如何将通用对象发布到Spring控制器？
[英]How to post generic objects to a Spring controller?
问题描述
I want to create a website that displays a form. 
我想创建一个显示表单的网站。 The fields of the form depend on a request parameter (and also the form backing bean). 表单的字段取决于请求参数（以及表单支持bean）。 This is my controller that renders the different forms: 这是我的控制器，呈现不同的形式：
@Controller
public class TestController {
@Autowired
private MyBeanRegistry registry;
@RequestMapping("/add/{name}")
public String showForm(@PathVariable String name, Model model) {
model.addAttribute("name", name);
model.addAttribute("bean", registry.lookup(name));
return "add";
}
}
The corresponding view looks like this: 相应的视图如下所示：
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="http://www.thymeleaf.org">
<head>
</head>
<body>
<form method="post" th:action="@{|/add/${name}|}" th:object="${bean}">
<th:block th:replace="|${name}::fields|"></th:block>
<button type="submit">Submit</button>
</form>
</body>
</html>
Following is an example fragment that displays the form fields: 以下是显示表单字段的示例片段：
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="http://www.thymeleaf.org">
<head>
</head>
<body>
<th:block th:fragment="fields">
<label for="firstName">First name</label><br />
<input type="text" id="firstName" th:field="*{firstName}" /><br />
<label for="lastName">Last name</label><br />
<input type="text" id="lastName" th:field="*{lastName}" />
</th:block>
</body>
</html>
The looked up bean would be like this: 查找的bean将如下所示：
public class MyExampleBean {
private String firstName;
private String lastName;
// Getters & setters
}
The form is rendered correctly, but how can I receive the form back in the controller? 表单呈现正确，但是如何才能在控制器中重新收到表单？ And how can I validate the submitted bean? 我如何验证提交的bean？ I tried the following method, but obviously it can not work: 我尝试了以下方法，但显然无法正常工作：
@RequestMapping(value = "/add/{name}", method = RequestMethod.POST)
public String processForm(@PathVariable String name, @Valid Object bean) {
System.out.println(bean);
return "redirect:/add/" + name;
}
Spring creates a new instance of Object but the submitted values are lost. Spring创建了Object的新实例，但是提交的值丢失了。 So how can I accomplish this task? 那么我该如何完成这项任务呢？
3 个解决方案
解决方案1
4 已采纳 2015-06-03 10:37:56
If you only wanted to deal with a limited number of beans, you could have one @RequestMapping method for each bean, all delegating to a private method that would do the job . 如果您只想处理有限数量的Bean，则可以为每个Bean使用一个@RequestMapping方法，所有方法都委派给可以完成此工作的私有方法。 You can find an example here . 您可以在此处找到示例。
If you want to be able to accept bean dynamically, you will have to do by hand what Spring does automagically : 如果您希望能够动态接受bean，则必须手动执行 Spring自动执行的操作：
- only use the request and not a model attribute 仅使用请求，而不使用模型属性
- find the bean in registry by the
PathVariablename通过PathVariable名称在注册表中找到bean - do explicitely the binding 明确地进行绑定
But hopefully Spring offers the subclasses of WebDataBinder as helpers : 但是希望Spring提供WebDataBinder的子类作为助手：
@RequestMapping(value = "/add/{name}", method = RequestMethod.POST)
public String processForm(@PathVariable String name, WebRequest request) {
//System.out.println(bean);
Object myBean = registry.lookup(name);
WebRequestDataBinder binder = new WebRequestDataBinder(myBean);
// optionnaly configure the binder
...
// trigger actual binding of request parameters
binder.bind(request);
// optionally validate
binder.validate();
// process binding results
BindingResult result = binder.getBindingResult();
...
return "redirect:/add/" + name;
}
解决方案2
0 2015-06-03 10:02:54
As for validation i don't know, but for retrieving the values, you could try the below 至于验证我不知道，但是要获取值，您可以尝试以下操作
(WARNING: i didn't try this code, as i couldn't at the time of writing). （警告：我没有尝试这段代码，因为在撰写本文时无法这样做）。
Change the processForm handler to handle HttpServletRequest insead of type Object , and get the sumbitted values from the paramters map, example : 更改processForm处理程序以处理类型为Object HttpServletRequest insead，并从paramters映射中获取汇总值，例如：
@RequestMapping(value="/add/{name}", method=RequestMethod.POST, consumes = MediaType.APPLICATION_FORM_URLENCODED_VALUE)
public String processForm(@PathVariable String name, HttpServletRequest request) {
Map<String, String[]> parameterMap = request.getParameterMap();
...
}
解决方案3
0 2015-06-03 10:34:27
You should make two changes to your code, 您应该对代码进行两项更改，
Annotate your
TestControllerwith@SessionAttributes("bean")it will keep your model attribute with the namebeanstored in the session用@SessionAttributes("bean")注释您的TestController，它将使用存储在会话中的名称bean保留模型属性Add
@ModelAttribute("bean")to yourprocessFormmethod, soprocessForm(@PathVariable String name, @Valid @ModelAttribute("bean") Object bean).将@ModelAttribute("bean")添加到您的processForm方法中，以便添加processForm(@PathVariable String name, @Valid @ModelAttribute("bean") Object bean)。 As the model attributebeanis registered as session attribute as well it will retrieve it from session, and will keep the values由于模型属性bean也注册为会话属性，因此它将从会话中检索它，并保留值
If your processForm method is residing in a different controller, make sure to annotate that controller with @SessionAttributes("bean") as well 如果您的processForm方法位于其他控制器中，请确保也使用@SessionAttributes("bean")注释该控制器。
The following should be an example of the working controller 以下应为工作控制器的示例
@SessionAttributes("bean")
@Controller
public class TestController {
@Autowired
private MyBeanRegistry registry;
@RequestMapping("/add/{name}")
public String showForm(@PathVariable String name, Model model) {
model.addAttribute("name", name);
model.addAttribute("bean", registry.lookup(name));
return "add";
}
@RequestMapping(value = "/add/{name}", method = RequestMethod.POST)
public String processForm(@PathVariable String name, @Valid @ModelAttribute("bean") Object bean) {
System.out.println(bean);
return "redirect:/add/" + name;
}
}
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