Implementing distributed caching with Java RMI

14 Sep 2023

Distributed caching is a technique used to improve the performance and scalability of applications by storing frequently accessed data in memory. This helps to reduce the load on the database and improve response times. In this article, we will explore how to implement distributed caching using Java RMI (Remote Method Invocation).

What is Java RMI?

Java RMI is a mechanism that allows objects in one Java Virtual Machine (JVM) to invoke methods on objects residing in another JVM, thereby enabling distributed computing. It provides a simple way to communicate and invoke methods on remote objects.

Setting up the Project

First, we need to set up our project by creating a Java interface that defines the methods for our caching system. Let’s call it CacheManager.

public interface CacheManager {
    void put(String key, Object value);
    Object get(String key);
    boolean containsKey(String key);
    void remove(String key);
}

Next, we need to create an implementation of the CacheManager interface. Let’s call this class DistributedCacheManager.

public class DistributedCacheManager implements CacheManager {
    private Map<String, Object> cache = new HashMap<>();

    @Override
    public void put(String key, Object value) {
        cache.put(key, value);
    }

    @Override
    public Object get(String key) {
        return cache.get(key);
    }

    @Override
    public boolean containsKey(String key) {
        return cache.containsKey(key);
    }

    @Override
    public void remove(String key) {
        cache.remove(key);
    }
}

Creating the Server

To implement distributed caching using Java RMI, we need to create a server class that publishes the DistributedCacheManager object. This class will extend the UnicastRemoteObject class provided by Java RMI.

public class CacheServer {
    public static void main(String[] args) {
        try {
            // Create an instance of the DistributedCacheManager
            CacheManager cacheManager = new DistributedCacheManager();

            // Publish the Remote Object using Java RMI
            CacheManager stub = (CacheManager) UnicastRemoteObject.exportObject(cacheManager, 0);

            // Register the Remote Object with the RMI registry
            Registry registry = LocateRegistry.getRegistry();
            registry.bind("CacheManager", stub);

            System.out.println("CacheServer ready!");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Creating the Client

Once the server is up and running, we can create a client application to interact with the distributed cache. The client class will use the RMI registry to lookup the CacheManager object and make remote method invocations.

public class CacheClient {
    public static void main(String[] args) {
        try {
            // Lookup the Remote Object from the RMI registry
            Registry registry = LocateRegistry.getRegistry();
            CacheManager cacheManager = (CacheManager) registry.lookup("CacheManager");

            // Use the CacheManager methods
            cacheManager.put("key", "value");
            Object value = cacheManager.get("key");
            System.out.println("Value: " + value);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Running the Application

To run the distributed caching application, follow these steps:

Run the CacheServer class to start the server.
Run the CacheClient class to test the caching operations.

Ensure that you have set up the RMI registry properly and have the necessary dependencies in your classpath.

Conclusion

In this article, we have seen how to implement distributed caching using Java RMI. By leveraging the power of remote method invocations, we can build scalable and performant applications that can offload the database and improve response times.