03_Django-GET Requests and POST Requests - Design Patterns and Template Layer

Video link: https://www.bilibili.com/video/BV1vK4y1o7jH

1. GET Requests and POST Requests#

Definition#

· Whether GET or POST, both are uniformly received by the view function, distinguishing specific request actions by judging request.method

· Example:

if requests.method == 'GET':
    Handle business logic for GET request
elif requests.method == 'POST':
    Handle business logic for POST request
else:
    Other request business logic

------------------------------------------------------------------

Demonstration

 <Project same name folder>/views.py
def test_get_post(request):
    if request.method == 'GET':
        pass
    elif request.method == 'POST':
        # Handle user submitted data
        pass
    else:
        pass
    return HttpResponse('--test get post is ok--')

GET Handling#

· GET request action is generally used to retrieve data from the server

· Scenarios that can generate GET requests:

- Entering URL in the browser address bar and pressing enter

- <a href="address?parameter=value&parameter=value">

- form form with method set to get

------------------------------------------------------------------

In the GET request method, if there is data to be passed to the server, it is usually done using query strings【Note: do not pass sensitive data】

URL format: xxx?parameter1=value1&parameter2=value2...

- For example: http://127.0.0.1:8000/page1`?a=100&b=200`

Server-side receives parameters

Retrieve data submitted by the client in the GET request

· Method example:
request.GET['parameter'] # QueryDict
request.GET.get('parameter', 'default value')
request.GET.getlist('parameter')
# mypage?a=100&b=200&c=300&b=400
# request.GET=QueryDict({'a': ['100'], 'b': ['200', '400'], 'c': ['300']})
# a = request.GET['a']
# b = request.GET['b'] # Error
------------------------------------------------------------------
Demonstration

http://127.0.0.1:8000/test_get_post?a=400
--test get post is ok--
Terminal
<QueryDict: {'a': ['400', '200', '100']}>
100
['400', '200', '100']
no c

 <Project same name folder>/urls.py
urlpatterns = [
    ...
    path('test_get_post', views.test_get_post)
]

 <Project same name folder>/views.py
def test_get_post(request):
    if request.method == 'GET':
        print(request.GET)
        print(request.GET['a'])
        # Survey = form get   Interests - checkbox
        print(request.GET.getlist('a'))
        print(request.GET.get('c', 'no c'))
    elif request.method == 'POST':
        # Handle user submitted data
        pass
    else:
        pass
    return HttpResponse('--test get post is ok--')
------------------------------------------------------------------

· Reflection: Can the previous calculator function be done with query strings?

http://127.0.0.1:8000/integer/operator/integer

http://127.0.0.1:8000/cal?x=10&y=20&op=add

POST Handling#

· POST request action is generally used to submit large/private data to the server

· The client passes data to the server through forms and other POST requests, such as:

· Server-side receives parameters

Determine if it is a POST request through request.method, such as:
if request.method == 'POST':
 Handle POST request data and respond
else:
 Handle non-POST request response
------------------------------------------------------------------

Using POST method to receive client data
request.POST['parameter'] # request.POST binds QueryDict
request.POST.get('parameter', '')
request.POST.getlist('parameter')
Disable csrf verification, otherwise Django will reject the POST request from the client with a 403 response

------------------------------------------------------------------

Disabling csrf verification

- Disable the CsrfViewMiddleware middleware in settings.py
MIDDLEWARE = [
	...
 # 'django.middleware.csrf.CsrfViewMiddleware',
 ...
]
------------------------------------------------------------------

Demonstration

http://127.0.0.1:8000/test_get_post
post is ok
Terminal
uname is cpen

 <Project same name folder>/urls.py
urlpatterns = [
    ...
    path('test_get_post', views.test_get_post)
]

 <Project same name folder>/views.py
POST_FORM = '''
<form method='post' action='/test_get_post'>
    Username: <input type='text' name='uname'>
    <input type='submit' value='Submit'>
</form>
'''
def test_get_post(request):
    if request.method == 'GET':
        return HttpResponse(POST_FORM)
    ...
---------------------------------------------------------------------------------------------------------------------------------

Summary

· Django handles GET requests

Using query strings - for small data transmission

· Django handles POST requests

Specifically for browser data submission

2. Django's Design Patterns and Template Layer#

MVC and MTV#

Traditional MVC#

MVC stands for Model-View-Controller pattern.

