我刚开始使用 Spring MVC,所以这可能是一个菜鸟错误。
每个请求都会重用 ModelAttribute。如何确保每个 POST 都以干净的对象开头?
我的控制器(MyController.java):
@Controller
public class MyController {
@RequestMapping(method = RequestMethod.POST)
public String processChoice(@ModelAttribute("myData") MyData myData, BindingResult bindingResult) {
System.out.println("POST: myData = " + myData);
return "redirect:/myview?choice=" + myData.getChoice();
}
@RequestMapping(method = RequestMethod.GET)
public String displayChoice(@RequestParam(required = false) String choice, Model model) {
System.out.println("GET: Choice = " + choice);
model.addAttribute("myData", new MyData(choice));
return "myview";
}
}
我的观点(myview.jsp):
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Spring Tests</title>
</head>
<body>
<form:form modelAttribute="myData" method="POST">
<form:select path="choice">
<option></option>
<option value="one">One</option>
<option value="two">Two</option>
</form:select>
<input type="submit" value="Choose"/>
</form:form>
<c:if test="${not empty myData.choice}">Choice = ${myData.choice}</c:if>
<c:if test="${empty myData.choice}">No choice</c:if>
</body>
</html>
连续单击“选择”按钮会附加所选值,而不是仅发布当前值:
GET: Choice = null
POST: myData = MyData [choice=two]
GET: Choice = two
POST: myData = MyData [choice=two,one]
GET: Choice = two,one
POST: myData = MyData [choice=two,one,]
GET: Choice = two,one,
POST: myData = MyData [choice=two,one,,one]
GET: Choice = two,one,,one