JSP

Using Session in Servlet/JSP

Categories: Java; Tagged with: Java • JSP • Servlet • Session; @ July 3rd, 2012 0:03

Using session in Servlet:

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.getWriter().write("Servlet HelloWorld!");
		
		HttpSession session = request.getSession(false);
		if(session == null) {
			response.sendRedirect("ServletLogin");
			return;
		}else {
			System.out.println(session.getId());
			Integer totalAccess = (Integer) session.getAttribute("totalAccess"); // Get session attribute;
			if(totalAccess == null) {
				totalAccess = 0;
			}
			
			totalAccess += 1;
			session.setAttribute("totalAccess", totalAccess); // set attribute
			
			response.getWriter().write("TotalAccess: " + session.getAttribute("totalAccess"));
		}

Using session in JSP:

Jsp page directive:

<%@ page
          [ language=”java” ]
          [ extends=”package.class” ]
          [ import=”{package.class | package.*}, …” ]
          [ session=”true | false” ]
          [ buffer=”none | 8kb | sizekb” ]
          [ autoFlush=”true | false” ]
          [ isThreadSafe=”true | false” ]
          [ info=”text” ]
          [ errorPage=”relativeURL” ]
          [ contentType=”mimeType [ ;charset=characterSet ]”   |   “text/html ; charset=ISO-8859-1” ]
          [ isErrorPage=”true | false” ]
%>

“session = true” by default. when access “session”, if session is not existing, will create one by default.
we can set:

<%-- Prevent the creation of a session –%><%@ page session="false">

to prevent the Creation of a Session in a JSP Page.

We didn’t mention about the thread safe of session, here is a post from IBM DW:
http://www.ibm.com/developerworks/library/j-jtp09238/index.html

JSP include 乱码解决方案

Categories: Java; Tagged with: Java • JSP; @ March 25th, 2011 23:25

JSP在include时如果不在被Include文件中声明编码, 在外部文件中将出现乱码. 解决方案就是:

在被Include jsp文件中声明:

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>

此时如果外部jsp编码为 utf-8 — 即: 两者utf-8大小写不同, 将会出现如下错误:

Page directive: illegal to have multiple occurrences of contentType with different values (old: text/html; charset=utf-8, new: text/html; charset=UTF-8)]

可通过配置Eclipse/MyEclipse jsp文件默认编码来避免不必要的操作: http://liguoliang.com/2011/set-eclipse-jsp-files-encoding-utf-8/

Eclipse/Myeclipse 设置JSP创建默认编码为UTF-8

Categories: Java; Tagged with: Eclipse • JSP; @ March 25th, 2011 23:00

Eclipse新建JSP默认编码为ISO8859-1, 不支持中文; 调整方法:

Window/Preferences/JSP Files, Encoding设置为: ISO 10646/Unicode(UTF-8)

Myeclipse设置基本同上, 可参考: http://tmsoft.lsxy.com/index.php?load=read&id=922