# Application Example

In this Demo, Application application-sample will be converted to appcontext and component

The fields in the application spec come from the parametes defined in the definition template
, so we must install Definition at first

Step 1: Install ComponentDefinition & Trait Definition
```
kubectl apply -f template.yaml
```
Step 2: Create a sample application in the cluster
```
kubectl apply -f application-sample.yaml
```
Step 3: View the application status
```
kubectl get -f application-sample.yaml -oyaml

// You can see the following
apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"core.oam.dev/v1beta1","kind":"Application","metadata":{"annotations":{},"name":"application-sample","namespace":"default"},"spec":{"components":[{"name":"myweb","properties":{"cmd":["sleep","1000"],"image":"busybox"},"traits":[{"properties":{"replicas":10},"type":"scaler"},{"properties":{"image":"nginx","name":"sidecar-test"},"type":"sidecar"},{"properties":{"http":{"server":80}},"type":"kservice"}],"type":"worker"}]}}
  ...   
spec:
  components:
  - name: myweb
    properties:
      cmd:
      - sleep
      - "1000"
      image: busybox
    traits:
    - properties:
        replicas: 10
      type: scaler
    - properties:
        image: nginx
        name: sidecar-test
      type: sidecar
    - properties:
        http:
          server: 80
      type: kservice
    type: worker
status:
  batchRollingState: ""
  components:
  - apiVersion: core.oam.dev/v1alpha2
    kind: Component
    name: myweb
  conditions:
  - reason: Available
    status: "True"
    type: Parsed
  - reason: Available
    status: "True"
    type: Built
  - reason: Available
    status: "True"
    type: Applied
  status: running
  ...
```

Step 4: View the oam CR generated by application

```
kubectl get appcontext/application-sample -oyaml

// appconfig is as follows
apiVersion: core.oam.dev/v1alpha2
kind: ApplicationContext
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"core.oam.dev/v1beta1","kind":"Application","metadata":{"annotations":{},"name":"application-sample","namespace":"default"},"spec":{"components":[{"name":"myweb","properties":{"cmd":["sleep","1000"],"image":"busybox"},"traits":[{"properties":{"replicas":10},"type":"scaler"},{"properties":{"image":"nginx","name":"sidecar-test"},"type":"sidecar"},{"properties":{"http":{"server":80}},"type":"kservice"}],"type":"worker"}]}}
  generation: 1
  labels:
    app.oam.dev/app-revision-hash: 99749f6e7a78024b
  name: application-sample
  namespace: default
  ownerReferences:
  - apiVersion: core.oam.dev/v1beta1
    controller: true
    kind: Application
    name: application-sample
    ...
spec:
  applicationRevisionName: application-sample-v1
status:
  conditions:
  - reason: ReconcileSuccess
    status: "True"
    type: Synced
  dependency: {}
  observedGeneration: 0
  workloads:
  - appliedComponentRevision: myweb-v1
    componentName: myweb
    componentRevisionName: myweb-v1
    traits:
    - traitRef:
        apiVersion: v1
        kind: Service
        name: myweb
    workloadRef:
      apiVersion: apps/v1
      kind: Deployment
      name: myweb-v1

kubectl get component/myweb -oyaml

// component is as follows
apiVersion: core.oam.dev/v1alpha2
kind: Component
metadata:
  generation: 1
  labels:
    app.oam.dev/name: application-sample
  name: myweb
  namespace: default
  ownerReferences:
  - apiVersion: core.oam.dev/v1beta1
    controller: true
    kind: Application
    name: application-sample
  ...
spec:
  workload:
    apiVersion: apps/v1
    kind: Deployment
    metadata:
      labels:
        app.oam.dev/component: myweb
        app.oam.dev/name: application-sample
        workload.oam.dev/type: worker
    spec:
      replicas: 10
      selector:
        matchLabels:
          app.oam.dev/component: myweb
      template:
        metadata:
          labels:
            app: myweb
            app.oam.dev/component: myweb
        spec:
          containers:
          - command:
            - sleep
            - "1000"
            image: busybox
            name: myweb
          - image: nginx
            name: sidecar-test
status:
  latestRevision:
    name: myweb-v1
    revision: 1
  observedGeneration: 1    
```