问题

在我的Java代码中，使用Spring Boot，我以前使用模型或POJO对象来更好地控制我的对象等。通常情况下，我会创建实体、存储库、服务、REST控制器，就像文档和课程建议的那样。
然而，现在我正在使用Thymeleaf模板、HTML，还有一点Bootstrap和CSS来创建浏览器界面。对于`@Controller`中的方法，我将Spring Model UI中的Model作为参数传递，像这样：

```java
@GetMapping("/employees")
private String viewAllEmployees(Model employeeModel) {
    employeeModel.addAttribute("listEmployees", employeeService.getAllEmployees());
    return "employeeList";
}

我的问题是：我如何使用我的POJO对象来替代org.springframework.ui.Model？

我第一个猜测是这样的：

public class EmployeeModel {
    
    private long employeeId;
    private String firstName;
    private String lastName;
    private String email;
    private String phone;
    private long companyId;
    //getter and setter methods
}

为了做到这一点，我必须@Override Model方法，这对我来说没问题。它看起来像是Java、Spring等在编译时不会出现问题，我可以在我的@Controller中像这样使用这个POJO对象：

@Controller
public class EmployeeController {
    @Autowired 
    private EmployeeService employeeService;    
    @GetMapping("/employees")
    private String viewAllEmployees(EmployeeModel employeeModel) {
        employeeModel.addAttribute("listEmployees", employeeService.getAllEmployees());
        return "employeeList";
    }
}

我运行代码，它启动了，显示了我的工作正常的/home端点，然而当我想要访问我的/employees端点，它应该显示我的员工列表时，它抛出了这个异常：

Method [private java.lang.String com.bojan.thyme.thymeApp.controller.EmployeeController.viewAllEmployees(com.bojan.thyme.thymeApp.model.EmployeeModel)] with argument values:[0] [type=org.springframework.validation.support.BindingAwareModelMap] [value={}] ] with root cause java.lang.IllegalArgumentException: argument type mismatch

请注意，REST控制器在浏览器和Postman中都正常工作。

是不是作为方法的String是问题所在？我的方法是否应该是其他类型，如List<EmployeeModel>或者可能是EmployeeModel本身？如果是这样的话，如何告诉方法我希望返回employeeList.html？

我真诚地希望有人能够帮助我解决这个问题

<details>
<summary>英文:</summary>

So far in my Java code with Spring Boot I was using models, or POJO objects to achieve better control of my objects, etc. Usually I am creating Entities, Repositories, Services, Rest controllers, just like documentation and courses are suggesting.
Now however I am working with Thymeleaf templates, HTML a bit of Bootstrap and CSS in order to create browser interface. For methods in `@Controller`, as parameter, I am passing Model from Spring Model UI like this:

    @GetMapping(&quot;/employees&quot;)
	private String viewAllEmployees(Model employeeModel) {
		employeeModel.addAttribute(&quot;listEmployees&quot;, employeeService.getAllEmployees());
		return &quot;employeeList&quot;;
	}

My question is: How can I use my POJO objects instead of org.springframework.ui.Model;?

My first guess was this:

    public class EmployeeModel implements Model{
	
	private long employeeId;
	private String firstName;
	private String lastName;
	private String email;
	private String phone;
	private long companyId;
	//getter and setter methods
    }

And in order to do that I have to `@Override` Model methods which is fine with me. And it looks like Java, Spring etc. does not complain in compile time, and I can use this POJO object in my `@Controller` like this:

    @Controller
    public class EmployeeController {
	@Autowired 
	private EmployeeService employeeService;	
	@GetMapping(&quot;/employees&quot;)
	private String viewAllEmployees(EmployeeModel employeeModel) {
		employeeModel.addAttribute(&quot;listEmployees&quot;, employeeService.getAllEmployees());
		return &quot;employeeList&quot;;
	}}

I run the code and it starts, shows my /home endpoint which works cool, however when I want to go to my /employees endpoing where it should show my eployees list it throws this: 

    Method [private java.lang.String com.bojan.thyme.thymeApp.controller.EmployeeController.viewAllEmployees(com.bojan.thyme.thymeApp.model.EmployeeModel)] with argument values:[0] [type=org.springframework.validation.support.BindingAwareModelMap] [value={}] ] with root cause java.lang.IllegalArgumentException: argument type mismatch

exception.

Please note that Rest controller is working perfectly in browser and Postman.

Is it possible that String as a method is the problem? Should my method be of some other type like `List&lt;EmployeeModel&gt;` or maybe `EmployeeModel ` itself? If it is so, how to tell the method that I want my employeeList.html to be returned?

I sincerely hope that someone can halp me with this one :)

</details>


# 答案1
**得分**: 1

&gt; 我怎样才能使用我的POJO对象替代org.springframework.ui.Model呢？

我认为当你使用Thymeleaf时，这不是最佳实践。根据他们的[文档][1]，你应该将你的对象附加到你的Model中。所以在你的控制器中，你将操作包含你的POJO的模型。

示例：

```java
@RequestMapping(value = "message", method = RequestMethod.GET)
public ModelAndView messages() {
    ModelAndView mav = new ModelAndView("message/list");
    mav.addObject("messages", messageRepository.findAll());
    return mav;
}

 @RequestMapping(value = "message", method = RequestMethod.GET)
    public ModelAndView messages() {
        ModelAndView mav = new ModelAndView("message/list");
        mav.addObject("messages", messageRepository.findAll());
        return mav;
    }

答案2

得分: 1

你应该始终将org.springframework.ui.Model用作参数。这个类基本上是一个带有键值对的Map，这些键值对可供Thymeleaf用于渲染。

你的第一个示例是正确的做法：

@GetMapping("/employees") //<1>
private String viewAllEmployees(Model model) {
    model.addAttribute("employees", employeeService.getAllEmployees()); //<2>
    return "employeeList"; //<3>
}

• <1> 这是视图将要呈现在的URL
• <2> 将任何你想要的Java对象作为属性添加到模型中
• <3> 返回Thymeleaf模板的名称。在默认的Spring Boot与Thymeleaf应用程序中，这将引用位于src/main/resources/templates/employeeList.html的模板。在该模板中，你可以通过${employees}来访问模型的值。

@GetMapping("/employees") //<1>
private String viewAllEmployees(Model model) {
    model.addAttribute("employees", employeeService.getAllEmployees()); // <2>
    return "employeeList"; // <3>
}