CODEWITHSUNDEEP
javacachingguava
ddxue
ddxue

Reputation: 71

Guava LoadingCache loads new value everytime for same key

I'm using the Guava LoadingCache to store results from database queries. However, despite not setting an eviction policy, doing a get on the cache through getFromCache() results in my debug point in the CacheLoader load() method being hit every time, therefore also resulting a debug point in the database query method getKeyFromDatabase() being hit every time.

Here is my code:

private final LoadingCache<String, QueryResult> cache;

public MyDao() {
    cache = CacheBuilder.newBuilder()
        .maximumSize(40)
        .build(new CacheLoader<String, QueryResult>() {
            @Override
            public QueryResult load(String key) throws DatabaseException {
                return getKeyFromDatabase(key);
            }
        });
}

public QueryResult getFromCache(String key) throws DatabaseException {
    try {
        return cache.get(key);
    } catch (ExecutionException e) {
        throw new DatabaseException(e);
    }
}

private QueryResult getKeyFromDatabase(String key) throws DatabaseException {
    try {
        ...
        return new QueryResult();
    } catch (SQLException e) {
        throw new DatabaseException(e);
    }
}

Am I missing something obvious here?

Upvotes: 4

Views: 2711

Answers (1)

ddxue
ddxue

Reputation: 71

Alright false alarm guys, guava is not actually broken (surprise surprise). The reason is cause the code that was instantiating the DAO was instantiating a new object every time, so a new cache was also instantiated every time. I made the cache a static variable and it now works.

Upvotes: 3

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