Add Data to Cache

After successfully connecting to the cache and gaining a valid cache handle, you can add data to the cache. This data is usually frequently accessed by the application and is not frequently modified. For example, you wish to add the products information of a store into the cache as it is frequently accessed for checking availability. This saves database trips as data can be accessed from the cache instead of accessing the database for each request.

NCache provides the Add() method and its overloads to facilitate adding objects to cache for the first time.

Add Operation Behavior

Add is a one-time operation. The same key cannot be added again if it already exists in the cache. For that you need to Insert it into the cache, which overwrites the value for the existing key.
Add returns CacheItemVersion, a value which internally marks the version of the cache item being added. For each subsequent update of the same item, this version will be updated. This is used in data concurrency scenarios to internally keep track of the updated objects, and is discussed in detail in the chapter Optimistic Locking.
In advanced cases, if data source is configured, data will be added to cache as well as the data source during the Add operation. For more details, refer to the chapter Data Source Providers.

Include the following namespaces in your application:
- Alachisoft.NCache.Client
- Alachisoft.NCache.Runtime.Exceptions
The application must be connected to cache before performing the operation.
Cache must be running.
Make sure that the data being added is serializable.
To ensure the operation is fail safe, it is recommended to handle any potential exceptions within your application, as explained in Handling Failures.

Include the following packages in your application:
- import com.alachisoft.ncache.web.caching.*;
- import com.alachisoft.ncache.runtime.exceptions.*;
The application must be connected to cache before performing the operation.
Cache must be running.
Make sure that the data being added is serializable.
To ensure the operation is fail safe, it is recommended to handle any potential exceptions within your application, as explained in Handling Failures.

Custom Object

You can add a single object to the cache using various overloads of the Add() method and add() in case of Java.

Warning

If the key already exists, an "OperationFailedException" will be thrown.

The following example adds an object of Product class and its associated key into the cache. This returns CacheItemVersion. If the key already exists, a "Specified key already exists" exception is thrown. The code sample then checks whether the key has been successfully added to cache or not.

Tip

One quick way to verify whether item has been added is to use either properties of the Cache class:

Count returns the number of items present in the cache.
Contains verifies if a specified key exists in the cache.

Recommendation: To ensure the operation is fail safe, it is recommended to handle any potential exceptions within your application, as explained in Handling Failures.

.NET/.NET Core
Java

try
{
    // Pre-condition: Cache is already connected

    // Get product from database against given product ID
    Product product = FetchProductFromDB(1001);

    // Generate a unique cache key for this product
    string key = $"Product:{product.ProductID}";

    // Add Product object to cache
    CacheItemVersion version = cache.Add(key, product);

    // Item added in cache successfully
}
catch (OperationFailedException ex)
{
    // NCache specific exception

    if(ex.ErrorCode == NCacheErrorCodes.KEY_ALREADY_EXISTS)
    {
        // An item with the same key already exists
    }
    else
    {
        // Exception can occur due to:
        // Connection Failures 
        // Operation Timeout
        // Operation performed during state transfer
    }
}
catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException
}

try
{
    // Pre-condition: Cache is already connected

    // Get product from database against given product ID
    Product product = fetchProductFromDB(1001);

    // Generate a unique cache key for this product
    String key = "Product:" + product.getProductID();

    // Add Product object to cache
    CacheItemVersion version = cache.add(key, product);

    // Item added in cache successfully
}
catch (OperationFailedException ex)
{
    // NCache specific exception

    if (ex.getErrorCode() == NCacheErrorCodes.KEY_ALREADY_EXISTS)
    {
        // An item with the same key already exists
    }
    else
    {
        // Exception can occur due to:
        // Connection Failures
        // Operation Timeout
        // Operation performed during state transfer
    }
}
catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException

}

CacheItem

CacheItem is a custom class provided by NCache which can be used to add data to the cache and also lets you set additional metadata associated with an object of this class. This metadata defines the properties of the item like expiration, dependencies and more. You can refer to all properties of CacheItem here. For Java, please refer to the properties of CacheItem here.

Warning

If the key already exists, an "OperationFailedException" will be thrown.

Tip

One quick way to verify whether item has been added, is to use either properties of the Cache class:

Count returns the number of items present in the cache.
Contains verifies if a specified key exists in the cache.

The following example adds a basic CacheItem containing the Product object into the cache; additional properties will be set against the CacheItem in successive chapters. If the key already exists, a "Specified key already exists" exception is thrown. The code sample then checks whether the key has been successfully added to cache or not.

