Query the database

Once you have connected to the database, you can execute Cypher queries through the method Driver.executableQuery().

Driver.executableQuery() was introduced with the version 5.8 of the driver.
For queries with earlier versions, use sessions and transactions.

Write to the database

To create a node representing a person named Alice, use the Cypher clause CREATE:

Create a node representing a person named Alice
// import java.util.Map;
// import java.util.concurrent.TimeUnit;
// import org.neo4j.driver.QueryConfig;

var result = driver.executableQuery("CREATE (:Person {name: $name})")  (1)
    .withParameters(Map.of("name", "Alice"))  (2)
    .withConfig(QueryConfig.builder().withDatabase("neo4j").build())  (3)
    .execute();
var summary = result.summary();  (4)
System.out.printf("Created %d records in %d ms.%n",
    summary.counters().nodesCreated(),
    summary.resultAvailableAfter(TimeUnit.MILLISECONDS));
1 The Cypher query
2 A map of query parameters
3 Which database the query should be run against
4 The summary of execution returned by the server

Read from the database

To retrieve information from the database, use the Cypher clause MATCH:

Retrieve all Person nodes
// import java.util.concurrent.TimeUnit;
// import org.neo4j.driver.QueryConfig;

var result = driver.executableQuery("MATCH (p:Person) RETURN p.name AS name")
    .withConfig(QueryConfig.builder().withDatabase("neo4j").build())
    .execute();

// Loop through results and do something with them
var records = result.records();  (1)
records.forEach(r -> {
    System.out.println(r);  // or r.get("name").asString()
});

// Summary information
var summary = result.summary();  (2)
System.out.printf("The query %s returned %d records in %d ms.%n",
    summary.query(), records.size(),
    summary.resultAvailableAfter(TimeUnit.MILLISECONDS));
1 records contains the result as a list of Record objects
2 summary contains the summary of execution returned by the server

Properties inside a Record object are embedded within Value objects. To extract and cast them to the corresponding Java types, use .as<type>() (eg. .asString(), asInt(), etc). For example, if the name property coming from the database is a string, record.get("name").asString() will yield the property value as a String object.

For more information, see Data types and mapping to Cypher types.

Update the database

To update a node’s information in the database, use the Cypher clauses MATCH and SET:

Update node Alice to add an age property
// import java.util.Map;
// import org.neo4j.driver.QueryConfig;

var result = driver.executableQuery("""
    MATCH (p:Person {name: $name})
    SET p.age = $age
    """)
    .withConfig(QueryConfig.builder().withDatabase("neo4j").build())
    .withParameters(Map.of("name", "Alice", "age", 42))
    .execute();
var summary = result.summary();
System.out.println("Query updated the database?");
System.out.println(summary.counters().containsUpdates());

To create a new relationship, linking it to two already existing node, use a combination of the Cypher clauses MATCH and CREATE:

Create a relationship :KNOWS between Alice and Bob
// import java.util.Map;
// import org.neo4j.driver.QueryConfig;

var result = driver.executableQuery("""
    MATCH (alice:Person {name: $name})  (1)
    MATCH (bob:Person {name: $friend})  (2)
    CREATE (alice)-[:KNOWS]->(bob)  (3)
    """)
    .withConfig(QueryConfig.builder().withDatabase("neo4j").build())
    .withParameters(Map.of("name", "Alice", "friend", "Bob"))
    .execute();
var summary = result.summary();
System.out.println("Query updated the database?");
System.out.println(summary.counters().containsUpdates());
1 Retrieve the person node named Alice and bind it to a variable alice
2 Retrieve the person node named Bob and bind it to a variable bob
3 Create a new :KNOWS relationship outgoing from the node bound to alice and attach to it the Person node named Bob

Delete from the database

To remove a node and any relationship attached to it, use the Cypher clause DETACH DELETE:

Remove the Alice node and all its relationships
// import java.util.Map;
// import org.neo4j.driver.QueryConfig;

// This does not delete _only_ p, but also all its relationships!
var result = driver.executableQuery("""
    MATCH (p:Person {name: $name})
    DETACH DELETE p
    """)
    .withConfig(QueryConfig.builder().withDatabase("neo4j").build())
    .withParameters(Map.of("name", "Alice"))
    .execute();
var summary = result.summary();
System.out.println("Query updated the database?");
System.out.println(summary.counters().containsUpdates());

Query parameters

Do not hardcode or concatenate parameters directly into queries. Instead, always use placeholders and specify the Cypher parameters, as shown in the previous examples. This is for:

  1. performance benefits: Neo4j compiles and caches queries, but can only do so if the query structure is unchanged;

  2. security reasons: see protecting against Cypher injection.

