0.8

spring.ai.vertex.ai.gemini.chat.options.topK

The maximum number of tokens to consider when sampling. The generative uses combined Top-k and nucleus sampling. Top-k sampling considers the set of topK most probable tokens.

-

spring.ai.vertex.ai.gemini.chat.options.topP

The maximum cumulative probability of tokens to consider when sampling. The generative uses combined Top-k and nucleus sampling. Nucleus sampling considers the smallest set of tokens whose probability sum is at least topP.

-

spring.ai.vertex.ai.gemini.chat.options.candidateCount

The number of generated response messages to return. This value must be between [1, 8], inclusive. Defaults to 1.

-

spring.ai.vertex.ai.gemini.chat.options.candidateCount

The number of generated response messages to return. This value must be between [1, 8], inclusive. Defaults to 1.

-

spring.ai.vertex.ai.gemini.chat.options.maxOutputTokens

The maximum number of tokens to generate.

-

spring.ai.vertex.ai.gemini.chat.options.frequencyPenalty

-

spring.ai.vertex.ai.gemini.chat.options.presencePenalty

-

spring.ai.vertex.ai.gemini.chat.options.functions

List of functions, identified by their names, to enable for function calling in a single prompt requests. Functions with those names must exist in the functionCallbacks registry.

-
All properties prefixed with spring.ai.vertex.ai.gemini.chat.options can be overridden at runtime by adding a request specific Runtime options to the Prompt call.

Runtime options

The VertexAiGeminiChatOptions.java provides model configurations, such as the temperature, the topK, etc.

On start-up, the default options can be configured with the VertexAiGeminiChatClient(api, options) constructor or the spring.ai.vertex.ai.chat.options.* properties.

At runtime you can override the default options by adding new, request specific, options to the Prompt call. For example to override the default temperature for a specific request:

ChatResponse response = chatClient.call(
    new Prompt(
        "Generate the names of 5 famous pirates.",
        VertexAiPaLm2ChatOptions.builder()
            .withTemperature(0.4)
        .build()
    ));
In addition to the model specific VertexAiChatPaLm2Options you can use a portable ChatOptions instance, created with the ChatOptionsBuilder#builder().

Function Calling

You can register custom Java functions with the VertexAiGeminiChatClient and have the Gemini Pro model intelligently choose to output a JSON object containing arguments to call one or many of the registered functions. This is a powerful technique to connect the LLM capabilities with external tools and APIs. Read more about Vertex AI Gemini Function Calling.

Multimodal

Multimodality refers to a model’s ability to simultaneously understand and process information from various sources, including text, images, audio, and other data formats. This paradigm represents a significant advancement in AI models.

Google’s Gemini AI models support this capability by comprehending and integrating text, code, audio, images, and video. For more details, refer to the blog post Introducing Gemini.

Spring AI’s Message interface supports multimodal AI models by introducing the Media type. This type contains data and information about media attachments in messages, using Spring’s org.springframework.util.MimeType and a java.lang.Object for the raw media data.

Below is a simple code example extracted from VertexAiGeminiChatClientIT.java, demonstrating the combination of user text with an image.

byte[] data = new ClassPathResource("/vertex-test.png").getContentAsByteArray();

var userMessage = new UserMessage("Explain what do you see o this picture?",
        List.of(new Media(MimeTypeUtils.IMAGE_PNG, data)));

ChatResponse response = chatClient.call(new Prompt(List.of(userMessage)));

Sample Controller

Create a new Spring Boot project and add the spring-ai-vertex-ai-palm2-spring-boot-starter to your pom (or gradle) dependencies.

Add a application.properties file, under the src/main/resources directory, to enable and configure the VertexAi Chat client:

spring.ai.vertex.ai.gemini.project-id=PROJECT_ID
spring.ai.vertex.ai.gemini.location=LOCATION
spring.ai.vertex.ai.gemini.chat.options.model=vertex-pro-vision
spring.ai.vertex.ai.gemini.chat.options.temperature=0.5
replace the api-key with your VertexAI credentials.

This will create a VertexAiGeminiChatClient implementation that you can inject into your class. Here is an example of a simple @Controller class that uses the chat client for text generations.

@RestController
public class ChatController {

    private final VertexAiGeminiChatClient chatClient;

    @Autowired
    public ChatController(VertexAiGeminiChatClient chatClient) {
        this.chatClient = chatClient;
    }

    @GetMapping("/ai/generate")
    public Map generate(@RequestParam(value = "message", defaultValue = "Tell me a joke") String message) {
        return Map.of("generation", chatClient.call(message));
    }

    @GetMapping("/ai/generateStream")
	public Flux<ChatResponse> generateStream(@RequestParam(value = "message", defaultValue = "Tell me a joke") String message) {
        Prompt prompt = new Prompt(new UserMessage(message));
        return chatClient.stream(prompt);
    }
}

Manual Configuration

The VertexAiGeminiChatClient implements the ChatClient and uses the VertexAI to connect to the Vertex AI Gemini service.

Add the spring-ai-vertex-ai-gemini dependency to your project’s Maven pom.xml file:

<dependency>
    <groupId>org.springframework.ai</groupId>
    <artifactId>spring-ai-vertex-ai-gemini</artifactId>
</dependency>

or to your Gradle build.gradle build file.

dependencies {
    implementation 'org.springframework.ai:spring-ai-vertex-ai-gemini'
}
Refer to the Dependency Management section to add the Spring AI BOM to your build file.

Next, create a VertexAiGeminiChatClient and use it for text generations:

VertexAI vertexApi =  new VertexAI(projectId, location);

var chatClient = new VertexAiGeminiChatClient(vertexApi,
    VertexAiGeminiChatOptions.builder()
        .withTemperature(0.4)
    .build());

ChatResponse response = chatClient.call(
    new Prompt("Generate the names of 5 famous pirates."));

The VertexAiGeminiChatOptions provides the configuration information for the chat requests. The VertexAiGeminiChatOptions.Builder is fluent options builder.