Tài liệu Controlling web application behavior

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ĐẠI HỌC QUỐC GIA TPHCM TRƯỜNG ĐẠI HỌC CÔNG NGHỆ THÔNG TIN Gvhd: Th.s Nguyễn Quang Minh    Location and purpose of web.xml Custom URLs Initialization parameters  Servlets  JSP Pages    Preloading pages Welcome pages Error pages • Location   Eclipse: WebContent/WEB INF/web xml Deployed: webAppName/WEB-INF/web.xml install_dir/conf/web.xml is Tomcat-specific! Ignore it! • When processed Only required to be read when server (app) starts Tomcat monitors web.xml and reloads Web app when web.xml changes Eclipse redeploys app when web xml changes. Eclipse redeploys app when web.xml changes. • Basic format Custom URLs (Servlet Mappings) Default servlet URL: http://host/webAppPrefix/servlet/ServletName  Convenient during development, but wrong for deployment  Init parameters, security settings, filters, etc. are  associated only with custom URLs  Default URL is long and cumbersome => How to make that URL shorter ??? • How to make The URL shorter ???  USE WEB.XML  USE @WEBSERVLET(“”)  Using web.xml: Servlet code:  web.xml entry (in ...)  package myPackage;... public class MyServlet extends HttpServet { ... } Give name to servlet MyName myPackage .MyServlet  Give address (URL mapping) to servlet MyName /MyAddress  Result: http://hostname/webappName/MyAddress  USING @WebServlet(“”): Before “public class MyServlet extends HttpServet”, add @WebServlet(“/MyAddress”) Examble:   Note: in both solution, the address must start with “/” You should always use custom URLs on deployed projects  URLs look cleaner and simpler and shorter.  URLs have more meaningful names– URLs have more meaningful names  You don't expose possibly proprietary class file names  You can use web.xml to assign init params laters  Does not work with …/servlet/myPackage.MyServlet  You can apply filters and security settings later (via web xml) in a more predictable and controllable manner Init param Init Param use to define data before the servlet start  =>How to do that ??? 1. Use WEB.XML 2. Use Constuctor  USING Web.xml A abc.A name DuyTai mail DuyTai@gmail.com A /A In Servlet, to get the param, we use: ServletConfig config = getServletConfig(); name = config.getInitParameter(“param_name");   Examble:  Examble:  Result: Init param for JSP page  Web.xml: KhoiTao /first.jsp name DuyTai KhoiTao /first.jsp JSP file:
  • First name: <%= name %>
<%! private String name; public void jspInit() {  } ServletConfig config = getServletConfig(); name = config.getInitParameter("name"); if (name == null) { name = "No first name"; } %>
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