Hello Guys,

Liferay store files using media and document which is default functionality of liferay. Liferay support all type file.

Below code download files with zip folder using "FileEntryID".

NOTE : Liferay fully support to Oracle JDK.

Follow below steps to download files from media and document in liferay.

Step 1 : Create serveResource URL with fileEntryId parameter's.

Step 2 : Put below code in MVCPortlet class.

      private static final String FILE_EXT_SEP = FilenameUtils.EXTENSION_SEPARATOR_STR;
    private static final String ZIP_FILE_EXT_NAME = "zip";
    private static final String ZIP_FILE_EXT = FILE_EXT_SEP + ZIP_FILE_EXT_NAME;
    private static int DEFAULT_DL_FILE_DOWNLOAD_CACHE_MAX_AGE = 1;

@ProcessAction(name="serveResource")
    public void serveResource(ResourceRequest resourceRequest,
            ResourceResponse resourceResponse) throws IOException 
    {

        UploadPortletRequest uploadRequest = PortalUtil.getUploadPortletRequest(resourceRequest);
        String files=(String)uploadRequest.getParameter("iFileEntryId");

        String [] fileIdsArray = getFileIds(files);
        logger.info("fileDownload   "+fileIdsArray[0]);
        if (null == fileIdsArray || files.isEmpty()) {
            SessionErrors.add(resourceRequest, "Please Select File.");
            resourceResponse.setProperty("portlet.http-status-code", "302");
            resourceResponse.addProperty("Location", resourceResponse.createRenderURL().toString());
            return;
        }

        setupResponseHeaders(resourceRequest, resourceResponse);

        try {

            downloadMultipleFilesInZip(resourceRequest, resourceResponse, fileIdsArray);
        } catch (PortalException e) {
            logger.debug("PortalException", e);
        }

    }

    private String[] getFileIds(String fileEntryIds) {
        String[] ids = fileEntryIds.split(",");
        return ids;
    }
private void setupResponseHeaders(ResourceRequest resourceRequest, ResourceResponse resourceResponse) {

        String zipFileMimeType = "application/zip";
        resourceResponse.setContentType(zipFileMimeType);
        int multipleFileDownloadCacheMaxAge = DEFAULT_DL_FILE_DOWNLOAD_CACHE_MAX_AGE;
        if (multipleFileDownloadCacheMaxAge > 0) {
            String cacheControlValue = "max-age=" + multipleFileDownloadCacheMaxAge + ", must-revalidate";
            resourceResponse.addProperty("Cache-Control", cacheControlValue);
        }

        String zipFileName = "ATTACHMENTS_" + new Date().getTime() + ZIP_FILE_EXT;
        String contentDispositionValue = "attachment; filename=\"" + zipFileName + "\"";
        logger.info("resourceResponse>>>> "+contentDispositionValue);
        resourceResponse.addProperty("Content-Disposition", contentDispositionValue);

    }
private void downloadMultipleFilesInZip(ResourceRequest resourceRequest, ResourceResponse resourceResponse, String[] fileIdsArray) throws PortalException {
    try {
        DownloadFilesZipHelper.exportMultipleFilesToZipFile( fileIdsArray, resourceResponse.getPortletOutputStream());
        logger.info("resourceResponse.getPortletOutputStream() >>>> "+resourceResponse.getPortletOutputStream().toString());
    } catch (Exception e) {
        String msg = "Error downloading files " + e.getMessage();
        logger.error(msg, e);
        throw new PortalException(msg, e);
    } 

Step 3 : Create DownloadFilesZipHelper.java and put below code.

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;

import org.apache.commons.io.FilenameUtils;

import com.liferay.portal.kernel.exception.PortalException;
import com.liferay.portal.kernel.exception.SystemException;
import com.liferay.portal.kernel.json.JSONArray;
import com.liferay.portal.kernel.json.JSONFactoryUtil;
import com.liferay.portal.kernel.json.JSONObject;
import com.liferay.portal.kernel.log.Log;
import com.liferay.portal.kernel.log.LogFactoryUtil;
import com.liferay.portal.kernel.repository.model.FileEntry;
import com.liferay.portal.kernel.util.StreamUtil;
import com.liferay.portlet.documentlibrary.service.DLAppServiceUtil;
import com.model.PatientEvents;
import com.service.PatientEventsLocalServiceUtil;

public class DownloadFilesZipHelper {

    private static final Log log = LogFactoryUtil.getLog(DownloadFilesZipHelper.class);

    public static void exportMultipleFilesToZipFile(String[] fileIdsArray, OutputStream outputStream) throws PortalException, SystemException, IOException{

        List<FileEntry> filesList = getMultipleFiles(fileIdsArray);
        if (!filesList.isEmpty()) {
            exportMultipleFilesToOutputStream(filesList, outputStream);
        }
    }

    public static List<FileEntry> getMultipleFiles(String[] fileIdsArray) throws PortalException, SystemException {

        long fileEntryId;
        List<FileEntry> fileEntryList = new ArrayList<FileEntry>();

        for (String fileEntry : fileIdsArray) {
            fileEntryId = Long.parseLong(fileEntry);
            fileEntryList.add(DLAppServiceUtil.getFileEntry(fileEntryId));
        }

        return fileEntryList;
    }

    public static void exportMultipleFilesToOutputStream( List<FileEntry> filesList, OutputStream outputStream) throws IOException, PortalException, SystemException {

        ZipOutputStream zipWriter = null;
        try{
            zipWriter = new ZipOutputStream(outputStream);
            exportMultipleFilesToZipWriter( filesList, zipWriter);
        }catch (Exception e) {
            log.debug("Exception", e);
        }finally{
            if (zipWriter != null) {
                zipWriter.close();
            }
        }
    }

    public static void exportMultipleFilesToZipWriter( List<FileEntry> filesList, ZipOutputStream zipOutputStream){

        InputStream fileInputStream = null;
        try {
            for (FileEntry fileEntry : filesList) {

                String zipEntryPath = buildZipEntryPath( fileEntry, "", zipOutputStream);

                fileInputStream = fileEntry.getContentStream();             

                zipOutputStream.putNextEntry(new ZipEntry(zipEntryPath));
                StreamUtil.transfer(fileInputStream, zipOutputStream, false);

            }
        } catch (Exception e) {         
            log.debug(e);           
        } finally {
            try {
                if (fileInputStream != null) {
                    fileInputStream.close();
                    fileInputStream = null;
                }
            } catch (IOException e) {
                log.debug("IOException", e);
            }           
        }
    }

    private static String buildZipEntryPath( FileEntry fileEntry,
            String folderPath, ZipOutputStream zipOutputStream) throws SystemException,
            PortalException {
        String fileEntryBaseName = fileEntry.getTitle();
        fileEntryBaseName = FilenameUtils.getBaseName(fileEntryBaseName);
        fileEntryBaseName = fileEntryBaseName.replaceAll("\\W+", "_");
        String zipEntryName = folderPath + fileEntryBaseName + FilenameUtils.EXTENSION_SEPARATOR_STR + fileEntry.getExtension();
        log.info("zipEntryName    "+zipEntryName);
        return zipEntryName;
    }
}