Principles
The configuration derivation features allows a new Ehcache configuration object to be derived via a transformation on an existing configuration object. This can be useful for:
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pre-processing an externally sourced configuration, adding additional settings before creating the cache manager.
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processing the configuration of an existing cache manager to generate a new configuration.
The basis of the configuration derivation API is the Configuration.derive() method that generates a builder seeded
with the configurations values
FluentConfigurationBuilder<?> derivedBuilder = configuration.derive(); (1)
Configuration configurationCopy = derivedBuilder.build(); (2)| 1 | Creates a builder seeded with the configuration’s state. |
| 2 | Configurations built using the builder are then functionally identical to the original configuration. |
Core Configuration Changes
The configuration builder returned by the derive method provide direct methods for modifying core configuration concepts:
setting a custom classloader:
Configuration withClassLoader = configuration.derive()
.withClassLoader(classLoader)
.build();adding a cache:
Configuration withCache = configuration.derive()
.withCache("cache", CacheConfigurationBuilder.newCacheConfigurationBuilder(
Long.class, String.class, ResourcePoolsBuilder.heap(10)))
.build(); |
→ |
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removing a cache:
Configuration withoutCache = configuration.derive()
.withoutCache("cache")
.build(); |
→ |
|
Updating a cache configuration uses a UnaryOperator that is run against a cache configuration
builder seeded using the existing cache configuration.
updating a cache, by adding a resource:
Configuration withOffHeap = configuration.derive()
.updateCache("cache", cache -> cache.updateResourcePools(
resources -> ResourcePoolsBuilder.newResourcePoolsBuilder(resources)
.offheap(100, MemoryUnit.MB)
.build()))
.build(); |
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|
Extended Configuration Changes
Ehcache is a pluggable system, so modifying many of the more complex configurations requires modifying both service creation configurations and service configurations:
adding a service creation configuration (constraining the default thread pool)
Configuration withBoundedThreads = configuration.derive()
.withService(new PooledExecutionServiceConfiguration()
.addDefaultPool("default", 1, 16))
.build(); |
→ |
|
updating a service creation configuration (changing the persistence path)
Configuration withUpdatedPersistence = configuration.derive()
.updateServices(DefaultPersistenceConfiguration.class,
existing -> new File("/var/persistence/path"))
.build(); |
→ |
|
adding a service configuration (setting a resilience strategy)
Configuration withThrowingStrategy = configuration.derive()
.updateCache("cache", existing -> existing.withService(
new DefaultResilienceStrategyConfiguration(new ThrowingResilienceStrategy<>())
))
.build(); |
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|
updating a service configuration (changing a clustered cache’s consistency)
Configuration changedConsistency = configuration.derive()
.updateCache("cache", cache -> cache.updateServices(
ClusteredStoreConfiguration.class,
existing -> Consistency.EVENTUAL)
)
.build(); |
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|
Removing a service
Removing a service often involves removing both service creation and a service configuration instances since a service instance its configuration are usually strongly coupled:
removing a service (making a cache manager non-clustered)
Configuration withoutClustering = configuration.derive()
.updateCaches(cache -> cache (1)
.withoutServices(ClusteredStoreConfiguration.class) (2)
.updateResourcePools(existing -> {
ResourcePoolsBuilder poolsBuilder = ResourcePoolsBuilder.newResourcePoolsBuilder(); (3)
for (ResourcePool pool : existing.getResourceTypeSet().stream() (4)
.filter(p -> !(p instanceof ClusteredResourceType)) (5)
.map(existing::getPoolForResource)
.toArray(ResourcePool[]::new)) {
poolsBuilder = poolsBuilder.with(pool); (6)
}
return poolsBuilder.build();
}))
.withoutServices(ClusteringServiceConfiguration.class) (7)
.build();| 1 | From all cache configurations… |
| 2 | remove any existing ClusteredStoreConfiguration instances. |
| 3 | Create a new resource pool builder… |
| 4 | From the existing resource pools… |
| 5 | filter out any clustered resources. |
| 6 | Add all remaining pools to the new resource pools instance |
| 7 | Finally remove the clustering service creation configuration |
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