Caffeine cache: Listen when the cache entry expired

By implementing RemovalListener, you can receive a notification when an entry is removed from a cache.

 

Example

Cache<Integer, Employee> cache = Caffeine.newBuilder().removalListener((key, value, cause) -> {

         if (cause.wasEvicted())

                  System.out.printf("key=%s, value=%s, cause=%s\n", key, value, cause.toString());

}).expireAfterWrite(10, TimeUnit.SECONDS).recordStats().build();

 

Find the below working application.

 

Employee.java

package com.sample.app.model;

public class Employee {

	private int id;
	private String firstName;
	private String lastName;

	public Employee(int id, String firstName, String lastName) {
		super();
		this.id = id;
		this.firstName = firstName;
		this.lastName = lastName;
	}

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getFirstName() {
		return firstName;
	}

	public void setFirstName(String firstName) {
		this.firstName = firstName;
	}

	public String getLastName() {
		return lastName;
	}

	public void setLastName(String lastName) {
		this.lastName = lastName;
	}

	@Override
	public String toString() {
		return "Employee [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + "]";
	}

}

 

App.java

package com.sample.app;

import java.util.Map;
import java.util.concurrent.TimeUnit;

import com.github.benmanes.caffeine.cache.Cache;
import com.github.benmanes.caffeine.cache.Caffeine;
import com.sample.app.model.Employee;

public class App {
	
	private static void printCache(Cache cache) {
		System.out.println("\nElements of cache are");
		Map map = cache.asMap();
		
		for(Object key : map.keySet()) {
			System.out.println(map.get(key));
		}
	}


	public static void main(String args[]) throws InterruptedException {
		Cache<Integer, Employee> cache = Caffeine.newBuilder().removalListener((key, value, cause) -> {
			if (cause.wasEvicted())
				System.out.printf("key=%s, value=%s, cause=%s\n", key, value, cause.toString());
		}).expireAfterWrite(10, TimeUnit.SECONDS).recordStats().build();

		Employee emp1 = new Employee(1, "Krishna", "Gurram");
		Employee emp2 = new Employee(2, "Gopi", "Battu");
		Employee emp3 = new Employee(3, "Saurav", "Sarkar");

		cache.put(emp1.getId(), emp1);
		cache.put(emp2.getId(), emp2);
		cache.put(emp3.getId(), emp3);

		System.out.println("Inserted 3 entries into the cache");
		printCache(cache);
		
		System.out.println("\nSleeping for 12 seconds");
		TimeUnit.SECONDS.sleep(12);

		cache.cleanUp();

		printCache(cache);
	}

}

Output

Inserted 3 entries into the cache

Elements of cache are
Employee [id=1, firstName=Krishna, lastName=Gurram]
Employee [id=2, firstName=Gopi, lastName=Battu]
Employee [id=3, firstName=Saurav, lastName=Sarkar]

Sleeping for 12 seconds
key=1, value=Employee [id=1, firstName=Krishna, lastName=Gurram], cause=EXPIRED
key=3, value=Employee [id=3, firstName=Saurav, lastName=Sarkar], cause=EXPIRED

Elements of cache are
key=2, value=Employee [id=2, firstName=Gopi, lastName=Battu], cause=EXPIRED

 

 

 

 

 

Previous                                                    Next                                                    Home