使用Graphene Python构建GraphQL × Flask × SQLAlchemy服务器

1 年 ago

清, 宇

3 minutes

本篇文章的內容。

この記事では、Graphene Python を利用した GraphQL × Flask × SQLAlchemy Server の構築方法をまとめたものとなっております

GraphQL 是一种（原则上）的技术

クエリに対して、JSON で結果を返す

请参考以下链接：
* https://qiita.com/syu_chan_1005/items/3350f1d12c17a77e98c7
* https://vitalify.jp/app-lab/20171006-graphql/
* https://tukumemo.com/graphql/

石墨烯是一种材料。

https://graphene-python.org/

运行环境

sqlite 3.24.0

直到移动

http://docs.graphene-python.org/projects/sqlalchemy/en/latest/tutorial/ の内容ベースで翻訳しております


## プロジェクト用のディレクトリを作成
mkdir flask_sqlalchemy
cd flask_sqlalchemy

## virtualenv 環境の作成と読み込み
virtualenv env
source env/bin/activate  # On Windows use `env\Scripts\activate`

## SQLAlchemy と graphene_sqlalchemy の pip install
pip install SQLAlchemy
pip install graphene_sqlalchemy

## Flask と Flask-GraphQL のインストール
pip install Flask
pip install Flask-GraphQL

模型的定义 de

# flask_sqlalchemy/models.py
from sqlalchemy import *
from sqlalchemy.orm import (scoped_session, sessionmaker, relationship,
                            backref)
from sqlalchemy.ext.declarative import declarative_base

engine = create_engine('sqlite:///database.sqlite3', convert_unicode=True)
db_session = scoped_session(sessionmaker(autocommit=False,
                                         autoflush=False,
                                         bind=engine))

Base = declarative_base()
# We will need this for querying
Base.query = db_session.query_property()


class Department(Base):
    __tablename__ = 'department'
    id = Column(Integer, primary_key=True)
    name = Column(String)


class Employee(Base):
    __tablename__ = 'employee'
    id = Column(Integer, primary_key=True)
    name = Column(String)
    hired_on = Column(DateTime, default=func.now())
    department_id = Column(Integer, ForeignKey('department.id'))
    department = relationship(
        Department,
        backref=backref('employees',
                        uselist=True,
                        cascade='delete,all'))

创建模式

GraphQL将对象表示为图结构，而不是常见的分层结构。

本次例子中，我们通过all_employees提供了列出所有员工的功能，并且通过节点提供了获取特定节点的功能。

创建一个名为 flask_sqlalchemy/schema.py 的文件，并按照以下方式进行编辑。

# flask_sqlalchemy/schema.py
import graphene
from graphene import relay
from graphene_sqlalchemy import SQLAlchemyObjectType, SQLAlchemyConnectionField
from models import db_session, Department as DepartmentModel, Employee as EmployeeModel


class Department(SQLAlchemyObjectType):
    class Meta:
        model = DepartmentModel
        interfaces = (relay.Node, )


class DepartmentConnection(relay.Connection):
    class Meta:
        node = Department


class Employee(SQLAlchemyObjectType):
    class Meta:
        model = EmployeeModel
        interfaces = (relay.Node, )


class EmployeeConnection(relay.Connection):
    class Meta:
        node = Employee


class Query(graphene.ObjectType):
    node = relay.Node.Field()
    # Allows sorting over multiple columns, by default over the primary key
    all_employees = SQLAlchemyConnectionField(EmployeeConnection)
    # Disable sorting over this field
    all_departments = SQLAlchemyConnectionField(DepartmentConnection, sort=None)

schema = graphene.Schema(query=Query)

创建在Flask上的GraphQL环境。

与 RESTful API 不同，GraphQL 只有一个访问 URL。

使用Flask创建一个服务器，在/graphql路径下公开GraphQL模式，并创建一个称为GraphiQL的接口，用于轻松执行查询操作。

Flask-GraphQL库可以支持实现此功能。

# flask_sqlalchemy/app.py
from flask import Flask
from flask_graphql import GraphQLView

from models import db_session
from schema import schema, Department

app = Flask(__name__)
app.debug = True

app.add_url_rule(
    '/graphql',
    view_func=GraphQLView.as_view(
        'graphql',
        schema=schema,
        graphiql=True # for having the GraphiQL interface
    )
)

@app.teardown_appcontext
def shutdown_session(exception=None):
    db_session.remove()

if __name__ == '__main__':
    app.run()

我试着创建一些数据

使用Python 3打开控制台。

>>> from models import engine, db_session, Base, Department, Employee
>>> Base.metadata.create_all(bind=engine)

>>> # Fill the tables with some data
>>> engineering = Department(name='Engineering')
>>> db_session.add(engineering)
>>> hr = Department(name='Human Resources')
>>> db_session.add(hr)

>>> peter = Employee(name='Peter', department=engineering)
>>> db_session.add(peter)
>>> roy = Employee(name='Roy', department=engineering)
>>> db_session.add(roy)
>>> tracy = Employee(name='Tracy', department=hr)
>>> db_session.add(tracy)
>>> db_session.commit()

GraphQL 测试操作

现在，准备工作已经完成。让我们从命令行启动服务器并检查其运行情况。

$ python3 ./app.py
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

启动后，请尝试访问 http://localhost:5000/graphql。

在左侧输入查询以验证功能。

{
  allEmployees {
    edges {
      node {
        id
        name
        department {
          name
        }
      }
    }
  }
}

通过这个，您可以确认查询的响应了。

构建一个简单的 GraphQL + DB 服务器时，本文的内容非常有用。

如果有运行不顺利的问题，可以尝试查看 Github 仓库中的示例并进行尝试。

非常感谢您耐心地阅读这篇长文❗️

给你一个额外的好处

似乎还有MongoDB的教程：
* https://graphene-mongo.readthedocs.io/en/latest/tutorial.html