数据交互一

1.JSP中9大内置对象类型

2.如何让重定向也带数据

①使用URL模板以路径变量和/或查询参数的形式传递参数。//只能传递简单类型的参数

示例：
@RequestMapping(method=RequestMethod.GET)
public String spittles(Model model){
//map类型也可以做为模型
model.addAttribute("pid", "wahahah");
model.addAttribute("username", "haha");
return "redirect:/spi/{username}";
//冲向的路径形式是：/spi/haha?pid=wahahah
}
@RequestMapping("/spi/{username}")
public void tets(@PathVariable("username")String username,String pid ){
System.out.println(username);
System.out.println(pid);
}

②通过flash属性发送数据。

通过flash其实是将数据放到会话中，然后再取出。
@RequestMapping(method=RequestMethod.GET)
public String spittles(RedirectAttributes model){
//map类型也可以做为模型
model.addFlashAttribute("spittles", spittleRespository.findSpittles(Long.MAX_VALUE, 20));
model.addAttribute("pid", "wahahah");
model.addAttribute("username", "haha");
return "redirect:/spittles/spi/{username}";
}
@RequestMapping("/spi/{username}")
public void tets(@PathVariable("username")String username,String pid ,Model model){
if(model.containsAttribute("spittles")){
Map<String, Object> asMap = model.asMap();
ArrayList<Spittle> list = (ArrayList<Spittle>) asMap.get("spittles");
System.out.println(Arrays.toString(list.toArray()));
}
System.out.println(username);
System.out.println(pid);
}