Download File Upload/Download HOWTO

File Upload/Download HOWTO
This document covers the simplest upload & download cases (with storage on
the local filesystem), and then extends those simple examples to cover storage in
a database. This is the script I followed during todayʼs File Upload/Download
Master Tutorial, updated for 4.0.
You should have some knowledge of WaveMaker already; especially dropping
widgets, creating database services, and some knowledge of Java.
It is organized into 4 sections; each section builds upon the previous ones.
Sample projects are included for the results of each section.
UPLOAD
Weʼll begin by creating a project that uploads files to the serverʼs local disk.
1. Create a new project (named anything.)
2. Create a new Java Service. Both the serviceId and className can be
anything; this guide will assume a serviceId of “fileTransfer” and a
className of “FileTransfer.”
3. Now, weʼll add a method to the Java Service. When youʼve pasted this in,
hit the save button and make sure everything works. Windows users,
youʼll have to change the location of UPLOADS; Mac and Linux users
should be fine, but they might choose a more appropriate location. Make
sure that directory exists, too.
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import org.apache.commons.io.IOUtils;
import org.springframework.web.multipart.MultipartFile;
import com.wavemaker.runtime.server.ParamName;
/**
* This is a client-facing service class. All
* public methods will be exposed to the client. Their return
* values and parameters will be passed to the client or taken
* from the client, respectively. This will be a singleton
* instance, shared between all requests.
*/
public class FileTransfer {
/** UPLOADS stores the location of files on disk.
Windows
users
* must update this; Mac & Linux should be fine. */
private File UPLOADS = new File("/tmp/uploads");
public void doUpload(@ParamName(name="file") MultipartFile
file) throws IOException {
File outputFile = new File(UPLOADS,
file.getOriginalFilename());
System.out.println("writing the content of uploaded
file to: "+outputFile);
FileOutputStream fos = new
FileOutputStream(outputFile);
IOUtils.copy(file.getInputStream(), fos);
file.getInputStream().close();
fos.close();
}
}
4. Now, switch to the designer. Add a FileUpload widget, and set the service
and operation to match the JavaService service name, and the method we
just created in the Java Service.
5. Hit run, and test your new file upload widget. You should see files appear
in where you set the UPLOAD variable.
DOWNLOAD
1. Copy the project to a new one.
2. Add the following imports into the top of your JavaService file.
import com.wavemaker.runtime.server.DownloadResponse;
import java.io.FileInputStream;
3. Add this new method into your JavaService, and hit save. Everything
should work.
public DownloadResponse doDownload(@ParamName(name="filename")
String filename) throws IOException {
DownloadResponse ret = new DownloadResponse();
File localFile = new File("/tmp/uploads", filename);
FileInputStream fis = new FileInputStream(localFile);
ret.setContents(fis);
ret.setFileName(filename);
return ret;
}
4. Switch back to the designer, and drop a new editor, with an onchange
javascript like this:
editor1Change: function(inSender, inDisplayValue, inDataValue) {
this.label1.setLink("services/fileTransfer.download?method=
doDownload&filename="+inDisplayValue);
},
5. Drop a new label (label1), change the label to download
6. Hit run to test your new download widget. You should enter the name of a
file youʼve already uploaded, blur out of the editor widget, and then hit the
download link to try to the download.
UPLOAD TO DB
1. Import the database (filedb.sql) into your MySQL installation, via something
like this:
> cat filedb.sql | mysql -u root
2. In the datamodel editor, import that database into your project.
3. Switch to the queries tab, make a new query called getMaxId, with the
query string:
select max(id) from Files
4. Hit run to generate the database service file (while the table files are
created on import, you need to run before the service class is generated &
compiled.)
5. Edit the java service, add:
import com.filedb.Filedb;
import com.filedb.data.Files;
import com.wavemaker.runtime.RuntimeAccess;
6.Replace the old doUpload method with this new one:
public void doUpload(@ParamName(name="file") MultipartFile file)
throws IOException {
Filedb filedb = (Filedb)
RuntimeAccess.getInstance().getService("filedb");
Files f = new Files();
f.setFilename(file.getOriginalFilename());
f.setId(filedb.getMaxId()+1);
System.out.println("writing the content of uploaded file
to: "+f.getFilename());
f.setContents(IOUtils.toByteArray(file.getInputStream()));
filedb.insert(f);
file.getInputStream().close();
}
7. Test your upload by running your application, try the upload widget (the
same widget we created above), and make sure your database has the
new rows.
DOWNLOAD FROM DB
1. Add a new query, named getFilesByName, and with the query string:
from Files _a where _a.filename=:filename
It should have a single bind parameter “filename”, type String.
2. Add a new import to the Java service:
import java.io.ByteArrayInputStream;
3. Replace the existing doDownload method with this one:
public DownloadResponse doDownload(@ParamName(name="filename")
String filename) throws IOException {
Filedb filedb = (Filedb)
RuntimeAccess.getInstance().getService("filedb");
DownloadResponse ret = new DownloadResponse();
Files file = filedb.getFilesByName(filename);
ret.setContents(new
ByteArrayInputStream(file.getContents()));
ret.setFileName(file.getFilename());
return ret;
}
4. Run your application, and verify that the download widget still works, and
that it retrieves information from the database (maybe by clearing our the
upload directory on disk.)