rootcastleco/rei-skills/azure-cosmos-java

Name: azure-cosmos-java
Author: rootcastleco

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npx vskill@latest install rootcastleco/rei-skills/azure-cosmos-java

SKILL.md

Azure Cosmos DB SDK for Java

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

Installation

xml

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

Or use Azure SDK BOM:

xml

<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

bash

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

Authentication

Key-based Authentication

java

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

java

import com.azure.cosmos.CosmosAsyncClient;
 
CosmosAsyncClient asyncClient = new CosmosClientBuilder()
    .endpoint(serviceEndpoint)
    .key(key)
    .buildAsyncClient();

With Customizations

java

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

java

// 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

java

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

java

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

java

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:

java

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

java

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.

🏰 Rei Skills — Curated by Rootcastle Engineering & Innovation | Batuhan Ayrıbaş
Engineering Beyond Boundaries | admin@rootcastle.com

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Source

SKILL.md in the repositoryCheckingskills/azure-cosmos-java/SKILL.md

Popularity

Repository stars: 6
Repository forks: 2
7-day trend score: 15

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