GraphAcademy

Using Neo4j with Java

The Driver

Handling results

Best practices

Using the driver

Introduction

In the Cypher Fundamentals course, you learned how to query Neo4j using Cypher.

To run Cypher statements in a Java application, you’ll need the Neo4j Java Driver. The driver acts as a bridge between your Java code and Neo4j, handling connections to the database and the execution of Cypher queries.

Creating a Driver Instance

Open the src/main/java/com/neo4j/app/App.java file.

Import the driver:

Java
import org.neo4j.driver.GraphDatabase;
import org.neo4j.driver.AuthTokens;

Creating a Driver Instance

Create a driver instance in main():

Java
public class App {
    public static void main(String[] args) {
        AppUtils.loadProperties();

        // Create a new Neo4j driver instance
        var driver = GraphDatabase.driver(
                System.getProperty("NEO4J_URI"), // (1)
                AuthTokens.basic(
                    System.getProperty("NEO4J_USERNAME"), // (2)
                    System.getProperty("NEO4J_PASSWORD"))
            );
    }
}

  1. The connection string for your Neo4j database

  2. Your Neo4j username and password

Best Practice

Create one Driver instance and share it across your entire application.

Verifying Connectivity

You can verify the connection by calling the verifyConnectivity() method.

Java
driver.verifyConnectivity();

Verify Connectivity

The verifyConnectivity() method will raise an exception if the connection cannot be made.

Running Your First Query

The executableQuery() method executes a Cypher query and returns the results.

Java
// (1)
var result = driver.executableQuery(
    "RETURN COUNT {()} AS count"
    ).execute();

// Get the first record
var records = result.records(); // (2)
var first = records.get(0);

// Print the count entry
System.out.println(first.get("count"));   // (3)

  1. executableQuery() runs a Cypher query to get the count of all nodes in the database

  2. records() returns a list of the records returned

  3. Keys from the RETURN clause are accessed using the get method

Full driver lifecycle

Once you have finished with the driver, call close() to release any resources held by the driver.

Java
driver.close();

Run the application

You can run the application to see the output:

bash
./mvnw compile exec:java -Dexec.mainClass="com.neo4j.app.App"

You can also run the application using the play button in your IDE.

Try with resources

You can use try-with-resources to automatically close the driver when the block is exited.

Java
try (
    var driver = GraphDatabase.driver(
        System.getProperty("NEO4J_URI"),
        AuthTokens.basic(
            System.getProperty("NEO4J_USERNAME"),
            System.getProperty("NEO4J_PASSWORD"))
    )
) {
    driver.verifyConnectivity();

    var result = driver.executableQuery(
        "RETURN COUNT {()} AS count"
        ).execute();
}

Lesson Summary

In this lesson you learned how to install the Neo4j Java Driver, create a Driver instance, verify connectivity to your database, and execute your first Cypher statement.

For async applications, use the AsyncGraphDatabase method.

In the next lesson, you will take a quiz to test your knowledge of installing and creating a driver instance.