How do we implement method cache in java

Question

I'd like to design my own annotation in order to cache results retrieved from an earlier database call.

For example:

public class CountryService {
 @MethodCache
 public List<Country> getCountries();

 @MethodCache
 public Country getCountryById(int countryId);

 @InvalidateMethodCache
 public Country getCountryById(int countryId);

}

I want to use this type of annotation for more/all of my methods. What do I need to implement this type of annotation?

@MethodCache: Cache the method result.
@InvalidateMethodCache: Clear the cache.

Answer 1

A solution when using spring-aop is to create an aspect to handle all methods annotated with your custom annotation. An crude implementation would look like this:

Map<String, Object> methodCache = new HahsMap<>();

@Around("execution(@(@com.mypack.MethodCache *) *)")
public Object cacheMethod(ProceedingJoinPoint pjp) {
     String cacheKey = getCacheKey(pjp);
     if ( methodCache.get(cacheKey)) {
          return methodCache.get(cacheKey);
     } else {
          Object result = pjp.proceed();
          methodCache.put(cacheKey, result);
          return result;
     }
}

private String getCacheKey(ProceedingJoinPoint pjp) {
     return pjp.getSignature().toString() + pjp.getTarget() + Arrays.asList(pjp.getArgs());
}

Answer 2

Well if have ready available annotaions,Better use them
While you can follow this, I hope this guides you

• Implement the interface CacheAnnotationParser
• extend AnnotationCacheOperationSource so that you put your own CacheAnnotationParser in addition to Spring one in the internal parsers collection
• Define your custom AnnotationCacheOperationSource to use the same id as Spring one does, so it will override Spring internal. If id matches, it should override Spring one cleanly.
  
  Like this: