Vaadin视图中的自动装配服务和组件不起作用 [英] Autowiring services in Vaadin view and components not working

问题描述

您好，程序员们！我对Vaadin来说还比较陌生，所以请饶恕我。
我正尝试将服务层自动连接到我的视图中，如下所示：

Hello fellow programmers! I am relatively new to Vaadin so spare me please. I am trying to autowire my service layer into my view as follows:

@Route("")
@PWA(name = "First time bruh", shortName = "Project Base")
public class MainView extends VerticalLayout {

    private TextField filterText = new TextField();
    private Grid<Customer> grid = new Grid<>(Customer.class);
    private CustomerForm customerForm = new CustomerForm(this);

    @Autowired
    private CustomerService customerService;

并且customerService依赖项注入正常工作，但是当我尝试在组件中使用它时，它返回null ：

and the customerService dependency injections works properly, however when i try to use it in a component it returns null:

@Route
public class CustomerForm extends FormLayout {

    @Autowired
    private CustomerService customerService;

我尝试使用@Component和@SpringComponent注释类，但是依赖项注入不起作用，并且我认为问题不是出自该类不是bean的事实，因为MainView类也不是bean。

I've tried annotating the class with @Component and @SpringComponent but the dependency injection does not work and i think that the problem does not come from the fact that the class is not a bean, because MainView Class is also not a bean.

我的愿望是自定义子组件我创建的可以访问服务层。

My wish is the custom sub components that i create to have access to the service layer.

在此先感谢您的帮助！

推荐答案

在Vaadin UI中，您只能在路由端点（具有 @Route 批注的视图）中注入，并且仅当该视图由导航到注释中指定的路线。 （因为只有这样，该视图的实例化才会自动完成。）

In Vaadin UI, you can inject only in route endpoints (views that have the @Route annotation), and only if that view is opened by navigating to the route specified in the annotation. (Because only then then instantiation of that view is done "automatically").

根据经验：每当您使用实例化某些对象时， new 关键字，注入/自动装配无效。

As a rule of thumb: Whenever you instantiate something yourself using the new keyword, injection/autowiring does not work.

我对您的情况了解是：

MainView ，在其中您要添加 CustomerForm 。

What I understand of your situation is:
You have a MainView, within that you want to add a CustomerForm.

以下是实现该目标的方法：

将 CustomerService 注入到 MainView ，并将 CustomerService 实例传递到 CustomerForm 的构造函数中

Here is how to achieve that:
Inject the CustomerService into the MainView, and pass the CustomerService instance into the constructor of CustomerForm

@Route
public class MainView extends VerticalLayout {
    public MainView(CustomerService customerService) { // customerService will be injected
        CustomerForm customerForm = new CustomerForm(customerService);
        add(customerForm);
    }
}

public class CustomerForm extends FormLayout {
    public CustomerForm (CustomerService customerService){
        ...
    }
}

另一种方法是使 CustomerForm a @Component （一定要记得在spring配置类中对其进行了正确的扫描），将服务注入其中，然后将整个表单注入到 MainView ：

Another approach would be to make the CustomerForm a@Component (do remember to scan it properly in the spring configuration class), inject the service into it, and then inject the whole form into the MainView:

@Route
public class MainView extends VerticalLayout {
    public MainView(CustomerForm customerForm) {  // customerForm will be injected
        add(customerForm);
    }
}

@Component
public class CustomerForm extends FormLayout {
    public CustomerForm (CustomerService customerService){ // customerService will be injected
        ...
    }
}

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