postgres-async-driver - Asynchronous PostgreSQL Java driver

Postgres-async-driver is a non-blocking Java driver for PostgreSQL. The driver supports connection pooling, prepared statements, transactions, all standard SQL types and custom column types.

Download

Postgres-async-driver is available on Maven Central.

<dependency>
    <groupId>com.github.alaisi.pgasync</groupId>
    <artifactId>postgres-async-driver</artifactId>
    <version>0.9</version>
</dependency>

Usage

Hello world

Querying for a set returns an rx.Observable that emits a single ResultSet.

Db db = ...;
db.querySet("select 'Hello world!' as message")
    .map(result -> result.row(0).getString("message"))
    .subscribe(System.out::println)

// => Hello world

Querying for rows returns an rx.Observable that emits 0-n Rows. The rows are emitted immediately as they are received from the server instead of waiting for the entire query to complete.

Db db = ...;
db.queryRows("select unnest('{ hello, world }'::text[] as message)")
    .map(row -> row.getString("message"))
    .subscribe(System.out::println)

// => hello
// => world

Creating a Db

Db is a connection pool that is created with ConnectionPoolBuilder

Db db = new ConnectionPoolBuilder()
    .hostname("localhost")
    .port(5432)
    .database("db")
    .username("user")
    .password("pass")
    .poolSize(20)
    .build();

Each connection pool will start only one IO thread used in communicating with PostgreSQL backend and executing callbacks for all connections.

Prepared statements

Prepared statements use native PostgreSQL syntax $index. Supported parameter types are all primitive types, String, BigDecimal, BigInteger, UUID, temporal types in java.sql package and byte[].

db.querySet("insert into message(id, body) values($1, $2)", 123, "hello")
    .subscribe(result -> out.printf("Inserted %d rows", result.affectedRows() ));

Transactions

A transactional unit of work is started with begin(). Queries issued to the emitted Transaction are executed in the same transaction and the tx is automatically rolled back on query failure.

db.begin()
    .flatMap(tx -> tx.querySet("insert into products (name) values ($1) returning id", "saw")
        .map(productsResult -> productsResult.row(0).getLong("id"))
        .flatMap(id -> tx.querySet("insert into promotions (product_id) values ($1)", id))
        .flatMap(promotionsResult -> tx.commit())
    ).subscribe(
        __ -> System.out.println("Transaction committed"),
        Throwable::printStackTrace);

Custom data types

Support for additional data types requires registering converters to ConnectionPoolBuilder

class JsonConverter implements Converter<example.Json> {
    @Override
    public Class<example.Json> type() {
        return example.Json.class;
    }
    @Override
    public byte[] from(example.Json json) {
        return json.toBytes();
    }
    @Override
    public example.Json to(Oid oid, byte[] value) {
        return new example.Json(new String(value, UTF_8));
    }
}

Db db = return new ConnectionPoolBuilder()
    ...
    .converters(new JsonConverter())
    .build();

Used in

• postgres.async for Clojure

References

• Scala postgresql-async
• PostgreSQL JDBC Driver