Property or field 'userName' cannot be found on null-CodePudding

here is the code:- form.html :

<div >
    <div >
        <div >
    
        
            <form th:action="@{/process}" method="post" th:object="${loginData}">
            
                <div >
                    <label for="exampleInputEmail1" >Email address</label> 
                    <input 
                        type="text"
                        name="userName" 
                        
                        
                        th:value="${loginData.userName}"
                        
                        id="exampleInputEmail1" 
                        aria-describedby="emailHelp">
                        
                </div>
                
                
                <div >
                    <label for="exampleInputPassword1" >Password</label>
                    
                    <input 
                        type="email"
                        name="email" 
                        
                        th:value="${loginData}"
                        
                        
                        id="exampleInputPassword1">
                </div>
                
                
                <div >
                    <input 
                        type="checkbox" 
                         
                        id="exampleCheck1">
                    
                    <label  for="exampleCheck1">Check me out</label>
                </div>
                
                <button type="submit" >Submit</button>
                
            </form>
            
        </div>
    </div>
</div>

MyController :

@GetMapping("/form") public String formHandler(Model m ) {

            System.out.println("opening form");
            LoginData loginData = new LoginData();
            if(loginData != null ) {
                m.addAttribute("login", new LoginData());
                System.out.println("YAY");
            }else {
                System.out.println("Bhag Bh*****ke");
            }
        
            return "form1";
        }
        
 //handler for process form
 @PostMapping("/process")
 public String processform(@ModelAttribute("loginData") LoginData loginData) {
            
    System.out.println(loginData);
    return"success";
}

success.html :

  <!doctype html>
    <html lang="en" xmlns:th="http://www.thymeleaf.org">
    <head>
      <meta charset="UTF-8" />
      <title>Success</title>
    </head>
    <body>
          <h1>Welcome to this success page</h1>
          <h1 th:text="${LoginData.userName}"></h1>
          <h1 th:text="${LoginData.email}"></h1>
          
    </body>
    </html>

saying error : Caused by: org.springframework.expression.spel.SpelEvaluationException: EL1007E: Property or field 'userName' cannot be found on null

CodePudding user response：

You haven't exactly specified which of the 2 pages are causing the issue, but I'm going to guess that it is the first one.

I would first try replacing the th:value tag with th:field in the username input:

<input 
type="text"
name="userName" 

th:field="*{userName}"
id="exampleInputEmail1" 
aria-describedby="emailHelp">

Since you have already defined the loginData object within the form tag:

th:object="${loginData}

The next input tag could also cause some issues, I'm guessing that this should accept the user's password:

<input
type="email" 
name="email" 
th:value="${loginData}" 
 
id="exampleInputPassword1">

You would want to update it to something like:

<input
    type="password" 
    th:field="*{password}" 
     
    id="exampleInputPassword1">

CodePudding user response：

The exception tells you that there is no model attribute with the name loginData. looking at the controller code after this that can be confirmed as you are adding a model attribute with name login not loginData m.addAttribute("login", new LoginData());

Also I'm not usre why you define a loginData variable in your controller, check if it's non null and than don't use it but create a new one

LoginData loginData = new LoginData();
if(loginData != null ) {
    m.addAttribute("login", new LoginData());
    System.out.println("YAY");
}