Stylishly saving source

Question

Simple tool to save a web page's source. A result of trying to learn and apply an MVC approach. The FXML is generated via Scene Builder, but included for completion.

I welcome any general feedback on how to improve anything but in particular:

1. There are many exceptions, current impression is that current handling is not ideal. What is the conventional wisdom on handling a plethora of io/connection errors?
2. API and methods utilized in reading and writing were changed several times. Thanks to @rolfl's answer to a related question, currently refactored to employ Java 8 streams, is this the most appropriate for purpose? Can it be cleaner? Faster?
3. Any conventions that should be followed, especially in regards to MVC, FXML.

The following is the source, with a line in the main class commented out so this may be executed if desired.

Main Class:

import java.io.IOException;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.paint.Color;
import javafx.scene.Scene;
import javafx.scene.image.Image;
import javafx.stage.Stage;
public class HTMLSave extends Application {
 public static void main(String[] args) {
 launch(args);
 }
 @Override
 public void start(Stage stage) {
 Parent root = null;
 try {
 root = FXMLLoader.load(getClass().getResource("HTML_Save.fxml"));
 } catch (IOException ioe) {
 System.err.println("Could not load FXML");
 }
 Scene scene = new Scene(root, Color.TRANSPARENT);
 scene.getStylesheets().add("html-save.css");
 stage.setScene(scene);
 stage.setTitle("HTML Saver");
 //stage.getIcons().add(new Image(getClass().getResourceAsStream("icon.png")));
 stage.show();
 }
}

Controller Class:

import java.awt.Desktop;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStreamReader;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.UncheckedIOException;
import java.io.Writer;
import java.net.URL;
import java.util.ResourceBundle;
import java.util.stream.Collectors;
import javafx.concurrent.Task;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.Cursor;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.Button;
import javafx.scene.control.ProgressBar;
import javafx.scene.control.TextField;
public class HTMLSaveController implements Initializable {
 @FXML
 private Button saveButton;
 @FXML
 private Button openButton;
 @FXML
 private TextField htmlField;
 @FXML
 private TextField filenameField;
 @FXML
 private ProgressBar progressBar;
 private String destinationFile;
 @Override
 public void initialize(URL location, ResourceBundle resources) {
 System.out.println("HTML Saver view successfully loaded.");
 }
 public void handleSaveRequest() {
 String filename = filenameField.getText();
 String url = htmlField.getText();
 if (url.isEmpty()) {
 errorAlert("URL missing", "Please paste in website address");
 } else if (filename.isEmpty()) {
 errorAlert("No filename", "Please enter a file name to save html");
 } else {
 destinationFile = filename + ".html";
 try (Writer destination = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(destinationFile), "UTF-8"))) {
 savePageSource(url, destination);
 } catch (IOException ioe) {
 System.err.println("Could not write to " + filename + '.');
 }
 }
 }
 public void handleOpenRequest() {
 try {
 Desktop.getDesktop().open(new File(destinationFile));
 } catch (IOException ioe) {
 System.err.println(destinationFile + " not found.");
 }
 }
 private void errorAlert(String message, String infoMessage) {
 Alert alert = new Alert(AlertType.ERROR);
 alert.setTitle("Error");
 alert.setHeaderText(message);
 alert.setContentText(infoMessage);
 alert.showAndWait();
 }
 private void savePageSource(String url, Writer destination) throws IOException {
 Task saveTask = new Task() {
 @Override
 protected Void call() throws IOException {
 updateProgress(0, 100);
 openButton.setDisable(true);
 try (BufferedReader reader = new BufferedReader(new InputStreamReader(new URL(url).openStream()))) {
 progressBar.setCursor(Cursor.WAIT);
 destination.write(reader.lines().collect(Collectors.joining("\n")));
 } catch (IOException ioe) {
 throw new UncheckedIOException(ioe);
 } 
 progressBar.setCursor(Cursor.DEFAULT);
 updateProgress(1, 1);
 openButton.setDisable(false);
 return null;
 }
 };
 progressBar.progressProperty().bind(saveTask.progressProperty());
 Thread savingThread = new Thread(saveTask);
 savingThread.start();
 try {
 savingThread.join();
 } catch (InterruptedException ie) {
 ie.printStackTrace();
 }
 }
}

