greetingSubmit method is quite confusing

[buptfarmer]

In this project, the following code lead me to a great misunderstanding, I want to share it, and maybe I can help others.

// GreetingController.java
 @PostMapping("/greeting")
    public String greetingSubmit(@ModelAttribute Greeting greeting) {
        return "result";
    }

// result.html
<p th:text="'content: ' + ${greeting.content}"/>

At first glance in the result.html, I thought greeting object may refer to the @ModelAttribute Greeting greeting, then I tried to make some modification to use another model OtherModel, but it turned out to be exception.
After google quite a while, I found out that here the ${greeting.content} is linked to the name of the model class rather than the name of the key.
So I believe that the proper way to do this is like this.

    @PostMapping("/greeting2")
    public String greetingSubmit(@ModelAttribute OtherModel greeting, Model model) {
        model.addAttribute("greeting", greeting);
        return "result";
    }

Thanks

[gregturn]

In this guide, there are two parts being shown: the current value of the Greeting object as well as an HTML FORM used to submit updates to that object to the server.

The following line of code is where Thymeleaf is given a greeting object to operate on:

model.addAttribute("greeting", greeting);

To change from Greeting to OtherModel, you'd have to alter both controller methods. "greeting" is the handle applied to it for the template.

This bit of Thymeleaf is used to show the current values of Greeting in the result.html template:

<h1>Result</h1>
<p th:text="'id: ' + ${greeting.id}" />
<p th:text="'content: ' + ${greeting.content}" />
<a href="/greeting">Submit another message</a>

In this case, the Greeting POJO fed into the template has both an id and a content attribute. (NOTE: Standard Java Bean rules apply).

When it comes time to build a form and POST it to the server, the same POJO is used to build an HTML FORM (greeting.html):

<form action="#" th:action="@{/greeting}" th:object="${greeting}" method="post">
    <p>Id: <input type="text" th:field="*{id}" /></p>
    <p>Message: <input type="text" th:field="*{content}" /></p>
    <p><input type="submit" value="Submit" /> <input type="reset" value="Reset" /></p>
</form>

• th:object="${greeting}" gets a hold of the greeting POJO.
• th:field="*{id}" references that bean's id field
• th:field="*{content}" references that bean's content field.

If you showed more details of your alteration, we might be able to debug further.