第1章--Web应用开发概述

Web应用开发概述

浏览器-服务器架构（BS-architecture）

browser/ App    ---- request ---->    server (database)

<- response/data --

protocol: HTTP（Hyper-Text Transfer Protocol)

have a try:

cmd: sudo nc -l 80  -- listen at the port of 80（port 80 is used by HTTP）

browser: type "localhost" in the address bar

these are the info that sent to the server(localhost)

meanwhile, the browser is waiting for the request (from the server)

try to type "hello" and ctrl+c

"hello" will be displayed in the browser

If we enter the address of a website, such as "http://study.163.com"

it is called URL (uniform resource locator) （统一资源定位）

In this case: "http://study.163.com/smartSpec/intro.html?name=163"

http: protocol, such as ftp, mailto

smartSpec/intro.html: request sent to the server

?name=163: data that sent to the server via GET method

Let's see what info can be sent via GET method

[html] view plain copy

    1. <html> <body>
    2. <form action="http://localhost/form_action.html" method="get">
    3. <p>First Name: <input type="text" name="fname" /></p>
    4. <p>Last Name: <input type="text" name="lname" /></p>
    5. <input type="submit" value="Submit" />
    6. </form> </body> </html>

1. open .html in the browser

2. type sudo nc -l 80 in terminal

3. submit the info

4. result

GET /form_action.html?fname=Lin&lname=Matt

What if we use POST as the method?

same steps as GET

but different result：

POST /form_action.html (no extra data shown explicitly after "/form_action.html")

but "fname=Lin&lname=Matt" will be displayed at the end.

furthermore, new property "content-length" added, which means the number of characters (data) sent to the server, which is fname=Lin&lname=Matt in this case)

After those info/data/request(shown above) has been sent to the server,

the server needs to give the feedback(response) back to the client/ browser.

feedback:

1. 静态页面（such as .html file, .img file)

2. 动态数据  (data retrieved by programs running on the server side based on the input (like first name/ last name in the previous example))

HTTP protocol: connectionless 无连接的

After a series of actions has done (request --> response)，the connection gets broken.

Advantages --> disconnect with those users who are not currently communicating with the server at that time, in other words, accessible to as many users as possible at the same time

Disadvantages: the server does not know who u r after one connection.

for example, after we log in, we expect that we do not need to log in again if we try to visit other relevant webpages.

--> solution: cookie

after the first-time connection, the client got a "number" from the server which identifies the client/ browser itself.

then the browser will store that number, and every time the client connects to the server, it will bring that number with it, and the server will know the client by checking that id number

that number in this example is called cookie.

Also, the cookie got its own expiry date, which is set by the server.

HTTP会话 (session) ：connection, request, response, close.

HTTP protocol: how to deal with the data in the database

background: when the client sends a request to the server, the program in the server always try to retrieve the relevant data from its database system, and then the program is going to generate an HTML file (or other file that can be understood by the browser), and sends back to the client as a response.

problem 1: the limitation of the number of connections between the database and the web server is much smaller than that between the client and the web server.

in other words, minimising the number of the connections btw database and the web server is required.

--> solution1: connection pool

creates a connection pool between the web server and the database which has limited connections.

each time the web server requires a connection to the database, it will ask the connection pool for the access of connection

--> solution2: cache

different clients might search for the same data during a short period of time

there is no need to run the program to retrieve the same data from the database repeatedly.

-- lower the workload of the database and speed up the reaction from the server

Java开发工程师(Web方向) - 01.Java Web开发入门 - 第1章.Web应用开发概述的更多相关文章

  1. Java开发工程师(Web方向) - 01.Java Web开发入门 - 第3章.Tomcat

    第3章--Tomcat Tomcat安装与运行 Tomcat:目前最常用的基于java的web应用服务器 本课程中所有的Java代码最终都需要部署到Tomcat中运行 Tomcat的配置文件是XML的 ...

  2. Java开发工程师(Web方向) - 01.Java Web开发入门 - 第6章.蜂巢

    第6章--蜂巢 蜂巢简介 网站开发完,就需要测试.部署.在服务器上运行. 网易蜂巢: 采用Docker容器化技术的云计算平台 https://c.163.com 容器管理:容器可被视作为云主机的服务器 ...

  3. Java开发工程师(Web方向) - 01.Java Web开发入门 - 第4章.Maven

    第4章--Maven Maven实战 Java Web应用的部署: 手动式: 编译:javac -cp $CATALINA_HOME/lib/servlet-api.jar web-inf/class ...

