TableColumnPrefsSaver.java

package org.obo.app.swing;

import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.prefs.BackingStoreException;
import java.util.prefs.Preferences;

import javax.swing.JTable;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.TableColumnModelEvent;
import javax.swing.event.TableColumnModelListener;
import javax.swing.table.TableColumn;

import org.apache.log4j.Logger;

/**
 * Persists user changes to column widths and order for a table using java.util.prefs.  Column
 * titles should be unique within the table.  If the column content (count or titles) is changed
 * between uses of a table, columns will be reset to the default order until the user moves them
 * again. Not only persists changes, but enacts the ordering on the table with orderColumns
 */
public class TableColumnPrefsSaver implements PropertyChangeListener, TableColumnModelListener {

	private int defaultColumnWidth;
	private JTable table;
	private String autoSaveName;

	/**
	 * Constructs a TableColumnPrefsSaver for the given table using a default column width of 150. 
	 * Column widths and order are persisted to the preferences datastore.  The autoSaveName should
	 *  be sufficiently unique to avoid conflicts with saved states for other tables.
	 */
	public TableColumnPrefsSaver(JTable aTable, String autoSaveName) {
		this(aTable, autoSaveName, 150);
	}

	/**
	 * Constructs a TableColumnPrefsSaver for the given table.  Column widths and order are persisted
	 * to the preferences datastore.  The autoSaveName should be sufficiently unique to avoid conflicts
	 * with saved states for other tables.  If no column width values are already saved for this table, the 
	 * defaultColumnWidth will be used.
	 */
	public TableColumnPrefsSaver(JTable aTable, String autoSaveName, int defaultColumnWidth) {
		this.table = aTable;
		this.autoSaveName = autoSaveName;
		this.defaultColumnWidth = defaultColumnWidth;
		this.table.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);
		this.sizeColumns();
		for (TableColumn column : this.getColumns()) {
			column.addPropertyChangeListener(this);
		}
		this.orderColumns();
		this.table.getColumnModel().addColumnModelListener(this);
	}

	@Override
	public void propertyChange(PropertyChangeEvent e) {
		if (e.getPropertyName().equals("width")) {
			this.saveColumnWidth((TableColumn)(e.getSource()));
		}
	}

	@Override
	public void columnAdded(TableColumnModelEvent e) {
		this.saveColumnOrdering();
	}

	@Override
	public void columnMarginChanged(ChangeEvent e) {}

	@Override
	public void columnMoved(TableColumnModelEvent e) {
		this.saveColumnOrdering();
	}

	@Override
	public void columnRemoved(TableColumnModelEvent e) {
		this.saveColumnOrdering();
	}

	@Override
	public void columnSelectionChanged(ListSelectionEvent e) {}

	/**
	 * Removes this object from listening to any tables or table columns.
	 */
	public void dispose() {
		for (TableColumn column : this.getColumns()) {
			column.removePropertyChangeListener(this);
		}
		this.table.getColumnModel().removeColumnModelListener(this);
	}

	private void sizeColumns() {
		for (TableColumn column : this.getColumns()) {
			final int width = this.getWidthPrefs().getInt(this.getColumnKey(column), this.defaultColumnWidth);
			column.setPreferredWidth(width);
		}
	}

	private void saveColumnWidth(TableColumn column) {
		this.getWidthPrefs().putInt(this.getColumnKey(column), column.getWidth());
	}

	private void orderColumns() {
		final List<String> prefNames;
		try {
			prefNames = Arrays.asList(this.getOrderPrefs().keys());
		} catch (BackingStoreException e) {
			log().error("Failed to read table column order from prefs", e);
			return;
		}
		final List<String> columnKeys = this.getAllColumnKeys();
		if (prefNames.containsAll(columnKeys) && columnKeys.containsAll(prefNames)) {
			for (TableColumn column : this.getColumns()) {
				final int newIndex = this.getOrderPrefs().getInt(this.getColumnKey(column), 0);
				final int currentIndex = this.getIndexOfColumn(column);
				final int columnCount = this.table.getColumnCount();
				if ((newIndex < columnCount) && (currentIndex < columnCount)) {
					this.table.getColumnModel().moveColumn(currentIndex, newIndex); 
				}
			}
		}
		this.saveColumnOrdering();
	}

	private void saveColumnOrdering() {
		try {
			this.getOrderPrefs().clear();
		} catch (BackingStoreException e) {
			log().error("Unable to store table column ordering", e);
			return;
		}
		for (int i = 0; i < this.table.getColumnModel().getColumnCount(); i++) {
			this.getOrderPrefs().putInt(this.getColumnKey(this.table.getColumnName(i)), i);
		}
	}

	private String getColumnName(TableColumn column) {
		return column.getHeaderValue().toString();
	}

	private String getColumnKey(TableColumn column) {
		return this.getColumnKey(this.getColumnName(column));
	}

	private String getColumnKey(String name) {
		final String hashCode = "" + name.hashCode();
		final int spaceForName = Preferences.MAX_KEY_LENGTH - hashCode.length();
		final String shortName = (name.length() > spaceForName) ? name.substring(0, spaceForName) : name;
		return shortName + hashCode;
	}

	private List<String> getAllColumnKeys() {
		List<String> keys = new ArrayList<String>();
		for (TableColumn column : this.getColumns()) {
			keys.add(this.getColumnKey(column));
		}
		return keys;
	}

	private List<TableColumn> getColumns() {
		return Collections.list(this.table.getColumnModel().getColumns());
	}

	private int getIndexOfColumn(TableColumn column) {
		return this.getColumns().indexOf(column);
	}

	private Preferences getPrefsRoot() {
		return Preferences.userNodeForPackage(this.getClass()).node(this.autoSaveName);
	}

	private Preferences getWidthPrefs() {
		return this.getPrefsRoot().node("width");
	}

	private Preferences getOrderPrefs() {
		return this.getPrefsRoot().node("order");
	}

	private static Logger log() {
		return Logger.getLogger(TableColumnPrefsSaver.class);
	}

}