HTTP状态400 - 必需字符串参数“xx”不存在 [英] HTTP Status 400 - Required String parameter 'xx' is not present
问题描述
我正在尝试创建一个简单的 Spring MVC 应用程序。
I'm trying to make a simple Spring MVC application.
这是我的 HelloController
package com.springapp.mvc;
import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
@Controller
@RequestMapping("/")
public class HelloController {
@RequestMapping(method = RequestMethod.GET)
public String printWelcome(ModelMap model,@RequestParam(value = "xx",required
=true)String xx) {
model.addAttribute("message", "Hello Mahdi");
return "hello";
}
}
和 JSP 文件：
<html>
<body>
<h1>${message}</h1>
<form action="/" method="GET">
<input type="text" name="xx">
<button type="submit">submit</button>
</form>
</body>
</html>
当我尝试运行应用程序时出现以下错误：
I'm getting the following error when I try to run the application:
HTTP Status 400 - Required String parameter 'xx' is not present
我是 Spring MVC 的新手，请帮忙。
推荐答案
您的使用案例需要两个操作：
Your use case requires two actions:
- 查看和编辑
< form> - 提交
< form>
- View and edit the
<form> - Submit the
<form>
这应该映射到两个处理程序方法
This should be mapped to two handler methods
@RequestMapping(method = RequestMethod.GET)
public String getForm() {
model.addAttribute("message", "Hello Mahdi");
return "hello"; // assume hello.jsp
}
@RequestMapping(params={"submit"}, method = RequestMethod.GET)
public String printWelcome(ModelMap model, @RequestParam(value = "xx",required=true) String xx) {
/*
Do something with submitted parameter
and return some view name
*/
}
如果要访问表单，可以将GET设置为 / 。当您提交表单时，您也可以执行GET到 / ，但是您还需要其他东西来区分请求。在这里，我使用了 params =submit。因此，您需要将提交输入更改为
When you want to access the form, you make a GET to /. When you submit the form, you can also do a GET to /, but you would need something else to distinguish the request. Here, I've used params="submit". So you need to change your submit input to
<input type="submit" name="submit">submit</button>
或者只是放置你已经使用过的参数（ params = { xx} ）。
or just put the parameter you're already using (params={"xx"}).
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