Download de arquivo com JSF - Duvida sobre o response!

Front-end
#1

Estou tento dificuldade para entender como obter um response e usar um stream através dele para enviar um arquivo !
Sempre obtenho o erro.

javax.servlet.ServletException: Servlet response already use Writer, OutputStream not possible

Segue o código …

public class Arquivo {

    private List<Download> downloadList = new ArrayList<Download>();
    private File[] fileList = new File("C:/Users/pirm/Downloads").listFiles();

    public Arquivo() {
        for (int i = 0; i < fileList.length; i++) {
            Download download = new Download(fileList[i]);
            downloadList.add(download);
        }
    }

    public List<Download> getDownloadList() {
        return downloadList;
    }

    public void setDownloadList(List<Download> downloadList) {
        this.downloadList = downloadList;
    }
}
public class Download {

    private File file;

    public Download(File file) {
        this.file = file;
    }

    public File getFile() {
        return file;
    }

    public void setFile(File file) {
        this.file = file;
    }

    public synchronized void download() {
        HttpServletResponse response = (HttpServletResponse) FacesContext.getCurrentInstance().getExternalContext().getResponse();

        response.setHeader("Content-Disposition", "attachment;filename=\"" + file.getName() + "\"");
        response.setContentLength((int) file.length());
        ServletOutputStream out = null;
        try {
            FileInputStream input = new FileInputStream(file);
            byte[] buffer = new byte[1024];
            out = response.getOutputStream();
            int i = 0;
            while ((i = input.read(buffer)) != -1) {
                out.write(buffer);
                out.flush();
            }
            FacesContext.getCurrentInstance().getResponseComplete();
        } catch (IOException err) {
            err.printStackTrace();
        } finally {
            try {
                if (out != null) {
                    out.close();
                }
            } catch (IOException err) {
                err.printStackTrace();
            }
        }
    }
}
<h:form id="arquivos">
                <rich:scrollableDataTable  id="DataTableScrool" value="#{Arquivo.downloadList}" var="downloadItem"
                                           frozenColCount="0"
                                           first="0"
                                           rows="40"
                                           width="300px"
                                           height="396px">
                    <rich:column width="50px">
                        <f:facet name="header" >
                            <h:outputText value="Download"/>
                        </f:facet>
                        <h:outputLink value="#{downloadItem.download()}">
                            <h:outputText value="Download"/>
                        </h:outputLink>
                    </rich:column>
                    <rich:column width="250px">
                        <f:facet name="header" >
                            <h:outputText value="Arquivo"/>
                        </f:facet>
                        <h:outputText value="#{downloadItem.getFile().getName()}">
                            <a4j:support event="onclick" reRender="DataTableScrool"/>
                        </h:outputText>
                    </rich:column>
                </rich:scrollableDataTable>
            </h:form>
#2

Dei uma melhorada no codigo.
É exatamente assim que gostaria de implementar

<h:form id="downloadForm">
                <rich:scrollableDataTable  id="DataTableScrool" value="#{ArquivoDownload.downloadList}" var="item"
                                           frozenColCount="0"
                                           first="0"
                                           rows="40"
                                           width="300px"
                                           height="396px">
                    <rich:column width="50px">
                        <f:facet name="header" >
                            <h:outputText value="Download"/>
                        </f:facet>
                        <h:commandLink value="Download" action="#{item.download()}" immediate="true"/>
                    </rich:column>
                    <rich:column width="250px">
                        <f:facet name="header" >
                            <h:outputText value="Arquivo"/>
                        </f:facet>
                        <h:outputText value="#{item.getFile().getName()}">
                            <a4j:support event="onclick" reRender="DataTableScrool"/>
                        </h:outputText>
                    </rich:column>
                </rich:scrollableDataTable>
            </h:form>

public class ArquivoDownload {

    private List<Download> downloadList = new ArrayList<Download>();
    private File[] fileList = new File("C:/Users/pirm/Downloads/").listFiles();

    public ArquivoDownload() {
        for (int i = 0; i < fileList.length; i++) {
            Download download = new Download(fileList[i]);
            downloadList.add(download);
        }
    }

    public List<Download> getDownloadList() {
        return downloadList;
    }

}

public class Download {

    private File file;

    public Download(File file) {
        this.file = file;
    }

    public File getFile() {
        return file;
    }

    public void setFile(File file) {
        this.file = file;
    }

    public synchronized void download() {
        System.out.println("Executei o download");
        HttpServletResponse response = (HttpServletResponse)FacesContext.getCurrentInstance().getExternalContext().getResponse();
        response.setHeader("Content-Disposition", "attachment;filename=\"" + file.getName() + "\"");
        response.setContentLength((int) file.length());
        try {
            FileInputStream input = new FileInputStream(file);
            ServletOutputStream out = response.getOutputStream();
            byte[] buffer = new byte[1024];
            int i;
            while ((i = input.read(buffer)) != -1) {
                out.write(buffer, 0, i);
            }
            out.flush();
            out.close();
            input.close();
            FacesContext.getCurrentInstance().getResponseComplete();
        } catch (IOException err) {
            err.printStackTrace();
        }
    }
}
#3

Outra melhorada no código …
Escrito como abaixo ele não apresenta erro, porém o download não inicia !!
Já tentei de tudo !

<h:form id="downloadForm">
                <rich:scrollableDataTable  id="DataTableScrool" value="#{ArquivoDownload.fileArray}" var="item"
                                           frozenColCount="0"
                                           first="0"
                                           rows="40"
                                           width="300px"
                                           height="396px">
                    <rich:column width="50px">
                        <f:facet name="header" >
                            <h:outputText value="Download"/>
                        </f:facet>
                        <h:commandLink action="#{ArquivoDownload.download}" value="Download" immediate="true">
                            <f:setPropertyActionListener target="#{ArquivoDownload.path}" value="#{item.absolutePath}"/>
                        </h:commandLink>
                    </rich:column>
                    <rich:column width="250px">
                        <f:facet name="header" >
                            <h:outputText value="Arquivo"/>
                        </f:facet>
                        <h:outputText value="#{item.name}"/>
                    </rich:column>
                </rich:scrollableDataTable>
</h:form>

Bean

public class ArquivoDownload {

    private File[] fileArray = new File("C:/Users/pirm/Downloads/").listFiles();
    private String path;

    public File[] getFileArray() {
        return fileArray;
    }

    public void setFileArray(File[] fileArray) {
        this.fileArray = fileArray;
    }

    public String getPath() {
        return path;
    }

    public void setPath(String path) {
        this.path = path;
    }

    public synchronized void download() {
        System.out.println("Metodo download()");
        File file = new File(path);
        HttpServletResponse response = (HttpServletResponse) FacesContext.getCurrentInstance().getExternalContext().getResponse();
        response.setHeader("Content-Disposition", "attachment;filename=\"" + file.getName() + "\"");
        response.setContentLength((int) file.length());
        try {
            FileInputStream input = new FileInputStream(file);
            ServletOutputStream out = response.getOutputStream();
            byte[] buffer = new byte[1024];
            int i;
            while ((i = input.read(buffer)) != -1) {
                out.write(buffer, 0, i);
            }
            out.flush();
            out.close();
            input.close();
            FacesContext.getCurrentInstance().getResponseComplete();
        } catch (IOException err) {
            err.printStackTrace();
        }
    }
}

Ele nem mostra a saida do metodo

System.out.println("Metodo download()");
#4

Estou com esse mesmo problema, alguem sabe como resolver?

#5

fiz uma implementação e um post sobre isso tem exemplo la do projeto para baixar

http://brunodanielmarinho.wordpress.com/2011/08/26/download-de-arquivos-do-servidor/

#6