Severlet learning foundation

<load-on-satrtup>x</load-on-satrtup>  x Small first


Httpservrlet request: The scope of action is only in one request
request.setAttribte(); Given value .


Four ways ：


setAttbute..（）;


HttpSession session :
HttpSession session=request.getSession(); Value .
1, stay respose.getSession , obtain
2, It works when the browser or server is not turned off
3,<session-time></session->
4, perform session.invalidate(); It will clear the data and invalidate
5,<session-config><session-timeout>10</session-timeout></session-config>
Wait for refresh time difference （10 minute ）
6,session.getId(); The server and browser are not paired session Invalid ！ And it doesn't repeat ！








Server browser relationship ！session.getId() ！SessionID()....>


The browser sends a request to the server , The server first judges , Whether the request carries a SessionID value
If this request does not carry one SessionID value , The server knows , This is the first time to access this server
The browser starts a session with the server
The server will respond to the request at the same time , Will produce a SessionID, As the identification of this session
Put this again. SessionID To browser , Browsers have one SessionID 了
When accessing the server again , The browser will carry that SessionID, Sent to the server
The server first determines whether the request carries a SessionID value , Now there is , Represents that this is not a request for a new session
If the time between two browser requests is too long , The waiting time of the server is exceeded , The server will delete this session object
After deleting , Send it to the server again , Because there is no such thing in the server session Object , You can't judge whether the request carries SessionID value
That is to say, I can't judge , Think this is the beginning of a new conversation , There will be another SessionID, As the logo of this new Conference
Put this again SessionID To browser , The browser has a new SessionID 了
At the beginning of the session , The server will automatically allocate a space (session object ),SessionID It's just session In the object






severletConfig 
Interface be-all severlet Can be called ,severletConfig A project is shared

ServletConfig fig=this.getServletConfig();

fig.getInitParameter(String src); Get all the files in the current directory

get ： SeverletConfig fig=this.getSeverletConfig();
Step by step ：     stay web It is defined <init-param><param-name>name</param-name>
                  <param-value>abc</param-value>
            </init-param>
Get value fig.getInitParameterName(); Get all
fig,getSeverLetContext();, To name one

get ：SeverletConfig fig=this.getSeverLetContext();

stay web Debugging code in

<!-- Jump -->
  <servlet>
    <servlet-name>severlet</servlet-name>
    <servlet-class>testSeverlet.severlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>severlet</servlet-name>
    <url-pattern>/severlet</url-pattern>
  </servlet-mapping>
  
  <!-- session test -->
  <servlet>
  <servlet-name>sessionT0</servlet-name>
  <servlet-class>sessionT.sessionT0</servlet-class>
  
  <!-- Set up  severletConfig   -->
      <init-param><param-name>name</param-name>
                  <param-value>abc</param-value>
      </init-param>
      
       <init-param><param-name>jdbc</param-name>
                  <param-value>jdbc://127.0.0.1:8080/std</param-value>
      </init-param>
      
  </servlet>
  <servlet-mapping>
    <servlet-name>sessionT0</servlet-name>
    <url-pattern>/sessionT0</url-pattern>
  </servlet-mapping>
  
  <!-- filter -->
  <filter>
  <filter-name>severletT1</filter-name>
  <filter-class>sessionT.severletT1</filter-class>

  </filter>
  <filter-mapping>
 <filter-name> severletT1</filter-name><!-- route -->
  <url-pattern>/*</url-pattern><!-- Filtered range  -->
  </filter-mapping>
  
stay class File code ：  

first class Debug class ：

public class severletT1 extends HttpServlet  implements Filter{
// @Override

/protected void doGet(HttpServletRequest request, HttpServletResponse response)
// throws ServletException, IOException {
// // TODO Auto-generated method stub
// doPost(request, response);
//}
// @Override
// protected void doPost(HttpServletRequest request, HttpServletResponse response)
// throws ServletException, IOException {
// // TODO Auto-generated method stub
ServletConfig fig2=this.getServletConfig();
    System.out.println(fig2.getInitParameter("name"));
    System.out.println(fig2.getInitParameterNames());
    ServletContext fig=this.getServletContext();
   System.out.println(fig.getAttribute("jdbc"));
//  
// }
// 
@Override
public void destroy() {
// TODO Auto-generated method stub
super.destroy();
}
@Override
public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain arg2) throws IOException, ServletException {
// TODO Auto-generated method stub
System.out.println("aandjkashdgasdgasjhdga");

}
@Override
public void init(FilterConfig arg0) throws ServletException {
// TODO Auto-generated method stub

}

the second class Debug class ：
public class sessionT0 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
         doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
HttpSession session=request.getSession();
request.setAttribute("name","gg");
request.setAttribute("pwd","123456");
session.setAttribute("name1","hh");
session.setAttribute("pwd1", "123hh");
  System.out.println(session.getId());
//session.invalidate(); // invalid
  
  
  
  
    ServletConfig  fig=this.getServletConfig();
    System.out.println(fig.getInitParameter("jdbc"));
    System.out.println(fig.getInitParameterNames());
    ServletContext fig2=this.getServletContext();
         fig2.getAttribute("jdbc");
    
// request.getRequestDispatcher("SE.jsp").forward(request, response);
// return;
}


}