Exploring the source code of the kubernetes API

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apiVersion: v1
kind: Pod
metadata:
  name: webserver
  labels:
    app: webserver
spec:
  containers:
  - name: webserver
    image: nginx
    ports:
    - containerPort: 80

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// source code from https://github.com/kubernetes/api/blob/master/core/v1/types.go
type Pod struct {
    // From the TypeMeta field name, you can see that this field defines the meta-information of the Pod type, similar to the object-oriented programming inside Class itself, similar to the API grouping, API version, etc. of the Pod type
    metav1.TypeMeta `json:",inline"`
    // The ObjectMeta field defines the meta-information for a single Pod object. Each kubernetes resource object has its own meta-information, such as name, namespace, tag, annotation, etc. kuberentes extracts these public properties as metav1.ObjectMeta, which becomes the parent class of the API object type
    metav1.ObjectMeta `json:"metadata,omitempty" protobuf:"bytes,1,opt,name=metadata"`
     // PodSpec represents the object definition specification for the Pod type, most representative of CPU and memory resource usage. This field corresponds to the spec field in YAML
    Spec PodSpec `json:"spec,omitempty" protobuf:"bytes,2,opt,name=spec"`
    // PodStatus indicates the status of the pod, such as whether it is running or hanging, the IP of the pod, etc. Kubernetes updates the PodStatus field based on the actual status of the pod in the Kubernetes updates the PodStatus field based on the actual status of the pod in the cluster
    Status PodStatus `json:"status,omitempty" protobuf:"bytes,3,opt,name=status"`
}

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// source code from https://github.com/kubernetes/api/blob/master/core/v1/types.go
type PodList struct {
    // PodList also needs to inherit from metav1.TypeMeta, after all, both object list and single object need type property.
    // PodList has more type description than []Pod type in yaml or json expression, when you need to build a list of objects based on YAML, you can deserialize it to PodList based on the type description, while []Pod can not, you must make sure that YAML is []Pod serialized result, otherwise an error will be reported. This does not allow for a generic object serialization/deserialization.
    metav1.TypeMeta `json:",inline"`
    // Unlike Pod, PodList inherits from metav1.ListMeta, which is the parent class of all resource object list types. ListMeta defines the common properties of all instances of the object list type.
    metav1.ListMeta `json:"metadata,omitempty" protobuf:"bytes,1,opt,name=metadata"`
    // The Items field is the essence of the PodList definition, and represents a list of Pod resource objects, so the PodList is []Pod with a few additions on top meta information related to the type and object list
    Items []Pod `json:"items" protobuf:"bytes,2,rep,name=items"`
}

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// source code from https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/types.go
//
// TypeMeta describes an individual object in an API response or request
// with strings representing the type of the object and its API schema version.
// Structures that are versioned or persisted should inline TypeMeta.
type TypeMeta struct {
    // Kind is a string value representing the REST resource this object represents.
    // Servers may infer this from the endpoint the client submits requests to.
    // Cannot be updated.
    Kind string `json:"kind,omitempty" protobuf:"bytes,1,opt,name=kind"`

    // APIVersion defines the versioned schema of this representation of an object.
    // Servers should convert recognized schemas to the latest internal value, and
    // may reject unrecognized values.
    APIVersion string `json:"apiVersion,omitempty" protobuf:"bytes,2,opt,name=apiVersion"`
}

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// source code from https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/types.go

func (obj *TypeMeta) GetObjectKind() schema.ObjectKind { return obj }

// SetGroupVersionKind satisfies the ObjectKind interface for all objects that embed TypeMeta
func (obj *TypeMeta) SetGroupVersionKind(gvk schema.GroupVersionKind) {
    obj.APIVersion, obj.Kind = gvk.ToAPIVersionAndKind()
}

// GroupVersionKind satisfies the ObjectKind interface for all objects that embed TypeMeta
func (obj *TypeMeta) GroupVersionKind() schema.GroupVersionKind {
    return schema.FromAPIVersionAndKind(obj.APIVersion, obj.Kind)
}

