Basic analysis of Servlet session technology

1. Cookies

1. Set cookies, the content is time

 Cookie cookie = new Cookie("LastAccessTime",System.currentTimeMillis()+"");cookie.setMaxAge(1*30*24*3600);//Set validity period of 1 month cookie.setPath("/Project name");//Cookie is provided when accessing the entire project

2. Obtain cookie information

 Cookie cookies[] = request.getCookies(); for(int i = 0;cookie!=null&&i<cookies.length;i++){ if(cookies[i].getName().equals("LastAccessTime")){ long cookieValues = Long.parseLong(cookies[i].getVlues());//Convert String to a decimal Long Date date = new Date(cookieValues); response.getWrite().print(date); }}

2. session(getSession()->session not used for 30 minutes)

1. Set session

 HttpSession session = request.getSession();session.setAttribute("name","hahahahahaha");

2. Get session

 HttpSession session = request.getSession();//HttpSession session = request.getSession(false);//Only get without creating String str = (String)session.getAttribute("name");

3. Session configuration, configuration time

 <seeion-config> <session-timeout>20</session-timeout> </session-config>

4. Session destroy

 HttpSession session = request.getSession();session.invalidate();//session.removeAttribute("XXX");//removeAttribute("XXX");//remove a session

5. Use address rewriting to get session, which will only be rewritten if cookie is disabled.

 request.getSession();String url1 = response.encodingURL("Address 1 that needs to be rewrite");String url2 = response.encodingURL("Address 2 that needs to be rewrite");PrintWriter out = response.getWriter;out.print("<a href = '"+url1+"'>XXXX</a>");out.print("<a href = '"+url2+"'>YYYY</a>");

3. Client form submission issues

1. Prevent submission of empty passwords

 <form action="/project/xxx" method ="post" onsubmit="return dosubmit(this)"> Username:<input type="text" name="username"><br/> Password:<input type="password" name = "password"><br/> <input type="submit" value="submit"></form><script> function dosubmit(obj){ if(obj.category.value==''){ alter("Please enter"); return false; } }</script>

2. Prevent repeated submissions

 <form action="/project/xxx" method ="post" onsubmit="return dosubmit()"> Username:<input type="text" name="username"><br/> Password:<input type="password" name = "password"><br/> <input type="submit" value="submit"></form><script> function dosubmit(){ var iscommitted = false; if(!iscommitted){ iscommitted = true; return true; }else{ return false; } }</script>

Summarize

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