flask的html模板的覆盖问题

原创

fushall 2018-05-22 23:29:30 ©著作权

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环境如下： win10、Python3.6.5、Flask1.0.2

项目结构如下:

/app
    /manage.py
    /main
        /views.py
        /templates
            index.html    
    /admin
        /views.py
        /templates 
            index.html

/app/main/views.py内容如下:

from flask import Blueprint, render_template
main = Blueprint('main', __name__, template_folder='templates')
@main.route('/')
def index():
    return render_template('index.html')

/app/admin/views.py内容如下：

from flask import Blueprint, render_template
admin = Blueprint('admin', __name__, template_folder='templates', url_prefix='/admin')
@admin.route('/')
def index():
    return render_template('index.html')

/app/manage.py内容如下:

from flask import Flask
from app.main import main
from app.admin import admin

def create_app():
    app = Flask(__name__)
    app.register_blueprint(main)
    app.register_blueprint(admin)
    return app

在cmd中输入flask run（执行前记得设置FLASK_APP、FLASK_DEBUG）。待程序跑起来后，在浏览器地址栏中输入127.0.0.1:5000，显示的是main蓝图的inde.html。输入127.0.0.1/admin/，显示的还是 main蓝图的index.html。奇怪,这是为什么呢？浮砂在网上搜索半天，最终在flask官方的 github上找到了相关issue，感兴趣的朋友可以看看。 Method render_template does not use blueprint specified template_folder #1361

此外，官方的文档中也有相关说明（Templates 部分）：blueprint-resources
为了方便新手朋友，浮砂翻译成了中文，部分地方进行了补充。

Templates
模板

If you want the blueprint to expose templates you can do that by providing the template_folder parameter to the :class:Blueprint constructor::
如果你想让蓝图暴露一些模板（比如flask-bootstrap扩展提供的"bootstrap/base.html"），可以给在构造Blueprint时，指定template_folder参数。

admin = Blueprint('admin', __name__, template_folder='templates')

For static files, the path can be absolute or relative to the blueprint resource folder.
对于静态的文件，路径可以是绝对或相对于蓝图资源文件夹的。

The template folder is added to the search path of templates but with a lower priority than the actual application's template folder. That way you can easily override templates that a blueprint provides in the actual application. This also means that if you don't want a blueprint template to be accidentally overridden, make sure that no other blueprint or actual application template has the same relative path. When multiple blueprints provide the same relative template path the first blueprint registered takes precedence over the others.
模板的全局搜索路径中会自动添加这个模板文件夹，并且它的优先级低于应用的模板文件夹。这样，你可以在实际应用中，轻而易举地覆盖某个蓝图的模板。也就是说，如果不想让某个蓝图模板莫名其妙地被覆盖，请确保其他的蓝图的模板相对路径不同于实际应用的模板相对路径。假如多个蓝图模板被指定了相同的相对路径，那么，当flask搜索模板的时候，先被注册的蓝图模板优先于后被注册的蓝图模板。

So if you have a blueprint in the folder yourapplication/admin and you want to render the template 'admin/index.html' and you have provided templates as a template_folder you will have to create a file like this: :file:yourapplication/admin/templates/admin/index.html. The reason for the extra admin folder is to avoid getting our template overridden by a template named index.html in the actual application template folder.
所以说，如果你在yourapplication/admin文件夹中编写了一个admin蓝图，而且你还想渲染admin/index.html，并且你也给 template_folder参数赋值了一个templates，那你就得像这样创建你的文件yourapplication/admin/templates/admin/index.html，额外的那个admin文件夹的存在，是为了不让实际应用的模板文件夹，把我们admin 蓝图的index.html文件覆盖掉。

To further reiterate this: if you have a blueprint named admin and you want to render a template called :file:index.html which is specific to this blueprint, the best idea is to lay out your templates like this::
再说一遍，如果你有一个名为admin的蓝图，并且你想渲染这个蓝图中的一个名为 index.html的模板，最好的办法，就是把admin蓝图的模板路径弄成像这样：

yourpackage/
    blueprints/
        admin/
            templates/
                admin/
                    index.html
            __init__.py

And then when you want to render the template, use :file:admin/index.html as the name to look up the template by. If you encounter problems loading the correct templates enable the EXPLAIN_TEMPLATE_LOADING config variable which will instruct Flask to print out the steps it goes through to locate templates on every render_template call.
此后，每当你想渲染admin蓝图的模板，只需在调用render_template函数时，把参数写成 admin/index.html就行了。假如你加载模板时遇到了问题，你可以把flask提供的一个名为 EXPLAIN_TEMPLATE_LOADING的配置项设置为可用。一旦启用了该配置，Flask就会在调用 render_template函数渲染模板时，把搜索模板的步骤全部输出出来，非常方便。

对于文章开头的例子，浮砂开启了flask的EXPLAIN_TEMPLATE_LOADING，再次访问 127.0.0.1:5000的时候，在cmd窗口中会有如下输出：

[2018-05-19 22:06:21,488] INFO in debughelpers: Locating template "index.html":
    1: trying loader of application "flask_server.app"
       class: jinja2.loaders.FileSystemLoader
       encoding: 'utf-8'
       followlinks: False
       searchpath:
         - D:\app\templates
       -> no match
    2: trying loader of blueprint "main" (flask_server.main)
       class: jinja2.loaders.FileSystemLoader
       encoding: 'utf-8'
       followlinks: False
       searchpath:
         - D:\app\main\templates
       -> found ('D:\\app\\main\\templates\\index.html')
    3: trying loader of blueprint "admin" (flask_server.admin)
       class: jinja2.loaders.FileSystemLoader
       encoding: 'utf-8'
       followlinks: False
       searchpath:
         - D:\app\admin\templates
       -> found ('D:\\app\\admin\\templates\\index.html')
Warning: multiple loaders returned a match for the template.
  The template was looked up from an endpoint that belongs to the blueprint "main".
  Maybe you did not place a template in the right folder?
  See http://flask.pocoo.org/docs/blueprints/#templates
127.0.0.1 - - [19/May/2018 22:06:21] "GET / HTTP/1.1" 200 -

根据官方给出的建议，浮砂尝试修改了项目的结构以及相关代码：

更改后的项目结构如下:
/app
    /manage.py
    /main
        /views.py
        /templates
            /main
                /index.html    
    /admin
        /views.py
        /templates
            /admin 
                index.html

/app/main/views.py内容如下:

from flask import Blueprint, render_template
main = Blueprint('main', __name__, template_folder='templates')
@main.route('/')
def index():
    return render_template('main/index.html')  # 修改后

/app/admin/views.py内容如下：

from flask import Blueprint, render_template
admin = Blueprint('admin', __name__, template_folder='templates', url_prefix='/admin')
@admin.route('/')
def index():
    return render_template('admin/index.html')  # 修改后

再次执行flask run（执行前记得设置FLASK_APP、FLASK_DEBUG），访问127.0.0.1:5000和 127.0.0.1:5000/admin，发现原来“被覆盖”的html页面已经能被正确地对应上了。