CSS:

.label {
 -fx-text-fill: rgb(166, 226, 46);
 -fx-font-weight: bold;
}
.button {
 -fx-text-fill: rgb(166, 226, 46);
 -fx-background-color: rgb(39, 40, 34);
 -fx-border-radius: 20;
 -fx-background-radius: 20;
 -fx-padding: 5;
}
.button:hover {
 -fx-text-fill: rgb(249, 38, 114);
}
.root{
 -fx-font-family: "Courier New";
 -fx-background: rgb(61, 61, 59);
 -fx-base: rgb(39, 40, 34);
}
.text-field:focused {
 -fx-background-color: #a9a9a9 , white , white;
 -fx-background-insets: 0 -1 -1 -1, 0 0 0 0, 0 -1 3 -1;
}
.progress-bar > .bar {
 -fx-background-color: linear-gradient(
 from 0px .75em to .75em 0px,
 repeat,
 rgb(253, 151, 31) 0%,
 rgb(253, 151, 31) 49%,
 derive(rgb(253, 151, 31), 30%) 50%,
 derive(rgb(253, 151, 31), 30%) 99%
 );
}

FXML:

<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.*?>
<?import javafx.scene.text.*?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<GridPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="174.0" prefWidth="474.0" xmlns="http://javafx.com/javafx/8.0.40" xmlns:fx="http://javafx.com/fxml/1" fx:controller="HTMLSaveController">
 <columnConstraints>
 <ColumnConstraints hgrow="SOMETIMES" maxWidth="309.0" minWidth="10.0" prefWidth="203.0" />
 <ColumnConstraints hgrow="SOMETIMES" maxWidth="398.0" minWidth="10.0" prefWidth="271.0" />
 </columnConstraints>
 <rowConstraints>
 <RowConstraints maxHeight="121.0" minHeight="10.0" prefHeight="114.0" vgrow="SOMETIMES" />
 <RowConstraints maxHeight="181.0" minHeight="10.0" prefHeight="129.0" vgrow="SOMETIMES" />
 <RowConstraints maxHeight="293.0" minHeight="10.0" prefHeight="121.0" vgrow="SOMETIMES" />
 </rowConstraints>
 <children>
 <Button fx:id="saveButton" defaultButton="true" mnemonicParsing="false" onAction="#handleSaveRequest" prefHeight="39.0" prefWidth="73.0" text="Save" textFill="#36d721" GridPane.columnIndex="1" GridPane.halignment="RIGHT" GridPane.rowIndex="2" GridPane.valignment="TOP">
 <font>
 <Font size="18.0" />
 </font>
 <cursor>
 <Cursor fx:constant="HAND" />
 </cursor></Button>
 <Label text="Paste Address: ">
 <font>
 <Font size="20.0" />
 </font></Label>
 <Label text="Enter Filename: " GridPane.rowIndex="1">
 <font>
 <Font size="20.0" />
 </font></Label>
 <TextField fx:id="htmlField" GridPane.columnIndex="1" />
 <TextField fx:id="filenameField" GridPane.columnIndex="1" GridPane.rowIndex="1" />
 <VBox prefHeight="123.0" prefWidth="205.0" GridPane.rowIndex="2">
 <children>
 <Button fx:id="openButton" disable="true" mnemonicParsing="false" onAction="#handleOpenRequest" prefHeight="39.0" prefWidth="81.0" text="Open" textFill="#6f2929">
 <font>
 <Font size="18.0" />
 </font>
 <cursor>
 <Cursor fx:constant="HAND" />
 </cursor>
 </Button>
 <ProgressBar fx:id="progressBar" prefWidth="200.0" progress="0.0">
 <cursor>
 <Cursor fx:constant="DEFAULT" />
 </cursor>
 </ProgressBar>
 </children>
 </VBox>
 </children>
</GridPane>

The result:

Application sample run