用于 p:selectOneMenu 转换器的应用范围 bean

Question

我已经通过 github 和 PrimeFaces 实现了 PrimeFaces selectOneMenu，但不清楚为什么将 themeservice-bean 定义为应用程序范围，例如

@Named
@ApplicationScoped
public class ThemeService {

    private List<Theme> themes;

    @PostConstruct
    public void init() {
        themes = new ArrayList<>();
        themes.add(new Theme(0, "Nova-Light", "nova-light"));
        themes.add(new Theme(1, "Nova-Dark", "nova-dark"));
        themes.add(new Theme(2, "Nova-Colored", "nova-colored"));
        themes.add(new Theme(3, "Luna-Blue", "luna-blue"));
        themes.add(new Theme(4, "Luna-Amber", "luna-amber"));
        themes.add(new Theme(5, "Luna-Green", "luna-green"));
        themes.add(new Theme(6, "Luna-Pink", "luna-pink"));
        themes.add(new Theme(7, "Omega", "omega"));
    }

    public List<Theme> getThemes() {
        return themes;
    } 
}

在我看来，同一个 bean 应该定义为视图/请求范围，因为列表可能需要填充不同的记录，但是当我更改范围时，它会给出错误

java.lang.NullPointerException
    at org.primefaces.showcase.convert.ThemeConverter.getAsObject(ThemeConverter.java:27)

转换器中的返回语句

                ThemeService service = (ThemeService) fc.getExternalContext().getApplicationMap().get("themeService");
                return service.getThemes().get(Integer.parseInt(value));

也许有人对此有所了解。

Answer 1

您尝试从仅存储应用程序范围 bean 的 applicationMap 获取请求或查看范围 bean。

尝试用getRequestMap或getViewMap替换getApplicationMap。

或者更好的是@Inject the themeService 到你的转换器中：

How to inject @EJB, @PersistenceContext, @Inject, @Autowired, etc in @FacesConverter?