Note
This feature is only available in NCache Enterprise.
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
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.
// Precondition: 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);
}
String customerKey = "Customer:ALFKI";
Customer customer = cache.get(customerKey, Customer.class);
if (customer == null) {
// Fetch customer from database and create a com.alachisoft.ncache.sample.NamedTags.Customer object
customer = Customer.fetchCustomerFromDB("Customer:ALFKI");
}
NamedTagsDictionary namedTags = new NamedTagsDictionary();
namedTags.add("VIP_Membership_Discount", 0.10);
CacheItem cacheItem = new CacheItem(customer);
cacheItem.setNamedTags(namedTags);
cache.insert(customerKey, cacheItem);
System.out.println("Customer added to cache: " + customerKey);
// This is an async method
// Precondition: 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
# Precondition: 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
Note
To ensure the operation is fail-safe, it is recommended to handle any potential exceptions within your application, as explained in Handling Failures.
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.
// 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);
String customerKey = "Customer:ALFKI";
Customer customer = cache.get(customerKey, Customer.class);
if (customer == null) {
// Fetch customer from database and create a com.alachisoft.ncache.sample.NamedTags.Customer object
customer = Customer.fetchCustomerFromDB("Customer:ALFKI");
}
// Create a new CacheItem
CacheItem cacheItem = new CacheItem(customer);
NamedTagsDictionary namedTags = new NamedTagsDictionary();
namedTags.add("VIP_Membership_Discount", 0.50);
cacheItem.setNamedTags(namedTags);
cache.insert(customerKey, cacheItem);
System.out.println("Customer with updated named tags inserted into cache: " + customerKey);
// This is an async method
// Precondition: 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
# Precondition: 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 a sample application for Named Tags on GitHub.
See Also
Tag Cache Data
SQL Query with NamedTags
SQL Delete with NamedTags
Data Expiration