fix npes in shoot and secret validators (#460)

```other operator
Fix NPEs in shoot and secret validators of `gardener-extension-validator-vsphere`
```

cmd/validator-vsphere/app/app.go

@@ -94,8 +94,8 @@ func NewValidatorCommand(ctx context.Context) *cobra.Command {
 			hookServer := mgr.GetWebhookServer()
 
 			log.Info("Registering webhooks")
-			hookServer.Register("/webhooks/validate", &webhook.Admission{Handler: &validator.Shoot{Logger: log.WithName("shoot-validator")}})
-			hookServer.Register("/webhooks/validate/secrets", &webhook.Admission{Handler: &validator.Secret{Logger: log.WithName("secret-validator")}})
+			hookServer.Register("/webhooks/validate", &webhook.Admission{Handler: validator.NewShootHandler(mgr, log)})
+			hookServer.Register("/webhooks/validate/secrets", &webhook.Admission{Handler: validator.NewSecretHandler(mgr, log)})
 
 			if err := mgr.AddReadyzCheck("informer-sync", gardenerhealthz.NewCacheSyncHealthz(mgr.GetCache())); err != nil {
 				return fmt.Errorf("could not add readycheck for informers: %w", err)

pkg/validator/secret_handler.go

@@ -25,13 +25,25 @@ import (
 	corev1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/equality"
 	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/runtime/serializer"
 	"sigs.k8s.io/controller-runtime/pkg/client"
+	"sigs.k8s.io/controller-runtime/pkg/manager"
 	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"
 
 	vspherevalidation "github.com/gardener/gardener-extension-provider-vsphere/pkg/apis/vsphere/validation"
 	"github.com/gardener/gardener-extension-provider-vsphere/pkg/vsphere"
 )
 
+// NewSecretHandler returns a new instance of a shoot handler.
+func NewSecretHandler(mgr manager.Manager, log logr.Logger) admission.Handler {
+	return &Secret{
+		client:    mgr.GetClient(),
+		decoder:   serializer.NewCodecFactory(mgr.GetScheme(), serializer.EnableStrict).UniversalDecoder(),
+		apiReader: mgr.GetAPIReader(),
+		Logger:    log.WithName("secret-validator"),
+	}
+}
+
 // Shoot validates shoots
 type Secret struct {
 	client    client.Client
@@ -78,15 +90,3 @@ func (s *Secret) Handle(ctx context.Context, req admission.Request) admission.Re
 
 	return admission.Allowed("valid secret")
 }
-
-// InjectClient injects the client.
-func (s *Secret) InjectClient(c client.Client) error {
-	s.client = c
-	return nil
-}
-
-// InjectAPIReader injects the given apiReader into the validator.
-func (s *Secret) InjectAPIReader(apiReader client.Reader) error {
-	s.apiReader = apiReader
-	return nil
-}

pkg/validator/shoot_handler.go

@@ -24,12 +24,24 @@ import (
 	"github.com/go-logr/logr"
 	admissionv1 "k8s.io/api/admission/v1"
 	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/runtime/serializer"
 	"sigs.k8s.io/controller-runtime/pkg/client"
+	"sigs.k8s.io/controller-runtime/pkg/manager"
 	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"
 
 	"github.com/gardener/gardener-extension-provider-vsphere/pkg/vsphere"
 )
 
+// NewShootHandler returns a new instance of a shoot handler.
+func NewShootHandler(mgr manager.Manager, log logr.Logger) admission.Handler {
+	return &Shoot{
+		client:    mgr.GetClient(),
+		decoder:   serializer.NewCodecFactory(mgr.GetScheme(), serializer.EnableStrict).UniversalDecoder(),
+		apiReader: mgr.GetAPIReader(),
+		Logger:    log.WithName("shoot-validator"),
+	}
+}
+
 // Shoot validates shoots
 type Shoot struct {
 	client    client.Client
@@ -78,15 +90,3 @@ func (v *Shoot) Handle(ctx context.Context, req admission.Request) admission.Res
 
 	return admission.Allowed("validations succeeded")
 }
-
-// InjectClient injects the client.
-func (v *Shoot) InjectClient(c client.Client) error {
-	v.client = c
-	return nil
-}
-
-// InjectAPIReader injects the given apiReader into the validator.
-func (v *Shoot) InjectAPIReader(apiReader client.Reader) error {
-	v.apiReader = apiReader
-	return nil
-}