Spring Boot Tutorial

Spring Boot - Software Setup and Configuration (STS/Eclipse/IntelliJ)

Prerequisite (Spring Core Concepts)

Spring Boot Core

Spring Boot with REST API

Spring Boot with Database and Data JPA

Spring Boot with Kafka

Spring Boot with AOP

Spring Boot - Cache Provider

Caching can significantly speed up applications by storing frequently accessed data in memory so it doesn't need to be recalculated or fetched from a slower source (like a database) repeatedly. Spring Boot provides easy integration with several caching providers through its caching starter and the use of the @EnableCaching annotation.

Here's a brief overview of the caching providers supported by Spring Boot and how to set them up:

1. In-Memory Cache:

Spring provides basic cache capabilities with its own in-memory cache manager called ConcurrentMapCacheManager.

Setup:

Add the dependency:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-cache</artifactId>
</dependency>

Enable caching in your main Spring Boot application class:

@SpringBootApplication
@EnableCaching
public class MyApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }
}

This will activate the default cache provider, which is the ConcurrentMapCacheManager.

2. EhCache:

EhCache is a popular and robust cache solution.

Setup:

Include the dependency:

<dependency>
    <groupId>org.ehcache</groupId>
    <artifactId>ehcache</artifactId>
</dependency>

Create an ehcache.xml configuration file in the src/main/resources directory and configure your caches.
Spring Boot will automatically configure EhCacheCacheManager if it detects the EhCache library in the classpath and an ehcache.xml file in the resources.

3. Caffeine:

Caffeine is a high-performance caching library which can be used as an in-memory cache.

Setup:

Include the dependency:

<dependency>
    <groupId>com.github.ben-manes.caffeine</groupId>
    <artifactId>caffeine</artifactId>
</dependency>

Spring Boot will automatically configure CaffeineCacheManager if it detects the Caffeine library in the classpath.

4. Redis:

Redis is an in-memory data structure store which can be used as a cache, message broker, etc.

Setup:

Include the dependency:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

Provide Redis connection properties in your application.properties or application.yml.
Spring Boot will auto-configure RedisCacheManager for you.

5. Hazelcast:

Hazelcast is an in-memory data grid, which is also often used for caching.

Setup:

Include the dependency:

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

Spring Boot will auto-configure HazelcastCacheManager for you.

Cache Configuration:

Regardless of the caching provider you choose, the method to define cacheable operations remains consistent. For example, to cache the result of a method, annotate it with @Cacheable:

@Cacheable(value = "books", key = "#isbn")
public Book findBookByIsbn(String isbn) {
    // ... method implementation
}

You can also use other annotations like @CacheEvict to remove data from the cache, or @CachePut to update it.

Note: It's important to be aware of the storage limits, especially for in-memory caches, and the potential for stale data when using caches. Proper cache eviction and expiration strategies should be in place to handle these concerns.

Configuring caching in Spring Boot:

Enable caching in a Spring Boot application using @EnableCaching.

Example:

// Enable caching in a Spring Boot application
@SpringBootApplication
@EnableCaching
public class MyApplication {
    // Application code
}

Using Ehcache with Spring Boot:

Integrate Ehcache as a caching provider in Spring Boot.

Example (with pom.xml dependency):

<!-- Ehcache dependency -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-cache</artifactId>
</dependency>
<dependency>
    <groupId>net.sf.ehcache</groupId>
    <artifactId>ehcache</artifactId>
</dependency>

Example (configuration):

// Ehcache configuration in Spring Boot
@Configuration
public class CacheConfig {

    @Bean
    public CacheManager cacheManager() {
        return new EhCacheCacheManager(ehCacheCacheManager().getObject());
    }

    @Bean
    public EhCacheManagerFactoryBean ehCacheCacheManager() {
        EhCacheManagerFactoryBean factory = new EhCacheManagerFactoryBean();
        factory.setConfigLocation(new ClassPathResource("ehcache.xml"));
        factory.setShared(true);
        return factory;
    }
}

Caching strategies in Spring Boot applications:

Choose caching strategies such as read-through, write-through, or write-behind.

Example:

// Read-through caching strategy
@Cacheable("myCache")
public String getData(String key) {
    // Read data from data source if not present in cache
    return fetchDataFromDataSource(key);
}

In-memory caching in Spring Boot:

Use an in-memory cache provider (e.g., Caffeine) for caching.

Example (with pom.xml dependency):

<!-- Caffeine dependency -->
<dependency>
    <groupId>com.github.ben-manes.caffeine</groupId>
    <artifactId>caffeine</artifactId>
</dependency>

Example (configuration):

// Caffeine configuration in Spring Boot
@Configuration
public class CacheConfig {

    @Bean
    public CacheManager cacheManager() {
        return new CaffeineCacheManager("myCache");
    }
}

Customizing cache providers in Spring Boot:

Implement a custom cache provider by extending CacheManager.

Example:

// Custom cache provider in Spring Boot
@Configuration
public class CustomCacheConfig {

    @Bean
    public CacheManager cacheManager() {
        return new CustomCacheManager();
    }
}

Integrating Redis as a cache provider in Spring Boot:

Use Redis as an external caching provider.

Example (with pom.xml dependency):

<!-- Redis dependency -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

Example (configuration):

// Redis configuration in Spring Boot
@Configuration
public class CacheConfig {

    @Bean
    public CacheManager cacheManager(RedisConnectionFactory redisConnectionFactory) {
        return RedisCacheManager.builder(redisConnectionFactory).build();
    }
}

Cache eviction policies in Spring Boot:

Define eviction policies for cache entries (e.g., time-based, size-based).

Example:

// Time-based eviction policy
@Cacheable(value = "myCache", key = "#key", condition = "#key.length() < 10")
public String getData(String key) {
    // Cache entry will expire after 10 minutes
    return fetchDataFromDataSource(key);
}

Conditional caching in Spring Boot:

Conditionally cache results based on specific conditions.

Example:

// Conditional caching based on a property
@Cacheable(value = "myCache", condition = "#{T(java.lang.System).getProperty('caching.enabled') == 'true'}")
public String getData(String key) {
    // Cache data if caching is enabled
    return fetchDataFromDataSource(key);
}