Retrieve from Cache

NCache utilizes the key-value architecture for retrieval of data residing in cache. The Get method is the primary method in the API to retrieve data.

Prerequisites

• Add the following Maven dependencies in your pom.xml file:

<dependency>
    <groupId>com.alachisoft.ncache</groupId>
    <!--for NCache Enterprise Edition--> 
    <artifactId>ncache-client</artifactId>
    <!--for NCache Professional Edition-->
    <artifactId>ncache-professional-client</artifactId>
    <version>x.x.x</version>
</dependency>

• Import the following packages in your application:

  • import javax.cache.CacheManager;
  • import javax.cache.Caching;
  • import javax.cache.spi.CachingProvider;
• Make sure that the data is serailized or registered with NCache Compact Serialization format.
• Make sure that the cache is running.

Retrieve a Single Item from Cache

In the following example we use the default get method to retrieve an object identified by “Product:1001”. This item has been previously added to the cache. The Get method returns a general object which needs to be cast accordingly. If the matching key does not exist in the cache, null value is returned by get.

try
{
    String key = "Product:1001";
    Product product = null;
    //null is returned if key does not exist in the cache.
    Object result;
    result = jCache.get(key);
    if (result != null) 
    {
        if (result instanceof Product) 
        {
            product = (Product) result;
        }
    }
}
catch(Exception ex)
{
    // Handle exception
}

Retrieve a CacheItem from Cache

In the following example we use the GetCacheItem method to retrieve an object identified by “Product:1001”. This item has previously been added to the cache. This method returns a CacheItem object whose value property encapsulates the data, which needs to be cast appropriately for further use in the application.

try
{
    String key = "Product:1001";
    Product product = null;
    CacheItem retrievedData = cache.getCacheItem(key);
    if (retrievedData != null) 
    {
        if (retrievedData.getValue() instanceof Product) 
        {
            product = (Product) retrievedData.getValue();
        }
    }
}
catch(Exception ex)
{
    // Handle Exception
}

Retrieve Bulk Data from Cache

For fetching a collection from cache, use the getBulk method. This method returns the collection of items in a HashMap; however NCache’s JCache API provider can also be used for the same purpose.

try
{
    //pre-condition: data already exists in the cache
    HashMap map = new HashMap();
    Map items = jCache.getAll(map.keySet());
    if (!items.isEmpty()) 
    {
        for (Iterator iter = items.values().iterator();iter.hasNext();)   
        {
            Product product = (Product) iter.next();
            //utilize product object accordingly
        }
    }
}
catch(Exception ex)
{
    // Handle Exception
}

See Also

Initialize Cache Add/Update in Cache
Remove Operation in Cache
Hibernate Caching
NCache Java Session Module