java - 如何在 JAXB 解码对象中使用依赖注入(inject)？

Question

我有一个工厂类

@ApplicationScoped /* 'ApplicationScoped' is not a must */
class MyFactory {

   @Inject
   private IService aService;

   ...
}

还有一个 JAXB 注释类

@XmlRootElement(name = "item")
class AnItem {

  @Inject
  MyFactory myFactory;

  ...
}

AnItem 由 JAXB 从 XML 文件实例化。 问题是 myFactory 是 null。如果我将其替换为

...
MyFactory myFactory = new MyFactory();
...

然后 myFactory.aService 为空。

如何在 JAXB 创建的类中使用依赖注入(inject)？

Answer 1

以下解决方案的灵感来自 Block of Adam Warski ，另见 BeanManager Javadoc

首先我需要两个实用方法:

import javax.enterprise.inject.spi.Bean;
import javax.enterprise.inject.spi.BeanManager;
import javax.naming.InitialContext;
import javax.naming.NamingException;

public class Utils {
  public static BeanManager getBeanManager() {
    try {
        InitialContext initialContext = new InitialContext();
        return (BeanManager) initialContext.lookup("java:comp/BeanManager");
    } catch (NamingException e) {
        throw new RuntimeException("Failed to retrieve BeanManager!", e);
    }
  }

  public static <T> T getBean(Class<T> c) {
    T result = null;
    BeanManager bm = getBeanManager();
    Set<Bean<?>> beans = bm.getBeans(c);
    if (! beans.isEmpty()) {
        Bean<?> bean = beans.iterator().next();
        result = c.cast(bm.getReference(bean, c, bm.createCreationalContext(bean)));
    }
    return result;
  }
}

Class AnItem 必须像这样改变:

@XmlRootElement(name = "item")
class AnItem {

  MyFactory myFactory = Utils.getBean(MyFactory.class);

  ...
}