Google AI Gemini Embeddings

https://ai.google.dev/gemini-api/docs/embeddings

Maven Dependency
API Key
Models Available
GoogleAiEmbeddingModel
Batch Embedding Processing

Maven Dependency

<dependency>
    <groupId>dev.langchain4j</groupId>
    <artifactId>langchain4j-google-ai-gemini</artifactId>
    <version>1.21.0</version>
</dependency>

API Key

Get an API key for free here: https://ai.google.dev/gemini-api/docs/api-key .

Models available

Check the list of available models in the documentation.

gemini-embedding-001
- Input token limit: 2,048
- Output dimension size: Flexible, supports: 128 - 3072, Recommended: 768, 1536, 3072

GoogleAiEmbeddingModel

The GoogleAiEmbeddingModel allows you to generate embeddings from text using Google AI Gemini's embedding models.

Basic Usage

EmbeddingModel embeddingModel = GoogleAiEmbeddingModel.builder()
    .apiKey(System.getenv("GEMINI_AI_KEY"))
    .modelName("gemini-embedding-001")
    .build();

Response<Embedding> response = embeddingModel.embed("Hello, world!");
Embedding embedding = response.content();

Embedding Multiple Texts

List<TextSegment> segments = List.of(
    TextSegment.from("First document"),
    TextSegment.from("Second document"),
    TextSegment.from("Third document")
);

Response<List<Embedding>> response = embeddingModel.embedAll(segments);
List<Embedding> embeddings = response.content();

Configuring the Embedding Model

EmbeddingModel embeddingModel = GoogleAiEmbeddingModel.builder()
    .apiKey(System.getenv("GEMINI_AI_KEY"))
    .modelName("gemini-embedding-001")
    .taskType(GoogleAiEmbeddingModel.TaskType.RETRIEVAL_DOCUMENT)
    .outputDimensionality(768)
    .titleMetadataKey("title")
    .maxRetries(3)
    .timeout(Duration.ofSeconds(30))
    .logRequestsAndResponses(true)
    .build();

Task Types

The taskType parameter optimizes the embedding for specific use cases:

RETRIEVAL_QUERY: For search queries
RETRIEVAL_DOCUMENT: For documents to be retrieved (default for document indexing)
SEMANTIC_SIMILARITY: For measuring text similarity
CLASSIFICATION: For text classification tasks
CLUSTERING: For grouping similar texts
QUESTION_ANSWERING: For Q&A systems
FACT_VERIFICATION: For fact-checking applications

Using Metadata for Document Titles

When using TaskType.RETRIEVAL_DOCUMENT, you can provide document titles via metadata:

EmbeddingModel embeddingModel = GoogleAiEmbeddingModel.builder()
    .apiKey(System.getenv("GEMINI_AI_KEY"))
    .modelName("gemini-embedding-001")
    .taskType(GoogleAiEmbeddingModel.TaskType.RETRIEVAL_DOCUMENT)
    .titleMetadataKey("title") // defaults to "title"
    .build();

TextSegment segment = TextSegment.from(
    "This is the document content",
    Metadata.from("title", "My Document Title")
);

Response<Embedding> response = embeddingModel.embed(segment);

Output Dimensionality

You can specify the output dimensionality to reduce the embedding size:

EmbeddingModel embeddingModel = GoogleAiEmbeddingModel.builder()
    .apiKey(System.getenv("GEMINI_AI_KEY"))
    .modelName("gemini-embedding-001")
    .outputDimensionality(256) // Reduce from default 768 dimensions
    .build();

Batch Processing

The model automatically batches requests when embedding multiple segments, with a maximum of 100 segments per batch for optimal performance.

Note: This is not the discounted batch API, instead this is a convenience method for processing multiple embeddings.

Batch Embedding Processing

The GoogleAiGeminiBatchEmbeddingModel provides an interface for processing large volumes of embedding requests asynchronously at a reduced cost (50% of standard pricing). It is ideal for non-urgent, large-scale embedding tasks with a 24-hour turnaround SLO.

