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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();