Basic concepts of Web
Static web
The data provided by html and css to everyone will never change
Dynamic web
The information provided to everyone will change. Everyone will see different information at different times and places; For example, Taobao; The technology stack includes servlet, jsp, asp and php
advantage:
web pages can be updated dynamically, and all users don't see the same page
Can interact with database (data persistence)
web server explanation
php
php development is fast, powerful, cross platform and simple code
Unable to carry large traffic (limitations)
JSP,Servlet
The BS architecture mainly promoted by sun company is developed based on java language and can bear the impact of the three high problems
BS architecture
Browser and server
CS architecture
Client and server
web server
Server is a passive operation, which is used to process some user requests and give users some response information
Tomcat
A free and open source lightweight application server is highly used in small systems and few concurrent users. It can run JSP pages and servlets
Http details
HTTP (Hypertext Transfer Protocol) is a simple request response protocol, which usually runs on top of TCP
Text: html, string...
Hypertext: picture, music, location, video, map...
Http request
Client - Request - server
Request URL:https://www.baidu.com/ request address Request Method:GET get Methods post method Status Code:200 OK Status code 200 Remote Address:14.215.177.39:443 Remote address
Request line
Request method in request line: GET
Request method: Get, Post...
get request
The request can carry fewer parameters and is limited in size. The data content will be displayed in the URL address bar of the browser, which is unsafe but efficient
post request
The parameters that can be carried by the request are not limited, the size is not limited, and the data content will not be displayed in the URL address bar of the browser. It is safe, but not efficient
Message header
Accept: Tell the browser what data types it supports Accept-Encoding: Which encoding format is supported GBK UTF-8 GB2312 Accept-Language: Tell the browser, locale Cache-Control: Cache control Connection: Tell the browser whether to disconnect or remain connected when the request is completed
Http response
Server response client
Cache-Control:private Cache control Connection:keep-alive connect Content-Encoding:gzip code Content-Type:text/html;charset=utf-8 type
Responder
Accept: Tell the browser what data types it supports Accept-Encoding: Which encoding format is supported GBK UTF-8 GB2312 Accept-Language: Tell the browser, locale Cache-Control: Cache control Connection: Tell the browser whether to disconnect or remain connected when the request is completed Host: host refrush: Tell the client how often to refresh Location: Repositioning web pages
Response status code
200: request response succeeded
3 * *: request redirection to another specified path
4 * *: resource not found
5 * *: server code error
HelloWorld
pom dependency
<dependency> <groupId>javax.servlet</groupId> <artifactId>javax.servlet-api</artfactId> <version>4.0.1</version> </dependency> <dependency> <groupId>javax.servlet.jsp</groupId> <artifactId>javax.servlet.jsp-api</artfactId> <version>2.3.3</version> </dependency>
public class HelloServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// Type of response: html
resp.setContentType("text/html");
// Gets the output stream of the response
PrintWriter writer = resp.getWriter();
writer.println("<html>");
writer.println("<head>");
writer.println("<title>hello hupf</title>");
writer.println("</head>");
writer.println("<body>");
writer.println("<h1>hello hupf</h1>");
writer.println("</body>");
writer.println("</html>");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
super.doPost(req, resp);
}
}
web.xml
<!DOCTYPE web-app PUBLIC
"-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd" >
<web-app>
<display-name>Archetype Created Web Application</display-name>
<!--web.xml Is to configure us web Core application of-->
<!--register Servlet-->
<servlet>
<servlet-name>helloServlet</servlet-name>
<servlet-class>com.hupf.servlet.HelloServlet</servlet-class>
</servlet>
<!--One servlet Corresponding to one mapping: mapping-->
<servlet-mapping>
<servlet-name>helloServlet</servlet-name>
<!--Request path-->
<url-pattern>/hello</url-pattern>
</servlet-mapping>
</web-app>
servlet interface sun company has two default implementation classes: HttpServlet and GenericServlet
Why mapping is needed: we write a JAVA program, but we need to access it through the browser, and the browser needs to connect to the web server, so we need to register the Servlet we write in the web server and give it a path that the browser can access
Servlet principle
The servlet is called by the web server. After receiving the browser request, the web server will call the servlet and call the service method to return the response to the servlet and the client
Mapping
- A servlet can specify a mapping path
<servlet>
<servlet-name>helloServlet</servlet-name>
<servlet-class>com.hupf.servlet.HelloServlet</servlet-class>
</servlet>
<!--One servlet Corresponding to one mapping: mapping-->
<servlet-mapping>
<servlet-name>helloServlet</servlet-name>
<url-pattern>/hello</url-pattern>
</servlet-mapping>
- A servlet can specify multiple mapping paths
<servlet>
<servlet-name>helloServlet</servlet-name>
<servlet-class>com.hupf.servlet.HelloServlet</servlet-class>
</servlet>
<!--One servlet Corresponding to one mapping: mapping-->
<servlet-mapping>
<servlet-name>helloServlet</servlet-name>
<url-pattern>/hello1</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>helloServlet</servlet-name>
<url-pattern>/hello2</url-pattern>
</servlet-mapping>
- A servlet can specify a generic mapping path
<servlet-mapping>
<servlet-name>helloServlet</servlet-name>
<url-pattern>/hello/*</url-pattern>
</servlet-mapping>
- Default request path
<servlet-mapping>
<servlet-name>helloServlet</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
- Specify some suffixes or prefixes, etc
<!--*The path of the project mapping cannot be added before the number-->
<servlet-mapping>
<servlet-name>helloServlet</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>