Creating Batch Embedding Jobs

Inline batch creation:

GoogleAiGeminiBatchEmbeddingModel batchModel = GoogleAiGeminiBatchEmbeddingModel.builder()
    .apiKey(System.getenv("GEMINI_AI_KEY"))
    .modelName("gemini-embedding-001")
    .taskType(GoogleAiEmbeddingModel.TaskType.RETRIEVAL_DOCUMENT)
    .outputDimensionality(768)
    .build();

// Create batch of text segments
List<TextSegment> segments = List.of(
    TextSegment.from("First document to embed"),
    TextSegment.from("Second document to embed"),
    TextSegment.from("Third document to embed")
);

// Submit the batch (generic API)
BatchResponse<Response<Embedding>> response = batchModel.submit(new BatchRequest<>(segments));

// Or, to set a Gemini-specific display name and priority, use GeminiBatchRequest:
BatchResponse<Response<Embedding>> response = batchModel.submit(GeminiBatchRequest.from(
    segments,
    "Document Embeddings Batch", // display name
    0L                           // priority (optional, defaults to 0)
));

File-based batch creation:

For larger batches, you can create a batch from an uploaded file:

// First, upload a file with batch requests
GeminiFiles filesApi = GeminiFiles.builder()
    .apiKey(System.getenv("GEMINI_AI_KEY"))
    .build();

GeminiFile uploadedFile = filesApi.uploadFile(
    Paths.get("batch_embeddings.jsonl"),
    "Batch Embedding Requests"
);

// Wait for file to be active
while (uploadedFile.isProcessing()) {
    Thread.sleep(1000);
    uploadedFile = filesApi.getMetadata(uploadedFile.name());
}

// Create batch from file
BatchResponse<Response<Embedding>> response = batchModel.submit("My Embedding Batch Job", uploadedFile);

Handling Batch Responses

A BatchResponse exposes the current state() together with the per-request results() and the responses() / errors() convenience views. Branch on the state() (use state().isTerminal() to tell whether the batch is still in progress):

BatchResponse<Response<Embedding>> response = batchModel.submit(new BatchRequest<>(segments));

if (!response.state().isTerminal()) {
    System.out.println("Batch is " + response.state());
    System.out.println("Batch ID: " + response.batchId());
} else if (response.state() == BatchState.SUCCEEDED) {
    System.out.println("Batch completed successfully!");
    for (Response<Embedding> embeddingResponse : response.responses()) {
        Embedding embedding = embeddingResponse.content();
        System.out.println("Embedding dimensions: " + embedding.dimension());
    }
} else {
    System.err.println("Batch " + response.state() + ": " + response.errors());
}

responses() and errors() are convenience views and are never null (empty when there is nothing to report).

Correlating Results with Requests

responses() and errors() are flat views that lose track of which input produced which outcome. When you need to map every outcome back to its originating segment, use results() instead: it returns one BatchItemResult per request, in the same order as the submitted segments, so the i-th result corresponds to the i-th segment. Each result is either a BatchItemResult.Success (carrying the response()) or a BatchItemResult.Failure (carrying the error()):

List<BatchItemResult<Response<Embedding>>> results = response.results();
for (int i = 0; i < results.size(); i++) {
    BatchItemResult<Response<Embedding>> item = results.get(i);
    if (item.isSuccess()) {
        System.out.println("Segment #" + i + " -> " + item.response().content().dimension() + " dimensions");
    } else {
        BatchError error = item.error();
        System.err.println("Segment #" + i + " failed: " + error.code() + " - " + error.message());
    }
}

Polling for Results

Since batch processing is asynchronous, you need to poll for results:

BatchResponse<Response<Embedding>> result = batchModel.submit(new BatchRequest<>(segments));
String batchId = result.batchId();

while (!result.state().isTerminal()) {
    Thread.sleep(5000); // Wait 5 seconds between polls
    result = batchModel.retrieve(batchId);
}

