allegro / json-cache

json-cache

A set of libraries focused on extracting abstraction layer for caching.

json-cache-jackson

A library that allows for customization of POJO deserializers in ObjectMapper by enhancing them with caching capabilities. Consider the following example:

public class CategoryParameter {

    private final int id;
    private final String value;

    public CategoryParameter(
            @JsonProperty("id") int id,
            @JsonProperty("value") String value
    ) {
        this.id = id;
        this.value = value;
    }

    // getters and setters
}

and the following JSON payload:

{
  categories: [
    {
      name: "cat 1",
      parameters: [
        {
          id: 10,
          value: "sanki"
        },
        {
          id: 111,
          value: "Nowy"
        },
        // ...
        {
          id: 123,
          value: "wartość"
        }
      ]
    },
    {
      name: "cat 2",
      parameters: [
        {
          id: 111,
          value: "Nowy"
        },
        {
          id: 555,
          value: "tak"
        },
        {
          id: 123,
          value: "wartość"
        }
      ]
    }
    // ...
  ]
}

Normally Jackson will spawn multiple instances of CategoryParameter even if such objects contain the same properties.

This library aims to reduce amount of consumed memory and computing time by caching and de-duplicating object instances (object pooling).

How to use

Follow those simple steps:

• add dependency for the module:

dependencies {
    implementation group: 'pl.allegro.tech', name: 'json-cache-jackson', version: '...'
    // above module doesn't supply dependent libraries to avoid dependency pollution, so make sure you include them yourself
    implementation group: 'com.fasterxml.jackson.core', name: 'jackson-databind', version: '...'
}

• supply a proper annotation:

@CacheableEntity(keyComponent = "id", cacheName = "categoryParametersCache")
public class CategoryParameter {
    //...
}

• implement cache resolver

public class MyCacheResolver implements CacheResolver {

    private final Map<String, EntityCache<?, ?>> cacheMap = new HashMap<>();

    @Override
    @SuppressWarnings("unchecked")
    public <K, V> EntityCache<K, V> resolveCache(String cacheName) {
        return (EntityCache<K, V>) cacheMap.computeIfAbsent(cacheName, key -> new MapBasedEntityCache<>());
    }

}

• configure Jackson's ObjectMapper

CacheResolver cacheResolver = new MyCacheResolver();
CacheKeyBuilderFactory keyBuilderFactory = new CacheKeyBuilderFactory(
        List.of(new JsonComponentExtractingStrategy())
);
Module cachedDeserializationModule = new CachedDeserializationModule(
        new CacheApplyingDeserializerModifier(keyBuilderFactory, cacheResolver)
);
ObjectMapper mapper = new ObjectMapper(); // or use existing
mapper.registerModule(cachedDeserializationModule);

and that's it - you're good to go :)