流动态资源出错.空值

Question

流动态资源出错.空值

重要提示:自2015年4月8日发布的PrimeFaces 5.2 final(社区发布)以来,此问题已得到修复.因此,如果您碰巧使用该版本或更新版本,则无需使用临时解决方法.

现在可以安全地修改先前给出的示例,如下所示.

public StreamedContent getImage() throws IOException {
    FacesContext context = FacesContext.getCurrentInstance();

    if (context.getCurrentPhaseId() == PhaseId.RENDER_RESPONSE) {
        return new DefaultStreamedContent();
    } else {
        String id = context.getExternalContext().getRequestParameterMap().get("id");
        byte[] bytes = Utils.isNumber(id) ? service.findImageById(Long.parseLong(id)) : null;
        return bytes == null ? null : new DefaultStreamedContent(new ByteArrayInputStream(bytes));
    }
}

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LONGBLOB在我厌倦了操作/管理存储在磁盘文件系统中的图像之后,我已经以BLOB()的形式将图像移动到数据库(MySQL).

因此,我正在<p:dataTable>如下显示图像(从这里公然复制:)).

<p:column headerText="Header">
    <p:graphicImage value="#{bannerBean.image}" height="200" width="200">
        <f:param name="id" value="#{row.bannerId}"/>
    </p:graphicImage>
<p:column>

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检索图像的bean如下所示.

@ManagedBean
@ApplicationScoped
public final class BannerBean
{
    @EJB
    private final BannerBeanLocal service=null;
    public BannerBean() {}

    public StreamedContent getImage() throws IOException {
        FacesContext context = FacesContext.getCurrentInstance();

        if (context.getCurrentPhaseId() == PhaseId.RENDER_RESPONSE) {
            return new DefaultStreamedContent();
        }
        else {
            String id = context.getExternalContext().getRequestParameterMap().get("id");
            byte[] bytes = service.findImageById(Long.parseLong(id));
            return bytes==null? new DefaultStreamedContent():new DefaultStreamedContent(new ByteArrayInputStream(bytes));
        }
    }
}

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只要底层数据库表的每一行中都有图像,这样就可以正常工作.

但是,数据库中的BLOB类型列在某些情况下是可选的,因此它也可以包含null值.

如果此时数据库中任何行中的此列,null则抛出以下异常.

SEVERE:   Error in streaming dynamic resource. null
WARNING:   StandardWrapperValve[Faces Servlet]: Servlet.service() for servlet Faces Servlet threw exception
java.lang.NullPointerException
    at org.primefaces.application.PrimeResourceHandler.handleResourceRequest(PrimeResourceHandler.java:127)
    at javax.faces.application.ResourceHandlerWrapper.handleResourceRequest(ResourceHandlerWrapper.java:153)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:643)
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:344)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
    at org.primefaces.webapp.filter.FileUploadFilter.doFilter(FileUploadFilter.java:70)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:256)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:316)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
    at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:357)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:260)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:188)
    at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:191)
    at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:168)
    at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:189)
    at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:288)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:206)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:136)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:114)
    at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
    at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:838)
    at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:113)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:115)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:55)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:135)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:564)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:544)
    at java.lang.Thread.run(Thread.java:722)

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那么如何管理nullBLOB以便这个异常消失呢？

返回new DefaultStreamedContent(new ByteArrayInputStream(new byte[0])),如果托管bean中的字节数组为null将抑制异常,但毕竟这不应该是一个解决方案.这是一个理想的解决方案？

在这种情况下,返回字节数组的EJB方法完全没有必要.

public byte[] findImageById(Long id)
{
    CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
    CriteriaQuery<byte[]>criteriaQuery=criteriaBuilder.createQuery(byte[].class);
    Root<BannerImages> root = criteriaQuery.from(BannerImages.class);
    criteriaQuery.multiselect(root.get(BannerImages_.bannerImage));
    ParameterExpression<Long>parameterExpression=criteriaBuilder.parameter(Long.class);
    criteriaQuery.where(criteriaBuilder.equal(root.get(BannerImages_.bannerId), parameterExpression));
    List<byte[]> list = entityManager.createQuery(criteriaQuery).setParameter(parameterExpression, id).getResultList();
    return list!=null&&!list.isEmpty()?list.get(0):null;
}

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Answer 1

Bal*_*usC 8

这是一个错误(至少是一个功能/技术设计错误)PrimeResourceHandler.它不应该假设动态资源或其内容永远不会null.它应该有条件地检查是否是这种情况,然后只是返回HTTP 404"未找到"响应.

换句话说,而不是

85    streamedContent = (StreamedContent) ve.getValue(eLContext);
86 
87    externalContext.setResponseStatus(200);
88    externalContext.setResponseContentType(streamedContent.getContentType());

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他们应该做的

85    streamedContent = (StreamedContent) ve.getValue(eLContext);
86 
87    if (streamedContent == null || streamedContent.getStream() == null) {
88        externalContext.responseSendError(HttpServletResponse.SC_NOT_FOUND, ((HttpServletRequest) externalContext.getRequest()).getRequestURI());
89        return;
90    }
91
92    externalContext.setResponseStatus(200);
93    externalContext.setResponseContentType(streamedContent.getContentType());

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这样你就可以从方法中返回null或者为空来生成一个像样的404.StreamedContentgetImage()

那么,你能做什么？

向他们报告并希望他们能解决它.更新他们在5.2版中修复了它.
和/或把一个副本的PrimeResourceHandler类在你的Web应用程序项目的Java源文件夹中,正是它自己的org.primefaces.application包,然后只需编辑它包括提到的变化,最后只是建立/部署你的web应用项目作为WAR如常.类中的类/WEB-INF/classes具有比JAR中更高的类加载优先级/WEB-INF/lib,因此将使用修改后的类.

该错误被列为未来版本的新功能.怎么可能,它以前一直在工作.差不多半年了,没有修好.对我来说,这是应该起作用的基本功能？!链接:https://code.google.com/p/primefaces/issues/detail？id = 7010&thanks = 7010&ts = 1401434015 (2认同)

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