ajax use

• Locks: shared locks and exclusive locks

  • lock in share mode shared lock to open the way (they have to open things, begin)
  • for update exclusive lock open (to begin)
  • Table lock Example: lock table app01_publish write
    • unlock tables;
  • create, update, delete, operation, MySQL automatic row-level mutex

  `
  Lock
  1. protostele
  select * from t1 where id = 1 for update; ( before writing the sentence have to open things, the begin)
  2.orm in
  . Models.T1.objects.select_for_update () filter (id = 1 )

• Four characteristics of things: atomicity, permanent, isolation, consistency.

  原生SQL中开启事物的两种方式：
  1.start transaction;
  2.beigin;
  提交事物
  commit;
  回滚
  roll_back
  
  orm中开启事物的三种方式
  1.
  DATABASES = {
    'ENGINE':'django.db.backends.mysql',
    'NAME':'day58',
    'HOST':'127.0.0.1',
    'PORT':3306,
    'USER':'root',
    'PASSWORd':'root',
  
    'ATOMIC_REQUESTS':TRUE,  # 全局开启事物，绑定的是http请求响应整个过程
  
  }
  2.
  from django.db import transaction
  
  @transaction.atomic
  def viewfunc(request):
    do_stuff()
  
  取消事物
  @transaction.non_atomic_requests
  def my_view(request):
    do_stuff()
  
  3.上下文
  from django.db import transaction
  
  def viewfunc(request):
    do_stuff()
    with transaction.atomic():
        do_more_stuff()
    do_other_stuff()
  
  

• Ajax (jQuery in): two features

  • Asynchronous request
  • Partial refresh

  $('#button').click(function(){
    $.ajax({
        url:'/login/', # 请求路径
        type:'post',  # 请求方式
      data:{       # 请求携带数据
            uname:$('#username'.val()),
          pwd:$('#password'.val()),
            csrfmiddlewaretoken:$('[name=csrfmiddlewaretoken]')
                #csrfmiddlewaretoken:"{{csrf_token}}"
        },
          success:function(res){
              console.log(res)
          },
          error:function(jqXHR,textStatus,err){
                console.log(arguments) 
          }
    })
  })
  
  爬虫中的请求：
  ret = requests.post('/login/',data={}) print(ret.content)

• Way external js file import to write code, then JS Code Summary Django template syntax can not be used, because the load order of the HTML file: URL- view ---- HTML template rendering --return to the browser - browser rendering - script of SRC- before going to request js file ---- JS file so the code at this time only to load into your HTML inside.