CacheManager in Spring Boot: A Step-by-Step Tutorial

Caching is a crucial aspect of optimizing the performance of your Spring Boot applications. It can significantly reduce the load on your database and improve response times for frequently accessed data. Spring Boot provides a simple and powerful caching mechanism using the CacheManager interface. This tutorial will guide you through using CacheManager in a real-time scenario where we fetch user details from a remote API and cache the results to enhance performance.

Prerequisites

• JDK 17 or later
• Maven or Gradle
• Spring Boot (version 3.2+ recommended)
• An API that provides user details (we'll use a mock service for this example)
• IDE (IntelliJ IDEA, Eclipse, etc.)

Step 1: Set Up a Spring Boot Project

Use Spring Initializr to create a new project with the following configuration:

• Project: Maven Project
• Language: Java
• Spring Boot: 3.2.x
• Dependencies: Spring Web, Spring Cache, Spring Boot DevTools

Download and unzip the project, then open it in your IDE.

Example Spring Boot Application

Create a Spring Boot application that fetches user details from a remote API and caches the results.

1.1 Application Class

package com.example.cachemanager;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class CacheManagerApplication {

    public static void main(String[] args) {
        SpringApplication.run(CacheManagerApplication.class, args);
    }
}

1.2 Enable Caching

Enable caching by adding the @EnableCaching annotation to your main application class.

package com.example.cachemanager;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cache.annotation.EnableCaching;

@SpringBootApplication
@EnableCaching
public class CacheManagerApplication {

    public static void main(String[] args) {
        SpringApplication.run(CacheManagerApplication.class, args);
    }
}

1.3 Create a User Service with Caching

Create a service class named UserService in the com.example.cachemanager.service package. This service will fetch user details from a remote API and cache the results.

package com.example.cachemanager.service;

import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;

@Service
public class UserService {

    private final RestTemplate restTemplate = new RestTemplate();

    @Cacheable("users")
    public String getUserDetails(String userId) {
        // Simulate a remote API call
        String url = "https://jsonplaceholder.typicode.com/users/" + userId;
        return restTemplate.getForObject(url, String.class);
    }
}

Explanation:

• @Cacheable("users"): Caches the result of the getUserDetails method. The cache is identified by the name "users".

1.4 Create a REST Controller

Create a controller class named UserController in the com.example.cachemanager.controller package.

package com.example.cachemanager.controller;

import com.example.cachemanager.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class UserController {

    @Autowired
    private UserService userService;

    @GetMapping("/users/{userId}")
    public String getUserDetails(@PathVariable String userId) {
        return userService.getUserDetails(userId);
    }
}

1.5 Configure Cache Manager

You can configure the CacheManager bean to customize your caching setup. Create a configuration class named CacheConfig in the com.example.cachemanager.config package.

package com.example.cachemanager.config;

import org.springframework.cache.CacheManager;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.cache.concurrent.ConcurrentMapCacheManager;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
@EnableCaching
public class CacheConfig {

    @Bean
    public CacheManager cacheManager() {
        return new ConcurrentMapCacheManager("users");
    }
}

Explanation:

• @Configuration: Indicates that the class declares one or more @Bean methods.
• @EnableCaching: Enables Spring’s annotation-driven cache management capability.
• ConcurrentMapCacheManager: A simple implementation of CacheManager backed by a ConcurrentHashMap.

1.6 application.properties Configuration

You can also configure some caching properties in the src/main/resources/application.properties file.

# src/main/resources/application.properties

# Enable caching in Spring Boot (enabled by default with @EnableCaching)
spring.cache.type=simple

Step 2: Test the Application

2.1 Run the Application

Run the Spring Boot application using your IDE or the command line:

./mvnw spring-boot:run

2.2 Verify Caching Behavior

Open a web browser or a tool like Postman and navigate to the following URL to test the caching:

1. Initial Request:

   • URL: http://localhost:8080/users/1
   • Method: GET
   • Response: (JSON response from the mock API, e.g., details of user 1)
   • Time taken: A few seconds (simulating a remote API call)

2. Subsequent Request:

   • URL: http://localhost:8080/users/1
   • Method: GET
   • Response: (JSON response from the mock API, same as above)
   • Time taken: Instant (result is retrieved from the cache)

You should notice that the first request takes a few seconds, but subsequent requests for the same user ID return instantly, demonstrating that the result is being cached.

Conclusion

In this real-time example, you have learned how to use CacheManager in Spring Boot to manage caching for a service that fetches user details from a remote API. We covered:

• Setting up a Spring Boot project with caching dependencies.
• Enabling caching in the application.
• Creating a service with caching to fetch user details.
• Creating a REST controller to expose the cached data.
• Configuring a simple CacheManager.
• Testing the caching behavior.

By following these steps, you can effectively use caching to optimize the performance of your Spring Boot applications, reducing the load on external APIs and improving response times.