Recommendation: To ensure the operation is fail safe, it is recommended to handle any potential exceptions within your application, as explained in Handling Failures.

.NET/.NET Core
Java

try 
{
    // Pre-condition: Cache is already connected

    // Get product from database against given product ID
    Product product = FetchProductFromDB(1001);

    // Generate a unique cache key for this product
    string key = $"Product:{product.ProductID}";

    // Create a new CacheItem for this product
    // You can OPTIONALLY specify multiple properties e.g. Priority, Expiration
    // These properties are explained in successive chapters

    var cacheItem = new CacheItem(product);
    // cacheItem.AbsoluteExpiration = DateTime.Now.AddMinutes(5);

    // Add CacheItem to cache
    CacheItemVersion version = cache.Add(key, cacheItem);
}
catch (OperationFailedException ex)     
{
    // NCache specific exception

    if(ex.ErrorCode == NCacheErrorCodes.KEY_ALREADY_EXISTS)
    {
        // An item with the same key already exists
    }
    else
    {
        // Exception can occur due to:
        // Connection Failures 
        // Operation Timeout
        // Operation performed during state transfer
    }
}
catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException
}

try 
{
    // Pre-condition: Cache is already connected

    // Get product from database against given product ID
    Product product = fetchProductFromDB(1001);

    // Generate a unique cache key for this product
    String key = "Product:" + product.getProductID();

    // You can OPTIONALLY specify multiple properties e.g. Priority, Expiration
    // These properties are explained in successive chapters
    CacheItem cacheItem = new CacheItem(product);
    // cacheItem.AbsoluteExpiration = DateTime.Now.AddMinutes(5);

    // Add CacheItem to cache
    CacheItemVersion version = cache.add(key, cacheItem);
} 
catch (OperationFailedException ex)
{
    // NCache specific exception

    if (ex.getErrorCode() == NCacheErrorCodes.KEY_ALREADY_EXISTS)
    {
        // An item with the same key already exists
    }
    else
    {
        // Exception can occur due to:
        // Connection Failures
        // Operation Timeout
        // Operation performed during state transfer
    }
}
catch (Exception ex) 
{
    // Any generic exception like ArgumentNullException or ArgumentException
}

CacheItem with Location Affinity

Note

This feature is only available in NCache Enterprise Edition.

You can also add a cache item using NCache's Location Affinity syntax. Location Affinity will store the cache item created with an identical key at the same node so that when the data is fetched from cache, the extra matching cost is saved.

Recommendation: To ensure the operation is fail safe, it is recommended to handle any potential exceptions within your application, as explained in Handling Failures.

.NET/.NET Core
Java

try 
{
    // Pre-condition: Cache is already connected

    // Get product from database against given product ID
    Product product = FetchProductFromDB(1001);

    // Unique product key for this product
    string productKey = "Product:1001";

    // Create a new CacheItem for this product
    var productCacheItem = new CacheItem(product);

    // Add CacheItem to cache
    CacheItemVersion version = cache.Add(key, productCacheItem);

    // Get order from database against given order ID
    Order order = FetchOrderFromDB(17);

    // Unique order key for this order using Location Affinity syntax
    // This will create an affinity for this orderKey with the respective productKey
    string orderKey = "Order_{Product:1001}";

    var orderCacheItem = new CacheItem(order);

    // Add order with Location Affinity to cache
    CacheItemVersion version = cache.Add(key, orderCacheItem);

}
catch (OperationFailedException ex)     
{
    // NCache specific exception

    if(ex.ErrorCode == NCacheErrorCodes.KEY_ALREADY_EXISTS)
    {
        // An item with the same key already exists
    }
    else
    {
        // Exception can occur due to:
        // Connection Failures 
        // Operation Timeout
        // Operation performed during state transfer
    }
}
catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException
}

try
{
    // Pre-condition: Cache is already connected

    // Get product from database against given product ID
    Product product = fetchProductFromDB(1001);

    // Unique product key for this product
    String productKey = "Product:1001";

    // Create a new CacheItem for this product
    CacheItem productCacheItem = new CacheItem(product);

    // Add CacheItem to cache
    CacheItemVersion version = cache.add(productKey, productCacheItem);

    // Get order from database against given order ID
    Order order = fetchOrderFromDB(17);

    // Unique order key for this order using Location Affinity syntax
    // This will create an affinity for this orderKey with the respective productKey
    String orderKey = "Order_{" + productKey + "}";

    CacheItem orderCacheItem = new CacheItem(order);

    // Add order with Location Affinity to cache
    CacheItemVersion cacheItemVersion = cache.add(orderKey, orderCacheItem);

}
catch (OperationFailedException ex)
{
    // NCache specific exception

    if (ex.getErrorCode() == NCacheErrorCodes.KEY_ALREADY_EXISTS)
    {
        // An item with the same key already exists
    }
    else
    {
        // Exception can occur due to:
        // Connection Failures
        // Operation Timeout
        // Operation performed during state transfer
    }
}
catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException
}

JsonObject

Note

This feature is only available in NCache Enterprise Edition.

You can add a JsonObject, JsonArray or JsonValue to the cache derived from JsonValueBase class provided by NCache. JsonObject is added in the cache against a unique key which lets you perform further operations using this key. For more detail regarding the topic, please refer to the Cache Data as JSON section.

Note

In order to use JsonValueBase, please add the following namespace in your application:

Alachisoft.NCache.Runtime.JSON

The following example adds a JsonObject in the cache along with various attributes.

.NET/.NET Core
Java

try
{
    // Pre-Condition: Cache is already connected
    // Cache is JSON serialized

    // Get product from database against given product ID
    Product product = FetchProductFromDB(1001);

    // Create a unique key for the object
    string key = $"Product:{product.ProductID}";

    // Create a new JSON object and set attributes
    // string values need to be added with JsonValue
    var jsonProduct = new JsonObject();
    jsonProduct.AddAttribute("ProductID", product.ProductID);
    jsonProduct.AddAttribute("ProductName", (JsonValue)product.ProductName);
    jsonProduct.AddAttribute("Category", (JsonValue)product.Category);
    jsonProduct.AddAttribute("UnitPrice", product.UnitPrice);
    jsonProduct.AddAttribute("UnitsInStock", product.UnitsInStock);

    // Add object in the cache with the key
    cache.Add(key, jsonProduct);
    // JsonObject will successfully be added to the cache
}
catch (OperationFailedException ex)
{
    if (ex.ErrorCode == NCacheErrorCodes.ATTRIBUTE_ALREADY_EXISTS)
    {
        // An attribute already exists with the same name
    }
    else if (ex.ErrorCode == NCacheErrorCodes.REFERENCE_TO_SELF)
    {
        // No object can contain a reference to itself
    }
    else
    {
        // Exception can occur due to:
        // Connection Failures 
        // Operation Timeout
        // Operation performed during state transfer
    }
}
catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException
}

try
{
    // Pre-Condition: Cache is already connected
    // Cache is JSON serialized

    // Get product from database against given product ID
    Product product = fetchProductFromDB(1001);

    // Create a unique key for the object
    String key = "Product:" + product.getProductID();

    // Create a new JSON object and set attributes
    // string values need to be added with JsonValue
    JsonObject jsonProduct = new JsonObject();
    jsonProduct.addAttribute("ProductID", new JsonValue(product.getProductID()));
    jsonProduct.addAttribute("ProductName", new JsonValue(product.getProductName()));
    jsonProduct.addAttribute("Category", new JsonValue(product.getCategory()));
    jsonProduct.addAttribute("UnitPrice", new JsonValue(product.getPrice()));
    jsonProduct.addAttribute("UnitsInStock", new JsonValue(product.getUnitsAvailable()));

    // Add object in the cache with the key
    cache.add(key, jsonProduct);
    // JsonObject will successfully be added to the cache
}
catch (OperationFailedException ex)
{
    if (ex.getErrorCode() == NCacheErrorCodes.ATTRIBUTE_ALREADY_EXISTS)
    {
        // An attribute already exists with the same name
    }
    else if (ex.getErrorCode() == NCacheErrorCodes.REFERENCE_TO_SELF)
    {
        // No object can contain a reference to itself
    }
    else
    {
        // Exception can occur due to:
        // Connection Failures
        // Operation Timeout
        // Operation performed during state transfer
    }
}
catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException
}

Data Structure

Note

This feature is only available in NCache Enterprise Edition.

You can also add data structures in cache when they are created. Moreover, you can further add data into the data type. For more detail on supported data structures, please refer to the section Data Structures in Cache.

The following code sample shows how a list of Product type can be created in cache against the cache key "ProductList" which must be unique. It then adds Product objects to the list.

