Add and Update Cache Data with Named Tags

Note

This feature is only available in NCache Enterprise Edition.

In order to associate named tags with any cache item, it is required to provide a list of named tags, each having two parameters that are key as a string which is the name of the tag, and value as any primitive type which is the assigned value to the key. NCache then allows you to associate your objects with these named tags. You can add items in the cache with named tags and then later retrieve these items from the cache using the previously added named tags.

When items are already added in the cache with certain named tags, NCache provides the user with an option of updating named tags already present in the cache.

Prerequisites

To learn about the standard prerequisites required to work with all NCache client side features please refer to the given page on Client Side API Prerequisites.
For API details, refer to: ICache, CacheItem, NamedTags, Add, Insert, Get, NamedTagsDictionary.

Add Named Tags

NCache provides a custom class, CacheItem that can be used to add data to the cache. This class encapsulates data as its value property. CacheItem also lets you set additional specifications associated with an object as a property of the NamedTags class.

In the following example, named tags are set by assigning them as a property of CacheItem.

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

    // In an online-store, VIP members are offered 10% discount
    // A customer with VIP membership has signed in to the website 

    string customerKey = $"Customer:ALFKI";
    Customer customer = cache.Get<Customer>(customerKey);

    // Get customer from database if not found in cache
    if (customer == null)
    {
        // Get customer from the database
        customer = FetchCustomerFromDB("ALFKI");

        // Create a new CacheItem
        var cacheItem = new CacheItem(customer);

        // Creating a Named Tags Dictionary
        var namedTags = new NamedTagsDictionary();

        // Adding Named Tags to the Dictionary where
        // Keys are the names of the tags as string type and Values are of primitive type
        namedTags.Add("VIP_Membership_Discount", 0.10 );

        // Setting the named tag property of the cacheItem
        cacheItem.NamedTags = namedTags;

        cache.Add(customerKey, 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 other generic exception like ArgumentNullException or ArgumentException
}

try
{    
    // Pre-condition: Cache is already connected
    // Get product from database against given productID
    Product product = fetchProductFromDB(1001);

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

    // Creating a Named Tags Dictionary
    NamedTagsDictionary productNamedTag = new NamedTagsDictionary();    

    // Adding Named Tags to the Dictionary where
    // Keys are the names of the tags as string type
    // Values are the instances of data, of primitive data structures. 
    productNamedTag.add("FlashSaleDiscount", 0.5);

    // Create a new CacheItem
    CacheItem cacheItem = new CacheItem(product);

    // Setting the named tag property of the cacheitem
    cacheItem.setNamedTags(productNamedTag);

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

    // CacheItem added successfully
}
catch (OperationFailedException ex)
{
    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 IllegalArgumentException or NullPointerException        
}

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

    // Get product from database against given productID
    val product = fetchProductFromDB(1001)

    // Create a unique cache key for this product
    val key = "Product:" + product.getProductId

    // Creating a Named Tags Dictionary
    val productNamedTag = NamedTagsDictionary()

    // Adding Named Tags to the Dictionary where
    // Keys are the names of the tags as string type
    // Values are the instances of data, of primitive data structures.
    productNamedTag.add("FlashSaleDiscount", 0.5)

    // Create a new CacheItem
    val cacheItem = new CacheItem(product)

    // Setting the named tag property of the cacheItem
    cacheItem.setNamedTags(productNamedTag)

    // Add product object to the cache
    val version = cache.add(key, cacheItem)

    // CacheItem added successfully
}
catch {
    case exception: Exception => {
      // Handle any errors
    }
}

// This is an async method
try
{
    // Pre-condition: Cache is already connected
    // Get product from database against given productID
    var product = this.fetchProductFromDB(1001);

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

    // Creating a Named Tags Dictionary
    var productNamedTag = new ncache.NamedTagsDictionary();

    // Adding Named Tags to the Dictionary where
    // Keys are the names of the tags as string type
    // Values are the instances of data, of primitive data structures.
    productNamedTag.add("FlashSaleDiscount", 0.5);

    // Create a new CacheItem
    // You alose need to specify the FQN(Fully Qualified Name) of the class
    var cacheItem = new ncache.CacheItem(product,"FQN.Product");

    // Setting the named tag property of the CacheItem
    cacheItem.setNamedTags(productNamedTag);

    // Add product object to the cache
    var version = await this.cache.add(key, cacheItem);

    // CacheItem added successfully
}
catch (error)
{
    // Handle errors
}

try:
    # Pre-condition: Cache is already connected
    # Get product from database against given productID
    product = fetch_product_from_db()

    # Create a unique cache key for this product
    key = "Product:" + product.get_product_id()

    # Creating a Named Tags Dictionary
    product_named_tag = ncache.NamedTagsDictionary()

    # Adding Named Tags to the Dict where
    # Keys are the names of the tags as string type
    # Values are the instances of data, of primitive data structures.
    product_named_tag.add("FlashSaleDiscount", 0.5)

    # Create a new CacheItem
    cache_item = ncache.CacheItem(product)

    # Setting the named tag property of the CacheItem
    cache_item.set_named_tags(product_named_tag)

    # Add product object to the cache
    version = cache.add(key, cache_item)

    # CacheItem added successfully
except Exception as exp:
    # Handle errors

Note

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

Update Named Tags Data through CacheItem

Updating named tags through CacheItem requires the item to be first fetched, its named tags to be modified, and then it is reinserted into the cache using the Insert method.

