Spring Boot ResourceLoader缓存用于静态资源

Question

I've got an endpoint which is doing some processing and at the end returns a static resource as byte[] inside a ResponseEntity . The current implementation of the service layer, which returns the static resource is the following.

@Service
public class MyService_Impl implements MyService {
    private ResourceLoader resourceLoader;

    @Autowired
    public MyService_Impl (ResourceLoader resourceLoader) {
        this.resourceLoader = resourceLoader;
    }

    @Override
    public byte[] getMyResource() throws IOException {
        Resource myResource = resourceLoader.getResource("classpath:/static/my-resource.gif");
        InputStream is = myResource.getInputStream();
        return IOUtils.toByteArray(is);
    }
}

At peak I see large increase in the response time of this endpoint and my feeling is that this is the bottleneck as about 100 threads are requesting this resource simultaneously. Is there a specific Spring Resource caching mechanism that I can use to keep this resource in memory or I need to introduce ehcache on getMyResource() method?

Answer 1

U can keep the converted gif object in a private variable inside the same object.

@Service
public class MyService_Impl implements MyService {
    private ResourceLoader resourceLoader;
    private byte[] gifContent;

    @Autowired
    public MyService_Impl (ResourceLoader resourceLoader) {
        this.resourceLoader = resourceLoader;
    }

    @Override
    public byte[] getMyResource() throws IOException {
        if(gifContent == null ){
        Resource myResource = resourceLoader.getResource("classpath:/static/my-resource.gif");
        InputStream is = myResource.getInputStream();
        gifContent = IOUtils.toByteArray(is);
        }
        return gitContent;
    }
}

This only reads the gif once and then returns every time the cached instance. But this may create increase the memory footprint of your object. Singleton objects are preferable. Just if u want to cache a single gif going for ehcache may not be a suitable case. U can also consider moving reading resource into Springs init method life cycle callback.

If u have multiple Gif which need to be dynamically served depending on the input(Key/Value) then u can go for any third party cache implementations like guava or ehcache.