Question

我试图将图像文件上传到数据库。在保存图像之前，我想将其显示给用户。

我有一个请求范围的bean，UserInfoBean（我无法改变请求范围）我试图用来保存数据，但是preview字节[调用paint时，为null。有没有办法能够保存preview或image，在调用paint（）时要访问的UploadItem？

info.xhtml代码：

<a4j:outputPanel id="preview" 
                    <a4j:mediaOutput id="imgPreview"
                                     element="img"
                                     mimeType="image/jpeg"
                                     createContent="#{userInfo.paint}"
                                     cacheable="false"
                                     style="width:150px; height:100px;" />
                    <br/>
 </a4j:outputPanel>

  <a4j:outputPanel id="signatureStampDisplay">
            <br/>                
            <rich:fileUpload fileUploadListener="#{userInfo.uploadImage}"
                             id="upload"
                             listHeight="40px"
                             acceptedTypes="#{userInfo.supportedTypes}"
                             ontyperejected="alert('Only JPG, GIF, PNG, BMP, and TIF files are accepted');"
                             maxFilesQuantity="1"
                             immediateUpload="true"
                             autoclear ="true"
                             disabled="#{userInfo.stampSet}">
                             <a4j:support event="onuploadcomplete"
                                          limitToList="true"
                                          reRender="preview"/>
            </rich:fileUpload>

        </a4j:outputPanel>

UserInfoBean的一部分，包含UploadItem图片和byte[]预览：

public void uploadImage(UploadEvent evt) throws IOException{
        image = evt.getUploadItem();
        if(image != null){
             //preview is a byte[]
             preview = FileUtils.readFileToByteArray(image.getFile());
        }
    }

public void paint(OutputStream stream, Object object) throws IOException{
        if(preview != null){
             stream.write(preview);
        }
    }

Answer 1

由于bean是请求范围，因此无法传递。

使用HttpSession对象javax.servlet.http.HttpSession;

我能够在需要时存储字节[] preview，在paint

中显示后将其从会话中删除

public void uploadImage(UploadEvent evt) throws IOException{
        image = evt.getUploadItem();
        if(image != null){
             preview = FileUtils.readFileToByteArray(signature.getFile());
             HttpSession session = (HttpSession) FacesContext.getCurrentInstance().getExternalContext().getSession(true);
             session.setAttribute("preview", preview);
        }
    }

public void paint(OutputStream stream, Object object) throws IOException{
        HttpSession session = (HttpSession) FacesContext.getCurrentInstance().getExternalContext().getSession(true);
        preview = (byte[]) session.getAttribute("preview");
        if(preview != null){
            stream.write(preview);
            stream.close();
            session.removeAttribute("preview");
            signaturePreview = null;
        }
    }

显示使用请求范围的bean上载的图像

1 个答案: