python - Google Cloud Endpoints API 的 DRY 代码

Question

我想避免使用样板代码为我的 Google App Engine 应用程序的不同模型创建 Google Cloud Endpoints API。假设我有一个 Post、User 和 Category 模型。数据存储在数据存储中。我想使用资源 posts、users 和 categories 创建一个 REST API。我为 posts 资源编写了以下代码:

import endpoints
from protorpc import messages
from protorpc import message_types
from protorpc import remote
from blog.models import Post
from cloud_endpoints import WEB_CLIENT_ID, ANDROID_CLIENT_ID, IOS_CLIENT_ID, ANDROID_AUDIENCE


class PostMessage(messages.Message):
    id = messages.StringField(1)
    title = messages.StringField(2)
    body = messages.StringField(3)


class PostMessageCollection(messages.Message):
    post_messages = messages.MessageField(PostMessage, 1, repeated=True)


def post_to_message(post):
    return PostMessage(
        id=str(post.key()),
        title=post.title,
        body=post.body)


ID_RESOURCE = endpoints.ResourceContainer(
    message_types.VoidMessage,
    id=messages.StringField(1, variant=messages.Variant.STRING))

PUT_RESOURCE = endpoints.ResourceContainer(
    PostMessage,
    id=messages.StringField(1, variant=messages.Variant.STRING))

POST_RESOURCE = endpoints.ResourceContainer(Post)


@endpoints.api(name='posts',
               version='v1',
               allowed_client_ids=[WEB_CLIENT_ID, ANDROID_CLIENT_ID, IOS_CLIENT_ID],
               audiences=[ANDROID_AUDIENCE])
class PostsApi(remote.Service):
    """List"""
    @endpoints.method(message_types.VoidMessage,
                      PostMessageCollection,
                      path='/posts',
                      http_method='GET',
                      name='posts.listPosts')
    def list(self, unused_request):
        post_messages = []
        for post in Post.all():
            post_messages.append(post_to_message(post))

        return PostCollection(post_messages=post_messages)

    """Get"""
    @endpoints.method(ID_RESOURCE,
                      PostMessage,
                      path='/posts/{id}',
                      http_method='GET',
                      name='posts.getPost')
    def get(self, request):
        try:
            return post_to_message(Post.get(request.id))

        except (IndexError, TypeError):
            raise endpoints.NotFoundException('Post %s not found.' % (request.id,))

    """Create"""
    @endpoints.method(POST_RESOURCE,
                      message_types.VoidMessage,
                      path='/posts',
                      http_method='POST',
                      name='posts.createPost')
    def create(self, request):
        post = Post(title=request.title, body=request.body)\
        post.put()
        return message_types.VoidMessage()

    """Update"""
    @endpoints.method(PUT_RESOURCE,
                      message_types.VoidMessage,
                      path='/posts/{id}',
                      http_method='POST',
                      name='posts.updatePost')
    def update(self, request):
        try:
            post = Post.get(request.id)
            post.title = request.title
            post.body = request.body
            return message_types.VoidMessage()
        except (IndexError, TypeError):
            raise endpoints.NotFoundException('Post %s not found.' % (request.id,))

    """Delete"""
    @endpoints.method(ID_RESOURCE,
                      message_types.VoidMessage,
                      path='/posts/{id}',
                      http_method='DELETE',
                      name='posts.deletePost')
    def delete(self, request):
        try:
            post = Post.get(request.id)
            post.delete()
            return message_types.VoidMessage()

        except (IndexError, TypeError):
            raise endpoints.NotFoundException('Post %s not found.' % (request.id,))

我可以复制/粘贴此代码并将“Post”更改为“Category”，然后编辑 PostMessage、PostMessageCollection 和 post_to_message，但这似乎是不好的做法。我不想重复自己。是否可以创建抽象 API 类并为 PostAPI、CategoryAPI 和 UserAPI 创建子类？或者是否有更好的方法来参数化 Post、PostMessage、PostMessageCollection、post_to_message 和资源路径 ( “/posts”、“/categories”和“/users”)这样我就不必为每个资源复制/粘贴类？这些类将具有相同的方法和相同的装饰器，我不想对每个资源重复这一点。我使用 Python 2.7。

Answer 1

我也偶然发现了同样的问题，不幸的是，这对于 google 云端点 是不可能的。方法装饰器需要请求描述(此处为 PostMessageCollection)。 message.Message 子类的请求描述不允许通过继承重用，因此所有消息类都必须完全定义，没有任何继承。

然而，您可以通过以下方式在某种程度上实现这一点(虽然我还没有测试过，但现在想到了 :)):

# All the message and response definitions have to be here, complete.

class PostMessage(messages.Message):
    id = messages.StringField(1)
    title = messages.StringField(2)
    body = messages.StringField(3)


class PostMessageCollection(messages.Message):
    post_messages = messages.MessageField(PostMessage, 1, repeated=True)


def post_to_message(post):
    return PostMessage(
        id=str(post.key()),
        title=post.title,
        body=post.body)


ID_RESOURCE = endpoints.ResourceContainer(
    message_types.VoidMessage,
    id=messages.StringField(1, variant=messages.Variant.STRING))

PUT_RESOURCE = endpoints.ResourceContainer(
    PostMessage,
    id=messages.StringField(1, variant=messages.Variant.STRING))

POST_RESOURCE = endpoints.ResourceContainer(Post)

# Now define all the 'Category' related messages here.


@endpoints.api(name='posts_n_categories',  # The name can be a common one.
               version='v1',
               allowed_client_ids=[WEB_CLIENT_ID, ANDROID_CLIENT_ID, IOS_CLIENT_ID],
               audiences=[ANDROID_AUDIENCE])
class BaseAPI(remote.Service):
    """List"""
    # Common defs go here.
    MessageCollection = messages.Message
    PATH = '/'
    NAME = ''

    @staticmethod
    def converter(x):
        raise NotImplemented

    iterator = []
    collection = messages.Message
    @endpoints.method(message_types.VoidMessage,
                      MessageCollection,
                      path=PATH,
                      http_method='GET',
                      name=NAME)
    def list(self, unused_request):
        # Do the common work here. You can 
        _messages = []
        for post in self.__class__.iterator.all():
            _messages.append(self.__class__.converter(post))

        return self.__class__.collection(post_messages=_messages)




@endpoints.api(name='posts',  # The name can be different.
               version='v1',
               allowed_client_ids=[WEB_CLIENT_ID, ANDROID_CLIENT_ID, IOS_CLIENT_ID],
               audiences=[ANDROID_AUDIENCE])
class PostAPI(Base):
    # Post specific defs go here.
    MessageCollection = PostMessageCollection
    PATH = '/posts'
    NAME = 'posts.listPosts'
    converter = post_to_message
    iterator = Post
    collection = PostCollection


# Define the category class here.

显然，它并没有节省多少时间。