Claude
b0c39a8d4c
Co-Authored-By: Claude Sonnet 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01B38FGKKam5SCGgwgduVAh3
64 lines
3.0 KiB
Markdown
64 lines
3.0 KiB
Markdown
[Home](../README.md) | Prev: [TTL](08-ttl.md) | Next: [Production checklist](10-production-checklist.md)
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# 9. Redis as the Spring cache
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The annotations (`@Cacheable`, `@CacheEvict`, keys, the self-invocation trap) are covered in
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[The Spring Cache Abstraction](https://ankurm.com/spring-cache-abstraction-cacheable-cacheevict-self-invocation-trap/) and its
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[companion project](../../caching). This chapter is only about what changes when the cache is Redis.
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With `spring-boot-starter-cache` and the Redis starter on the classpath and `@EnableCaching`, Boot
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picks `org.springframework.data.redis.cache.RedisCacheManager`
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([14-cache-default.txt](output/14-cache-default.txt)). [UserService](../src/main/java/com/ankurm/redis/cache/UserService.java)
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has two cached methods that differ only in whether the result is `Serializable`.
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## What the defaults store
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Keys are readable: `<cacheName>::<key>`, here `legacy::1`. The value is JDK-serialised, exactly as in
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[chapter 2](02-default-serialization.md):
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```
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$ redis-cli -p 6390 --no-raw GET legacy::1
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"\xac\xed\x00\x05sr\x00'com.ankurm.redis.model.SerializableUser..."
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```
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`spring.cache.redis.time-to-live=10m` works: `TTL legacy::1` is `600`.
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A result that is **not** `Serializable` is not cached, and the *method call fails*:
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```
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java.lang.IllegalStateException
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message: Cannot serialize value of type com.ankurm.redis.model.User without a serializer
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method body ran 2 time(s) in total
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```
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The body ran (twice in total: once for the good call, once for the failing one), the write to Redis threw, and
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the caller sees the exception. A `@Cacheable` on a method returning a non-Serializable type breaks that method.
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## Switching to JSON
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Declare a `RedisCacheConfiguration` bean. [JsonCacheConfig](../src/main/java/com/ankurm/redis/config/JsonCacheConfig.java)
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(active under the `json-cache` profile) does it with the same allow-listed Jackson 3 serializer as
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[chapter 4](04-json-serializers.md) ([15-cache-json.txt](output/15-cache-json.txt)):
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```
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$ redis-cli -p 6390 GET users::1
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{"@class":"com.ankurm.redis.model.User","id":1,"name":"Ankur"}
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```
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The non-Serializable record now caches, and the method body ran once for two calls.
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## The property that stops applying
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The test sets `spring.cache.redis.time-to-live=10m` **and** declares a bean with
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`entryTtl(Duration.ofMinutes(5))`. The key's TTL is `300`. When you define your own
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`RedisCacheConfiguration`, Boot used that bean and the `spring.cache.redis.time-to-live` property had no effect
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on the TTL. Put the TTL in the bean.
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## Going deeper
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- [RedisCacheDefaultTest](../src/test/java/com/ankurm/redis/RedisCacheDefaultTest.java) and [RedisCacheJsonTest](../src/test/java/com/ankurm/redis/RedisCacheJsonTest.java)
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- [Spring Boot: Caching, Redis](https://docs.spring.io/spring-boot/reference/io/caching.html#io.caching.provider.redis)
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- [Spring Data Redis: Redis Cache](https://docs.spring.io/spring-data/redis/reference/redis/redis-cache.html)
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[Home](../README.md) | Prev: [TTL](08-ttl.md) | Next: [Production checklist](10-production-checklist.md)
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