Object Database

All but the most trivial of Java applications have a need for persistence. The org.waterken.db library provides an easy and effective solution for using persistent Java objects.

This software is distributed as part of the Waterken^TM Server, under the Open Source MIT License.

Documentation

• javadoc

Example

Application object

package com.example.counter;

import org.waterken.db.Key;
import org.waterken.db.Transaction;

public final class
Counter implements java.io.Serializable {

    private int value;

    private
    Counter() {}

    public static Incrementor
    make() {
        final Transaction T = Transaction.current();
        return new Incrementor(T.create(new Counter()));
    }

    public static final class
    Incrementor implements java.io.Serializable {

        private Key scope;

        Incrementor(final Key scope) {
            this.scope = scope;
        }

        public int
        getValue() { return ((Counter)scope.query()).value; }

        public int
        increment() {
            final Counter m = (Counter)scope.update();
            return ++m.value;
        }
    }
}

Using a database

package com.example.counter;

import org.waterken.db.Body;
import org.waterken.db.Database;
import org.waterken.db.Root;

import java.io.File;

public final class
Main {

    public static Database
    create(final File root) {
        Database db = org.waterken.jdb.Database.create(root,
            org.waterken.module.java.Maker.make(new File[] {},
                org.waterken.module.confined.Maker.make()));
        db.execute(new Body() {
            public Object
            run(final Root root) {
                root.publish("my counter", Counter.make());
                return null;
            }
        });
        return db;
    }

    public static Database
    open(final File root) {
        return org.waterken.jdb.Database.open(root);
    }

    public static int
    incrementCounter(final Database db) {
        Integer r = (Integer)db.execute(new Body() {
            public Object
            run(final Root root) {
                Counter.Incrementor counter =
                    (Counter.Incrementor)root.access(null, "my counter");
                return new Integer(counter.increment());
            }
        });
        return r.intValue();
    }
}

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