【发布时间】：2020-12-31 12:04:50
【问题描述】：
第一次使用 Spring Boot 和 Hibernate 制作项目，我遇到了一个错误，我不知道如何修复。尝试提交表单以创建新的纱线对象时发生错误。
相关控制器（HomeController.java）：
@Controller
public class HomeController {
@Autowired
private BrandRepository brandRepository;
@Autowired
private ColorRepository colorRepository;
@Autowired
private WeightRepository weightRepository;
@Autowired
private YarnRepository yarnRepository;
@RequestMapping("")
public String index(Model model) {
model.addAttribute("title", "My Yarns");
return "index";
}
@GetMapping("yarn/add")
public String displayAddYarnForm(Model model) {
model.addAttribute("title", "Add Yarn");
model.addAttribute(new Yarn());
model.addAttribute("colors", colorRepository.findAll());
model.addAttribute("brands", brandRepository.findAll());
model.addAttribute("weights", weightRepository.findAll());
return "yarn/add";
}
@PostMapping("yarn/add")
public String processAddYarnForm(@ModelAttribute Yarn newYarn, Error errors,
Model model,
@RequestParam (required = false) Integer brand,
@RequestParam (required = false) Integer color,
@RequestParam (required = false) Integer weight) {
model.addAttribute("newYarn", newYarn);
Optional<Brand> yarnBrand = brandRepository.findById(brand);
Optional<Color> yarnColor = colorRepository.findById(color);
Optional <Weight> yarnWeight = weightRepository.findById(weight);
yarnRepository.save(newYarn);
return "redirect:";
}
}
表格（add.html）：
<!DOCTYPE html>
<html lang="en" xmlns:th="https://www.thymeleaf.org/">
<head th:replace="fragments :: head">
<meta charset="UTF-8">
</head>
<body>
<div th:replace="fragments :: page-header"></div>
<div class="container body-content">
<form method="post" style="max-width:600px;">
<div class="form-group">
<label th:for="name">Name</label>
<input class="form-control" th:field="${yarn.name}" />
</div>
<div class="form-group">
<label th:for="brand">Brand</label>
<select th:field="${yarn.brand}">
<option th:each="brand : ${brands}"
th:text="${brand.name}"
th:value="${brand.id}"></option>
</select>
<a th:href="@{'/brand/add'}">Add Brands</a>
</div>
<div class="form-group">
<label th:for="color">Color</label>
<select th:field="${yarn.color}">
<option th:each="color : ${colors}"
th:text="${color.name}"
th:value="${color.id}"></option>
</select>
<a th:href="@{'/color/add'}">Add Colors</a>
</div>
<div class="form-group">
<label th:for="weight">Weight</label>
<select th:field="${yarn.weight}">
<option th:each="weight : ${weights}"
th:text="${weight.name}"
th:value="${weight.id}"></option>
</select>
</div>
<input type="submit" value="Add Yarn" />
</form>
</div>
</body>
</html>
Yarn 模型：
@Entity
public class Yarn extends AbstractEntity{
@ManyToOne
private Brand brand;
@ManyToOne
private Weight weight;
@ManyToOne
private Color color;
public Yarn() {
}
public Yarn(Brand brand, Weight weight, Color color) {
this.brand = brand;
this.weight = weight;
this.color = color;
}
public Brand getBrand() {
return brand;
}
public void setBrand(Brand brand) {
this.brand = brand;
}
public Weight getWeight() {
return weight;
}
public void setWeight(Weight weight) {
this.weight = weight;
}
public Color getColor() {
return color;
}
public void setColor(Color color) {
this.color = color;
}
}
以及每个模型扩展的 AbstractEntity 类：
@MappedSuperclass
public abstract class AbstractEntity {
@Id
@GeneratedValue
private Integer id;
private String name;
public AbstractEntity() {
}
public Integer getId() {
return id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public AbstractEntity(String name) {
this.name = name;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
AbstractEntity that = (AbstractEntity) o;
return id == that.id;
}
@Override
public int hashCode() {
return Objects.hash(id);
}
}
（我也有颜色、重量、品牌的模型，但这些似乎是多余的） 和错误：
There was an unexpected error (type=Bad Request, status=400).
Validation failed for object='yarn'. Error count: 3
org.springframework.validation.BindException: org.springframework.validation.BeanPropertyBindingResult: 3 errors
Field error in object 'yarn' on field 'brand': rejected value [1]; codes [typeMismatch.yarn.brand,typeMismatch.brand,typeMismatch.one.philosopherstone.knittingconversions.models.Brand,typeMismatch]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [yarn.brand,brand]; arguments []; default message [brand]]; default message [Failed to convert property value of type 'java.lang.String' to required type 'one.philosopherstone.knittingconversions.models.Brand' for property 'brand'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'java.lang.String' to required type 'one.philosopherstone.knittingconversions.models.Brand' for property 'brand': no matching editors or conversion strategy found]
我不确定为什么表单发送的类型不匹配，任何帮助将不胜感激。
【问题讨论】：
-
好吧，看起来您正在尝试发送一个字符串（我认为它是 th:value="${brand.id}"），而不是作为您实体的一个字段的品牌本身。您应该找到一种将品牌对象从前端发送到后端的方法。我不使用 Thymeleaf，但我认为它不会那么复杂。
-
这个错误什么时候出现？当您发布表单或获取表单时？span>
-
我编辑了帖子，它在我提交表单时发生。把控制器的输入参数改成字符串，再转成整数，能解决问题吗？
-
好吧，通常最好发送一个包含所有参数的对象。我没有在前端使用过百里香，但请查看stackoverflow.com/questions/17669212/…
标签： java mysql spring-boot hibernate