Name: Understanding Model Objects and Model Life Cycles
Uploaded: 2022-3-7
Duration: 204 s
Description: SAP Commerce Cloud Developer Essentials video - Lesson 8 - Slides 40-81

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Understanding Model Objects and Model Life Cycles

<div id="content"><p tabindex="0">Models are the currency of the service layer. They are used to ferry data from the persistence layer to the service layer, and to exchange data between services in the service layer.</p><p tabindex="0">Models are explained in the following video.</p><div class="kalturaVideoLessonWrapper"><div aria-label="This video introduces the concept of models, their implementation, and application in SAP Commerce Cloud." class="kalturaVideoLessonContainer" data-testid="video" id="1_x0i6q1rh"></div></div></div>

Models

Exploring the Technical Essentials of SAP Commerce Cloud

<div><div><div>SAP Commerce Cloud Developer Essentials video - Lesson 8 - Slides 40-81</div></div></div>

By now, you know that Models are objects used to vary information between services in the Service Layer and the Persistence Layer and among services themselves. Models are classes defined by the Type Definitions found in each extension's items.xml file. They are automatically generated during the build process. Models are Plain Old Java Objects, that reside in the service layer and can carry information. This information is accessed using their attributes, so Models have getter and setter methods allowing these attributes to be accessed and modified as needed. Generated from Type Definitions, they represent a piece of database data. However, this representation is merely a snapshot. Models and the database data they represent are not automatically synchronized. That is the developer's responsibility, a part of maintaining a model's state. These states are part of The Model Lifecycle. When you plan to use a Model you either load it from the database with a Model Service 'get' operation or with a Flexible Search statement or you create a new instance of a model. For that, you can either use a plain Java constructor or the Model Service create method, which is the strongly preferred approach. Any default attribute values defined in the item type definition are automatically set if you use the Model Service create method. That's one of the reasons we recommend you use it instead of using a plain Java constructor. However, if you insist on creating a model using the new keywords, you can use the Model Service 'initDefaults' operation to set these default values. After that, you're able to work with the model, and if you like, change some of its attribute values. If you do modify the state of a model, that change will only be reflected in the database when you invoke the Model Service save method. Finally, when the data represented by a Model needs to be eliminated, you can delete it from the database by invoking the Model Service remove operation. Speaking of the Model Service the 'get' operation needs an item's PK to load the correct object. When you initiate a new Model by using its constructor, it needs to be manually added to the Model Context by invoking the Model Service attach operation. This is another reason you really should use the Model Service create operation, since it takes care of attaching the model to the Model Context. While the Model Context keeps track of changes made to attached objects, if you want these changes reflected in the database, you still need to manually save a model or all changed models at once. Finally, as we saw earlier, you can delete a model from the database using the Model Service remove operation. This covers model basics and the four stages in their Lifecycle.