Chat Model API Reference

public class VertexAiChatModel implements ChatModel {
    public ChatResponse chat(ChatRequest chatRequest);
    public static Builder builder();
}

/**
 * Generate chat completion from a chat request.
 *
 * @param chatRequest The chat request containing messages and configuration
 * @return ChatResponse containing the generated response
 */
public ChatResponse chat(ChatRequest chatRequest);

/**
 * Create a new builder for configuring a VertexAiChatModel.
 *
 * @return A new Builder instance
 */
public static Builder builder();

/**
 * Set the GCP API endpoint URL.
 *
 * @param endpoint The API endpoint (e.g., "https://us-central1-aiplatform.googleapis.com/v1/")
 * @return This builder
 */
public Builder endpoint(String endpoint);

/**
 * Set the Google Cloud Project ID.
 *
 * @param project The GCP project ID
 * @return This builder
 */
public Builder project(String project);

/**
 * Set the GCP region/location.
 *
 * @param location The region (e.g., "us-central1", "europe-west1")
 * @return This builder
 */
public Builder location(String location);

/**
 * Set the model publisher.
 *
 * @param publisher The publisher name, typically "google"
 * @return This builder
 */
public Builder publisher(String publisher);

/**
 * Set the model name/version.
 *
 * @param modelName The model name (e.g., "chat-bison@001", "gemini-pro")
 * @return This builder
 */
public Builder modelName(String modelName);

/**
 * Set the sampling temperature for randomness control.
 *
 * @param temperature Temperature value between 0.0 (deterministic) and 1.0 (random)
 * @return This builder
 */
public Builder temperature(Double temperature);

/**
 * Set the maximum number of output tokens.
 *
 * @param maxOutputTokens Maximum tokens in response (default: 200)
 * @return This builder
 */
public Builder maxOutputTokens(Integer maxOutputTokens);

/**
 * Set the top-K sampling parameter.
 *
 * @param topK Number of highest probability tokens to consider
 * @return This builder
 */
public Builder topK(Integer topK);

/**
 * Set the top-P (nucleus) sampling parameter.
 *
 * @param topP Cumulative probability threshold for token selection
 * @return This builder
 */
public Builder topP(Double topP);

/**
 * Set the maximum number of retry attempts on API failures.
 *
 * @param maxRetries Maximum retry attempts (default: 2)
 * @return This builder
 */
public Builder maxRetries(Integer maxRetries);

/**
 * Set custom Google Cloud credentials.
 *
 * @param credentials GoogleCredentials instance for authentication
 * @return This builder
 */
public Builder credentials(GoogleCredentials credentials);

/**
 * Build the VertexAiChatModel instance.
 *
 * @return Configured VertexAiChatModel instance
 */
public VertexAiChatModel build();

/**
 * @deprecated Since version 1.2.0, use builder() instead
 */
@Deprecated
public VertexAiChatModel(
    String endpoint,
    String project,
    String location,
    String publisher,
    String modelName,
    Double temperature,
    Integer maxOutputTokens,
    Integer topK,
    Double topP,
    Integer maxRetries
);

public class ChatResponse {
    public AiMessage aiMessage();
    public TokenUsage tokenUsage();
    public FinishReason finishReason();
}

public class AiMessage {
    public String text();
}

public class TokenUsage {
    public Integer inputTokenCount();
    public Integer outputTokenCount();
    public Integer totalTokenCount();
}

public enum FinishReason {
    STOP,           // Natural completion
    LENGTH,         // Max tokens reached
    SAFETY,         // Safety filter triggered
    RECITATION,     // Recitation detected
    OTHER           // Other reason
}

public class ChatRequest {
    public static Builder builder();
}

public Builder messages(ChatMessage... messages);
public Builder messages(List<ChatMessage> messages);
public ChatRequest build();

// User message
public class UserMessage implements ChatMessage {
    public static UserMessage from(String text);
}

// AI message
public class AiMessage implements ChatMessage {
    public static AiMessage from(String text);
}

// System message
public class SystemMessage implements ChatMessage {
    public static SystemMessage from(String text);
}

try {
    ChatResponse response = model.chat(request);
} catch (RuntimeException e) {
    // Catches all non-retryable errors after retries exhausted
}