Apache Wicket is a popular Java web application framework that allows developers to build complex and scalable web applications. One key aspect of building scalable applications is efficient caching. In this blog post, we will explore how to work with distributed caching in Apache Wicket applications using the popular caching library, Hazelcast.

What is Distributed Caching?

Distributed caching is a technique that allows caching data across multiple servers in a network. It helps improve application performance and scalability by reducing the load on your database and decreasing response times.

Why use Distributed Caching in Apache Wicket?

Caching is especially important in web applications where database queries and expensive computations can slow down the response times. By using distributed caching, Apache Wicket applications can store frequently accessed data in memory, making it faster to retrieve and reducing the load on the database.

Integrating Hazelcast in Apache Wicket

Here are the steps to integrate Hazelcast in your Apache Wicket application:

1. Add Hazelcast Dependency:

   Start by adding the Hazelcast dependency to your project’s pom.xml file:

   <dependency>
       <groupId>com.hazelcast</groupId>
       <artifactId>hazelcast</artifactId>
       <version>4.2.1</version>
   </dependency>
   

2. Configure Hazelcast:

   Configure Hazelcast by creating a hazelcast.xml file in your project’s classpath. This file contains the necessary configuration properties for Hazelcast. For example:

   <hazelcast xmlns="http://www.hazelcast.com/schema/config"
              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
              xsi:schemaLocation="http://www.hazelcast.com/schema/config http://www.hazelcast.com/schema/config/hazelcast-config-4.0.xsd">
   
       <network>
           <join>
               <multicast enabled="false"/>
               <tcp-ip enabled="true">
                   <member>127.0.0.1:5701</member>
                   <member>127.0.0.1:5702</member>
               </tcp-ip>
           </join>
       </network>
   
   </hazelcast>
   

3. Create Cache Manager:

   In your Wicket application’s initialization code, create a CacheManager instance using the Hazelcast configuration:

   import com.hazelcast.config.Config;
   import com.hazelcast.core.Hazelcast;
   import com.hazelcast.core.HazelcastInstance;
   import org.apache.wicket.Application;
   import org.apache.wicket.IInitializer;
   import org.apache.wicket.RuntimeConfigurationType;
   import org.apache.wicket.protocol.http.WebApplication;
   import org.apache.wicket.cache.hazelcast.HazelcastCacheManager;
   
   public class MyApplication extends WebApplication implements IInitializer {
   
       @Override
       public void init() {
           super.init();
          
           // Load Hazelcast configuration
           Config hazelcastConfig = new Config(getClass().getResourceAsStream("/hazelcast.xml"));
   
           // Create Hazelcast instance
           HazelcastInstance hazelcastInstance = Hazelcast.newHazelcastInstance(hazelcastConfig);
   
           // Create CacheManager using Hazelcast instance
           CacheManager cacheManager = new HazelcastCacheManager(hazelcastInstance);
   
           // Set CacheManager in application's settings
           getApplicationSettings().setCacheManager(cacheManager);
       }
          
       // Other application code...
   }
   

4. Use Caching in Apache Wicket:

   Once the Hazelcast integration is complete, you can start using caching in your Apache Wicket application. For example, to cache a frequently accessed database query result, you can do the following:

   import org.apache.wicket.util.crypt.ICrypt;
   import org.apache.wicket.util.crypt.AbstractCrypt;
   import org.apache.wicket.IClusterable;
   import org.apache.wicket.Application;
   
   public class MyPage extends WebPage {
       
       private final ICrypt crypt;
   
       public MyPage() {
           // Get the cache manager instance
           CacheManager cacheManager = Application.get().getApplicationSettings().getCacheManager();
          
           // Create or retrieve the cache
           Cache<String, Object> cache = cacheManager.getCache("myCache");
          
           // Try to retrieve the data from cache
           Object cachedResult = cache.get("myDataKey");
   
           if (cachedResult == null) {
               // If cache miss, perform expensive database query
               Object expensiveResult = performExpensiveQuery();
              
               // Store the result in cache
               cache.put("myDataKey", expensiveResult);
               cachedResult = expensiveResult;
           }
          
           // Use the cached result
           // ...
       }
       
       // Other page code...
   }
   

These are the basic steps to integrate Hazelcast and use distributed caching in Apache Wicket applications. By effectively caching frequently accessed data, you can significantly improve your application’s performance and scalability.

#distributedcaching #apachewicket