// Process final result
if (result.state() == BatchState.SUCCEEDED) {
    List<Response<Embedding>> embeddings = result.responses();
    System.out.println("Generated " + embeddings.size() + " embeddings");
} else {
    System.err.println("Batch did not succeed: " + result.state());
}

Managing Batch Jobs

Cancel a batch job:

String batchId = // ... obtained from submit(...)

try {
    batchModel.cancel(batchId);
    System.out.println("Batch cancelled successfully");
} catch (HttpException e) {
    System.err.println("Failed to cancel batch: " + e.getMessage());
}

Delete a batch job:

batchModel.deleteBatchJob(batchId);
System.out.println("Batch deleted successfully");

List batch jobs:

// List first page of batch jobs
BatchPage<Response<Embedding>> page = batchModel.list(new BatchPagination(10, null));

for (BatchResponse<Response<Embedding>> batch : page.batches()) {
    System.out.println("Batch: " + batch);
}

// Get next page if available
if (page.nextPageToken() != null) {
    BatchPage<Response<Embedding>> nextPage = batchModel.list(new BatchPagination(10, page.nextPageToken()));
}

File-Based Batch Processing

For advanced use cases, you can write batch requests to a JSONL file and upload it:

// Create a JSONL file with batch requests
Path batchFile = Files.createTempFile("batch", ".jsonl");

try (JsonLinesWriter writer = new StreamingJsonLinesWriter(batchFile)) {
    List<BatchFileRequest<TextSegment>> fileRequests = List.of(
        new BatchFileRequest<>("segment-1", TextSegment.from("First document")),
        new BatchFileRequest<>("segment-2", TextSegment.from("Second document")),
        new BatchFileRequest<>("segment-3", TextSegment.from("Third document"))
    );
    
    batchModel.writeBatchToFile(writer, fileRequests);
}

// Upload the file
GeminiFiles filesApi = GeminiFiles.builder()
    .apiKey(System.getenv("GEMINI_AI_KEY"))
    .build();

GeminiFile uploadedFile = filesApi.uploadFile(batchFile, "Batch Embedding Requests");

// Create batch from file
BatchResponse<Response<Embedding>> response = batchModel.submit("File-Based Embedding Batch", uploadedFile);

Using Metadata with Batch Embeddings

When using TaskType.RETRIEVAL_DOCUMENT, you can include document titles via metadata:

GoogleAiGeminiBatchEmbeddingModel batchModel = GoogleAiGeminiBatchEmbeddingModel.builder()
    .apiKey(System.getenv("GEMINI_AI_KEY"))
    .modelName("gemini-embedding-001")
    .taskType(GoogleAiEmbeddingModel.TaskType.RETRIEVAL_DOCUMENT)
    .titleMetadataKey("title")
    .build();

List<TextSegment> segments = List.of(
    TextSegment.from(
        "Content of first document",
        Metadata.from("title", "First Document Title")
    ),
    TextSegment.from(
        "Content of second document",
        Metadata.from("title", "Second Document Title")
    )
);

BatchResponse<Response<Embedding>> response = batchModel.submit(GeminiBatchRequest.from(
    segments, "Documents with Titles"));

Configuration

The GoogleAiGeminiBatchEmbeddingModel supports the same configuration options as GoogleAiEmbeddingModel:

GoogleAiGeminiBatchEmbeddingModel batchModel = GoogleAiGeminiBatchEmbeddingModel.builder()
    .apiKey(System.getenv("GEMINI_AI_KEY"))
    .modelName("gemini-embedding-001")
    .taskType(GoogleAiEmbeddingModel.TaskType.RETRIEVAL_DOCUMENT)
    .outputDimensionality(768)
    .titleMetadataKey("title")
    .maxRetries(3)
    .timeout(Duration.ofSeconds(30))
    .logRequestsAndResponses(true)
    .build();

