Thymeleaf Bean 名稱 'person' 的 BindingResult 和普通目標 object 都不能用作請求屬性

Question

據我所知，這是正確設置的，但我收到以下錯誤：

java.lang.IllegalStateException: Neither BindingResult nor plain target 
object for bean name 'person' available as request attribute

形式

<form action="#" th:action="@{/person}" th:object="${person}" method="post" th:required="required">
    <input type="text" th:field="*{subject}" class="contact col-md-6" placeholder="Name *" th:required="required"/>
    <input type="text" th:field="*{name}" class="contact col-md-6" placeholder="Name *" th:required="required"/>
    <input type="text" th:field="*{lastName}" class="contact col-md-6" placeholder="Name *" th:required="required"/>
    <input type="email" th:field="*{email}" class="contact noMarr col-md-6" placeholder="E-mail address *" th:required="required"/>
    <textarea name="comment" class="contact col-md-12" th:field="*{message}" placeholder="Message *"></textarea>
    <input type="submit" id="submit" class="contact submit" value="Send message"/>
</form>

人.java

public class Person {

    private int id;
    private String name;
    private String lastName;
    private String email;
    private String subject;
    private String message;

    ....
}

Controller

@Controller
public class ApplicationController {

    @RequestMapping(value = "/", method = RequestMethod.GET)
    public String indexPage() {
        return "index";
    }

    @RequestMapping(value="/person", method=RequestMethod.GET)
    public String contactForm(Model model) {
        model.addAttribute("person", new Person());
        return "index";
    }

    @RequestMapping(value="/person", method=RequestMethod.POST)
    public String contactSubmit(@ModelAttribute Person person, Model model) {
        model.addAttribute("person", person);
        return "result";
    }
}

我查看了Spring-boot 和 Thmeleaf 設置，看起來我的設置是相同的。

--------------------- 更新 1 ------------------------

我已更改我的 post 方法以包含 BindingResult，但沒有成功。

@RequestMapping(value="/person", method=RequestMethod.POST)
public String contactSubmit(@Valid @ModelAttribute Person person, BindingResult bindingResult, Model model) {

    if(bindingResult.hasErrors()){
        System.out.println("There was a error "+bindingResult);
        System.out.println("Person is: "+ person.getEmail());
        return "index";
    }

    model.addAttribute("person", person);
    return "result";
}

Answer 1

您忘記在@ModelAttribute之后添加BindingResult ：

@RequestMapping(value="/person", method=RequestMethod.POST)
public String contactSubmit(@ModelAttribute Person person, BindingResult bindingResult, Model model) {
    if (bindingResult.hasErrors()) {
        //errors processing
    }  
    model.addAttribute("person", person);
    return "result";
}

我已經回答了這樣的問題：

• html 表單驗證使用 thymeleaf 不工作 spring 啟動

Answer 2

Model 屬性必須在調用 post 方法之前初始化（使用 GET 方法）。 在您的情況下，您需要 controller 中的另一種方法，它執行model.addAttribute("person",new Person()); 並且必須在發布前調用。

請參考以下鏈接： https://spring.io/guides/gs/handling-form-submission/或http://forum.ZDB38BD6F666CEF7A2F938F392EB71FDA-Z.intarget-object-forResult-bean-nor-pla -miniDoniie-available-as-request-attribute-td4027859.html

它在 controller 中具有GetMapping和PostMapping 。

Answer 3

您需要為“person”聲明一個@ModelAttribute。 就像是：

@ModelAttribute("Myperson")
public Person newPerson() {
    return new Person();
}

然后，聲明你@PostMapping 並在@ModelAttribute 中設置名稱“person”。

@RequestMapping(value="/person", method=RequestMethod.POST)
public String contactSubmit(@ModelAttribute Person person, Model model) {
    model.addAttribute("person", person);
    return "result";
}

我希望它適用於閱讀本文的人:)

Answer 4

首先我有index.html中的表格

 @RequestMapping(value = "/", method = RequestMethod.GET)
    public String indexPage(){
        return "index";
    }

所以當我的表格：

<form th:action="@{/person}" th:object="${person}" method="post" >
                <input type="text" th:field="*{subject}" class="contact col-md-6" placeholder="Subject *" />
                <input type="text" th:field="*{name}" class="contact col-md-6" placeholder="Name *" />
                <input type="text" th:field="*{lastName}" class="contact col-md-6" placeholder="Last Name *" />
                <input type="email" th:field="*{email}" class="contact noMarr col-md-6" placeholder="E-mail address *" />
                <textarea name="comment" class="contact col-md-12" th:field="*{message}" placeholder="Message *" ></textarea>
                <input type="submit" id="submit" class="contact submit" value="Submit" />
                <input type="reset" value="Reset" />
            </form>

正在尋找/它正在使用上述方法，而不是：

@RequestMapping(value="/", method=RequestMethod.GET)
    public String contactForm(@Valid @ModelAttribute("person") Person person, BindingResult bindingResult,
                              HttpServletRequest request, Model model) throws IOException {

        if(bindingResult.hasErrors()){
            System.out.println("There was a error "+bindingResult);

            return "index";
        }

        model.addAttribute("person", new Person());
        return "index";
    }

哪個是正確的

我不得不刪除第一種方法並且它有效。