The package descriptor package.json is a JSON file that defines the build, deployment, and runtime dependencies of a JavaScript application in SAP HANA XS Advanced. The package.json file is mandatory for JavaScript applications and it is located in the general section of the project. As well as the application name and version, dependencies to other Node.js modules, the Node.js version, run scripts, and the main program are configured. The package descriptor package.json is used for the following purposes:
* To list the package dependencies: The package.json file contains a dependencies property that lists the names and versions of the Node.js modules that the application depends on. These modules are installed by the npm install command during the build process and are available in the node_modules folder of the application. The dependencies property can also specify the scope and type of the dependencies, such as devDependencies for development-only modules, or peerDependencies for modules that are required by other modules.
* To define the routes: The package.json file contains a sap.cloud.service property that defines the name of the service that the application provides or consumes. This name is used to generate the routes for the application in the XS advanced environment. The routes are defined in the xs-app.json file, which is located in the same folder as the package.json file. The routes specify the rules for forwarding requests to the back-end microservices or destinations.
The following purposes are not achieved by the package descriptor package.json, but by other files or tools:
* To define back-end destinations: The back-end destinations are defined in the mta.yaml file, which is the deployment descriptor file that specifies the metadata and dependencies for the multi-target application (MTA) project. The mta.yaml file is located in the root folder of the MTA project and is used by the Cloud Foundry environment to deploy the application. The back-end destinations are declared as resources of type org.cloudfoundry.existing-service or org.cloudfoundry.managed-service, and are bound to the application modules by the requires property.
* To set the router version: The router version is set by the @sap/approuter module, which is a Node.js module that provides the application router service for the XS advanced environment. The application router service is responsible for routing requests to the appropriate destinations and for authenticating users. The @sap/approuter module is installed by the npm install command during the build process and is available in the node_modules folder of the application. The version of the @sap/approuter module is specified in the dependencies property of the package.json file.
References:
* [SAP HANA Deployment Infrastructure Reference], Chapter 5: HDI with XS Advanced, Section 5.1:
Developing with the SAP Web IDE for SAP HANA, Subsection 5.1.2: Configure Application Routing (xs-app.json), pp. 101-104.
* [SAP HANA Platform Documentation], SAP HANA Developer Guide for SAP HANA XS Advanced Model, Chapter 4: Developing HTML5 Applications, Section 4.1: Developing HTML5 Applications Using SAP Web IDE for SAP HANA, Subsection 4.1.3: Configure Application Routing (xs-app.json), pp. 77-80.