<%@ page language="java" pageEncoding="utf-8" import="com.study.vo.*,java.util.*" %> <html> <head> </head> <body> <h2>使用普通方法获得作用域对象</h2> <b><%=request.getParameter("name")%></b><br/> <b><%=request.getAttribute("str")%></b><br/> <b><%=((User)request.getAttribute("user")).getAddress().getAddr()%></b><br/> <b><%=((ArrayList<User>)request.getAttribute("list")).get(0).getAddress().getAddr() %></b><br/> <b><%=((HashMap<String,User>)request.getAttribute("map")).get("user").getAddress().getAddr()%></b> <hr/> <h2>使用EL表达示获得作用域对象(优点：不用导包，阅读方法，代码更少)</h2> <b>${param.name}</b><br/> <b>${str}</b><br/> <b>${user.address.addr}</b><br/> <b>${list[0].address.addr}</b><br/> <b>${map.user.address.addr}</b><br/> <h2>EL表达式获取对象默认顺序</h2> <% pageContext.setAttribute("hello","pagecontext"); request.setAttribute("hello","request"); session.setAttribute("hello","session"); application.setAttribute("hello","application"); %> <b>pageContext-->request-->session-->application</b><br> <b>${pageScope.hello}</b><br> <b>${requestScope.hello}</b><br> <b>${sessionScope.hello}</b><br> <b>${applicationScope.hello}</b><br> <h2>EL表达式的算术运算</h2> <strong>不支持字符串连接</strong><br/> ${1+2}--${1-2}--${1>2}--${1==2?0:0}--${1+"2"} <h2>判断是否为空</h2> <b>${empty str}</b> <b>${empty test}</b> <h2>获得请求头数据 heard(了解)</h2> <b>${header }</b><br> <b>${header["cookie"] }</b><br> <b>${headerValues["cookie"]}</b> <h2>获得cookie数据</h2> <b>${cookie }</b><br> <b>${cookie.JSESSIONID }</b><br> <b>${cookie.JSESSIONID.name }</b><br> <b>${cookie.JSESSIONID.value }</b><br> </body> </html>
@Override public void service(HttpServletRequest request,HttpServletResponse response) throws IOException, ServletException { request.setCharacterEncoding("utf-8"); response.setContentType("text/html;charset=utf-8"); request.setAttribute("str","javase"); User u=new User(1, "javase", "javaee", "javame", new Address("china")); request.setAttribute("user",u); List<User> list=new ArrayList<User>(); list.add(u); request.setAttribute("list", list); Map<String,User> map=new HashMap<String,User>(); map.put("user",u); request.setAttribute("map",map); request.getRequestDispatcher("/ELStudy.jsp").forward(request, response); }