Note

In order to use data structures, the following additional namespaces must be added into your application:

Alachisoft.NCache.Client.DataTypes
Alachisoft.NCache.Client.DataTypes.Collections

.NET/.NET Core
Java

try
{
    // Pre-condition: Cache must be connected

    // Specify unique cache key for list
    string key = "ProductList";

    // Create list of Product type in cache
    IDistributedList<Product> list = cache.DataTypeManager
                                        .CreateList<Product>(key);

    // Check if the list exists in cache
    // using cache.Contains() 

    // Get products to add to list
    Product[] products = FetchProducts();

    foreach (var product in products)
    {
        // Add products to list
        list.Add(product);
    }
}
catch (OperationFailedException ex)
{
    // NCache specific exception

    if(ex.ErrorCode == NCacheErrorCodes.KEY_ALREADY_EXISTS)
    {
        // An item with the same key already exists
    }
    else
    {
        // Exception can occur due to:
        // Connection Failures 
        // Operation Timeout
        // Operation performed during state transfer
    }
}
catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException
}

try
{
    // Pre-condition: Cache must be connected

    // Specify unique cache key for list
    String key = "ProductList";

    // Create list of Product type in cache
    DistributedList<Product> list = cache.getDataStructuresManager().<Product>createList(key);

    // Check if the list exists in cache
    // using cache.Contains()

    // Get products to add to list
    Product[] products = fetchProducts();

    for (Product product : products)
    {
        // Add products to list
        list.add(product);
    }
}
catch (OperationFailedException ex)
{
    // NCache specific exception

    if (ex.getErrorCode() == NCacheErrorCodes.KEY_ALREADY_EXISTS)
    {
        // An item with the same key already exists
    }
    else
    {
        // Exception can occur due to:
        // Connection Failures
        // Operation Timeout
        // Operation performed during state transfer
    }
}
catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException
}

Recommendation: To ensure the operation is fail safe, it is recommended to handle any potential exceptions within your application, as explained in Handling Failures.

Bulk Items

NCache also allows synchronous bulk addition of items in a single call to reduce network cost. AddBulk() adds an array of CacheItem to the cache with the corresponding cache keys. The method returns a dictionary of all the keys that fail to add, along with the failure reason. For Java, NCache provides a method of addBulk to add an array of items in the cache.

Although a bulk operation is executed as a single operation, the failure of operations is treated individually. For example, if a bulk of 100 items is added to the cache and 20 of those items already exist in the cache, the remaining 80 items will be added to the cache. The keys of existing 20 items will be returned to the application as a dictionary of failed operations along with the failure reason.

Note

Any keys that fail to add and their failure reason will be returned as an IDictionary.

The following code adds a bulk of product items to the cache. If there are any keys that failed to add, the keys can be handled according to your business needs.

Recommendation: To ensure the operation is fail safe, it is recommended to handle any potential exceptions within your application, as explained in Handling Failures.

.NET/.NET Core
JAVA

try
{
    // Pre-condition: Cache is already connected

    // Fetch all products from database
    Product[] products = FetchProductsFromDB();

    //Create dictionary of items to be added to cache
    IDictionary<string, CacheItem> dictionary = new Dictionary<string, CacheItem>();

    foreach (var prod in products)
    {
        string key = $"Product:{prod.ProductID}";
        var cacheItem = new CacheItem(prod);

        //Add dictionary to cache
        dictionary.Add(key, cacheItem);
    }

    // Add bulk data
    IDictionary<string, Exception> keysFailedToAdd = cache.AddBulk(dictionary);

    //Check if keys failed to add
    if (keysFailedToAdd.Count > 0)
    {
        foreach (KeyValuePair<string, Exception> entry in keysFailedToAdd)
        {
            // Check failure reason
            if (entry.Value is OperationFailedException)
            {
                var ex = entry.Value as OperationFailedException;

                if(ex.ErrorCode == NCacheErrorCodes.KEY_ALREADY_EXISTS)
                {
                    // An item with the same key already exists
                }
            }
            else
            {
                // Any other exception
            }
        }
    }
}
catch (OperationFailedException ex)
{
    // Exception can occur due to:
    // Connection Failures 
    // Operation Timeout
    // Operation performed during state transfer
}
catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException
}

try
{
    // Pre-condition: Cache is already connected

    // Fetch all products from database
    Product[] products = fetchProducts();

