无法在p：graphicImage中显示图像

Question

我使用相同的代码使用p：graphicImage显示图像，但我无法找到它无效的原因。

我之前使用的是这个代码，因为在我的应用程序中，并不是每个数据库条目都有一个映像，所以我这样做是为了避免空blob。

现在我重写它与Display dynamic image from database with p:graphicImage and StreamedContent中的答案完全相同，但它仍然无效：（

我使用完全相同的代码在完全相同的p中显示图像：在另一个.xhtml中重复并且它完美地工作。

在调试会话期间，我看到它调用另一个在.xhtml中没有任何引用的ManagedBean。

    @ManagedBean
    @ViewScoped
    public class PatenteService implements Serializable {

        private StreamedContent fotoPatente;

        public StreamedContent getFotoPatente() throws IOException {
            String inputId = "";
            Patente p;
            byte[] bytes;
            FacesContext context = FacesContext.getCurrentInstance();

            byte[] defaultBytes; // ... Retrieve deafult image to show if db resgistry has it not

            if (context.getCurrentPhaseId() == PhaseId.RENDER_RESPONSE) {
                return new DefaultStreamedContent(new ByteArrayInputStream(defaultBytes));
            } else {
                inputId = context.getExternalContext().getRequestParameterMap().get("patenteId");

                if (!inputId.equals("")) {
                    p = (Patente) EManager.getInstance().createNamedQuery("Patente.findById").setParameter("id", Integer.parseInt(inputId)).getSingleResult();
                    bytes = p.getFoto();
                } else {
                    bytes = null;
                }

                if (bytes != null) {
                    return new DefaultStreamedContent(new ByteArrayInputStream(bytes));
                } else {
                    return new DefaultStreamedContent(new ByteArrayInputStream(defaultBytes));
                }
            }
        }

        public void setFotoPatente(StreamedContent fotoPatente) {
            this.fotoPatente = fotoPatente;
        }
    }

错误：

01-Sep-2017 18:13:19.716 GRAVE [http-nio-8080-exec-7] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [Faces Servlet] in context with path [/prorec] threw exception
 java.io.IOException: java.lang.NullPointerException
    at org.primefaces.application.resource.StreamedContentHandler.handle(StreamedContentHandler.java:103)
    at org.primefaces.application.resource.PrimeResourceHandler.handleResourceRequest(PrimeResourceHandler.java:95)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:643)
...
Caused by: java.lang.NullPointerException
    at com.sun.faces.mgbean.BeanManager$ScopeManager$ViewScopeHandler.getFromScope(BeanManager.java:566)
    at com.sun.faces.mgbean.BeanManager$ScopeManager.getFromScope(BeanManager.java:477)
01-Sep-2017 18:13:19.868 GRAVE [http-nio-8080-exec-4] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [Faces Servlet] in context with path [/prorec] threw exception
 java.io.IOException: java.lang.NullPointerException
    at org.primefaces.application.resource.StreamedContentHandler.handle(StreamedContentHandler.java:103)
    at org.primefaces.application.resource.PrimeResourceHandler.handleResourceRequest(PrimeResourceHandler.java:95)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:643)
...
Caused by: java.lang.NullPointerException
    at com.sun.faces.mgbean.BeanManager$ScopeManager$ViewScopeHandler.getFromScope(BeanManager.java:566)
    at com.sun.faces.mgbean.BeanManager$ScopeManager.getFromScope(BeanManager.java:477)
    at com.sun.faces.mgbean.BeanManager.getBeanFromScope(BeanManager.java:240)

01-Sep-2017 18:13:19.715 GRAVE [http-nio-8080-exec-7] org.primefaces.application.resource.StreamedContentHandler.handle Error in streaming dynamic resource.
 java.lang.NullPointerException
    at com.sun.faces.mgbean.BeanManager$ScopeManager$ViewScopeHandler.getFromScope(BeanManager.java:566)
    at com.sun.faces.mgbean.BeanManager$ScopeManager.getFromScope(BeanManager.java:477)
    at com.sun.faces.mgbean.BeanManager.getBeanFromScope(BeanManager.java:240)
...
01-Sep-2017 18:13:19.867 GRAVE [http-nio-8080-exec-4] org.primefaces.application.resource.StreamedContentHandler.handle Error in streaming dynamic resource.
 java.lang.NullPointerException
    at com.sun.faces.mgbean.BeanManager$ScopeManager$ViewScopeHandler.getFromScope(BeanManager.java:566)
    at com.sun.faces.mgbean.BeanManager$ScopeManager.getFromScope(BeanManager.java:477)
    at com.sun.faces.mgbean.BeanManager.getBeanFromScope(BeanManager.java:240)