Cache Listeners with Embedded Infinispan

What You Will Learn

How to create and register cache listeners in embedded Infinispan to react to entry creation and modification events.

Prerequisites

Java 17+

Step 1: Add the Embedded Dependency

Add Infinispan core to your pom.xml:

<dependency>
   <groupId>org.infinispan</groupId>
   <artifactId>infinispan-core</artifactId>
</dependency>

Step 2: Create a Listener Class

Annotate a class with @Listener and define handler methods using event annotations like @CacheEntryCreated and @CacheEntryModified:

   @Listener
   public static class MyListener {
      Map<String, String> created = new HashMap();
      Map<String, String> updated = new HashMap<>();

      @CacheEntryCreated
      public void entryCreated(CacheEntryCreatedEvent<String, String> event) {
         // We are only interested in the post event
         if (!event.isPre())
            created.put(event.getKey(), event.getValue());
            System.out.printf("Created %s\n", event.getKey());
      }

      @CacheEntryModified
      public void entryModified(CacheEntryModifiedEvent<String, String> event) {
         // We are only interested in the pre event
         if (event.isPre())
            updated.put(event.getKey(), event.getNewValue());
            System.out.printf("About to modify %s\n", event.getKey());
      }
   }

Each event fires twice — once before (isPre() == true) and once after (isPre() == false) the operation. Filter on the phase you need.

Step 3: Register the Listener

Add the listener to a cache instance:

      // Construct a simple local cache manager with default configuration
      cacheManager = new DefaultCacheManager();
      // Define local cache configuration
      cacheManager.defineConfiguration("local", new ConfigurationBuilder().build());
      // Obtain the local cache
      cache = cacheManager.getCache("local");

      listener = new MyListener();
      // Register a listener
      cache.addListener(listener);

Step 4: Trigger Events

Any cache operation triggers the corresponding listener methods:

      // Store some values
      cache.put("key1", "value1");
      cache.put("key2", "value2");
      cache.put("key1", "newValue");

Step 5: Run the Tutorial

mvn package exec:java

The output shows creation notifications for key1 and key2, and a modification notification when key1 is updated.

What’s Next

Try distributed caching with listeners in a cluster
Explore functional map API for lambda-based cache operations
Use distributed streams for processing cache data