Toolkit - Model Factory

This post if part of a series about the File System Toolkit - a custom content delivery API for SDL Tridion.

This post presents the Model Factory, an layer that offers CRUD operations on models backed by a cache and a file system provider.

The Model Factory is a singleton that allows the creation, retrieval, update and deletion of a model. It works using a CacheFactory and a File System Provider that acts as a data abstraction layer.

The Model Factory works on two types of models only: ComponentMeta and PageMeta. They are both generics passed to the factory methods or inferred from the returned type.

Method getOrCreate(TcmUri)

This method tries first to read a model from the cache. If it doesn't exist in cache, it tries to read it from the file system provider. If there is no such model on disk, then it will proceed to create a stub model that only has its TcmUri property set. The idea is that the user will populate the other model properties and will execute a updateModel.

public <T extends ItemMeta> T getOrCreateModel(TcmUri tcmUri) {
    T model;
    String key = cacheFactory.getKey(tcmUri);
    CacheElement<T> cacheElement = cacheFactory.get(key);

    if (cacheElement == null) {
        model = modelProvider.read(tcmUri);
    } else {
        model = cacheElement.getPayload();
    }

    if (model == null) {
        model = modelProvider.create(tcmUri);
        cacheFactory.put(key, model);
    }

    return model;
}

Method getModel(TcmUri)

This method is the most used method of the factory. It provides the read operation of a model from either the internal cache or from the file system provider. Usually the 'write' operations of this factory are called only by the Deployer extensions, during the publish/unpublish activities. The 'read' operation is used mainly in the Toolkit CD API.

public <T extends ItemMeta> T getModel(TcmUri tcmUri) {
    T model;
    String key = cacheFactory.getKey(tcmUri);
    CacheElement<T> cacheElement = cacheFactory.get(key);

    if (cacheElement == null) {
        model = modelProvider.read(tcmUri);
        if (model != null && model.getLastPublished() == null) {
            model = null;
        }
        cacheFactory.put(key, model);
    } else {
        model = cacheElement.getPayload();
    }

    return model;
}

Method updateModel(T model)

This method is a write operation that persists the model sent as parameter to the file system. It also places the updated model in the cache.

public <T extends ItemMeta> void updateModel(T model) {
    TcmUri tcmUri = model.getTcmUri();
    String key = cacheFactory.getKey(tcmUri);
    model = modelProvider.update(model);
    cacheFactory.put(key, model);
}

Method removeModel(TcmUri)

This method is a write operation that deletes a model from the file system and removes it from the cache.

public boolean removeModel(TcmUri tcmUri) {
    String key = cacheFactory.getKey(tcmUri);
    cacheFactory.remove(key);

    return modelProvider.delete(tcmUri);
}