    //Create Map of items to be added to cache
    java.util.Map<String, CacheItem> itemsMap = new java.util.HashMap<String, CacheItem>();

    for (Product product : products)
    {
        String key = "Product:" + product.getProductID();
        CacheItem cacheItem = new CacheItem(product);

        //Add Map to cache
        itemsMap.put(key, cacheItem);
    }

    // Add bulk data
    java.util.Map<String, Exception> keysFailedToAdd = cache.addBulk(itemsMap);

    //Check if keys failed to add
    if (keysFailedToAdd.size() > 0)
    {
        for (java.util.Map.Entry<String, Exception> entry : keysFailedToAdd.entrySet())
        {
            // Check failure reason
            if (entry.getValue() instanceof OperationFailedException)
            {
                OperationFailedException ex = (OperationFailedException) entry.getValue();
                if (ex.getErrorCode() == NCacheErrorCodes.KEY_ALREADY_EXISTS)
                {
                    // An item with the same key already exists
                }
            }
            else
            {
                // Any other exception
            }
        }
    }
}
catch (OperationFailedException ex)
{
    // Exception can occur due to:
    // Connection Failures
    // Operation Timeout
    // Operation performed during state transfer
}
catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException
}

Asynchronous API

Note

This feature is only available in NCache Enterprise Edition.

Asynchronous operations are performed in the background, so the client does not have to wait for the response from the server to execute further operations. The list of actions to be performed on the cache is maintained in a queue at the client side and a dedicated background thread keeps on sending them to the server side. Hence, all the operations are being executed in a pure asynchronous manner, increasing the efficiency of the client application.

AddAsync returns object of the Task class which can further be used according to the business needs of the client application. NCache provides three different status flags to notify the success or failure of the operation. For Java, addAsync method is used to add items in the cache asynchronously.

IsCanceled: Notifies if the AddAsync function is canceled.
IsCompleted: Notifies if the AddAsync function is completed.
IsFaulted: Notifies if the AddAsync function is faulted.

.NET/.NET Core
JAVA

try 
{
    // Pre-condition: Cache is already connected

    // Get product from database against given product ID
    Product product = FetchProductFromDB(1001);

    // Generate a unique cache key for this product
    string key = $"Product:{product.ProductID}";

    // Add Product object to cache
    Task task = cache.AddAsync(key, product);

    //This task object can be used as per your business needs
    if (task.IsFaulted)
    {
        // Task completed due to an unhandled exception
    }
}
catch (OperationFailedException ex)     
{
    // NCache specific exception
    // Exception can occur due to Connection Failure
}
catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException
}

try
{
    // Pre-condition: Cache is already connected

    // Get product from database against given product ID
    Product product = fetchProductFromDB(1001);

    // Generate a unique cache key for this product
    String key = "Product:" + product.getProductID();

    // Add Product object to cache
    FutureTask<CacheItemVersion> task = cache.addAsync(key, product);

    //This task object can be used as per your business needs
    if (task.isDone())
    {
        // Task completed due to an unhandled exception
    }
}
catch (OperationFailedException ex)
{
    // NCache specific exception
    // Exception can occur due to Connection Failure
}
catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException
}

Using ICache.Add for Distributed Locking

Due to its versatile nature, another wide use of Add operation is in locking the cache if it is being used by multiple applications.

For example, an environment is set such that as soon as any application connects to the cache, it adds a specific key which is known to all applications. And once the application is done using the cache, it removes the key from the cache. If the key is added successfully, it can proceed to use the cache according to its logic. However, if the key already exists, it means the cache is already being used by an application, and is "locked".

This is described in steps in the following diagram:

Add Data to Cache

App A and App B add the "WorkStarted" key as soon as the cache is started.
The key passed by App A is added to the cache before the one passed by App B.
App B gets a "Specified key already exists" exception. In this scenario, App B will wait for App A to finish its work, i.e., until it can successfully add the "WorkStarted" key.
App A removes the key from the cache once done with its work.
App B adds the key to cache again.
The key is added by App B successfully, locking the cache for other applications.

Additional Resources

NCache provides sample application for Basic Operations at:

GitHub
Shipped with NCache: *%NCHOME%\samples\dotnet\BasicOperations

Add Data to Cache

Pre-requisites

Custom Object

Warning

Tip

CacheItem

Warning

Tip

CacheItem with Location Affinity

Note

JsonObject

Note

Note

Data Structure

Note

Note

Bulk Items

Note

Asynchronous API

Note

Using ICache.Add for Distributed Locking

Additional Resources

See Also