Connect to CrateDB

Table of contents

The basics

Connect to CrateDB using the DriverManager class, like so:

Connection conn = DriverManager.getConnection("crate://localhost:5432/");

Note

For CrateDB versions 2.1.x and later, you must configure a database user when connecting.

Consult the Connection Properties section for more information.

See also

Consult the JDBC documentation for general information about using the DriverManager class.

The CrateDB JDBC driver provides the io.crate.client.jdbc.CrateDriver class. JDBC 4.0 will initialise this automatically if it is found on your class path.

Database connection URLs

A JDBC database is represented by special type of Uniform Resource Locator (URL) called a database connection URL.

The simplest database connection URL for CrateDB looks like this:

crate://<HOST>/

Here, <HOST> is the node host string.

A host string looks like this:

<HOST_ADDR>:<PORT>

Here, <HOST_ADDR> is the hostname or IP address of the CrateDB node and <PORT> is a valid psql.port number.

Example host strings:

  • localhost:5432
  • crate-1.vm.example.com:5432
  • 198.51.100.1:5432

You can specify a second CrateDB node, like so:

crate://<HOST_ADDR_1>,<HOST_ADDR_2>/

Here, <HOST_ADDR_1> and <HOST_ADDR_2> are the host strings for the first and second CrateDB nodes, respectively.

In fact, you can specify as many nodes as you like. Each corresponding host string must be separated from the previous one using a , character.

The driver will attempt to connect to each node in the order they appear. The first successul connection will be used, and all other nodes will be ignored for the duration of that connection.

Note

The last host string must be followed by a / character.

Schema selection

To specify a different schema, use the setSchema method, like so:

Connection conn = DriverManager.getConnection("crate://localhost:5432/");
conn.setSchema("my_schema");

Tip

The default CrateDB schema is doc, and if you do not specify a schema, this is what will be used.

However, you can query any schema you like by specifying it in the query.

Connection properties

Database connections have number of configurable properties.

Here’s a simple example:

Properties properties = new Properties();
properties.put("user", "crate");
Connection conn = DriverManager.getConnection(
    "crate://localhost:5432/", properties
);

Here, we set the user property to crate so that the driver will attempt to connect to the CrateDB node as the crate user.

Note

For simplicity, we only document use of the Properties class for setting properties. However, you can also set properties using URL parameters if you wish.

The CrateDB JDBC driver supports following properties:

strict:

If set to false, the CrateDB JDBC driver silently ignores unsupported JDBC features.

This will, for example, allow the driver to be used by most third-party applications that attempt to use transactional features.

Warning

Silently ignoring transactions may result in data corruption or data loss.

If set to true, the CrateDB JDBC driver behaves strictly according to CrateDB’s capabilities and the JDBC specification.

In strict mode, attempts to use unsupported features will result in an exception being raised.

Unsupported features include:

Defaults to false.

user:

Specifies the CrateDB user.

Defaults to the same string as the OS system user.

Note

Authentication was introduced in CrateDB versions 2.1.x.

If you are using CrateDB 2.1.x or later, you must supply a username. If you are using earlier versions of CrateDB, this argument is not supported.

See the compatibility notes for more information.

If you have not configured a custom database user, you probably want to authenticate as the CrateDB superuser, which is crate. The superuser does not have a password, so you can omit the password property.

If you are authenticating as a custom user, that user will need to have DQL privileges on the sys.nodes table, because this table is used for version negotiation.

password:

Sets the password for authentication.

ssl:

If set to true, the driver will attempt to establish a secure connection to CrateDB using SSL. If a secure connection is not possible, no connection will be made.

Defaults to false.

loadBalanceHosts:

If set to true, the driver will randomly shuffle the order of the host strings. Over multiple connection attempts, this distributes connection attempts across the whole cluster, functioning as client-side random load balancing. If false, the driver will try the hosts in the order they are defined.

Defaults to true.

Next steps

Use the standard JDBC API documentation for the rest of your setup process.

See also

Check out the sample application (and the corresponding documentation) for a practical demonstration of this driver in use.