结论：两种方式
a.如果没有进行action转发，在页面中el需要${sessionScope['org.springframework.web.servlet.support.SessionFlashMapManager.FLASH_MAPS'][0]['userId']}
b.如果进行了action转发则el直接${userId}
背景：框架中，两个web工程a,b,我的b工程开发了一个对外action接口，a来连，要实现的功能是，a的页面发起一个action请求，到达b的springmvc,通过验证后，打开一个b工程新的tab的新窗口，前端发请求可参考我的另一文章springMVC接受json并打开新页面
1.不进行action转发
controller代码：
@Controller @RequestMapping("/page/login") public class LoginController { @RequestMapping(value = "/redirect.do") public String doRedirect(RedirectAttributes redirectAttributes) { redirectAttributes.addFlashAttribute("userId", "ID001"); redirectAttributes.addFlashAttribute("userName", "mike");
redirectAttributes.addAttribute("flag", "opening"); return "redirect:../public/indexTest.jsp"; } }
jsp
<body> here is indexTest.jsp <br> userId is ${sessionScope['org.springframework.web.servlet.support.SessionFlashMapManager.FLASH_MAPS'][0]['userId']}<br>
userName is ${userName}<br> flag is ${flag}
param_flag is ${param.flag} </body>
这样可以正常输出 url:http://lolcalhost:8080/project/page/public/indexTest.jsp?flag=opening
here is indexTest.jsp
userId is ID001
userName is
flag is
param_flag is opening
在jsp中打印session和request
<%
System.out.println("page session parameter:"); //final HttpSession session = request.getSession(); final Enumeration se = session.getAttributeNames(); while (se.hasMoreElements()) { final String key = (String) se.nextElement(); System.out.println(key + "==" + session.getAttribute(key)); } System.out.println("print redirectpage page request parameter:"); final Enumeration reqEnum = request.getParameterNames(); while (reqEnum.hasMoreElements()) { final String s = (String) reqEnum.nextElement(); System.out.println(s + "==" + request.getParameter(s)); } System.out.println("print redirectpage page request attribute:"); final Enumeration reqEnum2 = request.getAttributeNames(); while (reqEnum2.hasMoreElements()) { final String s = (String) reqEnum2.nextElement(); System.out.println(s + "==" + request.getAttribute(s)); }
%>
console输出
page session parameter: org.springframework.web.servlet.support.SessionFlashMapManager.FLASH_MAPS==[FlashMap [attributes={userId=ID001, userName=mike} , targetRequestPath=/project/page/public/indexTest.jsp, targetRequestParams={flag=[opening]}]] print redirectpage page request parameter: flag==opening print redirectpage page request attribute:
说明：addFlashAttribute方法将参数放入了session中的flashmap中保存起来了，并且隐藏起来，不在浏览器中显示参数，同时传大对象也不受浏览器限制。而redirectAttributes.addAttribute方法则是将参数放到request域中。而且session.getAttribute("org.springframework.web.servlet.support.SessionFlashMapManager.FLASH_MAPS")出来的值不是标准的数组，用JSON.parse(str)运行时会报错，只能用el取。
不足：取值过于复杂
2.通过action二次转发
controller
@Controller @RequestMapping("/page/login") public class LoginController { @RequestMapping(value = "/redirect.do") public String doRedirect(RedirectAttributes redirectAttributes) { redirectAttributes.addFlashAttribute("userId", "ID001"); redirectAttributes.addFlashAttribute("userName", "mike"); redirectAttributes.addAttribute("flag", "opening"); return "redirect:../public/winOpenSucc.do"; }
@RequestMapping(value = "/winOpenSucc.do") public String redirectPage() { return "../public/indexTest.jsp" } }
jsp页面代码不变
输出 url:http://lolcalhost:8080/project/page/public/winOpenSucc.do?flag=opening
here is indexTest.jsp
userId is
userName is mike
flag is
param_flag is opening
jsp中session,request打印结果
page session parameter: print redirectpage page request parameter: flag==opening print redirectpage page request attribute: javax.servlet.forward.request_uri==/project/page/login/winOpenSucc.do javax.servlet.forward.context_path==/project javax.servlet.forward.servlet_path==/page/login/winOpenSucc.do javax.servlet.forward.query_string==flag=opening org.springframework.web.servlet.DispatcherServlet.INPUT_FLASH_MAP==FlashMap [attributes={userId=ID001, userName=mike}, targetR equestPath=/project/page/login/winOpenSucc.do, targetRequestParams={flag=[opening]}]
userId=ID001
userName=mike
说明：通过action二次转发（默认 return "forward:url"）,session中flashmap消失了，通过model（model,modelmap,@ModelAttribute都可以取到前一个action的包括flashAtrribute等参数）这个springmvc这个默认内置对象来接收第一个action redirect过来session中的参数，并自动保存在返回的model数据模型中，forward request依然延续存活（falg依然在值未变），并最终由spring转为request 的attribute中( ${userName}取到了值 )。
不足：浏览器中 url并没有改变，显示为action地址，没有达到需求
3.实现url改变并跟踪model的变化
3.1controller
@Controller @RequestMapping("/page/login") public class LoginController { @RequestMapping(value = "/redirect.do") public String doRedirect(RedirectAttributes redirectAttributes) { redirectAttributes.addFlashAttribute("userId", "ID001"); redirectAttributes.addFlashAttribute("userName", "mike"); redirectAttributes.addAttribute("flag", "opening"); return "redirect:../public/winOpenSucc.do"; } @RequestMapping(value = "/winOpenSucc.do") public String redirectPage() {
return "redirect:../public/indexTest.jsp" } }
jsp页面
输出 url:http://lolcalhost:8080/project/page/public/indexTest?userId=ID001?userName=mike
here is indexTest.jsp
userId is
userName is
flag is
param_flag is opening
说明：二次重定向redirect后，前面的request生命周期结束，新的request由于model对象的注入，将flashmap中的参数转给新的request parameter,
此时${param.userId} ${param.userName}可以取到值
不足：暴露了敏感参数值，flashmap中的对象参数（如3.2的userInfo实例对象，受url不传对象的限制）及request parameter(flag)转发后消失
3.2跟踪model
controller
@Controller @RequestMapping("/page/login") public class LoginController { @RequestMapping(value = "/redirect.do") public String doRedirect(RedirectAttributes redirectAttributes) { User user=new User(); user.setMyId="ID002"; user.setMyName="lili"; redirectAttributes.addFlashAttribute("userId", "ID001"); redirectAttributes.addFlashAttribute("userName", "mike"); //将存入session falshmap中，request刷新后失，优点是隐藏具不用手动清理 redirectAttributes.addAttribute("flag", "opening"); return "redirect:../public/winOpenSucc.do"; //旧request消亡，将产生新的request,flag参数将存入新request中的parameter } @RequestMapping(value = "/winOpenSucc.do") public String redirectPage(Model model,HttpServletRequest request) { System.out.println("print redirectpage controller model parameter:"); model.addAttribute("mdbefore", "before"); final Map map = model.asMap(); for (final Object obj : map.keySet()) { System.out.println(obj.toString() + "==" + map.get(obj)); } model.addAttribute("mdafter", "after"); System.out.println("print redirect controller request parameter:"); final Enumeration reqEnum = request.getParameterNames(); while (reqEnum.hasMoreElements()) { final String s = (String) reqEnum.nextElement(); System.out.println(s + "==" + request.getParameter(s)); }
System.out.println("print redirect controller request attribute:");
final Enumeration reqAttrs = request.getAttributeNames();
while (reqAttrs.hasMoreElements()) {
final String s = (String) reqAttrs.nextElement();
System.out.println(s + "==" + request.getAttribute(s));
}
System.out.println("print redirect controller session parameter:"); final HttpSession session = request.getSession(); final Enumeration se = session.getAttributeNames(); while (se.hasMoreElements()) { final String key = (String) se.nextElement(); System.out.println(key + "==" + session.getAttribute(key)); } return "redirect:../public/indexTest.jsp"; //旧request(带falg参数)消亡，产生新的request（全新的，不带任何参数）,model将自己的值注入新request.parameter中，并返回。 } }
console
print redirectpage controller model parameter: userInfo==com.xx.vdo.User@16675039 //此对象在redirect后，model注入新的request中时，消失 userId==ID001
userName==mike mdbefore==before print redirect controller request parameter: //后台第二个action中request 只有一个flag==opening参数 flag==opening
print redirect controller request attribute:
org.springframework.web.servlet.DispatcherServlet.INPUT_FLASH_MAP==FlashMap [attributes={userInfo=com.xx.vdo.User@16675039, userId=ID001,userName=mike}, targetRe
questPath=/ReportsTYKF/page/login/winOpenSucc.do, targetRequestParams={flag=[opening]}]
org.springframework.web.servlet.DispatcherServlet.FLASH_MAP_MANAGER==org.springframework.web.servlet.support.SessionFlashMapManager@c8398e7
org.springframework.web.servlet.DispatcherServlet.OUTPUT_FLASH_MAP==FlashMap [attributes={}, targetRequestPath=null, targetRequestParams={}]
print redirect controller session parameter:
jsp url:http://lolcalhost:8080/project/page/public/indexTest?userId=ID001&userName=mike&mdbefore=before&mdafter=after
jsp 中session,request打印结果：
page session parameter: print redirectpage page request parameter: //此处已无flag==opning,参数个数为4,即model将值在第二次redirect后注入新的request.parameter中， userId==ID001
userName==mike
mdbefore==before mdafter==after print redirectpage page request attribute:
4.完美实现flshmap参数安全，url地址改变，参数易存取。
其实2已经基本实现我们的需求，只是url没有变，如果我们要实现url的跳转，可以在jsp中增加代码。
前提：需求是外系统有一个菜单列表，点击后打开一个新窗口，跳转到本系统，并对连接进行安全检查，通过后相关信息存session，同时在页面初始化共公参数如操作员信息，同时做到不暴露敏感信息，最后进入本系统具体的页面。
<html> <head> <% String id="bb11234";
//out.println("<script language='javascript'>window.location='"+"page/public/carList.jsp?reqId="+id+"';</script>"); %> </head> <body> </body> <script type="text/javascript">
//这里可以对共公变量进行初始化,然后再进行页面转发
project.userInfo.userId=${userInfo.myId};
project.userInfo.userName=${userInfo.myName};
project.current.operatorName=${userName}; var operatorId=${userId}; window.location="page/public/reportList.jsp?id="+operatorId; </script > <html>
后记：如果jsp发请求打开外系统新页面，只能选择window.open,或者form提交。需要解决跨域问题且格式不好控制。ajax发请求只能等返回信息然后再在本系统中打开页面。相当于至少两次请求。后面会再写一篇关于springMVC打开新页面springMVC接受json并打开新页面。