  4. Java开发工程师(Web方向) - 01.Java Web开发入门 - 第5章.Git

    第5章--Git 版本控制简介 VCS (version control system) 版本控制系统:记录若干文件的修订记录的系统,帮助查阅/回到某个历史版本 LVCS本地 CVCS集中式(Cent ...

  5. Java开发工程师(Web方向) - 01.Java Web开发入门 - 第2章.HTTP协议简介

    第2章--HTTP协议简介 HTTP协议简介 Abstract: HTTP协议的特性,HTTP请求/响应的过程,HTTP请求/响应的报文格式等知识,最后会演示如何通过Chrome提供的开发者工具,去跟 ...

  6. Java软件工程师面试题：Java运行时异常与一般异常有什么不一样？

    异常表示程序运行过程中可能出现的非正常状态,运行时异常表示虚拟机的通常操作中可能遇到的异常,是一种常见运行错误.java编译器要求方法必须声明抛出可能发生的非运行时异常,但是并不要求必须声明抛出未被捕 ...

  7. Android开发工程师面试题之handler详解。android程序员，android开发面试资料，详解

    Message:消息:其中包含了消息ID,消息对象以及处理的数据等,由MessageQueue统一列队,终由Handler处理 Handler:处理者:负责Message发送消息及处理.Handler ...

  8. 前端开发工程师 - 05.产品前端架构 - 协作流程 & 接口设计 & 版本管理 & 技术选型 &开发实践

    05.产品前端架构 第1章--协作流程 WEB系统 角色定义 协作流程 职责说明 第2章--接口设计 概述 接口规范 规范应用 本地开发 第3章--版本管理 见 Java开发工程师(Web方向) - ...

  9. Java后端开发工程师是否该转大数据开发？

    撰写我对java后端开发工程师选择方向的想法,写给在java后端选择转方向的人 背景 看到一些java开发工程师,对java后端薪酬太悲观了.认为换去大数据领域就会高工资.觉得java后端没有前途.我 ...

随机推荐

  1. Linux环境进程间通信: 共享内存

    Linux环境进程间通信: 共享内存 第一部分 共享内存可以说是最有用的进程间通信方式,也是最快的IPC形式.两个不同进程A.B共享内存的意思是,同一块物理内存被映射到进程A.B各自的进程地址空间.进 ...

  2. The Linux Kernel

  3. H5基本标签

  4. Oracle中转义下划线

    原意是查询出所有的月粒度模型,但是在oracle中,下划线也代表匹配单一任何字符,导致15分钟粒度的模型也被查询出来,在此,需要对下划线做转义,使其只表示下划线的含义,可以使用ESCAPE()函数. ...

  5. java基础知识（初学）

    (小记) 文本文档方式可以下载notepad 在设置-新建-修改默认语言为java 编码为ANSI! java关键字特点:1.完全小写字母.如:public. java标识符:方法的名称,类的名称,变 ...

  6. Excel2013打开提示 文件格式和扩展名不匹配。文件可能已损坏或不安全。除非您信任其来源，否则请勿打开。是否仍要打开它?

    有的时候打开xls文档时,会提示“文件格式和扩展名不匹配.文件可能已损坏或不安全.除非您信任其来源,否则请勿打开.是否仍要打开它?” 遇到这种情况,我们需要 1.win键+R键,打开“运行“,输入re ...

  7. python 基于Anaconda import numpy 报错 Importing the multiarray numpy extension module failed.

    在windows中安装了 Anaconda 运行时报错 原因是系统环境变量起初并没有引入 E:\Tools\Anaconda\Library\bin 解决办法: 在系统环境变量中加入    E:\To ...

  8. hive 学习系列六 hive 去重办法的思考

    方法1,建立临时表,利用hive的collect_set 进行去重. create table if not exists tubutest ( name1 string, name2 string ...

  9. 【Hive五】Hive函数UDF

    Hive函数 系统自带的函数 查看系统自带的函数 查看系统自带的函数 show functions; 显示自带的函数的用法 desc function upper; 详细显示自带的函数的用法 desc ...

  10. Python学习 ：集合

    集合 Set 集合的创建 集合的创建只有一种方式 集合中的元素必须是不可变的数据类型 集合是无序的,可以通过 for 循环来遍历或者迭代器进行筛选 s=set('xiaoming') s1=['ale ...