Java using @value to construct a member field size

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;
            }
        });

Also https://stackoverflow.com/questions/27132348/when-to-use-constructor-injection-in-spring — rkosegi, Feb 03 '21 at 09:48

score 1 · Accepted Answer · answered Feb 03 '21 at 07:20

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

Java using @value to construct a member field size

1 Answers1