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This section gives an overview of the official Neo4j Java Driver and how to connect to a Neo4j database with a "Hello World" example.

1. About the official Java driver

Neo4j provides official drivers for a number of popular programming languages. These drivers are supported by Neo4j.

Community drivers also exist for many languages, but vary greatly in terms of feature sets, maturity, and support. To find more about community drivers, visit https://neo4j.com/developer/language-guides/.

The following languages and frameworks are officially supported by Neo4j:

Table 1. Supported languages and frameworks for the 4.x driver series
Language/framework Versions supported

.NET

Go

Go 1.10

Java

Java 8+ (latest patch releases).

JavaScript

All LTS versions of Node.JS, specifically the 4.x and 6.x series runtimes (https://github.com/nodejs/LTS).

Python

Python 3.5 and above.

The driver API is intended to be topologically agnostic. This means that the underlying database topology — single instance, Causal Cluster, etc. — can be altered without requiring a corresponding alteration to application code.

In the general case, only the connection URI needs to be modified when changes are made to the topology.

The official drivers do not support HTTP communication. If you need an HTTP driver, choose one of the community drivers.

See also the HTTP API documentation.

2. Driver versions and installation

Starting with Neo4j 4.0, the versioning scheme for the database, driver and protocol have all been aligned. This simplifies general compatibility concerns.

Cross-version compatibility is still available, and minimum support for current and previous versions between both server and driver is guaranteed. More specifically, this means that Neo4j 4.0 is guaranteed to be compatible with both 4.0 Drivers and 1.7 Drivers, and the 4.0 Drivers are guaranteed to be compatible with both Neo4j 4.0 and Neo4j 3.5. In cases where at least one peer is below version 4.0, communication will occur in fallback mode, limiting functionality to that available in the lowest-versioned component.

Drivers 1.7 do not support multiple databases and Neo4j Fabric, features introduced in Neo4j 4.0. To be able to run multiple databases online concurrently and to do distributed queries over them, you must upgrade Drivers from 1.7 to 4.0. For information, see 4.0 Migration Guide → Chapter 6. Upgrade Neo4j drivers.

Wherever possible, it is recommended to use the latest stable driver release available. This will provide the greatest degree of stability and will ensure that the full set of server functionality is available. The drivers, when used with Neo4j Enterprise Edition, come with full cluster routing support. The drivers make no explicit distinction between Enterprise Edition and Community Edition however, and simply operate with the functionality made available by Neo4j itself.

Example 1. Acquire the driver

To use the Java driver, it is recommended employing a dependency manager, such as Maven or Gradle. To find the latest version of the driver, visit the Maven Central Repository.

Dependencies

  • org.reactivestreams:reactive-streams

  • org.apache.logging.log4j:log4j (optional)

The driver is dependent on the Reactive Streams API, thus maintaining JDK 8 compatibility. To make optimal use of the reactive APIs, we suggest an additional framework like Project Reactor or RxJava2. Both implement the Reactive Streams API and provide an exhaustive set of operators.

Example 2. Installation via Maven

When using Maven, add the following block to the pom.xml file. The driver version can either be declared as a property (as in the first example) or as an explicit version number (as in the second).

<dependencies>
    <dependency>
        <groupId>org.neo4j.driver</groupId>
        <artifactId>neo4j-java-driver</artifactId>
        <version>$JAVA_DRIVER_VERSION</version>
    </dependency>
</dependencies>

In the following example, driver version 4.3.3 is added.

<dependencies>
    <dependency>
        <groupId>org.neo4j.driver</groupId>
        <artifactId>neo4j-java-driver</artifactId>
        <version>4.3.3</version>
    </dependency>
</dependencies>
Example 3. Installation via Gradle

For Gradle, a compile line will be required. Again, this can use a property or an explicit version number.

compile 'org.neo4j.driver:neo4j-java-driver:$JAVA_DRIVER_VERSION'

In the following example, a driver version 4.3.3 is added.

compile 'org.neo4j.driver:neo4j-java-driver:4.3.3'

The release notes for this driver are available here.

3. A "Hello World" example

The example below shows the minimal configuration necessary to interact with Neo4j through the Java driver:

Example 4. Hello World
import org.neo4j.driver.AuthTokens;
import org.neo4j.driver.Driver;
import org.neo4j.driver.GraphDatabase;
import org.neo4j.driver.Result;
import org.neo4j.driver.Session;
import org.neo4j.driver.Transaction;
import org.neo4j.driver.TransactionWork;

import static org.neo4j.driver.Values.parameters;
public class HelloWorldExample implements AutoCloseable
{
    private final Driver driver;

    public HelloWorldExample( String uri, String user, String password )
    {
        driver = GraphDatabase.driver( uri, AuthTokens.basic( user, password ) );
    }

    @Override
    public void close() throws Exception
    {
        driver.close();
    }

    public void printGreeting( final String message )
    {
        try ( Session session = driver.session() )
        {
            String greeting = session.writeTransaction( new TransactionWork<String>()
            {
                @Override
                public String execute( Transaction tx )
                {
                    Result result = tx.run( "CREATE (a:Greeting) " +
                                                     "SET a.message = $message " +
                                                     "RETURN a.message + ', from node ' + id(a)",
                            parameters( "message", message ) );
                    return result.single().get( 0 ).asString();
                }
            } );
            System.out.println( greeting );
        }
    }

    public static void main( String... args ) throws Exception
    {
        try ( HelloWorldExample greeter = new HelloWorldExample( "bolt://localhost:7687", "neo4j", "password" ) )
        {
            greeter.printGreeting( "hello, world" );
        }
    }
}

4. Driver API docs

For a comprehensive listing of all driver functionality, refer to the API documentation: https://neo4j.com/docs/api/java-driver/4.3/