• Application cache
  
• Second level (L2) cache
  
• Hybrid cache
  

• Cache size - defines how many elements a cache can hold;
• Cache eviction - algorithm defines what to do when the number of elements in cache exceeds the size (LRU, LFU, FIFO) & eviction percentage;
• Time-to-live - defines time after that a cache key should be remove from the cache (expired);

• open-source - LGPL
  
• based on some JBoss Cache code
  

• clustered caching library
  

• can be used as Key-Value No-SQL solution
  
• has Hibernate4 cache region&provider implementation
  

@Entity
@Table(name = "PRODUCT_CATEGORY")
@Cache(region = "productCategory.region", usage = CacheConcurrencyStrategy.TRANSACTIONAL)
public class ProductCategory {

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name = "CATEGORY_ID")
    private Long id;

    @Column(name = "NAME")
    private String name;

    @Cache(region = "productCategory.brands.region", usage = CacheConcurrencyStrategy.TRANSACTIONAL)
    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @JoinTable(name = "BRAND_CATEGORY", joinColumns = @JoinColumn(name = "CATEGORY_ID"), inverseJoinColumns = @JoinColumn(name = "BRAND_ID"))
    private List<ProductBrand> brands;
...
}

Cache<Object, Object> cache = new DefaultCacheManager().getCache();// Add a entry
cache.put("key", "value");
// Remove the entry from the cache
Object v = cache.remove("key");
// And replace it if missing
cache.putIfAbsent("key", "newValue");
cache.clear();
//By default entries are immortal but we can override this on a per-key basis and provide lifespans.
cache.put("key", "value", 5, SECONDS);

  <dependency>
       <groupId>com.hazelcast</groupId>
       <artifactId>hazelcast</artifactId>
       <version>3.2.1</version>
  </dependency>
  <dependency>
       <groupId>com.hazelcast</groupId>
       <artifactId>hazelcast-hibernate4</artifactId>
       <version>3.2.1</version>
   </dependency>
   <dependency>
       <groupId>com.hazelcast</groupId>
       <artifactId>hazelcast-spring</artifactId>
       <version>3.2.1</version>
   </dependency>

   <map name="default"/>

    <map name="productCategory.brands.region">
        <in-memory-format>OBJECT</in-memory-format>
        <backup-count>2</backup-count>
        <async-backup-count>0</async-backup-count>
        <time-to-live-seconds>90</time-to-live-seconds>
        <max-idle-seconds>0</max-idle-seconds>
        <eviction-policy>LRU</eviction-policy>
        <max-size policy="PER_NODE">5000</max-size>
        <eviction-percentage>30</eviction-percentage>
        <merge-policy>com.hazelcast.map.merge.PassThroughMergePolicy</merge-policy>
        <read-backup-data>true</read-backup-data>
    </map>
</hazelcast>

  <!-- SessionFactory bean with Hazelcast Hibernate properties -->
<prop key="hibernate.cache.region.factory_class">com.hazelcast.hibernate.HazelcastCacheRegionFactory</prop>
<prop key="hibernate.cache.hazelcast.configuration_file_path">hazelcast.xml</prop>
<prop key="hibernate.cache.hazelcast.use_lite_member">true</prop>
<prop key="hibernate.cache.hazelcast.shutdown_on_session_factory_close">false</prop>

 
@Entity
@Table(name = "PRODUCT_CATEGORY")
@Cache(region = "productCategory.region", usage = CacheConcurrencyStrategy.READ_WRITE)
public class ProductCategory {

	...
    @Cache(region = "productCategory.brands.region", usage = CacheConcurrencyStrategy.READ_WRITE)
    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @JoinTable(name = "BRAND_CATEGORY", joinColumns = @JoinColumn(name = "CATEGORY_ID"), inverseJoinColumns = @JoinColumn(name = "BRAND_ID"))
    private List<ProductBrand> brands;
	...
}

Config cfg = new Config();
HazelcastInstance instance = Hazelcast.newHazelcastInstance(cfg);
Map<Integer, String> mapCustomers = instance.getMap("customers");
mapCustomers.put(1, "Joe");
mapCustomers.put(2, "Ali");
mapCustomers.put(3, "Avi");