1. Request message format
The request message that the client sends an HTTP request to the server includes the following format:
It consists of four parts: request line, request header, blank line and request data. The following figure shows the general format of the request message.
GET request:
POST request:
Data format description:
1. Request line
// request method request url request protocol/version
// example: GET /login.html HTTP/1.1
Request method:
There are 7 request methods in the HTTP protocol, and 2 are commonly used
* GET：
1. The request parameters are in the request line, after the url.
2. The requested url length is limited
3. Less secure
* POST：
1. The request parameters are in the request body
2. There is no limit to the length of the requested url
3. Relatively safe
2. Request header: The client browser tells the server some information
Request header name: Request header value
Common request headers:
1. User-Agent: The browser tells the server that I visit the browser version information you use
The header information can be obtained on the server side to solve browser compatibility issues
2. Referer: http://localhost/login.html
Tell the server, where did I (the current request) come from?
effect:
1. Anti-leech
2. Statistical work
3. Request a blank line
Empty lines are used to separate the request header and request body of the POST request.
4. Request body (text):
Encapsulates the request parameters of the POST request message
1. The method of obtaining the request line data
GET /day14/demo1?name=zhangsan HTTP/1.1
method:
-
Get request method: GET
* String getMethod()
2. Get the virtual directory: /day14
* String getContextPath()
3. Obtain the Servlet path: /demo1
* String getServletPath()
4. Obtain the get method request parameter: name=zhangsan
* String getQueryString()
5. Get the request URI: /day14/demo1
* String getRequestURI(): /day14/demo1
* StringBuffer getRequestURL() :http://localhost/day14/demo1
* URL: Uniform Resource Locator: http://localhost/day14/demo1 People's Republic of China
* URI: Uniform Resource Identifier: /day14/demo1 Republic
6. Obtain protocol and version: HTTP/1.1
* String getProtocol()
7. Obtain the IP address of the client:
* String getRemoteAddr()
2. Get request header data
* method:
* String getHeader(String name): Get the value of the request header through the name of the request header
* Enumeration<String> getHeaderNames(): Get all request header names
3. Get the request body data:
* Request body: Only the POST request method has a request body, and the request parameters of the POST request are encapsulated in the request body
* Steps:
1. Get the stream object
* BufferedReader getReader(): Get character input stream, only character data can be manipulated
* ServletInputStream getInputStream(): Get byte input stream, which can operate all types of data
* Explained after file upload knowledge points
2. Then get the data from the stream object
4. Other common methods
1. General way to obtain request parameters: Regardless of get or post request methods, the following methods can be used to obtain request parameters
1. String getParameter(String name): Obtain the parameter value according to the parameter name username=zs&password=123
2. String[] getParameterValues(String name): Obtain the array of parameter values according to the parameter name hobby=xx&hobby=game
3. Enumeration<String> getParameterNames(): Get the parameter names of all requests
4. Map<String,String[]> getParameterMap(): Get the map collection of all parameters
* Chinese garbled problem:
* Get method: tomcat 8 has solved the problem of garbled characters in the get method
* post method: garbled characters
* Solution: Before getting the parameters, set the encoding of the request request.setCharacterEncoding("utf-8");
2. Request forwarding: a resource jump method inside the server
1. Steps:
1. Obtain the request forwarder object through the request object: RequestDispatcher getRequestDispatcher(String path)
2. Use the RequestDispatcher object to forward: forward(ServletRequest request, ServletResponse response)
2. Features:
1. The path in the browser address bar does not change
2. It can only be forwarded to the internal resources of the current server.
3. Forwarding is a request
3. Sharing data:
* Domain object: a scoped object that can share data within the scope
* request field: represents the scope of a request, generally used to share data among multiple resources for request forwarding
* method:
1. void setAttribute(String name,Object obj): store data
2. Object getAttitude(String name): get value by key
3. void removeAttribute(String name): remove the key-value pair by key
4. Get the ServletContext:
-
ServletContext getServletContext()
