One 、 Conversational Technology

1、 Concept : Share data in one session , stay web Middle finger , A communication between browser and server . Contains multiple requests , And multiple responses .

Data can be shared in multiple requests in a session .

2、 Client session technology :Cookie

Save the data on the client There's not much pressure on the server But the data is not secure ;Cookie By default, it is stored in the browser's memory

// send out cookie:

Cookie c = new Cookie(msg,hehe);

response.addCookie(c);

// Accept cookie:

Cookie[] cs = request.getCookies();

if(cs != null){

for(Cookie c : cs){

String name = c.getName();

if(msg.equals(name)){

String value = c.getValue();

}

}

}

// Set up Cookie Life time of , It can be made persistent

setMaxAge(int second):

Positive numbers : On the hard disk

negative : The default value is -1 In browser memory

0: Delete cookie

// Use cookie Deliver Chinese

Cookie uc = new Cookie(username, URLEncoder.encode(username, utf-8));// code

username = URLDecoder.decode(c.getValue(), utf-8);// decode

3、 Server session technology :Session

Save the data in the server Data security The server is under a lot of pressure ;session Depend on cookie There is

//1. obtain session

HttpSession session = request.getSession();

//2. Store the data

session.setAttribute(msg, hehe);

//3. get data

Object msg = session.getAttribute(msg);

// The destruction session

session.invalidate()

// The destruction session Overtime 30 It's going to be destroyed in a minute

session-config

session-timeout30/session-timeout

/session-config

Two 、jsp —— java servlet page

1、 Concept : It's a way to write HTML Language can also write Java Code page ,JSP The essence of Servlet

grammar :

%! int num=1000; % Generated Java The code is in the member position

% System.out.println(hello); % Generated code in service() In the method

%= hello world % out.print(hello word);

%-- jsp Special notes --% notes

2、 Three major instructions : To configure JSP Page properties or import some extra content

%@ Instruction names Property name = Property value %

1)page Instructions

language:java

import: Import package

pageEncoding:utf-8

autoFlush: Automatically refresh

buffer: Buffer size

errorPage: Specify the error page

isErrorPage: Whether it's an error page You can use built-in objects exception

2)taglib Instructions

Import extra content

%@ taglib uri=http://java.sun.com/jsp/jstl/core prefix=c %

prefix: Specify label prefix , This thing can be named at will

uri: Specify the uri( Unique identification )

3)include Instructions

Static inclusion %@include file= page % After inclusion , There will only be one .class file

3、 Six action tags

1)jsp:useBean id= Object name class= Package name . Class name scope= Scope of action (request/page/application/session)/

jsp:setProperty name=javaBean object property=javaBean Object property name param=username/

jsp:getProperty name=javaBean object property=javaBean Object property name /

2)jsp: include page=included.jsp flush=true / Dynamic inclusion Multiple .class Bytecode file

3) jsp:forward page=/index.jsp

jsp:param name=msg value=hehe/

/jsp:forward

4、 Nine built-in objects

1)out Output object Output data to client , Byte stream . Such as out.print(hello);

2)request Request object Receive client's http request

3)response The response object a:addCookie(Cookie cookie); b:sendRedirect(/wel.jsp)

4)session Conversation object getAttribute(String name)

5)application Application object It is ServletContext Class

6)page Page object representative jsp The entity itself , The current page is valid . amount to java Medium this

7)exception Exceptions Represents an exception at run time

8)pageContext Page context object pageContext Object provides the JSP Access to all objects and namespaces on the page

9)config Configuration object jsp Corresponding servlet Configuration of , You can get web.xml The initialization parameter in

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