nebula-java

Nebula Java is a Java client for developers to connect their projects to Nebula Graph.

Please be noted that nebula-JDBC(based on nebula-java) is the JDBC implementing for nebula graph.

NOTE: Nebula Java is not thread-safe.

Two main branches of this repository

In this repository, you can find two branches for the source code of Nebula Java of different versions.

The master branch

The master branch is for Nebula Java v2.0, which works with Nebula Graph v2.0 nightly.

This README file provides Java developers with instructions on how to connect to Nebula Graph v2.0.

The v1.0 branch

In the v1.0 branch, you can find source code of these:

• Nebula Java v1.0, which works with Nebula Graph v1.1.0 and earlier versions only.
• Nebula Graph Exchange, Nebula Spark Connector, Nebula Flink Connector, and nebula-algorithm.

For more information, see README of v1.0.

The v2.0.0-rc branch

The v2.0.0-rc branch works with Nebula Graph v2.0.0-beta and v2.0.0-rc1, but not for the latest nightly Nebula Graph.

Prerequisites

To use this Java client, do a check of these:

• Java 8 or a later version is installed.
• Nebula Graph is deployed. For more information, see Deployment and installation of Nebula Graph.

Modify pom.xml

If you use Maven to manage your project, add the following dependency to your pom.xml file. Replace 3.0-SNAPSHOT with an appropriate Nebula Java version. For more versions, visit releases.

<dependency>
    <groupId>com.vesoft</groupId>
    <artifactId>client</artifactId>
    <version>3.0-SNAPSHOT</version>
</dependency>

There are the version correspondence between client and Nebula:

Client version	Nebula Version
1.0.0	1.0.0
1.0.1	1.1.0,1.2.0
1.1.0	1.1.0,1.2.0
1.2.0	1.1.0,1.2.0,1.2.1
2.0.0-beta	2.0.0-beta
2.0.0-rc1	2.0.0-rc1
2.0.0	2.0.0,2.0.1
2.0.1	2.0.0,2.0.1
2.5.0	2.5.0,2.5.1
2.6.0	2.6.0,2.6.1
2.6.1	2.6.0,2.6.1
3.x	3.x
3.0-SNAPSHOT	nightly

Graph client example

To connect to the nebula-graphd process of Nebula Graph:

NebulaPoolConfig nebulaPoolConfig = new NebulaPoolConfig();
nebulaPoolConfig.setMaxConnSize(10);
List<HostAddress> addresses = Arrays.asList(new HostAddress("127.0.0.1", 9669), new HostAddress("127.0.0.1", 9670));

NebulaPool pool = new NebulaPool();
pool.init(addresses, nebulaPoolConfig);

Session session = pool.getSession("root", "nebula", false);

session.execute("SHOW HOSTS;");

session.release();

pool.close();

Graph SessionPool example

To use SessionPool, you must config the space to connect for SessionPool. The SessionPool is thread-safe, and support retry(release old session and get available session from SessionPool) for both connection error, session error and execution error(caused by bad storaged server), and the retry mechanism needs users to config retryTimes and intervalTime between retrys.

And SessionPool maintains servers' status, can isolation broken graphd server and auto routing restarted graphd server when you need to execute with new session， meaning your parallel is larger than the idle session number in the session pool.

List<HostAddress> addresses = Arrays.asList(new HostAddress("127.0.0.1", 9669));
String spaceName = "test";
String user = "root";
String password = "nebula";
SessionPoolConfig sessionPoolConfig = new SessionPoolConfig(addresses, spaceName, user, password);
sessionPoolConfig.setRetryTimes(3);
sessionPoolConfig.setIntervalTime(1000);

SessionPool sessionPool = new SessionPool(sessionPoolConfig);

if (!sessionPool.init()) {
  log.error("session pool init failed.");
  return;
}

ResultSet resultSet;

try {
    
  resultSet = sessionPool.execute("match (v:player) return v limit 1;");
  System.out.println(resultSet.toString());
  
} catch (IOErrorException | ClientServerIncompatibleException | AuthFailedException | BindSpaceFailedException e) {
    
  e.printStackTrace();
  System.exit(1);
  
} finally {
    
    sessionPool.close();
    
}