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HttpServletRequest有两个重载的getSession()方法,一个接受一个boolean的类型的值,另一个不带任何参数,getSession()方法和getSession(true)方法功能一样,就是如果对应的客户端已经产生过一个session,那么就会返回这个旧的session,否则,这个方法将会产生一个session ID并且和对应的客户端绑定在一起,而如果getSession(false)表示如果对应的客户端已经有对应的session,那么返回这个旧的session,否则不会产生新的session。可以使用HttpSession对象上的isNow()方法来判定这个session是否为新建的 HttpSession常用方法 public void setAttribute(String name,Object value) 一个保存信息到session的简单例子 sessionlogin.html 复制代码 代码如下: <meta name="keywords" content="keyword1,keyword2,keyword3" /> 复制代码 代码如下: package chap03; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; public class saveinfo extends HttpServlet { /** * Constructor of the object. */ public saveinfo() { super(); } /** * Destruction of the servlet. */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. * * This method is called when a form has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //如果用户输入过了用户名 则将其放在session中 if(request.getParameter("username")!=null); { HttpSession session = request.getSession(); session.setAttribute("username",request.getParameter("username")); } response.setContentType("text/html;charset=GBK"); PrintWriter out = response.getWriter(); out.println("session已经创建"); out.println(" "); out.println("跳转到其他<a>页面</a>"); } /** * The doPost method of the servlet. * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response); } /** * Initialization of the servlet. * * @throws ServletException if an error occurs */ public void init() throws ServletException { // Put your code here } }</pre> </div> <div> 复制代码 代码如下: package chap03; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; public class getsession extends HttpServlet { /** * Constructor of the object. */ public getsession() { super(); } /** * Destruction of the servlet. */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. * * This method is called when a form has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=GBK"); PrintWriter out = response.getWriter(); String username = ""; //此处不是创建session 而是去取已经创建的session HttpSession session = request.getSession(); //如果已经取到,说明已经登录 if(session!=null) { username = (String)session.getAttribute("username"); out.println("获得创建的Session"); out.println(" "); out.println("登录名:"+username); } else { response.sendRedirect("../sessionlogin.html"); } } /** * The doPost method of the servlet. * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response); } /** * Initialization of the servlet. * * @throws ServletException if an error occurs */ public void init() throws ServletException { // Put your code here } }</pre> </div> <div></div> <div> |
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