org.mapdb.Atomic Java Examples

public static void main(String[] args) {
    DB db = DBMaker.newTempFileDB().make();

    //open or create new map
    Map<Long, String> map = db.getTreeMap("map");

    // open existing or create new Atomic record with given name
    // if no record with given name exist, new recid is created with value `0`
    Atomic.Long keyinc = Atomic.getLong(db, "map_keyinc");


    // Allocate new unique key to use in map
    // Atomic.Long will use `compare-and-swap` operation to atomically store incremented value
    // Key values can be used only for single insert
    // key == 1
    Long key = keyinc.incrementAndGet();
    map.put(key, "some string");

    // insert second entry,
    // key==2
    map.put(keyinc.incrementAndGet(), "some other string");

    System.out.println(map);

}
 

public void saveReferenceNetwork(Network network) throws IOException {
    Objects.requireNonNull(network);
    if (!config.getMapDb().isPersistent()) {
        this.referenceNetwork = network;
    } else if (this.referenceNetwork == null || !this.referenceNetwork.getId().equals(network.getId())) {
        DataSource dataSource = new FileDataSource(storeDir, network.getId());
        Properties parameters = new Properties();
        parameters.setProperty("iidm.export.xml.indent", "true");
        Exporters.export("XIIDM", network, parameters, dataSource);
        Atomic.String reference = db.atomicString("referenceNetwotk").createOrOpen();
        String oldNet = reference.get();
        reference.set(network.getId() + ".xiidm");
        this.referenceNetwork = network;
        if (oldNet != null) {
            Files.delete(Paths.get(storeDir.toString(), oldNet));
        }
    }
}
 

/**
 * @return a local non-thread safe copy of the database
 */
private Map<String, Object> localCopy() {
  return db.getAll().entrySet().stream().map(entry -> {
    Object struct = entry.getValue();
    if (struct instanceof Set)
      return Pair.of(entry.getKey(), newHashSet((Set) struct));
    else if (struct instanceof List)
      return Pair.of(entry.getKey(), newArrayList((List) struct));
    else if (struct instanceof Map)
      return Pair.of(entry.getKey(), new BackupMap((Map) struct));
    else if (struct instanceof Atomic.Var)
      return Pair.of(entry.getKey(), BackupVar.createVar(((Atomic.Var) struct).get()));
    return Pair.of(entry.getKey(), struct);
  }).collect(toMap(pair -> (String) pair.a(), Pair::b));
}
 

public static void main(String[] args) {

        DB db = DBMaker.newMemoryDB().make();
        //
        // TreeMap has build in support for lazily loaded values.
        // In that case each value are not stored inside node,
        // but in separate record.
        //
        // use DB.createTreeMap to create TreeMap with non-default parameters

        boolean valuesStoredOutsideNodes = true;
        Map map = db.createTreeMap("name",32, valuesStoredOutsideNodes, null, null, null);
        map.put("key","this string is loaded lazily with 'map.get(key)' ");


        //
        // Other option for lazily loaded record is to use Atomic.Var.
        // In this case you have singleton record with name.
        // As bonus you can update reference in thread-safe atomic manner.
        //
        Atomic.Var<String> record =
                Atomic.createVar(db, "lazyRecord", "aaa", db.getDefaultSerializer());

        record.set("some value");
        System.out.println(record.get());


        // Last option is to use low level Engine storage directly.
        // Each stored record gets assigned unique recid (record id),
        // which is latter used to get or update record.
        // Your code should store only recid as reference to object.
        // All MapDB collections are written this way.

        //insert new record
        long recid = db.getEngine().put("something", Serializer.STRING_SERIALIZER);

        //load record
        String lazyString = db.getEngine().get(recid, Serializer.STRING_SERIALIZER);

        //update record
        db.getEngine().update(recid, "new value", Serializer.STRING_SERIALIZER);


        //I hope this example helped!
        db.close();

    }
 

@Override
public <T> Var<T> getVar(String name) {
  return new MapDBVar<>((Atomic.Var<T>) db.atomicVar(name).createOrOpen());
}
 

public MapDBVar(Atomic.Var<T> var) {
  this.var = var;
}