Question

我尝试使用@Injection，所以从这里开始一个简单的例子：

界面

public interface NumberGenerator {
    String generateNumber();
}

bookService的

public class BookServices {

    @Inject
    @ThirteenNumber
    private NumberGenerator generator;

    public Book createBook(String title){
        return new Book(title, generator.generateNumber());
    }
}

图书对象

public class Book {

    private String title;
    private String isbn;

    public Book() {
    }

    public Book(String title, String isbn) {
        this.title = title;
        this.isbn = isbn;
    }

    //getters and setters
}

CDI

@Named(value = "injectionTest") 
@ViewScoped 
public class InjectionTest implements Serializable {

    public void showResult() {
        BookServices bookService = new BookServices();
        Book book = bookService.createBook("Java book");
        System.out.println(book.toString());
    }

    //...
}

十三号实施

@ThirteenNumber
public class IsbnGenerator implements NumberGenerator{

    @Override
    public String generateNumber(){
        return "13-84333-" + Math.abs(new Random().nextInt());
    }
}

问题

当我尝试拨打bookService.createBook("Java book")时，它会java.lang.NullPointerException generator.generateNumber()，我认为它不会调用正确的@Qualifier，试图解决此问题，使用此功能链接，Java EE 7 CDI - Injection doesn't work, sending NullPointerException我添加所有依赖项但问题仍然相同？

我错过了什么吗？

注意我知道What is a NullPointerException, and how do I fix it?

谢谢。

Answer 1

问题是new BookServices()课程中的InjectionTest。 new运算符会中断CDI。只需@Inject BookServices bean。

@Inject @ThirteenNumber抛出NullPointException

1 个答案: