Objective is to build a multi-modular CAP Java application supporting multi-tenancy where the services within each module can be used to fulfil individual business logics and can use the same models. The structure is:

|-- db/

`-- data-model.cds

|--app/

|--approuter/

|--mtx/sidecar/

|--srv1

`-- monitoringservice.cds

`--pom.xml

|--srv2

`-- integrationservice.cds

`--pom.xml

Note: The services should be distinct for each sub module.

Add the following in parent pom.xml

<commands>
   <command>deploy db srv2 --to h2 --dry &gt; srv2/src/main/resources/schema.sql</command>
   <command>deploy db srv1 --to h2 --dry &gt; srv1/src/main/resources/schema.sql</command>
</commands>

srv/pom.xml

<commands>
    <command>build --for java --src srv1</command>
    <command>deploy db srv1 --to h2 --dry &gt;"${project.basedir}/src/main/resources/schema.sql" 
    </command>
</commands>

srv2/pom.xml

<commands>
   <command>build --for java --src srv2</command>
   <command>deploy db srv2 --to h2 --dry &gt;"${project.basedir}/src/main/resources/schema.sql"</command>
</commands>

Use the below command to clean install:

mvn clean install

For each module use:

mvn clean install -pl srv1 -am
mvn clean install -pl srv2 -am

Add the following in the .cdsrc.json

{
    "requires": {
        "multitenancy": true
    },
    "build": {
        "target": ".",
        "tasks": [
            {
                "for": "java",
                "src": "srv1",
                "options": {
                  "model": [
                    "db",
                    "srv1",
                    "app"
                  ]
                }
            },
            {
                "for": "java",
                "src": "srv2",
                "options": {
                  "model": [
                    "db",
                    "srv2",
                    "app"
                  ]
                }
            },
            {
                "for": "mtx-sidecar"
            },
            {
                "for": "hana",
                "src": "db",
                "options": {
                  "model": [
                    "db",
                    "srv1",
                    "srv2",
                    "app"
                  ]
                }
            }
        ]
    },
    "hana": {
        "deploy-format": "hdbtable"
    }
}

Note: To create a multi-tenant application add mtxs to the project and add the same .cdsrc.json in /mtx/sidecar

Add the srv2 module in mta.yaml:

# --------------------- SERVER MODULE ------------------------
  - name: mis-srv2
    # ----------------------------------------------------------
    deployed-after:
      - mis-mtx-sidecar
    type: java
    path: srv2
    properties:
      SPRING_PROFILES_ACTIVE: cloud
      CDS_MULTITENANCY_APPUI_TENANTSEPARATOR: "-"
      JBP_CONFIG_COMPONENTS: "jres: ['com.sap.xs.java.buildpack.jre.SAPMachineJRE']"
      JBP_CONFIG_SAP_MACHINE_JRE: "{ use_offline_repository: false, version: 17.+ }"
    parameters:
      memory: 2048M
      disk-quota: 1024M
      buildpack: sap_java_buildpack
      routes:
        - route: "${app-prefix}-${service_route}.${default-domain-host}"
    build-parameters:
      builder: custom
      commands: [mvn clean package]
      build-result: "target/*-exec.[wj]ar"
    provides:
      - name: srv-api2 # required by consumers of CAP services (e.g. approuter)
        properties:
          srv-url: "${protocol}://${app-prefix}-${service_route}.${default-domain-host}"
    requires:
      - name: mis-uaa
      - name: mis-service-manager
      - name: mis-saas-registry
      - name: mtx-sidecar
        properties:
          CDS_MULTITENANCY_MTXS_ENABLED: true
          CDS_MULTITENANCY_SIDECAR_URL: ~{url}
      - name: approuter_api
        properties:
          CDS_MULTITENANCY_APPUI_URL: ~{url}

Add the dependencies in mtx-sidecar,app-router and saas-registry in mta.yaml for both the modules:

 # ----------------- MTX-SIDECAR MODULE -----------------------
  - name: mis-mtx-sidecar
    # ----------------------------------------------------------
    type: nodejs
    path: mtx/sidecar
    build-parameters:
      builder: custom
      build-result: gen
      commands:
        - npm run build
      requires:
        - name: mis-srv1
        - name: mis-srv2
    parameters:
      memory: 512M
      disk-quota: 1024M
    requires:
      - name: mis-uaa
      - name: mis-service-manager
    provides:
      - name: mtx-sidecar
        properties:
          url: ${default-url}

# --------------------- APPROUTER MODULE ---------------------
  - name: mis-approuter
    # ----------------------------------------------------------
    type: approuter.nodejs
    path: mis-approuter
    requires:
      - name: mis-html-repo-runtime
      - name: mis-uaa
      - name: mis-saas-registry
      - name: srv-api1
      - name: srv-api2
    parameters:
      disk-quota: 256M
      memory: 256M
      keep-existing-routes: true
      routes:
        - route: "${app-prefix}-${approuter_route}.${default-domain-host}"
    provides:
      - name: approuter_api
        properties:
          url: "${protocol}://${app-prefix}-${approuter_route}.${default-domain-host}"
    properties:
      TENANT_HOST_PATTERN: "^(.*)-${app-prefix}-${approuter_route}.${default-domain-host}"
      destinations:
        - name: backend
          url: "~{srv-api1/srv-url}"
        - name: backend2
          url: "~{srv-api2/srv-url}"
          forwardAuthToken: true

- name: mis-saas-registry
    type: org.cloudfoundry.managed-service
    parameters:
      service: saas-registry
      service-plan: application
    requires:
      - name: srv-api1
      - name: srv-api2

Build the application with the command:

mbt build -t gen --mtar mta.tar

Individual modules can be build using mbt :

mbt module-build -m=mis-srv2 -t gen --mtar mta.tar
mbt module-build -m=mis-srv1 -t gen --mtar mta.tar

Advantages of multi-modular:

• Loosely coupled business logics
• Separated code logics
• Lesser conflicts with code merges
• Easier to test
• Need not deploy all the modules for any individual business logic changes

Co-Author: [email protected]