TextAreaTableCell, see Stack Overflow question: http://stackoverflow.com/questions/27666382/editable-multiline-cell-in-tableview

TextAreaTableCell.java

import javafx.beans.binding.Bindings;
import javafx.beans.property.ObjectProperty;
import javafx.beans.property.SimpleObjectProperty;
import javafx.scene.control.Cell;
import javafx.scene.control.TableCell;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TextArea;
import javafx.scene.input.KeyCode;
import javafx.util.Callback;
import javafx.util.StringConverter;
import javafx.util.converter.DefaultStringConverter;

public class TextAreaTableCell<S, T> extends TableCell<S, T> {

	public static <S> Callback<TableColumn<S, String>, TableCell<S, String>> forTableColumn() {
		return forTableColumn(new DefaultStringConverter());
	}

	public static <S, T> Callback<TableColumn<S, T>, TableCell<S, T>> forTableColumn(final StringConverter<T> converter) {
		return list -> new TextAreaTableCell<>(converter);
	}

	private static <T> String getItemText(Cell<T> cell, StringConverter<T> converter) {
		return converter == null ? cell.getItem() == null ? "" : cell.getItem()
				.toString() : converter.toString(cell.getItem());
	}

	private static <T> TextArea createTextArea(final Cell<T> cell, final StringConverter<T> converter) {
		TextArea textArea = new TextArea(getItemText(cell, converter));
		textArea.setOnKeyReleased(t -> {
			if (t.getCode() == KeyCode.ESCAPE) {
				cell.cancelEdit();
				t.consume();
			}
			else if(t.getCode() == KeyCode.ENTER && t.isShiftDown()) {
				if (converter == null) {
					throw new IllegalStateException(
						"Attempting to convert text input into Object, but provided "
							+ "StringConverter is null. Be sure to set a StringConverter "
							+ "in your cell factory.");
				}
				cell.commitEdit(converter.fromString(textArea.getText()));
				t.consume();	
			}
		});
		textArea.prefRowCountProperty().bind(Bindings.size(textArea.getParagraphs()));
		return textArea;
	}

	private void startEdit(final Cell<T> cell, final StringConverter<T> converter) {
		textArea.setText(getItemText(cell, converter));

		cell.setText(null);
		cell.setGraphic(textArea);

		textArea.selectAll();
		textArea.requestFocus();
	}

	private static <T> void cancelEdit(Cell<T> cell, final StringConverter<T> converter) {
		cell.setText(getItemText(cell, converter));
		cell.setGraphic(null);
	}

	private void updateItem(final Cell<T> cell, final StringConverter<T> converter) {
		
		if (cell.isEmpty()) {
			cell.setText(null);
			cell.setGraphic(null);
			
		} else {
			if (cell.isEditing()) {
				if (textArea != null) {
					textArea.setText(getItemText(cell, converter));
				}
				cell.setText(null);
				cell.setGraphic(textArea);
			} else {
				cell.setText(getItemText(cell, converter));
				cell.setGraphic(null);
			}
		}
	}

	private TextArea textArea;
	private ObjectProperty<StringConverter<T>> converter = new SimpleObjectProperty<>(this, "converter");

	public TextAreaTableCell() {
		this(null);
	}

	public TextAreaTableCell(StringConverter<T> converter) {
		this.getStyleClass().add("text-area-table-cell");
		setConverter(converter);
	}

	public final ObjectProperty<StringConverter<T>> converterProperty() {
		return converter;
	}

	public final void setConverter(StringConverter<T> value) {
		converterProperty().set(value);
	}

	public final StringConverter<T> getConverter() {
		return converterProperty().get();
	}

	@Override
	public void startEdit() {
		if (!isEditable() || !getTableView().isEditable() || !getTableColumn().isEditable()) {
			return;
		}
		
		super.startEdit();

		if (isEditing()) {
			if (textArea == null) {
				textArea = createTextArea(this, getConverter());
			}

			startEdit(this, getConverter());
		}
	}

	@Override
	public void cancelEdit() {
		super.cancelEdit();
		cancelEdit(this, getConverter());
	}

	@Override
	public void updateItem(T item, boolean empty) {
		super.updateItem(item, empty);
		updateItem(this, getConverter());
	}

}

Should not be textArea.appendText("\n"), but rather textArea.insertText(textArea.getCaretPosition(), "\n"). With your code, when the caret is within the text, "Enter" adds a new line at the end. It took me a long time to figure this out.

I found that in the createTextArea method using textArea.setOnKeyReleased(... let an extra newline get in there before commiting. Using textArea.setOnKeyPressed(... instead fixed that for me. (Also, thanks @limitedAtonement and @DominikStyp for the tips.)

I'm new to Gists—if you can edit them, I can't figure out how—but I do have a fork with the above-mentioned improvements.

An improvement to the text area sizing:

   private void startEdit(final Cell<T> cell, final StringConverter<T> converter) {
        textArea.setText(getItemText(cell, converter));

        cell.setText(null);
        cell.setGraphic(textArea);

        // Make sure the text area stays the right size:
        /* The following solution is courtesy of James_D: https://stackoverflow.com/a/22733264/5432315 */
        // Perform a lookup for an element with a css class of "text"
        // This will give the Node that actually renders the text inside the
        // TextArea
        Node text = textArea.lookup(".text");
        // Bind the preferred height of the text area to the actual height of the text
        // This will make the text area the height of the text, plus some padding
        // of 20 pixels, as long as that height is between the text area's minHeight
        // and maxHeight. The max height will be the height of its parent (usually).
        textArea.prefHeightProperty().bind(Bindings.createDoubleBinding(() ->
                text.getBoundsInLocal().getHeight(), text.boundsInLocalProperty()).add(20)
        );


        textArea.selectAll();
        textArea.requestFocus();
    }

Thanks for this! I adapted it for a kotlin implementation that also wraps the text in the cell.

https://gist.github.com/maroc81/6c60d5ae11fdf79099e50fe308509a27