Using preferences

The following will create three commands. One of set the preference values. The next will display the values and the last will clear the preference values.

Create a new project "de.vogella.preferences.test" (see Eclipse RCP Tutorials for details). Use the "Hello RCP" as a template.

Create the following commands with the following default handler. Add these commands to the menu.

Table 1. Commands

Command	Default Handler	Description
de.vogella.preferences.test.setPreferences	de.vogella.preferences.test.handler.SetPreferences	Sets the initial values of Preferences
de.vogella.preferences.test.deletePreferences	de.vogella.preferences.test.handler.DeletePreferences	Deletes the preference values
de.vogella.preferences.test.showPreferences	de.vogella.preferences.test.handler.ShowPreferences	Displays the preference values

Create the following coding in the default handler.

   
package de.vogella.preferences.test.handler;

import org.eclipse.core.commands.AbstractHandler;
import org.eclipse.core.commands.ExecutionEvent;
import org.eclipse.core.commands.ExecutionException;
import org.eclipse.core.runtime.preferences.ConfigurationScope;
import org.osgi.service.prefs.BackingStoreException;
import org.osgi.service.prefs.Preferences;

public class SetPreferences extends AbstractHandler {

 public Object execute(ExecutionEvent event) throws ExecutionException {
  // This would be using instance scope
  // Preferences preferences = new InstanceScope()
  // .getNode("de.vogella.preferences.test");
  // This is using configuration scope
  Preferences preferences = new ConfigurationScope()
    .getNode("de.vogella.preferences.test");
  // This would be using default n scope
  // Preferences preferences = new DefaultScope()
  // .getNode(Application.PLUGIN_ID);
  Preferences sub1 = preferences.node("note1");
  Preferences sub2 = preferences.node("node2");
  sub1.put("h1", "Hello");
  sub1.put("h2", "Hello again");
  sub2.put("h1", "Moin");

  try {
   // Forces the application to save the preferences
   preferences.flush();
  } catch (BackingStoreException e) {
   e.printStackTrace();
  }
  return null;
 }

}

  

   
package de.vogella.preferences.test.handler;

import org.eclipse.core.commands.AbstractHandler;
import org.eclipse.core.commands.ExecutionEvent;
import org.eclipse.core.runtime.preferences.ConfigurationScope;
import org.osgi.service.prefs.BackingStoreException;
import org.osgi.service.prefs.Preferences;

public class DeletePreferences extends AbstractHandler {

 @Override
 public Object execute(ExecutionEvent event) {
  Preferences preferences = new ConfigurationScope()
    .getNode("de.vogella.preferences.test");
  Preferences sub1 = preferences.node("note1");
  Preferences sub2 = preferences.node("node2");
  // Delete the existing settings
  try {
   sub1.clear();
   sub2.clear();
  } catch (BackingStoreException e) {
   e.printStackTrace();
  }
  // Forces the application to save the preferences
  try {
   preferences.flush();
  } catch (BackingStoreException e) {
   e.printStackTrace();
  }
  return null;
 }
}

  

   
package de.vogella.preferences.test.handler;

import org.eclipse.core.commands.AbstractHandler;
import org.eclipse.core.commands.ExecutionEvent;
import org.eclipse.core.commands.ExecutionException;
import org.eclipse.core.runtime.preferences.ConfigurationScope;
import org.eclipse.jface.dialogs.MessageDialog;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.ui.handlers.HandlerUtil;
import org.osgi.service.prefs.Preferences;

public class ShowPreferences extends AbstractHandler {
 @Override
 public Object execute(ExecutionEvent event) throws ExecutionException {
  Shell shell = HandlerUtil.getActiveWorkbenchWindowChecked(event)
    .getShell();
  Preferences preferences = new ConfigurationScope()
    .getNode("de.vogella.preferences.test");
  Preferences sub1 = preferences.node("note1");
  Preferences sub2 = preferences.node("node2");
  MessageDialog.openInformation(shell, "Info", sub1.get("h1", "default"));
  MessageDialog.openInformation(shell, "Info", sub1.get("h2", "default"));
  MessageDialog.openInformation(shell, "Info", sub2.get("h1", "default"));
  return null;
 }
}

  

Run and test your program. If you set the preferences and re-start the program the values should still be stored in the application.