The following example first fetches the CacheItem, creates a list with the newly named tags, and then reinserts the CacheItem in the cache along with the modified named tag list. Hence, it overwrites the value of existing named tags.

Warning

Providing Null named tag array will throw an ArgumentNullException.

    // Pre-condition: Cache is already connected

    // Store Owner has increased VIP membership discount to 12%

    string customerKey = $"Customer:ALFKI";
    Customer customer = cache.Get<Customer>(customerKey);

    // Get the customer from database if not found in the cache
    if (customer == null)
    {
        customer = FetchCustomerFromDB("ALFKI");
    }

    // Create a new CacheItem
    var cacheItem = new CacheItem(customer);

    // Creating a Named Tags Dictionary
    var newNamedTags = new NamedTagsDictionary();

    // Add Named Tag with the updated discount value to the Dictionary
    newNamedTags.Add("VIP_Membership_Discount", 0.12);

    // Updates the named tags with the new named tags
    // Overrides the value of the existing named tags
    cacheItem.NamedTags = newNamedTags;

    //Reinserts the updated cacheItem into the cache with the modified named tags
    cache.Insert(customerKey, cacheItem);

    // Pre-condition: Cache is already connected
    // Get cache item from cache against given key
    String key = "Products:1001";
    CacheItem cacheItem = cache.getCacheItem(key);

    // Create a Named Tags Dictionary
    NamedTagsDictionary newProductNamedTag = new NamedTagsDictionary();

    // Adding Named Tags to the Dictionary where
    // Keys are the names of the tags as string type
    // Values are the updated instances of data, of primitive data types. 
    newProductNamedTag.add("FlashSaleDiscount", 0.7);

    // Updates the named tags with the new named tags
    // Overrides the value of the existing named tags
    cacheItem.setNamedTags(newProductNamedTag);

    //Re-inserts the cacheItem into cache with modified named tags
    CacheItemVersion version = cache.insert(key, cacheItem);

    // cacheItem is successfully added in cache with modified named tags

    // Pre-condition: Cache is already connected

    // Get cache item from cache against given key
    val key = "Products:1001"
    val cacheItem = cache.getCacheItem(key)

    // Create a Named Tags Dictionary
    val newProductNamedTag = new NamedTagsDictionary

    // Adding Named Tags to the Dictionary where
    // Keys are the names of the tags as string type
    // Values are the updated instances of data, of primitive data types.
    newProductNamedTag.add("FlashSaleDiscount", 0.7)

    // Updates the named tags with the new named tags
    // Overrides the value of the existing named tags
    cacheItem.setNamedTags(newProductNamedTag)

    //Re-inserts the cacheItem into cache with modified named tags
    val version = cache.insert(key, cacheItem)

    // cacheItem is successfully added in cache with modified named tags

     // This is an async method

    // Pre-condition: Cache is already connected
    // Get cache item from cache against given key
    var key = "Product:1001";
    var cacheItem = await this.cache.getCacheItem(key);

    // Create a Named Tags Dictionary
    var newProductNamedTag = new ncache.NamedTagsDictionary();

    // Adding Named Tags to the Dictionary where
    // Keys are the names of the tags as string type
    // Values are the updated instances of data, of primitive data types.
    newProductNamedTag.add("FlashSaleDiscount", 0.7);

    // Updates the named tags with the new named tags
    // Overrides the value of the existing named tags
    cacheItem.setNamedTags(newProductNamedTag);

    //Re-inserts the cacheItem into cache with modified named tags
    var version = await this.cache.insert(key, cacheItem);

    // cacheItem is successfully added in cache with modified named tags


    # Pre-condition: Cache is already connected
    # Get cache item from cache against given key
    key = "Product:1001"
    cache_item = cache.get_cacheitem(key)

    # Create a Named Tags Dictionary
    new_product_named_tag = ncache.NamedTagsDictionary()

    # Adding Named Tags to the Dict where
    # Keys are the names of the tags as string type
    # Values are the updated instances of data, of primitive data types.
    new_product_named_tag.add("FlashSaleDiscount", 0.7)

    # Updates the named tags with the new named tags
    # Overrides the value of the existing named tags
    cache_item.set_named_tags(new_product_named_tag)

    # Re-insert the cacheItem into cache with modified named tags
    version = cache.insert(key, cache_item)

    # cacheItem is successfully added in cache with modified named tags

Additional Resources

NCache provides sample application for Named tags on GitHub.

Add and Update Cache Data with Named Tags

Note

Prerequisites

Add Named Tags

Note

Update Named Tags Data through CacheItem

Warning

Additional Resources

See Also