一個(gè)java類，運(yùn)行在服務(wù)器端的，處理web請(qǐng)求
//客戶端跳轉(zhuǎn)
response.sendRedirect()
//服務(wù)器端跳轉(zhuǎn)
RequsetDispatcher dispatcher=request.getRequestDispatcher("/...");
dispatcher.forward(request,response);
dispatcher.include()
1 out
struts中用PrintWriter out=request.getWriter()得到
2 request
(1)String getParameter(String name)         根據(jù)頁(yè)面表單組件名稱獲取頁(yè)面提交數(shù)據(jù)
(2)String[] getParameterValues(String name) 獲取一個(gè)頁(yè)面表單組件對(duì)應(yīng)多個(gè)值時(shí)的用戶的請(qǐng)求數(shù)據(jù)
(3)void setCharacterEncoding(String name)   指定每個(gè)請(qǐng)求的編碼，在調(diào)用request.getParameter()方法之前進(jìn)行設(shè)置，可以用于解決中文亂碼
(4)request.getRequestDispatcher(String path)返回一個(gè)javax.servlet.RequestDispatcher對(duì)象，該對(duì)象的forward方法用于轉(zhuǎn)發(fā)請(qǐng)求
   javax.servlet.RequestDispatcher dispatcher=request.getRequestDispatcher("/a.jsp(目標(biāo)頁(yè)面)");
   dispatcher.forward(request,response);
3 response
response.sendRedirect(String location)重定向一個(gè)URL

4 session
(1)void setAttribute(String key,Object value)
(2)Object getAttribute(String key)
(3)HttpSession request.getSession()
(4)HttpSession request.getSession(boolean true)
(5)void session.setMaxInactiveInterval(2)//設(shè)置會(huì)話過期時(shí)間
(6)void invalidate()//銷毀session,刪除HttpSession對(duì)象及數(shù)據(jù)
(7)void remove(String key)
(8)boolean isNew()//是否是最新會(huì)話
在web.xml中配置session默認(rèn)過期時(shí)間
 <session-config>
  <session-timeout>5</session-timeout>//單位為分鐘
 </session-config>
5 applicate->servletContext
(1)void setAttribute(String key,Object value)
(2)Object getAttribute(String key)
6 pageContext
6 service方法