Java using @value to construct a member field size [duplicate]

Question

I am using guava cache where I want to keep maximum size configurable. I tried using @value for this but the problem is private member cache gets created before @value injection. How can I read this size from config properties? The code I am currently using is given below

@Component
public class DataProcessor {

@Value("${cacheSize}")
private long cacheSize;
@Value(value = "${rawSensorDataTopic}")
private String rawSensorDataTopic;

private LoadingCache<String, DataPacketGroup> rfPacketsCache = CacheBuilder.newBuilder().maximumSize(cacheSize)
        .concurrencyLevel(1).expireAfterWrite(15, TimeUnit.MINUTES)
        .build(new CacheLoader<String, DataPacketGroup>() {
            @Override
            public DataPacketGroup load(String key) throws Exception {
                return null;
            }
        });

use constructor injection

rkosegi
– rkosegi

2021-02-03 05:31:43 +00:00
Commented Feb 3, 2021 at 5:31 — rkosegi
– rkosegi, Commented Feb 3, 2021 at 5:31
Just always use constructor injection.

chrylis -cautiouslyoptimistic-
– chrylis -cautiouslyoptimistic-

2021-02-03 06:13:34 +00:00
Commented Feb 3, 2021 at 6:13 — chrylis -cautiouslyoptimistic-
– chrylis -cautiouslyoptimistic-, Commented Feb 3, 2021 at 6:13
Also stackoverflow.com/questions/27132348/…

rkosegi
– rkosegi

2021-02-03 09:48:23 +00:00
Commented Feb 3, 2021 at 9:48 — rkosegi
– rkosegi, Commented Feb 3, 2021 at 9:48

Jens · Accepted Answer · 2021-02-03 07:20:39Z

1

You can put the cache creation in a method that is annotated with @PostConstruct

@Component
public class DataProcessor {

@Value("${cacheSize}")
private long cacheSize;
@Value(value = "${rawSensorDataTopic}")
private String rawSensorDataTopic;

private LoadingCache<String, DataPacketGroup> rfPacketsCache;

@PostConstruct
private void createcache() {
     CacheBuilder.newBuilder().maximumSize(1000)
        .concurrencyLevel(1).expireAfterWrite(15, TimeUnit.MINUTES)
        .build(new CacheLoader<String, DataPacketGroup>() {
            @Override
            public DataPacketGroup load(String key) throws Exception {
                return null;
            }
        });
}

This method will be executed if the bean is constructed and the properties are injected

answered Feb 3, 2021 at 7:20

Jens

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