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Modeled Curator - Caching, Typed Parameters and Versioning

In addition to its main features Modeled Curator also supports integrated caching, typed parameters and versioning.

Caching​

ModeledFramework instances can be wrapped with a facade that uses a Curator cache internally. All read operations use this cache instead of making direct ZooKeeper calls. You can also listen for node changes. E.g.,

ModeledFramework<MyModel> modeledClient = ModeledFramework.wrap(client, myModelSpec);
CachedModeledFramework<MyModel> cached = modeledClient.cached();
cached.start();

// reads come from the cache
cached.read().whenComplete(...) ...

cached.listenable.addListener((type, path, stat, model) -> {
    // type is NODE_ADDED, NODE_UPDATED, etc.
});

Unresolved Paths and Caching​

If the last node in the ModelSpec's path is a parameter, CachedModeledFramework will automatically listen to the parent path. E.g.,

ZPath path = ZPath.parseWithIds("/root/instance/{id}");
ModelSpec<MyModel> modelSpec = ModelSpec.builder(path, serializer);
ModeledFramework<MyModel> modeledClient = ModeledFramework.wrap(modelSpec, client, modelSpec);

CachedModeledFramework<MyModel> cached = modeledClient.cached();
cached.start(); // automatically listens to "/root/instance" and below

Typed Parameters​

The "resolve" methods in ZPath et al. consume untyped Objects. Ideally, we should be able to specify parameters in a strongly typed manner. Modeled Curator's "type" templates provide this. You can specify typed parameters for ZPaths, ModelSpecs and ModeledFramework. The Pub-Sub Example shows how to use typed parameters with ModeledFramework.

Typed interfaces are provided for up to 10 parameters and are named TypedZPath, TypedZPath2, TypedModelSpec, TypedModelSpec2, TypedModeledFramework, TypedModeledFramework2, etc.

Here's an example of a TypedModeledFramework that models a Person and uses two parameters to generate the path, a Group and an Organization:

TypedModeledFramework2<Person, Group, Organization> clientTemplate = TypedModeledFramework2.from(
    ModeledFrameworkBuilder.build(),
    personModelSpec
);

...

Group group = ...
Organization organization = ...
ModeledFramework<Person> modeledClient = clientTemplate.resolve(asyncClient, group, organization);
client.set(person);

TypedZPath and TypedModelSpec work similarly.

Versioning​

Modeled Curator supports associating a ZNode version with a model object via the Versioned interface and the VersionedModeledFramework APIs. To read a model along with its ZNode version use:

ModeledFramework<Person> client = ...

client.versioned().read().whenComplete((value, e) -> {
    if ( value != null ) {
        // value's type is Versioned<Person>
        Person personModel = value.model();
        int znodeVersion = value.version();
    }
});

VersionedModeledFramework has set/update APIs which automatically use the version from the Versioned instance.