'Spring boot + thymeleaf in IntelliJ: cannot resolve vars

I'm writing a short web form application using spring boot and thymeleaf on IntelliJ, but it seems that in the html file, all fields in the model cannot be resolved. Here is my code:

Controller class:

@Controller
public class IndexController{

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

    @RequestMapping(value="/", method = RequestMethod.POST)
    public String addNewPost(@Valid Post post, BindingResult bindingResult, Model model){
        if(bindingResult.hasErrors()){
            return "index";
        }
        model.addAttribute("title",post.getTitle());
        model.addAttribute("content",post.getContent());
        return "hello";
    }
}

Model Class:

public class Post {

    @Size(min=4, max=35)
    private String title;

    @Size(min=30, max=1000)
    private String content;

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }
}

Then is the index.html:

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head lang="en">

    <title>Spring Framework Leo</title>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
</head>
<body>

<h3>Spring Boot and Thymeleaf</h3>


    <form action="#" th:action="@{/}"  th:object="${post}" method="post">
        <table>
            <tr>
                <td>Title:</td>
                <td><input type="text" th:field="*{title}" /></td>
                <td th:if="${#fields.hasErrors('title')}" th:errors="*{title}">Title error message</td>
            </tr>
            <tr>
                <td>Content:</td>
                <td><input type="text" th:field="*{content}" /></td>
                <td th:if="${#fields.hasErrors('content')}" th:errors="*{content}">Content error message</td>
            </tr>
            <tr>
                <td><button type="submit">Submit post</button></td>
            </tr>
        </table>
    </form>

There are always red lines under "post", "title" and "content", but I don't know how to solve it. Is it a problem of IntelliJ or just a problem of my code?

Solution 1:^[1]

If your IntelliJ version is < 2017.3, it is, as Andrew wrote, a known error IDEA-132738. There is a workaround how to get rid of the error marks in the IDE. IntelliJ also supports the semi-automatic generation of the below mentioned code:

You can use Alt+Enter shortcut to invoke intention "Declare external variable in comment annotation" in order to get rid of "unresolved model attribute" in your views.

Add the following code to your html file:

<!--/* Workaround for bug https://youtrack.jetbrains.com/issue/IDEA-132738 -->
    <!--@thymesVar id="post" type="your.package.Post"-->
    <!--@thymesVar id="title" type="String"-->
    <!--@thymesVar id="content" type="String"-->
<!--*/-->

If you use extensions objects constructed automatically by ThymeLeaf, such as #temporals from thymeleaf-extras-java8time for conversion of java.time objects:

<span th:text="${#temporals.format(person.birthDate,'yyyy-MM-dd')}"></span>

and IntelliJ cannot resolve them, use similar code, and just add # in front of the object name:

<!--@thymesVar id="#temporals" type="org.thymeleaf.extras.java8time.expression.Temporals"-->

If your IntelliJ version is >= 2017.3 (however some people complain that it still does not work for them), the issue IDEA-132738 should be fixed (@FloatOverflow: "I confirm that in version 2017.3 build 25.Oct.2017 the problem has been solved"):

Status 2017.3

Support for Spring Boot autoconfigured MVC applications is complete, all bundled autoconfiguration view types are supported.

Fix versions: 2017.3

Solution 2:^[2]

I had two different portions of code: the first was showing the error and the second was not doing it. I observed that there is a difference in the xmlns:th attribute.

First Page: Not working!

<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:th="http://www.thymeleaf.org">

Second Page: Working!

<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:th="http://thymeleaf.org">

I removed the www. and it works for me!

Solution 3:^[3]

This is a problem with IntelliJ: IDEA-132738.

Basically IntelliJ is unable to locate the model variables when Spring Boot has been used to autoconfigure everything.

Solution 4:^[4]

I want to add one more thing. As stated above, the issue has been fixed in IntelliJ 2017.3. I can also confirm this.

However, I noticed that this is only true if you define all your attributes directly inside the responsible controller function, like e.g. this:

@RequestMapping(value = "/userinput")
public String showUserForm(Model model){
    model.addAttribute("method", "post");
    model.addAttribute("user", new User());
    return "userform";
}

If you are using a sub-function in which you define the model attributes (see Example below), IntelliJ can still not find the attributes in the HTML template.

