这是一个使用 thymeleaf 模板管理器的 Spring Boot 应用程序。它有一个简单的带有下拉菜单的表单。选项是从数据库填充的，它们的名称(或 ID)都可以在表单上正确显示，但选择选项并提交表单后，给定选定变量的值仍为 0。
虽然我获得了变量 content 的正确值，但 categoryId 在提交后始终具有值 0(如果我将其类型从 int 更改为 Integer，则为 null)。
我猜测该模型未正确“链接”到 jokeForm 但我不知道如何正确链接它。我正在关注example 1 。我希望有人只需快速查看我的代码就可以轻松发现问题。 submitForm() 方法中出现代码中断。
HTML 表单:
<html>
<body>
<form action="#" th:action="@{/new}" th:object="${jokeForm}" method="post">
<table>
<tr>
<td>Content:</td>
<td><input type="text" th:field="*{content}" /></td>
<td th:if="${#fields.hasErrors('content')}" th:errors="*{content}">Content Error</td>
</tr>
<tr>
<td>Category:</td>
<td>
<select name="categoryId" th:field="*{categoryId}">
<option value="0" th:each="category : ${categories}"
th:value="${category.id}"
th:utext="${category.name}"/>
<!-- <option th:each="category : *{categories}"
th:value="*{category.id}"
th:utext="*{category.name}"/> -->
</select>
</td>
<td th:if="${#fields.hasErrors('categoryId')}" th:errors="*{categoryId}">category Error</td>
</tr>
<tr>
<td><button type="submit">Submit</button></td>
</tr>
</table>
</form>
</body>
</html>
Controller
@GetMapping("/new")
public String showForm( Model model) {
DEBUG("showForm");
JokeForm form = new JokeForm();
categories = categoryRepository.findAll();
DEBUG(categories.get(0).toString());
DEBUG(categories.get(1).toString());
//form.setCategories(categories); //not working
model.addAttribute("jokeForm", form);
model.addAttribute("categories",categories);
return "form";
}
@PostMapping("/new")
@ResponseBody
public String submitForm(@ModelAttribute JokeForm jokeForm) {
DEBUG("submitForm");
//String content = jokeForm.getContent();
DEBUG(jokeForm.getContent());
DEBUG(jokeForm.getCategoryId().toString());
Joke j = new Joke();
j.setContent(jokeForm.getContent());
//j.setCategoryId(jokeForm.getCategoryId());
//DEBUG(Integer.toString(jokeForm.getCategoryId()));
//CAUSES ERROR value of CategoryId is Integer -> null System.out.println(Integer.toString(jokeForm.getCategoryId()));
//PRODUCES ERROR value of CategorId is int (because no category matches) j.setCategory(categoryRepository.findById(jokeForm.getCategoryId().intValue()).get(0));
jokeRepository.save(j); //save
return "Saved";
}
笑话表单
public class JokeForm {
@NotEmpty(message = "content may not be empty")
private String content;
@NotEmpty(message = "category may not be empty")
private int categoryId; //int-> 0, Integer -> null
/*
@NotEmpty(message = "category may not be empty")
private Category category;
public Category getCategory() {
return category;
}
public void setCategory(Category category) {
this.category = category;
}
private List<Category> categories;
public List<Category> getCategories() {
return categories;
}
public void setCategories(List<Category> categories) {
this.categories = categories;
} */
public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
public Integer getCategoryId() {
return categoryId;
}
public void setCategory(Integer categoryId) {
this.categoryId = categoryId;
}
}
最佳答案
您设置value="0"对于所有选项。
<select>应该是:
<select th:field="*{categoryId}">
<option th:each="category : ${categories}"
th:value="${category.id}"
th:utext="${category.name}"/>
<!-- <option th:each="category : *{categories}"
th:value="*{category.id}"
th:utext="*{category.name}"/> -->
</select>
编辑:
并添加( setter )setCategoryId()在 JokeForm 类中
关于java - MVC : Value in dropdown menu doesn't set to selected value - remains 0，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/56194998/