3.9.8.3. FileLoader Interface
The FileLoader
interface allows you to work with file storage using the same set of methods on both middle and client tiers. Uploading and downloading of files is performed using streams:
-
saveStream()
– saves anInputStream
contents into file storage. -
openStream()
– returns an input stream to load a file contents from file storage.
Both client-side and server-side implementations of |
As an example of using FileLoader
let’s consider a simple task of saving a user input into the text file and displaying the file content in another field on the same screen.
The screen contains two textArea
fields. Suppose the user inputs text in the first textArea
, clicks the buttonIn
below, and the text is saved to the FileStorage
. The second textArea
will display the content of the saved file on buttonOut
click.
Below is the fragment of the screen XML descriptor:
<hbox margin="true"
spacing="true">
<vbox spacing="true">
<textArea id="textAreaIn"/>
<button id="buttonIn"
caption="Save text in file"
invoke="onButtonInClick"/>
</vbox>
<vbox spacing="true">
<textArea id="textAreaOut"
editable="false"/>
<button id="buttonOut"
caption="Show the saved text"
invoke="onButtonOutClick"/>
</vbox>
</hbox>
The screen controller contains two methods invoked on buttons click:
-
In the
onButtonInClick()
method we create a byte array from the firsttextArea
input. Then we create aFileDescriptor
object and define the new file name, extension, size, and creation date with its attributes.Then we save the new file with the
saveStream()
method ofFileLoader
, passing theFileDescriptor
to it and providing the file content with anInputStream
supplier. We also commit theFileDescriptor
to the data store using theDataManager
interface. -
In the
onButtonOutClick()
method we extract the content of the saved file using theopenStream()
method of theFileLoader
. Then we display the content of the file in the secondtextArea
.
import com.haulmont.cuba.core.entity.FileDescriptor;
import com.haulmont.cuba.core.global.DataManager;
import com.haulmont.cuba.core.global.FileLoader;
import com.haulmont.cuba.core.global.FileStorageException;
import com.haulmont.cuba.core.global.Metadata;
import com.haulmont.cuba.gui.components.AbstractWindow;
import com.haulmont.cuba.gui.components.TextArea;
import com.haulmont.cuba.gui.upload.FileUploadingAPI;
import org.apache.commons.io.IOUtils;
import javax.inject.Inject;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
public class FileLoaderScreen extends AbstractWindow {
@Inject
private Metadata metadata;
@Inject
private FileLoader fileLoader;
@Inject
private DataManager dataManager;
@Inject
private TextArea textAreaIn;
@Inject
private TextArea textAreaOut;
private FileDescriptor fileDescriptor;
public void onButtonInClick() {
byte[] bytes = textAreaIn.getRawValue().getBytes();
fileDescriptor = metadata.create(FileDescriptor.class);
fileDescriptor.setName("Input.txt");
fileDescriptor.setExtension("txt");
fileDescriptor.setSize((long) bytes.length);
fileDescriptor.setCreateDate(new Date());
try {
fileLoader.saveStream(fileDescriptor, () -> new ByteArrayInputStream(bytes));
} catch (FileStorageException e) {
throw new RuntimeException(e);
}
dataManager.commit(fileDescriptor);
}
public void onButtonOutClick() {
try {
InputStream inputStream = fileLoader.openStream(fileDescriptor);
textAreaOut.setValue(IOUtils.toString(inputStream, StandardCharsets.UTF_8));
} catch (FileStorageException | IOException e) {
throw new RuntimeException(e);
}
}
}