Question

尝试获取blob并将其转换为流式内容。我得到了字节，它们确实被转换为ByteArrayInputStream，我正在返回StremedContent图像，但我一直得到这个：

    SEVERE: Servlet.service() for servlet [Faces Servlet] in context with path [/ConfigEmployee] threw exception
    java.io.IOException: java.lang.NullPointerException
Caused by: java.lang.NullPointerException
    at org.primefaces.application.resource.StreamedContentHandler.handle(StreamedContentHandler.java:56)
    ... 21 more

第56行有：externalContext.setResponseContentType(streamedContent.getContentType());

我需要补充一点，每个Image对象返回两次流内容。

图片bean：

public Image(byte[] bytes,String name)
    {
        this.id=new MyDatabase().getLastId("image")+1;
        this.name=name;
        this.byteData=bytes;

        InputStream is=new ByteArrayInputStream(bytes);
        this.image = new DefaultStreamedContent(is,"image/png");

    }
public StreamedContent getImage() 
    {
        return image;
    }

HTML代码

<div class="dataTable">
            <h:form id="imageList">
                <p:dataTable var="img" value="#{imageView.images}" rowKey="#{img.id}" rows="10" lazy="true" paginator="true">
                    <p:column headerText="Image">
                        <p:graphicImage style="width:80px; height:80px" value="#{img.image}" />
                    </p:column>
                    <p:column width="200" headerText="Name">
                        <h:outputText value="#{img.name}" />
                    </p:column>
                    <p:column width="200" headerText="Edit">
                        <h:commandButton value="Enter" actionListener="#{imageView.convertImage(img)}" action="Image?faces-redirect=true" />
                    </p:column>
                </p:dataTable>


            </h:form>
        </div>

延迟加载

@Override
    public List<Image> load(int first, int pageSize, String sortField, SortOrder sortOrder,
            Map<String, Object> filters)
    {
        db.openDatabase();
        ResultSet rs = db.getImage();

        List<Image> imgList = new ArrayList<Image>();

        try
        {
            if (rs.last())
                this.setRowCount(rs.getRow());

            for (rs.absolute(first); rs.next() && first <= (first + pageSize); first++)
            {
                imgList.add(new Image(rs.getBytes("byteData"), rs.getString("name")));

            }
        }
        catch (SQLException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        finally
        {
            db.closeDatabase();
        }
        return imgList;
    }

Primefaces 5.1，JSF 2.2，Tomcat v7.0

Answer 1

bean的范围是什么，它应该是View或Session作用域，您必须更改访问bean的方式。对于动态创建的图像，正在发送两个请求。一个呈现HTML，呈现img标记。比第二个，基于 src 属性触发。模型必须保留后续请求中的值。

所有人都在这里精美地解释Display dynamic image from database with p:graphicImage and StreamedContent

p：graphicImage streamContent nullpointer

1 个答案: