当前，当我单击“退款”按钮时，$ {messages}和$ {changes}会显示在url上，而不是显示在jsp正文中。
网址看起来像这样localhost：8080 / name /？messages = Nice + Try％21＆changes = Quarters％3A + 0 +％7C + Nickels％3A + 0％0ADimes％3A + 0 +％7C + Pennies％3A + 0
在jsp主体中什么也没有出现。
我尝试了c：out value =“ $ {changes}”，但是没有用。
我也曾尝试将requestMethod更改为POST，但不走运。
块引用
JSP
<div class='row text-center' id='change-display'>
<div id="change">
${changes} <---- should display the string, but nothing shows up here.
</div>
</div>
<div class='row text-center' id='getChangeButtonDiv'>
<a href="Money/refund">
<button class='btn btn-purchase' type='button' id='refund-button'>
<p>Refund</p> <------- refund button
</button>
</a>
</div>
@RequestMapping(value="/refund", method=RequestMethod.GET)
public String refund(Model model) throws PersistenceException{
BigDecimal zero = new BigDecimal(0);
BigDecimal total = service.calculateInsertedTotal();
int quarterInt=0, dimeInt=0, nickelInt=0, pennyInt=0;
String message="Here is your refund!";
if(total.compareTo(zero) != 1){
message="Nice Try!";
}else{
while(total.compareTo(quarter)==0||total.compareTo(quarter)== 1){
quarterInt ++;
total = total.subtract(quarter);
}
while(total.compareTo(dime)==0||total.compareTo(dime)== 1){
dimeInt ++;
total = total.subtract(dime);
}
while(total.compareTo(nickel)==0||total.compareTo(nickel)== 1){
nickelInt ++;
total = total.subtract(nickel);
}
while(total.compareTo(nickel)==0||total.compareTo(nickel)== 1){
nickelInt ++;
total = total.subtract(nickel);
}
}
String quarterString = "Quarters: "+ quarterInt;
String dimeString = "Dimes: "+ dimeInt;
String nickelString = "Nickels: "+ nickelInt;
String pennyString = "Pennies: "+ pennyInt;
String changes = quarterString + " | " + nickelString
+"\n"+dimeString + " | " + pennyString;
service.removeMoney();
model.addAttribute("messages", message);
model.addAttribute("changes", changes);
return "redirect:/";
}
最佳答案
实际上，您的attributes丢失了，因为您使用的是redirect:/而不是forward，当您从一个请求重定向到另一个请求时，会创建一个新的http请求，因此附加到旧请求的model将会丢失意味着您的属性消息和更改也将丢失，因此要解决此问题，您必须将属性保存在RedirectAttributes中：
@RequestMapping(value="/refund", method=RequestMethod.GET)
public String refund(Model model, RedirectAttributes redirectModel) throws PersistenceException{
//...
redirectModel.addFlashAttribute("messages", message);
redirectModel.addFlashAttribute("changes", changes);
return "redirect:/";
}