You may provide query parameters as a map through the .withParameters() method.

var result = driver.executableQuery("MATCH (p:Person {name: $name}) RETURN p")
    .withParameters(Map.of("name", "Alice"))
    .withConfig(QueryConfig.builder().withDatabase("neo4j").build())
    .execute();
There can be circumstances where your query structure prevents the usage of parameters in all its parts. For those rare use cases, see Dynamic values in property keys, relationship types, and labels.

Error handling

A query run may fail for a number of reasons, with different exceptions being raised. Some of them are due to Cypher syntax errors, permission issues, or other forms of misconfiguration/misusage. The choice of how to handle those exceptions is up to your application: whether you want to be defensive (for example check if there are records to process to avoid NoSuchRecordException), or whether you want to catch and handle the exceptions as they arise.

The driver automatically retries to run a failed query, if the failure is deemed to be transient (for example due to temporary server unavailability). An exception will be raised if the operation keeps failing after a number of attempts.

Query configuration

You can supply further configuration parameters to alter the default behavior of .executableQuery(). You do so through the method .withConfig(), which takes a QueryConfig object.

Database selection

It is recommended to always specify the database explicitly with the .withDatabase("<dbName>") method, even on single-database instances. This allows the driver to work more efficiently, as it saves a network round-trip to the server to resolve the home database. If no database is given, the user’s home database is used.

// import org.neo4j.driver.QueryConfig;

var result = driver.executableQuery("MATCH (p:Person) RETURN p.name")
    .withConfig(QueryConfig.builder().withDatabase("neo4j").build())
    .execute();
Specifying the database through the configuration method is preferred over the USE Cypher clause. If the server runs on a cluster, queries with USE require server-side routing to be enabled. Queries may also take longer to execute as they may not reach the right cluster member at the first attempt, and need to be routed to one containing the requested database.

Request routing

In a cluster environment, all queries are directed to the leader node by default. To improve performance on read queries, you can use the method .withRouting(RoutingControl.READ) to route a query to the read nodes.

// import org.neo4j.driver.QueryConfig;
// import org.neo4j.driver.RoutingControl;

var result = driver.executableQuery("MATCH (p:Person) RETURN p.name")
    .withConfig(QueryConfig.builder()
        .withDatabase("neo4j")
        .withRouting(RoutingControl.READ)
        .build())
    .execute();

Although executing a write query in read mode likely results in a runtime error, you should not rely on this for access control. The difference between the two modes is that read transactions will be routed to any node of a cluster, whereas write ones will be directed to the leader. In other words, there is no guarantee that a write query submitted in read mode will be rejected.

Run queries as a different user

You can execute a query under the security context of a different user with the method .withImpersonatedUser("<username>"), specifying the name of the user to impersonate. For this to work, the user under which the Driver was created needs to have the appropriate permissions. Impersonating a user is cheaper than creating a new Driver object.

// import org.neo4j.driver.QueryConfig;

var result = driver.executableQuery("MATCH (p:Person) RETURN p.name")
    .withConfig(QueryConfig.builder()
        .withDatabase("neo4j")
        .withImpersonatedUser("somebodyElse")
        .build())
    .execute();

When impersonating a user, the query is run within the complete security context of the impersonated user and not the authenticated user (i.e. home database, permissions, etc.).

