Crate Java Client

For a more detailed documentation how to set up and use the Crate client please refer to the client documentation on `https://crate.io/docs/`_.

The client module exposes a very simple interface to query Crate using SQL.

Installation

Maven

The easiest way to use the crate client is to include it as a dependency using Maven:

<dependency>
    <groupId>io.crate</groupId>
    <artifactId>crate-client</artifactId>
    <version>...</version>
</dependency>

You can find the latest version of the client on Bintray.

From Source

See :ref:`Development <client_develop>` for further details.

Usage

A minimal example is just a few lines of code:

import io.crate.client.CrateClient;

CrateClient client = new CrateClient("server1.crate.org:4300", "server2.crate.org:4300");
SQLResponse r = client.sql("select firstName, lastName from users").actionGet();

System.out.println(Arrays.toString(r.cols()));
// outputs ["firstName", "lastName"]

for (Object[] row: r.rows()){
    System.out.println(Arrays.toString(row));
}
// outputs the users. For example:
// ["Arthur", "Dent"]
// ["Ford", "Perfect"]

The CrateClient takes multiple servers as arguments. They are used in a round-robin fashion to distribute the load. In case a server is unavailable it will be skipped.

By default, the column data types are not serialized. In order to get these, one must defined it at the SQLRequest object:

import io.crate.client.CrateClient;

CrateClient client = new CrateClient("server1.crate.org:4300", "server2.crate.org:4300");

SQLRequest request = new SQLRequest("select firstName, lastName from users");
request.includeTypesOnResponse(true);

SQLResponse r = client.sql().actionGet();

// Get the data type of the first column
DataType dataType = r.columnTypes()[0]
System.out.print(dataType.getName())
// outputs: "string"

Note

Queries are executed asynchronous. client.sql("") will return a Future<SQLResponse> and code execution is only blocked if .actionGet() is called on it.

Logging

Crate client relies on Elastic Search ESLogger facility which itself defaults to log4j framework.

Using Slf4j

In order to configure the crate client to use Slf4j, you need to configure the ESLoggerFactory to use Slf4j by using the following command (typically in your entry point):

ESLoggerFactory.setDefaultFactory(new Slf4jESLoggerFactory());