Question

我正在学习如何使用Spring Boot和Thymeleaf。我有一个问题，我在表单列表中向Thymeleaf页面提供了特定对象的列表。当用户选择值并发布结果时，结果是所选对象的字符串，并且与我要在其中存储值的对象不兼容。

这听起来像是一纸空话，下面是代码。

我的问题是：是否仍然可以确保Thymeleaf返回对象列表？

输入：一个类将一堆配料传递给表单 此类将“成分”类的“列表”传递给表单（此过滤无关紧要-插入一个列表作为model属性的值，键是成分的类型）

@GetMapping
public String showDesignForm(Model model) {
    List<Ingredient> ingredients = new ArrayList<>();
    ingredientRepo.findAll().forEach(i -> ingredients.add(i));  
    Type[] types = Ingredient.Type.values();
    for (Type type : types) {
        model.addAttribute(type.toString().toLowerCase(), filterByType (ingredients, type));
    }   
    model.addAttribute("taco", new Taco()); 
    return "design";
}

Thymeleaf获取该列表并将其显示在复选框中

<!DOCTYPE html>
<html
xmlns:th="http://www.thymeleaf.org">
<head>
<title>Taco Cloud</title>
<link rel="stylesheet" th:href="@{/styles.css}" />
</head>
<body>
<h1>Design your taco!</h1>
<img th:src="@{/images/TacoCloud.png}"/>
<form method="POST" th:object="${taco}">
<div class="grid">
<div class="ingredient-group">
<h3>Designate your wrap:</h3>
<div th:each="ingredient : ${wrap}">
<input name="ingredients" type="checkbox" th:value="${ingredient}" />
<span th:text="${ingredient.name}">INGREDIENT</span><br/>
</div>
</div>
<div class="ingredient-group">
<h3>Pick your protein:</h3>
<div th:each="ingredient : ${protein}">
<input name="ingredients" type="checkbox" th:value="${ingredient}" />
<span th:text="${ingredient.name}">INGREDIENT</span><br/>
</div>
</div>
<div class="ingredient-group">
<h3>Choose your cheese:</h3>
<div th:each="ingredient : ${cheese}">
<input name="ingredients" type="checkbox" th:value="${ingredient}" />
<span th:text="${ingredient.name}">INGREDIENT</span><br/>
</div>
</div>
<div class="ingredient-group">
<h3>Determine your veggies:</h3>
<div th:each="ingredient : ${veggies}">
<input name="ingredients" type="checkbox" th:value="${ingredient}" />
<span th:text="${ingredient.name}">INGREDIENT</span><br/>
</div>
</div>
<div class="ingredient-group">
<h3>Select your sauce:</h3>
<div th:each="ingredient : ${sauce}">
<input name="ingredients" type="checkbox" th:value="${ingredient}" />
<span th:text="${ingredient.name}">INGREDIENT</span><br/>
</div>
</div>
</div>
<div>
<h3>Name your taco creation:</h3>
<input type="text" th:field="*{name}"/>
<br/>
<button>Submit your taco</button>
</div>
</form>
</body>
</html>

目标类别：期望返回的值为列表

package tacos; import java.util.Date; import java.util.List; import javax.validation.constraints.NotNull; import javax.validation.constraints.Size; import lombok.Data; @Data public class Taco { private Long id; private Date createdAt; @NotNull @Size(min=5, message="Name must be at least 5 characters long") private String name; @Size(min=1, message="You must choose at least 1 ingredient") private List<Ingredient> ingredients; }

错误：

对象“ taco”在字段“成分”上的字段错误：拒绝的值[Ingredient（id = FLTO，name = Flour Tortilla，type = WRAP），Ingredient（id = CHED，name = Cheddar，type = CHEESE）] ;代码[typeMismatch.taco.ingredients，typeMismatch.ingredients，typeMismatch.java.util.List，typeMismatch]；参数[org.springframework.context.support.DefaultMessageSourceResolvable：代码[taco.ingredients，ingredients];参数[];默认消息[成分]]；默认消息[无法将类型'java.lang.String []'的属性值转换为属性'成分'的必需类型'java.util.List'；嵌套异常为java.lang.IllegalStateException：无法将属性“ ingredients [0]”的类型“ java.lang.String”的值转换为所需的类型“ tacos.Ingredient”：找不到匹配的编辑器或转换策略]

Answer 1

我看过一个视频，该视频帮助在Thymeleaf页面的String结果和Spring中的POST方法之间创建了一个转换器。

sparse matrix

Answer 2

我在某些代码中遇到了相同的问题，但是我通过使用Spring JPA克服了它。但是，如果您使用的不是Spring JPA，则可以将此转换器用于您的应用程序。根据您的代码，Ingredient的属性ID为String。这样的代码将。

@Component
public class IngredientConverter implements Converter<String, Ingredient> {

private final IngredientRepo ingredientRepo;

@Autowired
public IngredientConverter(IngredientRepo ingredientRepo) {

    this.ingredientRepo = ingredientRepo;
}

@Override
public Ingredient convert(String source) {

      List<Ingredient> ingredients = new ArrayList<>();

      ingredientRepo.findAll().forEach(i -> ingredients.add(i));

      for (Ingredient ingredient : ingredients) {

        // You may use equal() method
        if (ingredient.getId() == source)

            return ingredient;
      }

      return null;
   }

}

Answer 3

您应将private List<Ingredient> ingredients;更改为private List<String> ingredients;

Thymeleaf返回一个String数组而不是List <object>

3 个答案: