<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
var dbResponse = client.createDatabaseIfNotExists("myDatabase");
var database = client.getDatabase(dbResponse.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", "john@example.com"))
    .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("john.doe@example.com");
        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");

var query = new com.azure.cosmos.models.SqlQuerySpec(
    "SELECT * FROM c WHERE c.status = @status",
    java.util.List.of(new com.azure.cosmos.models.SqlParameter("@status", "active")));
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

When to Use

This skill is applicable to execute the workflow or actions described in the overview.

Limitations

Use this skill only when the task clearly matches the scope described above.
Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.

The CRUD example requires a User model whose serialized partition-key property matches the container path. The shown new PartitionKey(user.getId()) is valid only when that actual partition-key value equals the ID; otherwise pass the model's true partition-key value. Keep sample writes/deletes in an authorized test container, bound RU costs, and close clients on shutdown. Reactive subscriptions need completion/error handling; do not infer completion from calling subscribe().

azure-cosmos-java

Azure Cosmos DB SDK for Java

Installation