Azure Cosmos Java — Agent Skill by Microsoft

From the author

Azure Cosmos DB SDK for Java. NoSQL database operations with global distribution, multi-model support, and reactive patterns. Triggers: "CosmosClient java", "CosmosAsyncClient", "cosmos database java", "cosmosdb java", "document database java".

— the description by Microsoft

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

The Azure Cosmos DB SDK for Java provides a comprehensive set of tools for developers to integrate NoSQL database operations into Java applications. It supports both synchronous and asynchronous programming models, allowing for flexible interaction with databases, containers, and items. The SDK includes features for managing consistency levels, configuring connection modes, and handling geo-distributed data, alongside built-in support for error handling and request unit monitoring.

What it does

Provides client classes for account, database, and container-level operations.
Supports both synchronous and asynchronous (reactive) execution patterns.
Enables CRUD operations on database items with partition key support.
Allows for SQL-based querying of documents within containers.
Offers configuration options for consistency levels and preferred regions.
Includes mechanisms for monitoring request unit (RU) consumption.

When to use it

When building Java applications that require connectivity to Azure Cosmos DB.
When you need to perform NoSQL database operations within a Java environment.
When implementing reactive patterns for database interactions.
When managing multi-region data distribution in Azure.

Advantages

Native Java support for Azure Cosmos DB features.
Flexible client configuration for various consistency and connection requirements.
Comprehensive error handling and retry logic.
Supports both simple synchronous and complex asynchronous workflows.

Usage examples

“How do I initialize a synchronous CosmosClient in Java?”: The SDK provides the CosmosClientBuilder class to configure and build a CosmosClient using an endpoint and key.
“Show me how to perform a CRUD operation using the async client.”: The SDK uses reactive patterns to chain createItem, readItem, replaceItem, and deleteItem operations on a CosmosAsyncContainer.
“How can I query items from a container?”: You can use the queryItems method on a CosmosContainer, providing a SQL query string and request options to retrieve items.

Install

Download the skill as a ZIP:
https://mp-staging.autogineer.com/agent-skills/microsoft/azure-cosmos-java/download

Unzip it into the cross-client skills folder of your project:

mkdir -p .agents/skills && unzip azure-cosmos-java.zip -d .agents/skills

Documentation by Microsoft

Azure Cosmos DB SDK for Java

Client library for Azure Cosmos DB NoSQL API with global distribution and reactive patterns.

Installation

<dependency>
    <groupId>com.azure</groupId>
    <artifactId>azure-cosmos</artifactId>
    <version>LATEST</version>
</dependency>

Or use Azure SDK BOM:

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>com.azure</groupId>
            <artifactId>azure-sdk-bom</artifactId>
            <version>{bom_version}</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

<dependencies>
    <dependency>
        <groupId>com.azure</groupId>
        <artifactId>azure-cosmos</artifactId>
    </dependency>
</dependencies>

Environment Variables

COSMOS_ENDPOINT=https://<account>.documents.azure.com:443/
COSMOS_KEY=<your-primary-key>

Authentication

Key-based Authentication

import com.azure.cosmos.CosmosClient;
import com.azure.cosmos.CosmosClientBuilder;

CosmosClient client = new CosmosClientBuilder()
    .endpoint(System.getenv("COSMOS_ENDPOINT"))
    .key(System.getenv("COSMOS_KEY"))
    .buildClient();

Async Client

import com.azure.cosmos.CosmosAsyncClient;

CosmosAsyncClient asyncClient = new CosmosClientBuilder()
    .endpoint(serviceEndpoint)
    .key(key)
    .buildAsyncClient();

With Customizations

import com.azure.cosmos.ConsistencyLevel;
import java.util.Arrays;

CosmosClient client = new CosmosClientBuilder()
    .endpoint(serviceEndpoint)
    .key(key)
    .directMode(directConnectionConfig, gatewayConnectionConfig)
    .consistencyLevel(ConsistencyLevel.SESSION)
    .connectionSharingAcrossClientsEnabled(true)
    .contentResponseOnWriteEnabled(true)
    .userAgentSuffix("my-application")
    .preferredRegions(Arrays.asList("West US", "East US"))
    .buildClient();

Client Hierarchy

Class	Purpose
`CosmosClient` / `CosmosAsyncClient`	Account-level operations
`CosmosDatabase` / `CosmosAsyncDatabase`	Database operations
`CosmosContainer` / `CosmosAsyncContainer`	Container/item operations

Core Workflow

Create Database

// Sync
client.createDatabaseIfNotExists("myDatabase")
    .map(response -> client.getDatabase(response.getProperties().getId()));

