在JavaEE中使用@inject注释时的NullPointerException

Question

@Singleton
public class QuotesLoaderBean {

Properties quotes;
Properties names;
@Inject
public QuoteRepository repo;

public QuotesLoaderBean() {
}

@PostConstruct
public void init() {
    InputStream quotesInput = this.getClass().getClassLoader().getResourceAsStream("quotes.properties");
    InputStream namesInput = this.getClass().getClassLoader().getResourceAsStream("names.properties");

    quotes = new Properties();
    names = new Properties();
    try {
        quotes.load(quotesInput);
        names.load(namesInput);
    } catch (IOException ex) {
        Logger.getLogger(QuotesLoaderBean.class.getName()).log(Level.SEVERE, null, ex);
    }
}

public Citation createCitation(String quote) {
    Citation citation = new Citation();
    citation.setQuote(quote);
    citation.setWho(getName());
    repo.save();
    return citation;
}

public Citation getCitation() {
    Citation citation = new Citation();
    citation.setQuote(getQuote());
    citation.setWho(getName());
    return citation;
}

public String getQuote() {
    Enumeration keys = quotes.propertyNames();
    int elementNumber = new Random().nextInt(quotes.keySet().size());
    return quotes.getProperty(getElement(keys, elementNumber));
}

public String getName() {
    Enumeration keys = names.propertyNames();
    int elementNumber = new Random().nextInt(names.keySet().size());
    return names.getProperty(getElement(keys, elementNumber));
}

private String getElement(Enumeration keys, int elementNumber) {
    int i = 0;
    while (keys.hasMoreElements()) {
        if (i == elementNumber) {
            return (String) keys.nextElement();
        } else {
            i++;
            keys.nextElement();
        }
    }
    return null;
}
}

@Singleton
public class QuoteRepository {

public String save() {
    Gson gson = new GsonBuilder().create();
    return "Saved...";
}

}

Answer 1

当我测试createCitation方法时，我总是得到一个NullPointerException

您不能简单地测试您的应用程序，因为您将创建对象的责任委托给了容器，而容器在单元测试中（我假设您使用它）是不存在的。

public Citation createCitation(String quote) {
    Citation citation = new Citation();
    citation.setQuote(quote);
    citation.setWho(getName());
    repo.save(); // repo isn't initialized
    return citation;
}

如果要测试代码，请模拟repo对象或使用集成测试。