sqrt81xmy/mytomcat

This is the process of the study in the Tomcat

Welcome to the Tomcat1.0:

This is the first time that I write the tomcat by myself

For more details, you can refer to this url: https://www.liaoxuefeng.com/wiki/1545956031987744/1545956151525409

Knowledge:

Section 1:

In this project, I have implemented the filter、connector、servlet、session

• Summarize the connection between these components:

• filter

  filter is used to satisfy some fixed constraints such as "authentication"、"login check"..

  In that case, we use a lot of filters to consist FilterChain, and the way of selecting the filters is to match the RequestUrl and the filter Pattern Url. In order to execute this chain, it uses the recursion called doFilter, each filter on this chain executes the doFilter fuction, and back to the recursion on the chain. For example:

     @Override
      public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse) throws IOException, ServletException {
          int total = filters.size();
          if(cnt<total){
              cnt++;
              this.filters.get(cnt-1).doFilter(servletRequest,servletResponse,this);
          }
      }
  

  After the filters[cnt-1] executes the doFilter fuction, it will call the doFilter fuction of the chain which refers to the this in the last line of the code.

• servlet

  servlet is the container of a webapp, only if your app contains one PatternUrl.

  In servlet, it runs one fuction which maps one PatternUrl. For example, a Pattern is /index(/.*)*, this pattern represents all the url begin with the /index. And if you use the @RequestMapping("/index(/.*)*") on the Index fuction, this Index fuction will run on one servlet. If you have other Url, it will run on the other servlet.

  This is the example:

    public class IndexServlet extends HttpServlet {
      @Override
      protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
          resp.setHeader("Content-Type", "text/html; charset=utf-8");
          PrintWriter writer = resp.getWriter();
          writer.write("<h1> Index</h1> <p> Liang Zhuge </p>");
          writer.close();
      }
    }
  //httpServletMappings.add(new ServletMapping("/index(/.*)*",new IndexServlet()));
  

  Trick: This means that one servlet can maps to multiple urls, but one url only maps to one servlet

• connector

  connector is the somehow gateway of the service, and the starter of the ServletContext. And we should know that http and https will use two different connectors.

  Last but not least, in the connector, we can initialize the filter、servlet

• session

  A session will establish only when a user first get/post to your server.

  When a user first connect to the server, your server should build a session for this user, and return a sessionId which is the only one to this session. And in the next connection, the user can send his/her get/post to the server with this sessionId, and your server will get the session by this id in the SessionManager.

  This sessionId could be cookie、token...