Caffeine: Set custom eviction policy

By setting custom Expiry instance, we can set the expiry time at each entry level.

 

Example

Cache<Integer, Employee> cache = Caffeine.newBuilder().expireAfter(new Expiry<Integer, Employee>() {
	@Override
	public long expireAfterCreate(Integer key, Employee emp, long currentTime) {
		return TimeUnit.SECONDS.toNanos(emp.getExpiryTime());
	}

	@Override
	public long expireAfterUpdate(Integer key, Employee emp, long currentTime, long currentDuration) {
		return currentDuration;
	}

	@Override
	public long expireAfterRead(Integer key, Employee emp, long currentTime, long currentDuration) {
		return currentDuration;
	}
}).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;
	private long expiryTime;

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

	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;
	}

	public long getExpiryTime() {
		return expiryTime;
	}

	public void setExpiryTime(long expiryTime) {
		this.expiryTime = expiryTime;
	}

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

}

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.github.benmanes.caffeine.cache.Expiry;
import com.sample.app.model.Employee;
import com.sample.app.service.EmployeeService;

public class App {

	private static void printCache(Cache cache) {
		System.out.println("Elements in the 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().expireAfter(new Expiry<Integer, Employee>() {
			@Override
			public long expireAfterCreate(Integer key, Employee emp, long currentTime) {
				return TimeUnit.SECONDS.toNanos(emp.getExpiryTime());
			}

			@Override
			public long expireAfterUpdate(Integer key, Employee emp, long currentTime, long currentDuration) {
				return currentDuration;
			}

			@Override
			public long expireAfterRead(Integer key, Employee emp, long currentTime, long currentDuration) {
				return currentDuration;
			}
		}).build();

		Employee emp1 = new Employee(1, "Krishna", "Gurram", 5l);
		Employee emp2 = new Employee(2, "Gopi", "Battu", 8l);
		Employee emp3 = new Employee(3, "Saurav", "Sarkar", 15l);

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

		printCache(cache);

		System.out.println("\nAbout to sleep for 10 seconds");
		TimeUnit.SECONDS.sleep(10);

		/*
		 * Since cache eviction is done asynchronously, let's execute pending
		 * maintenance operations needed by the cache
		 */
		System.out.println("\nPerforming cleanup operations\n");
		cache.cleanUp();

		printCache(cache);

	}

}

Output

Elements in the cache are
Employee [id=1, firstName=Krishna, lastName=Gurram, expiryTime=5]
Employee [id=2, firstName=Gopi, lastName=Battu, expiryTime=8]
Employee [id=3, firstName=Saurav, lastName=Sarkar, expiryTime=15]

About to sleep for 10 seconds

Performing cleanup operations

Elements in the cache are
Employee [id=3, firstName=Saurav, lastName=Sarkar, expiryTime=15]

 

 

 

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