Charles Lamb's Blog

Terrific example! And, yes, it makes a lot of sense to have a lighweight persistence mechanism such as Berkeley DB...

I took the liberty of rewriting the code to make it more "JavaFXish" so that it shows a few interesting language features:

import java.io.File;
import com.sleepycat.je.Cursor;
import com.sleepycat.je.Database;
import com.sleepycat.je.DatabaseConfig;
import com.sleepycat.je.DatabaseEntry;
import com.sleepycat.je.Environment;
import com.sleepycat.je.EnvironmentConfig;
import com.sleepycat.je.JEVersion;
import com.sleepycat.je.OperationStatus;
import com.sleepycat.je.Transaction;

doSomeJEOps();

operation doSomeJEOps() {

    var theDb = initJE();

    var txn = null;

    initJE();

    // txn's type is inferred from its first non-null assignment

    txn = theDb.environment.beginTransaction(null, null);

    for (i in [0..9]) {

	    put(theDb, txn, "foo{i}", "bar{i}");

    }

    txn.commit();

    // built-in println() provides convenient access to stdout

    println("Retrieval by key: foo0 => {get(theDb, null, 'foo0')}");

    // Assignment invokes empty constructor. variable type is inferred

    var key = DatabaseEntry;

    // Assignment invokes empty constructor. variable type is inferred

    var val = DatabaseEntry;

    // variable type is inferred from first assignment

    var cursor = theDb.openCursor(null, null);

    println('Retrieval by cursor');

    while (cursor.getNext(key, val, null) == OperationStatus.SUCCESS) {

	    println("{new String(key.getData())} => {new String(val.getData())}");

    }

    closeJE();

}

operation initJE() {

    // var envConfig's type is inferred from assignment

    var envConfig = EnvironmentConfig { // empty constructor invoked

        allowCreate: true // java properties are set declaratively

        transactional: true

    };

    // var env's type is inferred from assignment

    var env = new Environment(new File('c:/temp/blort'), envConfig);

    // var dbConfig's type is inferred from assignment

    var dbConfig = DatabaseConfig { // empty constructor invoked

        allowCreate: true // Java properties are set declaratively

        transactional: true

    };

    // var db's type is inferred from assignment

    var db = env.openDatabase(null, 'foo', dbConfig);

    return db; // operation initJE's type is inferred from its return value

}

operation closeJE() {

    theDb.close();

    theDb.environment.close();

}

operation put(theDb:Database, txn:Transaction, theKey:String, theVal:String) {

    // var keyDE's type is inferred from assignment

    var keyDE = new DatabaseEntry(theKey.getBytes());

    // var keyDE's type is inferred from assignment

    var valDE = new DatabaseEntry(theVal.getBytes());

    // var status' type is inferred from assignment

    var status = theDb.put(txn, keyDE, valDE);

    if (status <> OperationStatus.SUCCESS) {

	    throw status; // objects of any type can be thrown

    }

}

operation get(theDb:Database, txn:Transaction, theKey:String) {

    // var keyDE's type is inferred from assignment

    var keyDE = DatabaseEntry { // empty constructor is invoked

        data: theKey.getBytes() // java property is set declaratively

    };

    // var valDE's type is inferred from assignment

    var valDE = DatabaseEntry;

    // var status' type is inferred from assignment

    var status = theDb.get(txn, keyDE, valDE, null);

    if (status <> OperationStatus.SUCCESS) {

	    throw status; // objects of any type can be thrown

    }

    // operations get's type is inferred from its return value

    return new String(valDE.getData());

}

If i have understood what JavaFX is i don't think this will make available JE on the Java ME platform or not immediately at least.

JE rely on J2SE 1.4 or higher and uses for example java.io.File and related classes, but these classes are not available in J2ME or at least in devices based on CLDC/MIDP.

This is one of the issues i have faced trying to use Berkeley DB Java Edition on BlackBerry device.

David, you are correct that this will still not bring JE to a J2ME environment. There are a handful of things in the code which force reliance on Java 1.4: assertions, java.nio calls, and using of java.util.log classes.

Charles Lamb