// Async with chaining
asyncClient.createDatabaseIfNotExists("myDatabase")
    .map(response -> asyncClient.getDatabase(response.getProperties().getId()))
    .subscribe(database -> System.out.println("Created: " + database.getId()));

Create Container

asyncClient.createDatabaseIfNotExists("myDatabase")
    .flatMap(dbResponse -> {
        String databaseId = dbResponse.getProperties().getId();
        return asyncClient.getDatabase(databaseId)
            .createContainerIfNotExists("myContainer", "/partitionKey")
            .map(containerResponse -> asyncClient.getDatabase(databaseId)
                .getContainer(containerResponse.getProperties().getId()));
    })
    .subscribe(container -> System.out.println("Container: " + container.getId()));

CRUD Operations

import com.azure.cosmos.models.PartitionKey;

CosmosAsyncContainer container = asyncClient
    .getDatabase("myDatabase")
    .getContainer("myContainer");

// Create
container.createItem(new User("1", "John Doe", "[email protected]"))
    .flatMap(response -> {
        System.out.println("Created: " + response.getItem());
        // Read
        return container.readItem(
            response.getItem().getId(),
            new PartitionKey(response.getItem().getId()),
            User.class);
    })
    .flatMap(response -> {
        System.out.println("Read: " + response.getItem());
        // Update
        User user = response.getItem();
        user.setEmail("[email protected]");
        return container.replaceItem(
            user,
            user.getId(),
            new PartitionKey(user.getId()));
    })
    .flatMap(response -> {
        // Delete
        return container.deleteItem(
            response.getItem().getId(),
            new PartitionKey(response.getItem().getId()));
    })
    .block();

Query Documents

import com.azure.cosmos.models.CosmosQueryRequestOptions;
import com.azure.cosmos.util.CosmosPagedIterable;

CosmosContainer container = client.getDatabase("myDatabase").getContainer("myContainer");

String query = "SELECT * FROM c WHERE c.status = @status";
CosmosQueryRequestOptions options = new CosmosQueryRequestOptions();

CosmosPagedIterable<User> results = container.queryItems(
    query,
    options,
    User.class
);

results.forEach(user -> System.out.println("User: " + user.getName()));

Key Concepts

Partition Keys

Choose a partition key with:

High cardinality (many distinct values)
Even distribution of data and requests
Frequently used in queries

Consistency Levels

Level	Guarantee
Strong	Linearizability
Bounded Staleness	Consistent prefix with bounded lag
Session	Consistent prefix within session
Consistent Prefix	Reads never see out-of-order writes
Eventual	No ordering guarantee

Request Units (RUs)

All operations consume RUs. Check response headers:

CosmosItemResponse<User> response = container.createItem(user);
System.out.println("RU charge: " + response.getRequestCharge());

Best Practices

Reuse CosmosClient — Create once, reuse throughout application
Use async client for high-throughput scenarios
Choose partition key carefully — Affects performance and scalability
Enable content response on write for immediate access to created items
Configure preferred regions for geo-distributed applications
Handle 429 errors with retry policies (built-in by default)
Use direct mode for lowest latency in production

Error Handling

import com.azure.cosmos.CosmosException;

try {
    container.createItem(item);
} catch (CosmosException e) {
    System.err.println("Status: " + e.getStatusCode());
    System.err.println("Message: " + e.getMessage());
    System.err.println("Request charge: " + e.getRequestCharge());
    
    if (e.getStatusCode() == 409) {
        System.err.println("Item already exists");
    } else if (e.getStatusCode() == 429) {
        System.err.println("Rate limited, retry after: " + e.getRetryAfterDuration());
    }
}

Reference Links

Resource	URL
Maven Package	https://central.sonatype.com/artifact/com.azure/azure-cosmos
API Documentation	https://azuresdkdocs.z19.web.core.windows.net/java/azure-cosmos/latest/index.html
Product Docs	https://learn.microsoft.com/azure/cosmos-db/
Samples	https://github.com/Azure-Samples/azure-cosmos-java-sql-api-samples
Performance Guide	https://learn.microsoft.com/azure/cosmos-db/performance-tips-java-sdk-v4-sql
Troubleshooting	https://learn.microsoft.com/azure/cosmos-db/troubleshoot-java-sdk-v4-sql

Files

ATTRIBUTION.mdAdded by AutoGineer958 B
LICENSELicence file added by AutoGineer1.1 KiB
SKILL.md7.3 KiB
references/examples.md11.7 KiB

Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Security

No issues found by our static scan· No issues found

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Download ZIP

The ZIP holds the skill’s files, its licence files and an ATTRIBUTION.md. Download azure-cosmos-java.zip