Chapter 5. Reading Data From Entity Stores

Table of Contents

Retrieving a Single Object
Retrieving Multiple Objects
ExampleInventoryRead.class

Once you have written objects to an EntityStore you can read them back again at a later time. To do this, you use either the primary or the secondary key used by the entity that you want to retrieve.

It is possible to retrieve a single object by using its primary key. You can also retrieve multiple objects in the form of a collection, if the key that you use is capable of referring to more than one object.

Retrieving a Single Object

To retrieve a single object, you must use an index that is capable of returning just one object. A primary index is one such index, as is a ONE_TO_ONE or ONE_TO_MANY secondary index.

To retrieve the object, use the index's get() method, providing to it the index value that is used by the desired object. For example, the following uses the primary key for the Inventory class to retrieve the object with SKU Trifdess2zJsGi:

PrimaryIndex<String,Inventory> inventoryBySku =
    store.getPrimaryIndex(String.class, Inventory.class);
Inventory inventory = inventoryBySku.get("Trifdess2zJsGi");