英文:
How to bind user input with a BigDecimal object field in Spring MVC?
问题
在我的项目中，我有一个类，其中一个字段是 `BigDecimal` 类型。
```java
@Entity
public class Product {
// ...
@DecimalMin("0.01")
private BigDecimal price;
// ...
}
在 thymeleaf 中，我有一个表单，用于输入该类的字段，负责 price 的部分是：
<form ...>
<input type="number" step="any" th:field="*{price}">
</form>
当从该表单返回 @ModelAttribute 时，product 的 price 字段为 null。当 price 是 double 类型时，它是有效的。我该如何使其工作？我想到了一个解决方法 - 将此输入作为 @RequestParam，然后使用 double 值手动初始化 Product.price，但是否有某种解决方案让 thymeleaf 为我执行这些操作？
<details>
<summary>英文:</summary>
In my project I have a class with `BigDecimal` as one of its fields.
```java
@Entity
public class Product {
// ...
@DecimalMin("0.01")
private BigDecimal price;
// ...
}
In thymeleaf I have a form with inputs for fields of this class and the one responsible for price is:
<form ...>
<input type="number" step="any" th:field="*{price}">
</form>
When the @ModelAttribute is returned from this form, the price field of product is null. It used to work when the price was a double. How can I make this work? I thought of a workaround - to have this input as a @RequestParam and then initialize the Product.price using the double value 'manually' but is there some solution so that thymeleaf does that for me?
答案1
得分: 2
以下是您要翻译的内容：
这应该可以工作。我刚刚使用Spring Boot 2.3.0进行了如下测试：
我正在使用一个表单数据对象，因为直接在表单中使用实体会使责任过多：
import javax.validation.constraints.DecimalMin;
import java.math.BigDecimal;
public class ProductFormData {
@DecimalMin("0.01")
private BigDecimal price;
public BigDecimal getPrice() {
return price;
}
public void setPrice(BigDecimal price) {
this.price = price;
}
}
控制器如下：
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
@Controller
@RequestMapping("/product")
public class ProductController {
@GetMapping
public String product(Model model) {
model.addAttribute("product", new ProductFormData());
return "product";
}
@PostMapping
public String doSaveProduct(@ModelAttribute("product") ProductFormData formData) {
System.out.println("formData = " + formData.getPrice());
return "redirect:/product";
}
}
以及product.html模板如下：
<!DOCTYPE html>
<html lang="en" xmlns:th="http:www.thymeleaf.org">
<head>
<meta charset="UTF-8">
<title>Product</title>
</head>
<body>
<h1>Product</h1>
<form th:action="@{/product}" th:object="${product}" method="post">
<input type="number" step="any" th:field="*{price}">
<button type="submit">submit</button>
</form>
</body>
</html>
当我在表单中输入一个数字并点击“提交”时，我可以在控制台中看到打印出的值。
英文:
That should work. I just tested this using Spring Boot 2.3.0 as follows:
I am using a form data object, as directly using your entity for a form clutters reposibilities too much IMO:
import javax.validation.constraints.DecimalMin;
import java.math.BigDecimal;
public class ProductFormData {
@DecimalMin("0.01")
private BigDecimal price;
public BigDecimal getPrice() {
return price;
}
public void setPrice(BigDecimal price) {
this.price = price;
}
}
With a controller like this:
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
@Controller
@RequestMapping("/product")
public class ProductController {
@GetMapping
public String product(Model model) {
model.addAttribute("product", new ProductFormData());
return "product";
}
@PostMapping
public String doSaveProduct(@ModelAttribute("product") ProductFormData formData) {
System.out.println("formData = " + formData.getPrice());
return "redirect:/product";
}
}
And the product.html template like this:
<!DOCTYPE html>
<html lang="en" xmlns:th="http:www.thymeleaf.org">
<head>
<meta charset="UTF-8">
<title>Product</title>
</head>
<body>
<h1>Product</h1>
<form th:action="@{/product}" th:object="${product}" method="post">
<input type="number" step="any" th:field="*{price}">
<button type="submit">submit</button>
</form>
</body>
</html>
When I type a number in the form and press 'submit', I see the value printed in the console.
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