01_8_session
01_8_session
1. session总结
1.1服务器的一块内存(存key-value)
1.2和客户端窗口对应(子窗口)(独一无二)
1.3客户端和服务器有对应的SessionID
1.4客户端服务器端发送SessionID的时候两种方式
- cookie(内存cookie)
- rewrite URL
1.5浏览器禁掉cookie，就不能使用session（使用cookie实现session）
1.6如果想安全的使用session(不论客户端是否禁止cookie)，只能使用URL重写(大大增加编程负担)，很多网站要求客户端打开cookie
2.例子
2.1ShowSession.java
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html; charset=utf-8");
PrintWriter out = response.getWriter();
String title = "Session Tracking Example";
HttpSession session = request.getSession(true);
String heading;
Integer accessCount = (Integer) session.getAttribute("accessCount");
System.out.println(accessCount);
if (accessCount == null) {
accessCount = new Integer(0);
heading = "Welcom, Newcomer";
System.out.println(accessCount);
} else {
heading = "Welcome Back";
accessCount = new Integer(accessCount.intValue() + 1);
}
session.setAttribute("accessCount", accessCount);
/*Integer access = (Integer) session.getAttribute("accessCount");
System.out.println(access);*/
out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
out.println("<HTML>");
out.println(" <HEAD><TITLE>Session追踪</TITLE></HEAD>");
out.println(" <BODY>");
out.print("<H1 ALIGN=\"CENTER\">" + heading + "</H1>");
out.print("<H2 ALIGN=\"CENTER\">Information on Your Session:</H2>");
out.println("<TABLE BORDER=\"1\" ALIGN=\"CENTER\"><TR><TH>Info Type</TH><TH>Value</TH></TR><TR><TD>Creation Time</TD><TD>" + new Date(session.getCreationTime())+ "</TD></TR><TR><TD>Time of Last Access</TD><TD>" + new Date(session.getLastAccessedTime()) + "</TD></TR><TR><TD>Number of Previous Accesses</TD><TD>" + accessCount+ "</TD></TR></TABLE>");
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
2.2SessionInfoServlet.java
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html; charset=utf-8");
PrintWriter out = response.getWriter();
HttpSession session = request.getSession(true);
out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
out.println("<HTML>");
out.println(" <HEAD><TITLE>Session Info Servlet</TITLE></HEAD>");
out.println(" <BODY>");
out.print("<H3>Session Information</H3>");
out.print("New Session:" + session.isNew());
out.println("<BR/>Session ID:" + session.getId());
out.println("<BR/>Session Creation Time:" + new Date(session.getCreationTime()));
out.println("<BR/>Session Last Accessed Time:" + new Date(session.getLastAccessedTime()));
out.println("<H3>Request Information</H3>");
out.println("Session ID from Request:" + request.getRequestedSessionId());
out.println("<BR/>Session ID Via Cookie:" + request.isRequestedSessionIdFromCookie());
out.println("<BR/>Session ID Via rewritten URL:" + request.isRequestedSessionIdFromURL());
out.println("<BR/>Valid Sesion ID:" + request.isRequestedSessionIdValid());
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
2.3URLSession.java
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html; charset=utf-8");
PrintWriter out = response.getWriter();
HttpSession session = request.getSession(true);
out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
out.println("<HTML>");
out.println(" <HEAD><TITLE>Session 追踪</TITLE></HEAD>");
out.println(" <BODY>");
out.print("session id:" + session.getId() + "<br/>");
out.print("from url:" + request.isRequestedSessionIdFromUrl() + "<br/>");
out.print("from cookie:" + request.isRequestedSessionIdFromCookie() + "<br/>");
out.println("<a href=" + response.encodeURL(request.getRequestURL().toString()) + "> test </a><br/>");
out.println("<a href=" + request.getRequestURL().toString() + "> test </a><br/>");
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
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