Example:

@RequestMapping(value = "/userinput")
public String showUserForm(Model model){
    return doIt(model);
}

private String doIt(Model model) {
    model.addAttribute("method", "post");
    model.addAttribute("user", new User());
    return "userform";
}

So, always make sure you put your code directly inside the view function!

Solution 5:^[5]

Manually enabling it, worked for me in Intellij 2018.1.6 Ultimate Edition. Steps followed

Open the Project tool window (e.g. View | Tool Windows | Project).
Right-click the project or the module folder and select Add Framework Support.
In the left-hand pane of the Add Frameworks Support dialog that opens, select the Thymeleaf checkbox.

Official reference : https://www.jetbrains.com/help/idea/thymeleaf.html#0c8052be

Solution 6:^[6]

In my case the problem was that I had the following in my application.properties:

spring.thymeleaf.prefix=file:src/main/resources/templates/

spring.thymeleaf.cache=false

Once I removed these properties, the spring mvc mappings are detected by Intellij again (in the Ultimate version, I'm using 2018.1). Also the thymeleaf objects are working now.

I used these properties to support fast development where a refresh would reload the thymeleaf template files.

To solve this issue, I use the following -D option in my run configuration of my spring boot application to tell spring boot where my property files are during development:

-Dspring.config.location=/dev/application/conf/application.properties

Solution 7:^[7]

There is one more interesting situation ,if you DONT return directly the object from your controller ,Intellij will not recognize the variable ,but she will still work

Solution 8:^[8]

This problem comes from thymeleaf web link.

The problem:xmlns:th="http://www.thymeleaf.org"

The solution: xmlns:th="http://thymeleaf.org"

Solution 9:^[9]

For those who come from ReactJS and want to use Springboot as a backend.

I forgot to add html boilerplate code in the html, that's why I'm seeing this error. don't forget adding boilerplate code.

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>HTML 5 Boilerplate</title>
    <link rel="stylesheet" href="style.css">
  </head>
  <body>
    <script src="index.js"></script>
  </body>
</html>

Solution 10:^[10]

This was happening to me on Ultimate 2021.2.1.

In one @GetMapping method, I used @ModelAttribute('transactionForm'). The Thymeleaf page for that method didn't have errors.

But in another @GetMapping method, I didn't use @ModelAttribute('newCustomerForm'). The Thymeleaf page for that method had the errors. When I added the @ModelAttribute to the method, the errors went away. And when I took it out, the errors came back.

I know Spring MVC doesn't require the @ModelAttribute if the name of the model is the same as the class name. So I shouldn't have to do this, and I'm only doing this to appease the IDE.

Solution 11:^[11]

I had the same problem and fixed it (ultimate 2021.3.2). Intellij has a hard time guessing the type of the attribute(s).

Keep www in the namespace xmlns:th="http://www.thymeleaf.org" otherwise Intellij won't parse thymeleaf tags

If you initialize one model in a controler,

don't use a method's return, declare a variable

String titre=post.getTitle();
model.addAttribute("title",titre);

don't add attributes through sub methods, keep it in the main block

@GetMapping("/book")
public String ver(Model model) {
...
model.addAttribute("title", title);
return "frontpage";
}

and don't use complex operator like the ternary one

model.addAttribute("titles", titles.size() > 0 ? titles : null);

If you initialize 2 or 3 models in you controler, don't push null values

model.addAttribute("employees", null);

Solution 12:^[12]

I was resolve like following click Alt + Enter

Lets try it!!!

Solution 13:^[13]

This feature is supported in the Ultimate edition only.

Click here for more details

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1	Community
Solution 2	Mustapha El Kojji
Solution 3	Andrew
Solution 4	user7346048
Solution 5	Ajinkya
Solution 6	Ekkelenkamp
Solution 7	Georgi Peev
Solution 8	samet kaya
Solution 9	stoneshishang
Solution 10	rdguam
Solution 11	Cybergrenouille
Solution 12	cng.buff
Solution 13	Sasikumar Murugesan

'Spring boot + thymeleaf in IntelliJ: cannot resolve vars

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