尽管@@ wired服务始终使用必填字段，但Spring @Autowired服务却奇怪地为空

问题描述

我正在使用pojo来处理表单请求，并且尝试使用Autowired访问服务。但是无论我尝试更改什么，它都会始终返回null。我将发布我的所有代码，请仔细阅读。

CategoryAddForm：

在此页面中，我尝试使用categoryService，但它似乎为空（null），当我尝试在服务中使用任何函数时，会得到nullpointerexception。我没有尝试在任何地方初始化自动装配类。

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
@Component
public class CategoryAddForm {
    private Long id;
    private String title;
    private String description;
    private String language;
    private String image_url;

    @Autowired
    CategoryService categoryService;

    public Category save() {
        Category category;
        if(this.id==null) {
            if(this.language==null || this.language.trim().equals("en")) {
                category = Category.builder()
                        .title_en(this.title)
                        .description_en(this.description)
                        .image_url(this.image_url)
                        .en_available(true)
                        .count(0l).build();
                System.out.println("New for English: \n id: "+this.id+" \n title:"+this.title+"\n description: "+this.description+"\n language: "+this.language);
                System.out.println(categoryService);
//                categoryService.save(category);
            }
            else {
                category = Category.builder()
                        .title_np(this.title)
                        .description_np(this.description)
                        .np_available(true)
                        .en_available(false)
                        .count(0l).build();
                System.out.println("New for Nepali: \n id: "+this.id+" \n title:"+this.title+"\n description: "+this.description+"\n language: "+this.language);
                System.out.println(categoryService);
//                categoryService.save(category);
            }
        }
        else {
            if(this.language==null || this.language.trim().equals("en")) {
                category = Category.builder()
                        .id(this.id)
                        .title_en(this.title)
                        .description_en(this.description)
                        .en_available(true)
                        .image_url(this.image_url).build();
            }
            else {
                category = Category.builder()
                        .id(this.id)
                        .title_np(this.title)
                        .description_np(this.description)
                        .np_available(true)
                        .image_url(this.image_url).build();
            }
        }
        System.out.println(category);
    return categoryService.save(category);

    }
}

表单页面：

此页面将categoryForm对象发送到/ save控制器中，该控制器调用CategoryAddForm内部的保存功能

            <form th:action="@{'/admin/category/save'}" method="post" th:object="${categoryForm}">
                <div class="form-group my-1 p-2 row">
                    <label for="categoryTitle">Title</label>
                    <input type="title" class="form-control" name="title" id="categoryTitle" th:field="*{title}">
                </div>
                <div class="form-group my-1 p-2 row">
                    <label for="categoryDescription">Description</label>
                    <textarea rows="5" type="description" class="form-control" name="description" id="categoryDescription" th:field="*{description}">
                    </textarea>
                </div>
                <div class="form-check my-1 p-2 row">
                    <label for="languages">Select Language</label>
                    <div id="languages" class="row ml-2">

                        <div class="col-2" >
                            <input class="form-check-input" type="radio" value="en" th:field="*{language}" id="englishLanguage" th:selected="selected">
                            <label class="form-check-label" for="englishLanguage">
                                English
                            </label>
                        </div>
                        <div class="col-2" >
                            <input class="form-check-input" type="radio" value="ne" th:field="*{language}" id="nepaliLanguage">
                            <label class="form-check-label" for="nepaliLanguage">
                                Nepali
                            </label>
                        </div>
                    </div>
                </div>
                <button type="submit" class="btn btn-primary m-2">Submit</button>
            </form>

类别服务实施： 仅供参考，证明我没有做错任何事情。

@Service
public class CategoryServiceImpl implements CategoryService {
    @Autowired
    private CategoryRepository repository;
    @Override
    public Category save(Category document) {
        return repository.save(document);
    }

    @Override
    public Category getById(Long id) {
        return repository.getone(id);
    }

    @Override
    public void delete(Category document) {
        repository.delete(document);
    }

    @Override
    public void deleteById(Long id) {
        repository.deleteById(id);
    }

    @Override
    public List<Category> getAllCategories() {
        return repository.findAll();
    }
}

在CategoryAdminController中保存路由：

此函数从表单中获取categoryAddForm，并在categoryAddForm中调用save（）函数。

@PostMapping(value = "/save")
public ModelAndView submitCategory(@modelattribute("categoryForm") CategoryAddForm categoryForm,BindingResult result){
    categoryForm.save();
    if(result.hasErrors()){
        return new ModelAndView("redirect:/admin/category/add?error");
    }
    return new ModelAndView("redirect:/admin/category/add");
}

解决方法

问题在于，每次请求时您都在创建一个新的CategoryAddForm，并且您没有让spring管理您的bean。如果您要创建CategorAddForm的新实例，spring不会知道他需要向其中注入您的服务。我认为您可以尝试通过构造函数进行注入。