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Reactive Relational Database Connectivity H2 Implementation

Java CI with Maven

Maven Central

This project contains the H2 implementation of the R2DBC SPI. This implementation is not intended to be used directly, but rather to be used as the backing implementation for a humane client library.

This driver provides the following features:

  • Filesystem or in-memory instances

  • Explict transactions

  • Execution of prepared statements with bindings

  • Execution of batch statements without bindings

  • Read and write support for all data types except LOB types (e.g. BLOB, CLOB)

Since this driver runs on top of the internals of H2, there is risk of change. r2dbc-h2 does not guarantee compatibility except against the version of H2 found in the build file. Because various parts of H2 are blocking, like file and network access, the only non-blocking assurances are in the layers above H2. Nevertheless, r2dbc-h2 is a great way to warm up to the usage of R2DBC with a small footprint.

Code of Conduct

This project is governed by the R2DBC Code of Conduct. By participating, you are expected to uphold this code of conduct. Please report unacceptable behavior to

Getting Started

Here is a quick teaser of how to use R2DBC H2 in Java:

URL Connection Factory Discovery for In-Memory Databases

ConnectionFactory connectionFactory = ConnectionFactories.get("r2dbc:h2:mem:///testdb");

Publisher<? extends Connection> connectionPublisher = connectionFactory.create();

URL Connection Factory Discovery for File Databases

ConnectionFactory connectionFactory = ConnectionFactories.get("r2dbc:h2:file///my/relative/path");

Publisher<? extends Connection> connectionPublisher = connectionFactory.create();

Programmatic Connection Factory Discovery

ConnectionFactoryOptions options = builder()
    .option(DRIVER, "h2")
    .option(PROTOCOL, "...")  // file, mem
    .option(HOST, "…")
    .option(USER, "…")
    .option(PASSWORD, "…")
    .option(DATABASE, "…")

ConnectionFactory connectionFactory = ConnectionFactories.get(options);

Publisher<? extends Connection> connectionPublisher = connectionFactory.create();

// Alternative: Creating a Mono using Project Reactor
Mono<Connection> connectionMono = Mono.from(connectionFactory.create());

Supported ConnectionFactory Discovery Options

Option Description


Must be h2.


Must be file, mem, or tcp. Requires database if set (Optional)


Only for tcp protocol: Server hostname to connect to. (Optional)


Only for tcp protocol: Server port to connect to. (Optional)


Login username.


Login password.


Database to use. For file protocol: Relative (r2dbc:h2:file//../relative/file/name) or absolute (r2dbc:h2:file///absolute/file/name) file name. For mem protocol: In-memory database name (r2dbc:h2:mem:///testdb).


Pass-thru of well-known H2 options such as DB_CLOSE_DELAY=10&MODE=DB2. See io.r2dbc.h2.H2ConnectionOption for all options. (Optional)


A semicolon-delimited list of H2 configuration options(options=DB_CLOSE_DELAY=10;DB_CLOSE_ON_EXIT=true;…). (Optional)

Programmatic Configuration

H2ConnectionFactory connectionFactory = new H2ConnectionFactory(H2ConnectionConfiguration.builder()
    .option(H2ConnectionOption.DB_CLOSE_DELAY, "-1")

Mono<Connection> connection = connectionFactory.create();

Programmatic In-Memory Database Configuration

CloseableConnectionFactory connectionFactory = H2ConnectionFactory.inMemory("testdb");

Mono<Connection> connection = connectionFactory.create();


Artifacts can be found on Maven Central.


If you’d rather like the latest snapshots of the upcoming major version, use our Maven snapshot repository and declare the appropriate dependency version.


  <name>Sonatype OSS Snapshot Repository</name>

Setting query params

H2 uses index parameters that are prefixed with $. The following SQL statement makes use of parameters:

INSERT INTO person (id, first_name, last_name) VALUES ($1, $2, $3)

Parameters are referenced using the same identifiers when binding these:

    .createStatement("INSERT INTO person (id, first_name, last_name) VALUES ($1, $2, $3)")
    .bind("$1", 1)
    .bind("$2", "Walter")
    .bind("$3", "White")

Geometry support

r2dbc-h2 will automatically register support for JTS Toplogy Suite and handle it’s Geometry types if org.locationtech.jts:jts-core is on the classpath.

To enable, add this to your build:

Be sure to plug in your version of JTS!

Also read H2’s reference documentation on GEOMETRY types.

We also support params binding as

  • index bind(1, "Walter"). Notice that passing an integer means index (zero-based) references.

  • $ symbol bind("$2", "Walter"). H2 supports postgres params notation.

  • Object (Integer) bind(yourIntegerAsObject, "Walter"). If you index (int) was converted into object by a framework

Running JMH Benchmarks

Running the JMH benchmarks builds and runs the benchmarks without running tests.

 $ ./mvnw clean install -Pjmh

Getting Help

Having trouble with R2DBC? We’d love to help!

Reporting Issues

R2DBC uses GitHub as issue tracking system to record bugs and feature requests. If you want to raise an issue, please follow the recommendations below:

  • Before you log a bug, please search the issue tracker to see if someone has already reported the problem.

  • If the issue doesn’t already exist, create a new issue.

  • Please provide as much information as possible with the issue report, we like to know the version of R2DBC H2 that you are using and JVM version.

  • If you need to paste code, or include a stack trace use Markdown ``` escapes before and after your text.

  • If possible try to create a test-case or project that replicates the issue. Attach a link to your code or a compressed file containing your code.

Building from Source

You don’t need to build from source to use R2DBC H2 (binaries in Maven Central), but if you want to try out the latest and greatest, R2DBC H2 can be easily built with the maven wrapper. You also need JDK 1.8.

 $ ./mvnw clean install

If you want to build with the regular mvn command, you will need Maven v3.5.0 or above.

Also see CONTRIBUTING.adoc if you wish to submit pull requests. Commits require Signed-off-by (git commit -s) to ensure Developer Certificate of Origin.

Staging to Maven Central

To stage a release to Maven Central, you need to create a release tag (release version):

  1. ci/ <release-version> <next-snapshot-version> (e.g. ci/ 0.8.5.RELEASE 0.8.6.BUILD-SNAPSHOT)

  2. git checkout release

  3. git reset --hard v<release-version> (e.g. git reset --hard v0.8.5.RELEASE, observe the v prefix)

  4. git push --force

This push will trigger a Maven staging build (see


This project is released under version 2.0 of the Apache License.