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I need to share static hashmaps which will be init on run-time using Spring 3.1.

I need to create a real singleton bean (not necessarily singleton scope) which will hold all my static hashmaps.

The hashmap will be modifiable also in run-time and it has to be available for all my spring beans.

  1. the bean that hold the static map has to be alive as long as the application is running
  2. the bean need to be accessed by all spring beans.
  3. the hashmaps need to be concurrent and thread safe. The hashmap might have like 100 entries and will be accessed in a very high rate.

How could I achive this? Thanks in advance,

Gray
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rayman
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    What is the problem with a normal singleton scope bean holding ConcurrentHashMaps? Why must the maps be static? – Kevin Jul 19 '12 at 15:24
  • There is no problem with normal singleton bean except the fact that I I need that bean to be alive as long as my application living. – rayman Jul 22 '12 at 07:27
  • By "a real singleton bean" did you mean persistent storage for data (after server shutdown and startup data is remembered) or just create new hashmap after server startup? If it's second case, singleton scope is perfectly fine. – Grzegorz Rożniecki Jul 24 '12 at 17:23

2 Answers2

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I agree with @Kevin's comment (ConcurrentHashMap beans), but just found nice Spring 3.1 addition: ConcurrentMapCacheFactoryBean. The docs says:

FactoryBean for easy configuration of a ConcurrentMapCache when used within a Spring container.

I found also this blog post, which proposes use of the bean with @Cacheable annotation:

<bean id="cacheManager"
        class="org.springframework.cache.support.SimpleCacheManager">
    <property name="caches">
        <set>
            <bean class="org.springframework.cache.concurrent.ConcurrentMapCacheFactoryBean"
                  p:name="default"/>
        </set>
    </property>
</bean>

Haven't tried it but seems nicely integrated with Spring stuff.

Grzegorz Rożniecki
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  • But why would I need caching here? just need a singleton been which will hold static access data that could be modified.. – rayman Jul 22 '12 at 07:28
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i am not 100% aware about your need but you can create your own scope by section 3.5.5 Custom scopes, this will ensure pure singleton instance and injectable to all beans. and may be you can solve thread safe by having proper synchronized method or map

Jigar Parekh
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  • Cant I create a pure singleton instance inject-able without using custom scopes? isnt it a bit overhead for this? – rayman Jul 22 '12 at 07:31
  • why do u think that it could be overhead? – Jigar Parekh Jul 23 '12 at 05:25
  • Because I am sure there is already known scope\way which could make a bean as a singleton and globally accessed. that's pretty common feature to have in frameworks. – rayman Jul 23 '12 at 07:58