Java Object Query

package example;

import com.db4o.*;
import com.db4o.config.ConfigScope;
import com.db4o.config.annotations.Indexed;
import com.db4o.cs.*;
import com.db4o.query.Predicate;
import com.db4o.ta.TransparentActivationSupport;
import com.db4o.ta.TransparentPersistenceSupport;
import java.io.File;

public class db4odemo {

    public static class Node {

        @Indexed
        public String name;
        public Node Left;
        public Node Right;
        public int Size = 99;
    }

    public static void main(String[] args) {

        String dbname = "/tmp/node.j.db";
        new File(dbname).delete();
        long internalId;
        String objectId;

        var cfg = Db4oClientServer.newServerConfiguration();

        cfg.common().objectClass(Node.class).cascadeOnActivate(true);
        cfg.common().objectClass(Node.class).cascadeOnUpdate(true);
        cfg.common().objectClass(Node.class).cascadeOnDelete(true);
        cfg.common().objectClass(Node.class).callConstructor(true);

        cfg.common().add(new TransparentActivationSupport());
        cfg.common().add(new TransparentPersistenceSupport());
        cfg.file().generateUUIDs(ConfigScope.GLOBALLY);

        try (var server = Db4oClientServer.openServer(cfg, dbname, 0)) {

            try (var oc = server.openClient()) {
                var root = new Node();
                root.name = "Root";

                root.Left = new Node();
                root.Left.name = "Left";

                root.Right = new Node();
                root.Right.name = "Right";

                root.Right.Right = new Node();
                root.Right.Right.name = "Right.Right";

                oc.store(root);

                oc.commit();
            }

            try (var oc = server.openClient()) {
                var metaInfo = oc.ext().storedClass(Node.class);
                // list a fields and check if they have a index
                for (var field : metaInfo.getStoredFields()) {
                    if (field.hasIndex()) {
                        System.out.println("The field '" + field.getName() + "' is indexed");
                    } else {
                        System.out.println("The field '" + field.getName() + "' isn't indexed");
                    }
                }
            }

            try (var oc = server.openClient()) {
                var qo = new Node();
                qo.name = "Root";
                var ns = oc.queryByExample(qo);
                var root = ns.next();
                System.out.println(root.Right.Right.name);

                internalId = oc.ext().getID(root);
                objectId = oc.ext().getObjectInfo(root).getUUID().toString();
            }

            try (var oc = server.openClient()) {
                System.out.println(objectId);
                var root = oc.ext().getByUUID(Node.class, objectId);
                System.out.println(root.Right.Right.name);
            }

            try (var oc = server.openClient()) {
                System.out.println(internalId);
                var root = oc.ext().getByID(Node.class, internalId);
                System.out.println(root.Right.Right.name);
            }

            //Use Native Query, recommended
            try (var oc = server.openClient()) {
                var ns = oc.query(new Predicate<Node>() {
                    @Override
                    public boolean match(Node n) {
                        return n.name.equals("Root");
                    }
                });
                var root = ns.get(0);
                System.out.println(root.Right.Right.name);
            }
            try (var oc = server.openClient()) {
                var ns = oc.query(new Predicate<Node>() {
                    @Override
                    public boolean match(Node n) {
                        return n.name.equals("Right.Right");
                    }
                });
                var r_r = ns.get(0);
                System.out.println(r_r.name);
            }
            // S.O.D.A. not recommended, dynamic program
            try (var oc = server.openClient()) {
                var q = oc.query();
                q.constrain(Node.class);
                q.descend("name").constrain("Root").equal();
                var ns = q.execute(Node.class);
                for (var n : ns) {
                    n.Right.Right.name += ".Update";
                    oc.store(n);
                }
                oc.commit();
            }
            //Use Complex Native Query
            try (var oc = server.openClient()) {
                var ns = oc.query(new Predicate<Node>() {
                    @Override
                    public boolean match(Node n) {
                        return n.name.compareTo("Right.Right") > 0
                                && n.name.length() > "Root".length();
                    }
                });
                var r_r = ns.get(0);
                System.out.println(r_r.name);
            }

        }

        var ecfg = Db4oEmbedded.newConfiguration();
        ecfg.common().objectClass(Node.class).cascadeOnActivate(true);
        ecfg.common().objectClass(Node.class).cascadeOnUpdate(true);
        ecfg.common().objectClass(Node.class).cascadeOnDelete(true);
        ecfg.common().objectClass(Node.class).callConstructor(true);

        ecfg.common().add(new TransparentActivationSupport());
        ecfg.common().add(new TransparentPersistenceSupport());
        ecfg.file().generateUUIDs(ConfigScope.GLOBALLY);

        try (var oc = Db4oEmbedded.openFile(ecfg, dbname)) {

            System.out.println(objectId);
            var root = oc.ext().getByUUID(Node.class, objectId);
            System.out.println(root.Right.Right.name);

            System.out.println(internalId);
            root = oc.ext().getByID(Node.class, internalId);
            System.out.println(root.Right.Right.name);

        }

        ecfg = Db4oEmbedded.newConfiguration();
        ecfg.common().objectClass(Node.class).cascadeOnActivate(true);
        ecfg.common().objectClass(Node.class).cascadeOnUpdate(true);
        ecfg.common().objectClass(Node.class).cascadeOnDelete(true);
        ecfg.common().objectClass(Node.class).callConstructor(true);

        ecfg.common().add(new TransparentActivationSupport());
        ecfg.common().add(new TransparentPersistenceSupport());
        ecfg.file().generateUUIDs(ConfigScope.GLOBALLY);

        try (var oc = Db4oEmbedded.openFile(ecfg, dbname)) {

            try (var see = oc.ext().openSession()) {
                System.out.println(objectId);
                var root = see.ext().getByUUID(Node.class, objectId);
                System.out.println(root.Right.Right.name);
            }

            try (var see = oc.ext().openSession()) {
                System.out.println(internalId);
                var root = see.ext().getByID(Node.class, internalId);
                System.out.println(root.Right.Right.name);
            }

        }

        System.out.println("End.");
    }

}

OUTPUT

The field 'v4ouuid' is indexed
The field 'name' is indexed
The field 'Left' isn't indexed
The field 'Right' isn't indexed
The field 'Size' isn't indexed
Right.Right
3s57fz2hukt13c4angdpefkxuiggymz4uor58i18dgkywk7lamqewp0a2mlr4cvsatz810
Right.Right
31
Right.Right
Right.Right
Right.Right
Right.Right.Update
3s57fz2hukt13c4angdpefkxuiggymz4uor58i18dgkywk7lamqewp0a2mlr4cvsatz810
Right.Right.Update
31
Right.Right.Update
3s57fz2hukt13c4angdpefkxuiggymz4uor58i18dgkywk7lamqewp0a2mlr4cvsatz810
Right.Right.Update
31
Right.Right.Update
End.