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// source code from https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/types.go
//
// ObjectMeta is metadata that all persisted resources must have, which includes all objects
// users must create.
type ObjectMeta struct {
    // Name must be unique within a namespace. Is required when creating resources, although
    // some resources may allow a client to request the generation of an appropriate name
    // automatically. Name is primarily intended for creation idempotence and configuration
    // definition.
    Name string `json:"name,omitempty" protobuf:"bytes,1,opt,name=name"`

    // GenerateName is an optional prefix, used by the server, to generate a unique
    // name ONLY IF the Name field has not been provided.
    // Populated by the system. Read-only.
    GenerateName string `json:"generateName,omitempty" protobuf:"bytes,2,opt,name=generateName"`

    // Namespace defines the space within which each name must be unique. An empty namespace is
    // equivalent to the "default" namespace, but "default" is the canonical representation.
    // Not all objects are required to be scoped to a namespace - the value of this field for
    // those objects will be empty.
    Namespace string `json:"namespace,omitempty" protobuf:"bytes,3,opt,name=namespace"`

    // SelfLink is a URL representing this object.
    // Populated by the system. Read-only.
    SelfLink string `json:"selfLink,omitempty" protobuf:"bytes,4,opt,name=selfLink"`

    // UID is the unique in time and space value for this object. It is typically generated by
    // the server on successful creation of a resource and is not allowed to change on PUT
    // operations.
    // Populated by the system. Read-only.
    UID types.UID `json:"uid,omitempty" protobuf:"bytes,5,opt,name=uid,casttype=k8s.io/kubernetes/pkg/types.UID"`

    // An opaque value that represents the internal version of this object that can
    // be used by clients to determine when objects have changed. May be used for optimistic
    // concurrency, change detection, and the watch operation on a resource or set of resources.
    // Clients must treat these values as opaque and passed unmodified back to the server.
    // They may only be valid for a particular resource or set of resources.
    // Populated by the system. Read-only.
    ResourceVersion string `json:"resourceVersion,omitempty" protobuf:"bytes,6,opt,name=resourceVersion"`

    // A sequence number representing a specific generation of the desired state.
    // Populated by the system. Read-only.
    Generation int64 `json:"generation,omitempty" protobuf:"varint,7,opt,name=generation"`

    // CreationTimestamp is a timestamp representing the server time when this object was
    // created. It is not guaranteed to be set in happens-before order across separate operations.
    // Clients may not set this value. It is represented in RFC3339 form and is in UTC.
    // Populated by the system. Read-only.
    CreationTimestamp Time `json:"creationTimestamp,omitempty" protobuf:"bytes,8,opt,name=creationTimestamp"`

    // DeletionTimestamp is RFC 3339 date and time at which this resource will be deleted. This
    // field is set by the server when a graceful deletion is requested by the user, and is not
    // directly settable by a client. The resource is expected to be deleted (no longer visible
    // from resource lists, and not reachable by name) after the time in this field, once the
    // finalizers list is empty. As long as the finalizers list contains items, deletion is blocked.
    // Once the deletionTimestamp is set, this value may not be unset or be set further into the
    // future, although it may be shortened or the resource may be deleted prior to this time.
    // For example, a user may request that a pod is deleted in 30 seconds. The Kubelet will react
    // by sending a graceful termination signal to the containers in the pod. After that 30 seconds,
    // the Kubelet will send a hard termination signal (SIGKILL) to the container and after cleanup,
    // remove the pod from the API. In the presence of network partitions, this object may still
    // exist after this timestamp, until an administrator or automated process can determine the
    // resource is fully terminated.
    // If not set, graceful deletion of the object has not been requested.
    //
    // Populated by the system when a graceful deletion is requested.
    // Read-only.
    DeletionTimestamp *Time `json:"deletionTimestamp,omitempty" protobuf:"bytes,9,opt,name=deletionTimestamp"`

