Request object, response object, session object

Hello everyone , I meet you again , I'm your friend, Quan Jun .

Just a list of some simple knowledge points , As notes , If you want to study specifically , I still need to look for professional books

request object 
 effect ： Get the information provided by the user 
 grammar ： Is to implement the ServletRequest An instance of the interface class 
   Use a table to check one of the servers JSP Page submission information 
 Common methods ：
 Set the encoding mode ： for example （ To prevent Chinese characters from being garbled ）
request.setCharacterEncoding(“gb2312”);
 Same effect ：String str = request.getParameter(“message”);
byte[] b = str.getBytes(“ISO-8859-1”);
Str = new String(b);
getProtocol()  Get the protocol used to submit information  getServletPath()  Obtain requested JSP Directory of page files  getContextPath()  Get the current of the request web Service catalog  getContentLength()  Get the length of the submitted information  getMethod()  How to get the submitted information , for example ：post、get getHeader(s : String)  obtain http The header file consists of parameters s The value of the specified header name .s It can be for ：accept,accept-language,content-type, accept-encoding,user-agent,host,content-length,connection,cookie getHeaderNames()  Get the enumeration type of the header name  getHeaders(s : String)  An enumeration that gets all the values of the specified header name in the header file  getRemoteAdr()  Get the user's IP Address  getRemoteHost()  Get the user machine name of the user  getServletPort()  Get server pin  GetParameterNames()  Get submitted information name An enumeration of parameter values  

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response object 
 effect ： Respond dynamically to user requests , Send data to the client 
 for example  ：page Instructions for contentType Specify a value to determine the response MIME type . If you want to change this value dynamically, you can use ：
response.setContentType(s : String);   s The value of can be ：text/jtml; text/plain; image/gif; image/x-xbitmap; image/jpeg; image/pjpeg; application/x-shockwave-flash;application/vnd.ms-powerpoint; application/vnd-ms-execel; application/msword etc. 
 Both the request and the response contain some method headers 
 Use ：response.addHeader(head : String, value : String);
 or response.setHeader(head : String, value : String);
 Dynamically add new response and header values 
 for example ：response.setHeader(“Reflesh”, “5”); each 5 Seconds to refresh the page 
response Redirect 
 grammar ：response.setRedirect(url : URL);
response Status line 
 grammar ：response.setStatus(n : int);

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session object 
 explain ： from Tomcat Responsible for creating objects , It is used to store various information submitted by users during accessing the server page . Each object is assigned a String Type of ID Number （ have access to session.getId(); obtain ）, Store in Cookie in , The same user is in different text service directories session Different from each other .
 Realization session The uniqueness of the object ： The general client supports Cookie, The uniqueness of the object has been realized .
 If there is no support , Then you can rewrite URL To achieve session The uniqueness of the object . call encodeURL(id : String) or encodeRedirectURL(id : String) Method , To the new URL Add parameters in , take session Object's id Pass on the past .
setAttribute(key : String, obj : Object) : void   Store the object , Add index 
getAttribute(key : String) : Object   Use index , Get objects 
getAttributeNmaes() : Enumeration  Generate an enumeration object , have access to nextElems()  Traverse session  Keywords corresponding to each object in 
removeAttribute(key : String) : void   Remove the object corresponding to the keyword 
getCreationTime() : long   obtain session When it was created ( millisecond )
getLastAccessedTime() : long   session The last time it was operated ( millisecond )
getMaxInactiveInterval() : int    Get the longest daze time ( second )
setMaxInactiveInterval(interval : int)   Set the longest daze time ( second )
isNew() : boolean   Judge session Whether it is newly created 
invalidate() : void    send session Invalid 

session Life cycle of ：
1. call invalidate() Method , send session Invalid 
2. The set maximum daze time is reached 
3. Shut down the server 

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