Important Constraints

Size Limit: The inline API supports a total request size of 20 MB or under
Batch Size: Maximum of 100 segments per batch for optimal performance
Cost: Batch processing offers 50% cost reduction compared to real-time requests
Turnaround: 24-hour SLO, though completion is often much quicker
Use Cases: Best for large-scale embedding generation for document indexing or semantic search

Example: Complete Workflow

GoogleAiGeminiBatchEmbeddingModel batchModel = GoogleAiGeminiBatchEmbeddingModel.builder()
    .apiKey(System.getenv("GEMINI_AI_KEY"))
    .modelName("gemini-embedding-001")
    .taskType(GoogleAiEmbeddingModel.TaskType.RETRIEVAL_DOCUMENT)
    .outputDimensionality(768)
    .build();

// Prepare batch of text segments
List<TextSegment> segments = new ArrayList<>();
for (int i = 0; i < 500; i++) {
    segments.add(TextSegment.from(
        "Document content #" + i,
        Metadata.from("title", "Document " + i)
    ));
}

// Submit batch
BatchResponse<Response<Embedding>> result = batchModel.submit(GeminiBatchRequest.from(
    segments, "Large Document Collection", 0L));
String batchId = result.batchId();

// Poll for completion
int attempts = 0;
int maxAttempts = 720; // 1 hour with 5-second intervals
while (!result.state().isTerminal()) {
    if (attempts++ >= maxAttempts) {
        throw new RuntimeException("Batch processing timeout");
    }
    Thread.sleep(5000);
    result = batchModel.retrieve(batchId);
    System.out.println("Status: " + result.state());
}

// Process results
if (result.state() == BatchState.SUCCEEDED) {
    List<Response<Embedding>> embeddings = result.responses();
    System.out.println("Generated " + embeddings.size() + " embeddings");

    // Store embeddings in your vector database
    for (int i = 0; i < embeddings.size(); i++) {
        Embedding embedding = embeddings.get(i).content();
        System.out.println("Embedding " + i + " has " + embedding.dimension() + " dimensions");
        // vectorStore.add(embedding, segments.get(i));
    }
} else {
    System.err.println("Batch did not succeed: " + result.state());
}

Request/response API and capabilities

Besides the builder-level taskType(...) shown above, GoogleAiEmbeddingModel supports the request/response API with per-call parameters:

Per-call parameters: input_type (EmbeddingInputType.QUERY / DOCUMENT) lets you embed queries and documents differently without configuring two model instances. For gemini-embedding-001 it is applied via Gemini's RETRIEVAL_QUERY / RETRIEVAL_DOCUMENT task type. Gemini Embedding 2 does not accept the task type parameter, so it is applied as a prompt instruction instead (task: search result | query: ... for a query, title: none | text: ... for a document) — this happens automatically.
Multimodal (gemini-embedding-2-preview, Gemini Embedding 2): natively embeds interleaved text + image into a single embedding. Earlier models (e.g. gemini-embedding-001) are text-only. Images must be provided as base64 (ImageContent).
Listeners: configure via GoogleAiEmbeddingModel.builder().listeners(...).

See Embedding Model for the request/response API and multimodal usage.

Learn more

If you're interested in learning more about the Google AI Gemini embedding models, please have a look at the documentation.

Table of Contents​

Maven Dependency​

API Key​

Models available​

GoogleAiEmbeddingModel​

Basic Usage​

Embedding Multiple Texts​

Configuring the Embedding Model​

Task Types​

Using Metadata for Document Titles​

Output Dimensionality​

Batch Processing​

Batch Embedding Processing​

Creating Batch Embedding Jobs​

Handling Batch Responses​

Correlating Results with Requests​

Polling for Results​

Managing Batch Jobs​

File-Based Batch Processing​

Using Metadata with Batch Embeddings​

Configuration​

Important Constraints​

Example: Complete Workflow​

Request/response API and capabilities​

Learn more​

Table of Contents