File upload 如何删除已上载的图像以替换primefaces中的另一个图像？

我只是primefaces的初学者，我只是想知道如何删除上传的文件。另一个问题是，在标签中，我可以显示上载的文件以进行更新或删除吗？这是否得到了法律的支持？我上传的文件尚未在磁盘或数据库中，但仍然是一个对象。我的代码如下。请帮帮我或者给我一些建议

这是fileupload.xhtml

这是我的web.xml

<servlet>
    <servlet-name>Faces Servlet</servlet-name>
    <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
    <servlet-name>Faces Servlet</servlet-name>
    <url-pattern>*.xhtml</url-pattern>
</servlet-mapping>

<context-param>
    <description>State saving method: 'client' or 'server' (=default). See JSF Specification 2.5.2</description>
    <param-name>javax.faces.STATE_SAVING_METHOD</param-name>
    <param-value>server</param-value>
</context-param>
<listener>
    <listener-class>com.sun.faces.config.ConfigureListener</listener-class>
</listener>

<filter>
    <filter-name>PrimeFaces FileUpload Filter</filter-name>
    <filter-class>org.primefaces.webapp.filter.FileUploadFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>PrimeFaces FileUpload Filter</filter-name>
    <servlet-name>Faces Servlet</servlet-name>
</filter-mapping>

private UploadedFile uploadFile;
public UploadedFile getUploadFile() {
    return uploadFile;
}

public void setUploadFile(UploadedFile uploadFile) {
    this.uploadFile = uploadFile;
}

public void handleFileUpload(FileUploadEvent event){
    uploadFile = event.getFile();
    System.out.println("UploadFileName is" + uploadFile.getFileName());

    byte[]image = event.getFile().getContents();
    productCode.setImage(image);
}

<servlet>
    <servlet-name>Faces Servlet</servlet-name>
    <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
    <servlet-name>Faces Servlet</servlet-name>
    <url-pattern>*.xhtml</url-pattern>
</servlet-mapping>

<context-param>
    <description>State saving method: 'client' or 'server' (=default). See JSF Specification 2.5.2</description>
    <param-name>javax.faces.STATE_SAVING_METHOD</param-name>
    <param-value>server</param-value>
</context-param>
<listener>
    <listener-class>com.sun.faces.config.ConfigureListener</listener-class>
</listener>

<filter>
    <filter-name>PrimeFaces FileUpload Filter</filter-name>
    <filter-class>org.primefaces.webapp.filter.FileUploadFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>PrimeFaces FileUpload Filter</filter-name>
    <servlet-name>Faces Servlet</servlet-name>
</filter-mapping>