    // Number of seconds allowed for this object to gracefully terminate before
    // it will be removed from the system. Only set when deletionTimestamp is also set.
    // May only be shortened.
    // Read-only.
    DeletionGracePeriodSeconds *int64 `json:"deletionGracePeriodSeconds,omitempty" protobuf:"varint,10,opt,name=deletionGracePeriodSeconds"`

    // Map of string keys and values that can be used to organize and categorize
    // (scope and select) objects. May match selectors of replication controllers
    // and services.
    Labels map[string]string `json:"labels,omitempty" protobuf:"bytes,11,rep,name=labels"`

    // Annotations is an unstructured key value map stored with a resource that may be
    // set by external tools to store and retrieve arbitrary metadata. They are not
    // queryable and should be preserved when modifying objects.
    Annotations map[string]string `json:"annotations,omitempty" protobuf:"bytes,12,rep,name=annotations"`

    // List of objects depended by this object. If ALL objects in the list have
    // been deleted, this object will be garbage collected. If this object is managed by a controller,
    // then an entry in this list will point to this controller, with the controller field set to true.
    OwnerReferences []OwnerReference `json:"ownerReferences,omitempty" patchStrategy:"merge" patchMergeKey:"uid" protobuf:"bytes,13,rep,name=ownerReferences"`

    // Must be empty before the object is deleted from the registry. Each entry
    // is an identifier for the responsible component that will remove the entry
    // from the list. If the deletionTimestamp of the object is non-nil, entries
    // in this list can only be removed.
    // Finalizers may be processed and removed in any order.  Order is NOT enforced
    // because it introduces significant risk of stuck finalizers.
    // finalizers is a shared field, any actor with permission can reorder it.
    // If the finalizer list is processed in order, then this can lead to a situation
    // in which the component responsible for the first finalizer in the list is
    // waiting for a signal (field value, external system, or other) produced by a
    // component responsible for a finalizer later in the list, resulting in a deadlock.
    // Without enforced ordering finalizers are free to order amongst themselves and
    // are not vulnerable to ordering changes in the list.
    Finalizers []string `json:"finalizers,omitempty" patchStrategy:"merge" protobuf:"bytes,14,rep,name=finalizers"`

    // The name of the cluster which the object belongs to.
    // This is used to distinguish resources with same name and namespace in different clusters.
    // This field is not set anywhere right now and apiserver is going to ignore it if set in create or update request.
    ClusterName string `json:"clusterName,omitempty" protobuf:"bytes,15,opt,name=clusterName"`

    // ManagedFields maps workflow-id and version to the set of fields
    // that are managed by that workflow. This is mostly for internal
    // housekeeping, and users typically shouldn't need to set or
    // understand this field. A workflow can be the user's name, a
    // controller's name, or the name of a specific apply path like
    // "ci-cd". The set of fields is always in the version that the
    // workflow used when modifying the object.
    ManagedFields []ManagedFieldsEntry `json:"managedFields,omitempty" protobuf:"bytes,17,rep,name=managedFields"`
}

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// source code from https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/meta.go
//
// Object lets you work with object metadata from any of the versioned or
// internal API objects. Attempting to set or retrieve a field on an object that does
// not support that field (Name, UID, Namespace on lists) will be a no-op and return
// a default value.
type Object interface {
    GetNamespace() string
    SetNamespace(namespace string)
    GetName() string
    SetName(name string)
    GetGenerateName() string
    SetGenerateName(name string)
    GetUID() types.UID
    SetUID(uid types.UID)
    GetResourceVersion() string
    SetResourceVersion(version string)
    GetGeneration() int64
    SetGeneration(generation int64)
    GetSelfLink() string
    SetSelfLink(selfLink string)
    GetCreationTimestamp() Time
    SetCreationTimestamp(timestamp Time)
    GetDeletionTimestamp() *Time
    SetDeletionTimestamp(timestamp *Time)
    GetDeletionGracePeriodSeconds() *int64
    SetDeletionGracePeriodSeconds(*int64)
    GetLabels() map[string]string
    SetLabels(labels map[string]string)
    GetAnnotations() map[string]string
    SetAnnotations(annotations map[string]string)
    GetFinalizers() []string
    SetFinalizers(finalizers []string)
    GetOwnerReferences() []OwnerReference
    SetOwnerReferences([]OwnerReference)
    GetClusterName() string
    SetClusterName(clusterName string)
    GetManagedFields() []ManagedFieldsEntry
    SetManagedFields(managedFields []ManagedFieldsEntry)
}

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// source code from https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/meta.go
//
type ObjectMetaAccessor interface {
    GetObjectMeta() Object
}

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// source code from https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/types.go
//
// ListMeta describes metadata that synthetic resources must have, including lists and
// various status objects. A resource may have only one of {ObjectMeta, ListMeta}.
type ListMeta struct {
    // selfLink is a URL representing this object.
    // Populated by the system.
    // Read-only.
    SelfLink string `json:"selfLink,omitempty" protobuf:"bytes,1,opt,name=selfLink"`

    // String that identifies the server's internal version of this object that
    // can be used by clients to determine when objects have changed.
    // Value must be treated as opaque by clients and passed unmodified back to the server.
    // Populated by the system.
    // Read-only.
    ResourceVersion string `json:"resourceVersion,omitempty" protobuf:"bytes,2,opt,name=resourceVersion"`

    // continue may be set if the user set a limit on the number of items returned, and indicates that
    // the server has more data available. The value is opaque and may be used to issue another request
    // to the endpoint that served this list to retrieve the next set of available objects. Continuing a
    // consistent list may not be possible if the server configuration has changed or more than a few
    // minutes have passed. The resourceVersion field returned when using this continue value will be
    // identical to the value in the first response, unless you have received this token from an error
    // message.
    Continue string `json:"continue,omitempty" protobuf:"bytes,3,opt,name=continue"`

    // remainingItemCount is the number of subsequent items in the list which are not included in this
    // list response. If the list request contained label or field selectors, then the number of
    // remaining items is unknown and the field will be left unset and omitted during serialization.
    // If the list is complete (either because it is not chunking or because this is the last chunk),
    // then there are no more remaining items and this field will be left unset and omitted during
    // serialization.
    // Servers older than v1.15 do not set this field.
    // The intended use of the remainingItemCount is *estimating* the size of a collection. Clients
    // should not rely on the remainingItemCount to be set or to be exact.
    RemainingItemCount *int64 `json:"remainingItemCount,omitempty" protobuf:"bytes,4,opt,name=remainingItemCount"`
}

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// source code from https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/meta.go
//
// ListInterface lets you work with list metadata from any of the versioned or
// internal API objects. Attempting to set or retrieve a field on an object that does
// not support that field will be a no-op and return a default value.
type ListInterface interface {
    GetResourceVersion() string
    SetResourceVersion(version string)
    GetSelfLink() string
    SetSelfLink(selfLink string)
    GetContinue() string
    SetContinue(c string)
    GetRemainingItemCount() *int64
    SetRemainingItemCount(c *int64)
}

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// source code from https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/meta.go
//
// ListMetaAccessor retrieves the list interface from an object
type ListMetaAccessor interface {
    GetListMeta() ListInterface
}

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// source code from: https://github.com/kubernetes/apimachinery/blob/master/pkg/runtime/interfaces.go
//
// Object interface must be supported by all API types registered with Scheme. Since objects in a scheme are
// expected to be serialized to the wire, the interface an Object must provide to the Scheme allows
// serializers to set the kind, version, and group the object is represented as. An Object may choose
// to return a no-op ObjectKindAccessor in cases where it is not expected to be serialized.
type Object interface {
    // used to access type metadata(GVK)
    GetObjectKind() schema.ObjectKind
    // DeepCopyObject needed to implemented by each kubernetes API type definition,
    // usually by automatically generated code.
    DeepCopyObject() Object
}

