Thymeleaf Bean 名称“person”的 BindingResult 和普通目标对象都不能用作请求属性

Question

据我所知，这是正确设置的，但我收到以下错误：

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

表格

<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>

Person.java

public class Person {

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

    ....
}

控制器

@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 and Thmeleaf setup，看起来我的设置是相同的。

--------- 更新 1 -----------

我已更改我的 post 方法以包含 BindingResult，但没有成功。

@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

您忘记在您的@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";
}

我已经回答了这样的问题：

• html form validation using thymeleaf not working spring boot

Answer 2

在调用 post 方法之前，必须初始化模型属性（使用 GET 方法）。 在您的情况下，您需要在控制器中再使用一种方法来执行 model.addAttribute("person",new Person()); 并且必须在发布之前调用它。

参考以下链接： https://spring.io/guides/gs/handling-form-submission/ 要么 http://forum.thymeleaf.org/Neither-BindingResult-nor-plain-target-object-for-bean-name-miniDoniie-available-as-request-attribute-td4027859.html

它在控制器中有GetMapping 和PostMapping。

Answer 3

首先我有index.html中的表格

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

所以当我的表格：

<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>

正在寻找/，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";
    }

这是正确的！

我不得不删除第一个方法，它奏效了。