Knowledge summary of request

Request：
    1. request Objects and response The principle of objects
        1. request and response Objects are created by the server . Let's use them
        2. request Object to get the request message ,response Object to set the response message
    
    2. request Object inheritance Architecture ：    
        ServletRequest        --     Interface
            |     Inherit
        HttpServletRequest    -- Interface
            |     Realization
        org.apache.catalina.connector.RequestFacade class (tomcat)

    3. request function ：
        1. Get request message data
            1. Get request line data
                * GET /day14/demo1?name=zhangsan HTTP/1.1
                * Method ：
                    1. Get request method ：GET
                        * String getMethod()  
                    2. (*) Get virtual directory ：/day14
                        * String getContextPath()
                    3. obtain Servlet route : /demo1
                        * String getServletPath()
                    4. obtain get Mode request parameters ：name=zhangsan
                        * String getQueryString()
                    5. (*) Get request URI：/day14/demo1
                        * String getRequestURI():        /day14/demo1
                        * StringBuffer getRequestURL()  :http://localhost/day14/demo1

                        * URL: Uniform resource locator ： http://localhost/day14/demo1     The People's Republic of China
                        * URI： Uniform resource identifiers : /day14/demo1                     republic
                    
                    6. Get the protocol and version ：HTTP/1.1
                        * String getProtocol()

                    7. Get the... Of the client IP Address ：
                        * String getRemoteAddr()
                    
            2. Get request header data
                * Method ：
                    * (*)String getHeader(String name): Get the value of the request header by the name of the request header
                    * Enumeration<String> getHeaderNames(): Get all request header names
                
            3. Get request body data :
                * Request body ： Only POST Request mode , There's a requester , Encapsulate... In the request body POST Requested request parameters
                * step ：
                    1. Get stream object
                        *  BufferedReader getReader()： Get character input stream , Only character data can be operated
                        *  ServletInputStream getInputStream()： Get byte input stream , All types of data can be manipulated
                            * Explain after uploading the knowledge points of the file

                    2. Then take the data from the flow object
                
                
        2. Other features ：
            1. Get request parameters in general ： Regardless of get still post The following methods can be used to obtain request parameters in both request methods
                1. String getParameter(String name): Get the parameter value according to the parameter name    username=zs&password=123
                2. String[] getParameterValues(String name): Get the array of parameter values according to the parameter name  hobby=xx&hobby=game
                3. Enumeration<String> getParameterNames(): Get all requested parameter names
                4. Map<String,String[]> getParameterMap(): Get... For all parameters map aggregate

                * Chinese code scrambling ：
                    * get The way ：tomcat 8 Have already put get The problem of disorderly pattern has been solved
                    * post The way ： It's messy
                        * solve ： Before getting the parameters , Set up request The coding request.setCharacterEncoding("utf-8");
                           This request.setCharacterEncoding("utf-8"); that will do
                    
            2. Request forwarding ： A way to jump resources inside the server
                1. step ：
                    1. adopt request Object get request forwarder object ：RequestDispatcher getRequestDispatcher(String path)
                    2. Use RequestDispatcher Object to forward ：forward(ServletRequest request, ServletResponse response) 

                2. characteristic ：
                    1. The browser address bar path does not change
                    2. It can only be forwarded to the internal resources of the current server .
                    3. Forwarding is a request

            3. Shared data ：
                * Domain object ： An object of scope , Data can be shared in scope
                * request Domain ： Represents the scope of a request , It is generally used to share data among multiple resources for request forwarding
                * Method ：
                    1. void setAttribute(String name,Object obj): Store the data
                    2. Object getAttitude(String name): Get value by key
                    3. void remove  (String name): Remove key value pairs by key