使用@Autowired将依赖关系注入到使用“new ...”创建的对象中。 [英] Injecting dependencies using @Autowired into objects created with "new ..."

问题描述

将bean注入helper类时遇到问题。它基本上是这样的：我在页面构造函数中创建了一个对象，它可以完成一些工作，返回一些数据并在页面上显示这些数据。在此辅助对象中，应通过 @Autowired 注释注入服务。但是，当我使用它时，我总是得到一个空指针异常。我也试过 @SpringBean 但它没有帮助。另一方面，当我使用 @SpringBean 将此服务直接注入页面时，它可以访问并且正常工作。你知道问题出在哪里吗？

I have a problem with injecting a bean into a helper class. It works basically like this: I create an object in the page constructor that does some work, returns some data and I show these on the page. In this helper object, a service should be injected via @Autowired annotation. However, I always get a null pointer exception when I use it. I also tried @SpringBean but it didn't help. On the other hand, when I inject this service directly into the page with @SpringBean, it's accessible and works fine. Do you know where the problem is?

这是页面：

public class Page extends BasePage {
    public Page() {
        HelperObject object = new HelperObject(new Application("APP_NAME"));
        String result = object.getData();

        add(new Label("label", result));
    }
}

帮助对象：

public class HelperObject {
    private Application app;

    @Autowired
    private Service service;

    public HelperObject(Application app) {
        this.app = app;
    }

    public String getData() {
        // use service, manipulate data, return a string
    }
}

推荐答案

@SpringBean 仅注入依赖于继承自Wicket的组件的类。 @Autowired 仅将依赖项注入Spring自己创建的类中。这意味着您不能自动将依赖项注入您使用 new 创建的对象。

@SpringBean only injects dependencies into classes that inherit from Wicket's Component. @Autowired only injects dependencies into classes created by Spring itself. That means you can't automatically inject a dependency into an object you create with new.

（编辑：你也可以通过在构造函数中注入来向您的类添加 @SpringBean 注入：
InjectorHolder.getInjector（）。inject（this）; ）

( you can also add a @SpringBean injection to your class by injecting in the constructor: InjectorHolder.getInjector().inject(this);)

我的正常解决方法是使用我的应用程序类来提供帮助。 （我对你使用新应用程序（...）感到有些困惑。我认为这实际上不是 org.apache.wicket .Application 。）例如：

My normal workaround for this is to use my application class to help. (I'm a little puzzled by your use of new Application(...). I assume this isn't actually org.apache.wicket.Application.) For example:

public class MyApplication extends AuthenticatedWebApplication implements
    ApplicationContextAware {

    private ApplicationContext ctx;

    public void setApplicationContext(ApplicationContext applicationContext)
        throws BeansException {
        this.ctx = applicationContext;
    }

    public static MyApplication get() {
        return (MyApplication) WebApplication.get();
    }

    public static Object getSpringBean(String bean) {
        return get().ctx.getBean(bean);
    }

    public static <T> T getSpringBean(Class<T> bean) {
        return get().ctx.getBean(bean);
    }

    ....
}

在我的Spring应用程序上下文中：

In my Spring application context:

<!-- Set up wicket application -->
<bean id="wicketApplication" class="uk.co.humboldt.Project.MyApplication"/>

我的帮助对象然后按需查找服务：

My helper object then looks up the service on demand:

public class HelperObject {

    private Service getService() {
        return MyApplication.getSpringBean(Service.class);
    }

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