A full example

package demo;

import java.util.Map;
import java.util.List;
import java.util.concurrent.TimeUnit;

import org.neo4j.driver.AuthTokens;
import org.neo4j.driver.GraphDatabase;
import org.neo4j.driver.Record;
import org.neo4j.driver.QueryConfig;
import org.neo4j.driver.RoutingControl;

public class App {

    public static void main(String... args) {
        final String dbUri = "<URI for Neo4j database>";
        final String dbUser = "<Username>";
        final String dbPassword = "<Password>";

        try (var driver = GraphDatabase.driver(dbUri, AuthTokens.basic(dbUser, dbPassword))) {

            List<Map> people = List.of(
                Map.of("name", "Alice", "age", 42, "friends", List.of("Bob", "Peter", "Anna")),
                Map.of("name", "Bob", "age", 19),
                Map.of("name", "Peter", "age", 50),
                Map.of("name", "Anna", "age", 30)
            );

            try {

                //Create some nodes
                people.forEach(person -> {
                    var result = driver.executableQuery("CREATE (p:Person {name: $person.name, age: $person.age})")
                        .withConfig(QueryConfig.builder().withDatabase("neo4j").build())
                        .withParameters(Map.of("person", person))
                        .execute();
                });

                // Create some relationships
                people.forEach(person -> {
                    if(person.containsKey("friends")) {
                        var result = driver.executableQuery("""
                            MATCH (p:Person {name: $person.name})
                            UNWIND $person.friends AS friend_name
                            MATCH (friend:Person {name: friend_name})
                            CREATE (p)-[:KNOWS]->(friend)
                             """)
                            .withConfig(QueryConfig.builder().withDatabase("neo4j").build())
                            .withParameters(Map.of("person", person))
                            .execute();
                    }
                });

                // Retrieve Alice's friends who are under 40
                var result = driver.executableQuery("""
                    MATCH (p:Person {name: $name})-[:KNOWS]-(friend:Person)
                    WHERE friend.age < $age
                    RETURN friend
                     """)
                    .withConfig(QueryConfig.builder()
                        .withDatabase("neo4j")
                        .withRouting(RoutingControl.READ)
                        .build())
                    .withParameters(Map.of("name", "Alice", "age", 40))
                    .execute();

                // Loop through results and do something with them
                result.records().forEach(r -> {
                    System.out.println(r);
                });

                // Summary information
                System.out.printf("The query %s returned %d records in %d ms.%n",
                    result.summary().query(), result.records().size(),
                    result.summary().resultAvailableAfter(TimeUnit.MILLISECONDS));

            } catch (Exception e) {
                System.out.println(e.getMessage());
                System.exit(1);
            }
        }
    }
}

For more information see API documentation → Driver.executableQuery().

Glossary

LTS

A Long Term Support release is one guaranteed to be supported for a number of years. Neo4j 4.4 is LTS, and Neo4j 5 will also have an LTS version.

Aura

Aura is Neo4j’s fully managed cloud service. It comes with both free and paid plans.

Cypher

Cypher is Neo4j’s graph query language that lets you retrieve data from the database. It is like SQL, but for graphs.

APOC

Awesome Procedures On Cypher (APOC) is a library of (many) functions that can not be easily expressed in Cypher itself.

Bolt

Bolt is the protocol used for interaction between Neo4j instances and drivers. It listens on port 7687 by default.

ACID

Atomicity, Consistency, Isolation, Durability (ACID) are properties guaranteeing that database transactions are processed reliably. An ACID-compliant DBMS ensures that the data in the database remains accurate and consistent despite failures.

eventual consistency

A database is eventually consistent if it provides the guarantee that all cluster members will, at some point in time, store the latest version of the data.

causal consistency

A database is causally consistent if read and write queries are seen by every member of the cluster in the same order. This is stronger than eventual consistency.

NULL

The null marker is not a type but a placeholder for absence of value. For more information, see Cypher → Working with null.

transaction

A transaction is a unit of work that is either committed in its entirety or rolled back on failure. An example is a bank transfer: it involves multiple steps, but they must all succeed or be reverted, to avoid money being subtracted from one account but not added to the other.

backpressure

Backpressure is a force opposing the flow of data. It ensures that the client is not being overwhelmed by data faster than it can handle.

transaction function

A transaction function is a callback executed by an executeRead or executeWrite call. The driver automatically re-executes the callback in case of server failure.

Driver

A Driver object holds the details required to establish connections with a Neo4j database.