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// source code from: https://github.com/kubernetes/apimachinery/blob/master/pkg/api/meta/meta.go
//
// Accessor takes an arbitrary object pointer and returns meta.Interface.
// obj must be a pointer to an API type. An error is returned if the minimum
// required fields are missing. Fields that are not required return the default
// value and are a no-op if set.
func Accessor(obj interface{}) (metav1.Object, error) {
    switch t := obj.(type) {
    case metav1.Object:
        return t, nil
    case metav1.ObjectMetaAccessor:
        if m := t.GetObjectMeta(); m != nil {
            return m, nil
        }
        return nil, errNotObject
    default:
        return nil, errNotObject
    }
}

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// source code from https://github.com/kubernetes/api/blob/master/core/v1/zz_generated.deepcopy.go
//
// DeepCopyObject is an autogenerated deepcopy function, copying the receiver, creating a new runtime.Object.
func (in *ConfigMap) DeepCopyObject() runtime.Object {
    if c := in.DeepCopy(); c != nil {
        return c
    }
    return nil
}

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type Pod struct {
    metav1.TypeMeta `json:",inline"`
    metav1.ObjectMeta `json:"metadata,omitempty" protobuf:"bytes,1,opt,name=metadata"`
    Spec PodSpec `json:"spec,omitempty" protobuf:"bytes,2,opt,name=spec"`
    Status PodStatus `json:"status,omitempty" protobuf:"bytes,3,opt,name=status"`
}

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type k8sUnstructuredObject struct {
    Object map[string]interface{}
}

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// soure code from: https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/unstructured/unstructured.go
//
type Unstructured struct {
    // Object is a JSON compatible map with string, float, int, bool, []interface{}, or
    // map[string]interface{} children.
    Object map[string]interface{}
}

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import (
    "k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
    "k8s.io/apimachinery/pkg/runtime/serializer/yaml"
)

var manifest = `
apiVersion: v1
kind: pod
metadata:
  name: web
spec:
  ...
`
// convert yaml to unstructured
objs := &unstructured.Unstructured{}
dec := yaml.NewDecodingSerializer(unstructured.UnstructuredJSONScheme)
dec.Decode([]byte(manifest), nil, obj)

labels := obj.GetLabels()
labels["owner"]="xxx"
obj.SetLabels(labels)

dynamicClient.Resource().Namespace(namespace).Create(context.TODO(), obj, metav1.CreateOptions{})

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import "k8s.io/client-go/kubernetes"

clientset, err := kubernetes.NewForConfig(config)

pod := &Corev1.Pod{}
pod.Name = "web"
pod.Spec = pod.PodSpec{
    ...
}

clientset.CoreV1().Pods(apiv1.NamespaceDefault).Create(pod)

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import "k8s.io/client-go/dynamic"

client, _ := dynamic.NewForConfig(config)
podGVR := schema.GroupVersionResource{Group: "core", Version: "v1", Resource: "pods"}

pod := &unstructured.Unstructured{
    Object: map[string]interface{}{
        "apiVersion": "v1",
        "kind":       "Pod",
        "metadata": map[string]interface{}{
            "name": "web",
        },
        "spec": map[string]interface{}{
            "serviceAccount": "default",
            ...
        }
    }
}

client.Resource(podGVR).Namespace(namespace).Create(context.TODO(), pod, metav1.CreateOptions{})

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// source code from: https://github.com/kubernetes/apimachinery/blob/master/pkg/runtime/converter.go
//
// UnstructuredConverter is an interface for converting between interface{}
// and map[string]interface representation.
type UnstructuredConverter interface {
    ToUnstructured(obj interface{}) (map[string]interface{}, error)
    FromUnstructured(u map[string]interface{}, obj interface{}) error
}