M Model Layer, mainly used for encapsulating the database layer

V View Layer, used to present results to the user (WHAT + HOW)

C Controller, used to handle requests, retrieve data, and return results (important)

Purpose: Reduce coupling between modules (decoupling)

Django's MTV Pattern#

MTV stands for Model-Template-View pattern.

M Model Layer is responsible for interacting with the database

T Template Layer is responsible for rendering content to the browser (HOW)

V View Layer is the core, responsible for receiving requests, retrieving data, and returning results (WHAT)

Purpose: Reduce coupling between modules (decoupling)

---------------------------------------------------------------------------------------------------------------------------------

Template Layer#

What is a Template#

A template is an html page that can dynamically change based on dictionary data

Templates can dynamically generate corresponding HTML pages based on the dictionary data passed in the view

Template Configuration#

Create a template folder <Project Name>/templates

In settings.py, configure the TEMPLATES option

1. BACKEND: Specify the template engine

2. DIRS: Template search directories (can be one or more)

3. APP_DIRS: Whether to search for template files in the templates folder of the application

4. OPTIONS: Options related to templates

· The part that needs to be modified in the configuration

Set DIRS - 'DIRS': [os.path.join(BASE_DIR, 'templates')],

------------------------------------------------------------------

Demonstration
 <Project same name folder>/settings.py
TEMPLATES = [
    {
        ...
        'DIRS': [os.path.join(BASE_DIR, 'templates')],
        ...

Template Loading Methods#

Option 1 - Load the template through loader and respond via HttpResponse (Characteristics: cumbersome)

In the view function:
from django.template import loader
# 1. Load the template through loader
t = loader.get_template("template filename")
# 2. Convert t to HTML string
html = t.render(dictionary data)
# 3. Return the converted string content to the browser using the response object
return HttpResponse(html)
--------------------------------------------------------------------------------------

Demonstration

http://127.0.0.1:8000/test_html
 <Project same name folder>/urls.py
urlpatterns = [
    ...
    path('test_html', views.test_html)
]

 <Project same name folder>/views.py
def test_html(request):
    from django.template import loader
    t = loader.get_template('test_html.html')
    html = t.render()
    return HttpResponse(html)

 <Project folder>/templates/test_html.html
<h3>I am from the template layer~~~~</h3>
---------------------------------------------------------------------------------------------------------------------------------

Option 2 - Directly load and respond to the template using render() (Characteristics: convenient, widely used)

In the view function:
from django.shortcuts import render
return render(request, 'template filename', dictionary data)
--------------------------------------------------------------------------------------

Demonstration

http://127.0.0.1:8000/test_html
 <Project same name folder>/views.py
def test_html(request):
    # Option 2
    from django.shortcuts import render
    return render(request, 'test_html.html')

Interaction Between View Layer and Template Layer#

In the view function, Python variables can be encapsulated in a dictionary and passed to the template

Example:

def xxx_view(request):
dic = {
"variable1": "value1",
"variable2": "value2",
}
return render(request, 'xxx.html', dic)

In the template, we can use {{ variable name }} syntax to call the variables passed from the view

--------------------------------------------------------------------------------------

Demonstration

http://127.0.0.1:8000/test_html
 <Project same name folder>/urls.py
urlpatterns = [
    ...
    path('test_html', views.test_html)
]

 <Project same name folder>/views.py
def test_html(request):
    from django.shortcuts import render
    dic = {'username': 'peng', 'age': 23}
    return render(request, 'test_html.html', dic)

 <Project folder>/templates/test_html.html
<h3>{{ username }} is from the template layer~~~~</h3>