QueryExample.java

package org.springmodules.db4o.examples.chapter1;

import java.util.Iterator;

import org.springmodules.db4o.examples.Pilot;
import org.springframework.context.support.AbstractApplicationContext;

import com.db4o.ObjectContainer;
import com.db4o.ObjectSet;
import com.db4o.query.Constraint;
import com.db4o.query.Query;

/**
 * This class corresponds with the class <code>QueryExample</code> from the
 * Db4o tutorial.
 * 
 * @author Daniel Mitterdorfer
 * @since 07.12.2005
 * 
 */
public class QueryExample {
	private static void listResult(ObjectSet result) {
		for (Iterator it = result.iterator(); it.hasNext();) {
			Pilot pilot = (Pilot) it.next();
			System.out.println(pilot.toString());
		}
	}

	public static void storeFirstPilot(ObjectContainer db) {
		Pilot pilot1 = new Pilot("Michael Schumacher", 100);
		db.set(pilot1);
		System.out.println("Stored " + pilot1);
	}

	public static void storeSecondPilot(ObjectContainer db) {
		Pilot pilot2 = new Pilot("Rubens Barrichello", 99);
		db.set(pilot2);
		System.out.println("Stored " + pilot2);
	}

	public static void retrieveAllPilots(ObjectContainer db) {
		Query query = db.query();
		query.constrain(Pilot.class);
		ObjectSet result = query.execute();
		listResult(result);
	}

	public static void retrievePilotByName(ObjectContainer db) {
		Query query = db.query();
		query.constrain(Pilot.class);
		query.descend("name").constrain("Michael Schumacher");
		ObjectSet result = query.execute();
		listResult(result);
	}

	public static void retrievePilotByExactPoints(ObjectContainer db) {
		Query query = db.query();
		query.constrain(Pilot.class);
		query.descend("points").constrain(new Integer(100));
		ObjectSet result = query.execute();
		listResult(result);
	}

	public static void retrieveByNegation(ObjectContainer db) {
		Query query = db.query();
		query.constrain(Pilot.class);
		query.descend("name").constrain("Michael Schumacher").not();
		ObjectSet result = query.execute();
		listResult(result);
	}

	public static void retrieveByConjunction(ObjectContainer db) {
		Query query = db.query();
		query.constrain(Pilot.class);
		Constraint constr = query.descend("name").constrain("Michael Schumacher");
		query.descend("points").constrain(new Integer(99)).and(constr);
		ObjectSet result = query.execute();
		listResult(result);
	}

	public static void retrieveByDisjunction(ObjectContainer db) {
		Query query = db.query();
		query.constrain(Pilot.class);
		Constraint constr = query.descend("name").constrain("Michael Schumacher");
		query.descend("points").constrain(new Integer(99)).or(constr);
		ObjectSet result = query.execute();
		listResult(result);
	}

	public static void retrieveByComparison(ObjectContainer db) {
		Query query = db.query();
		query.constrain(Pilot.class);
		query.descend("points").constrain(new Integer(99)).greater();
		ObjectSet result = query.execute();
		listResult(result);
	}

	public static void retrieveByDefaultFieldValue(ObjectContainer db) {
		Pilot somebody = new Pilot("Somebody else", 0);
		db.set(somebody);
		Query query = db.query();
		query.constrain(Pilot.class);
		query.descend("points").constrain(new Integer(0));
		ObjectSet result = query.execute();
		listResult(result);
		db.delete(somebody);
	}

	public static void retrieveSorted(ObjectContainer db) {
		Query query = db.query();
		query.constrain(Pilot.class);
		query.descend("name").orderAscending();
		ObjectSet result = query.execute();
		listResult(result);
		query.descend("name").orderDescending();
		result = query.execute();
		listResult(result);
	}

	public static void clearDatabase(ObjectContainer db) {
		ObjectSet result = db.get(new Pilot(null, 0));
		while (result.hasNext()) {
			db.delete(result.next());
		}
	}

	/**
	 * @param args
	 *            Command line arguments. This appliation does not check any of
	 *            these arguments.
	 */
	public static void main(String[] args) {
		AbstractApplicationContext ctx = ExampleUtils.getContext();
		ObjectContainer db = (ObjectContainer) ctx.getBean(ExampleUtils.CONTAINER_BEAN_ID);
		try {
			storeFirstPilot(db);
			storeSecondPilot(db);
			retrieveAllPilots(db);
			retrievePilotByName(db);
			retrievePilotByExactPoints(db);
			retrieveByNegation(db);
			retrieveByConjunction(db);
			retrieveByDisjunction(db);
			retrieveByComparison(db);
			retrieveByDefaultFieldValue(db);
			retrieveSorted(db);
			clearDatabase(db);
		} finally {
			ctx.close();
		}
	}
}