neo4j-driver-java-skill

When to Use

Java/Kotlin code connecting to Neo4j (Aura or self-managed)
Setting up driver, sessions, transactions in Maven/Gradle projects
Debugging result handling, error recovery, connection pool issues
Async (
```
CompletableFuture
```
) or reactive (Project Reactor / RxJava) Neo4j access

When NOT to Use

Cypher query authoring/optimization →
```
neo4j-cypher-skill
```
Driver version upgrades →
```
neo4j-migration-skill
```

Spring Data Neo4j (

@Node

@Relationship

Neo4jRepository

) →

neo4j-spring-data-skill

Dependency

Maven

xml

<dependency>
    <groupId>org.neo4j.driver</groupId>
    <artifactId>neo4j-java-driver</artifactId>
    <version>6.0.5</version>
</dependency>

Gradle

groovy

implementation 'org.neo4j.driver:neo4j-java-driver:6.0.5'

Check latest: https://central.sonatype.com/artifact/org.neo4j.driver/neo4j-java-driver

Environment Variables

Standard pattern for connection config — never hardcode credentials:

java

String uri      = System.getenv().getOrDefault("NEO4J_URI",      "neo4j://localhost:7687");
String user     = System.getenv().getOrDefault("NEO4J_USERNAME",  "neo4j");
String password = System.getenv().getOrDefault("NEO4J_PASSWORD",  "");
String database = System.getenv().getOrDefault("NEO4J_DATABASE",  "neo4j");

Spring Boot: inject via

@Value("${spring.neo4j.uri}")

application.properties

properties

spring.neo4j.uri=neo4j+s://xxx.databases.neo4j.io
spring.neo4j.authentication.username=neo4j
spring.neo4j.authentication.password=secret

Driver Lifecycle

One

Driver

per application — thread-safe, expensive to create. Implement

AutoCloseable

or use try-with-resources.

java

// Long-lived singleton
var driver = GraphDatabase.driver(
    "neo4j+s://xxx.databases.neo4j.io",          // Aura TLS+routing
    AuthTokens.basic(user, password));
driver.verifyConnectivity();                      // fail fast

// Short-lived (tests / CLI)
try (var driver = GraphDatabase.driver(uri, AuthTokens.basic(user, password))) {
    driver.verifyConnectivity();
    // ...
}

URI schemes:

URI	Use
`neo4j://localhost`	Unencrypted, cluster routing
`neo4j+s://xxx.databases.neo4j.io`	TLS + cluster routing (Aura)
`bolt://localhost:7687`	Unencrypted, single instance
`bolt+s://localhost:7687`	TLS, single instance

Auth options:

AuthTokens.basic(u,p)

AuthTokens.bearer(token)

AuthTokens.kerberos(b64)

AuthTokens.none()

Choosing the Right API

API	When	Auto-retry	Streaming
`driver.executableQuery()`	Default for most queries	✅	❌ eager
`session.executeRead/Write()`	Large results, callback control	✅	✅
`session.beginTransaction()`	Multi-method, external coordination	❌	✅
`session.run()`	Self-managing queries ( `CALL IN TRANSACTIONS` )	❌	✅
`driver.asyncSession()`	Non-blocking `CompletableFuture`	✅	✅
`driver.rxSession()`	Reactor/RxJava backpressure	✅	✅

CALL { … } IN TRANSACTIONS

and

USING PERIODIC COMMIT

self-manage their transaction — use

session.run()

only.

executableQuery

and

executeRead/Write

will fail for these queries.

executableQuery

— Default

java

// Read — route to replicas
var result = driver.executableQuery("""
        MATCH (p:Person {name: $name})-[:KNOWS]->(friend)
        RETURN friend.name AS name
        """)
    .withParameters(Map.of("name", "Alice"))
    .withConfig(QueryConfig.builder()
        .withDatabase("neo4j")            // always specify — avoids home-db round-trip
        .withRouting(RoutingControl.READ)
        .build())
    .execute();

result.records().forEach(r -> System.out.println(r.get("name").asString()));
long ms = result.summary().resultAvailableAfter(TimeUnit.MILLISECONDS);

// Write
driver.executableQuery("CREATE (p:Person {name: $name, age: $age})")
    .withParameters(Map.of("name", "Bob", "age", 30))
    .withConfig(QueryConfig.builder().withDatabase("neo4j").build())
    .execute();

Never string-interpolate Cypher. Always

.withParameters(Map.of(...))

Managed Transactions (

executeRead

executeWrite

)

Sessions are NOT thread-safe — one per request/thread, always close.

java

try (var session = driver.session(SessionConfig.builder()
        .withDatabase("neo4j").build())) {

    // Read → replica routing
    var names = session.executeRead(tx -> {
        var result = tx.run(
            "MATCH (p:Person) WHERE p.name STARTS WITH $prefix RETURN p.name AS name",
            Map.of("prefix", "Al"));
        return result.stream().map(r -> r.get("name").asString()).toList(); // collect INSIDE
    });

    // Write → leader routing
    session.executeWriteWithoutResult(tx ->
        tx.run("CREATE (p:Person {name: $name})", Map.of("name", "Carol"))
    );
}

Result must be consumed INSIDE the callback

Result

is a lazy cursor tied to the open transaction. Transaction closes when callback returns — any read after that throws

ResultConsumedException

java

// ❌ Returns Result — already closed by the time caller uses it
var result = session.executeRead(tx ->
    tx.run("MATCH (p:Person) RETURN p.name AS name"));
result.stream().forEach(...); // throws ResultConsumedException

// ✅ Collect to List inside callback
var names = session.executeRead(tx ->
    tx.run("MATCH (p:Person) RETURN p.name AS name")
      .stream().map(r -> r.get("name").asString()).toList());

Callback rules

Consume each
```
Result
```
before next
```
tx.run()
```
— multiple open cursors = undefined behaviour.
No side effects (HTTP, email, metric increments) — callback may be retried on transient errors.
Use
```
MERGE
```
(idempotent), not
```
CREATE
```
, for retry-safe writes.
```
executeRead
```
→ replica;
```
executeWrite
```
→ leader.

TransactionConfig — timeouts & metadata

java

var config = TransactionConfig.builder()
    .withTimeout(Duration.ofSeconds(5))
    .withMetadata(Map.of("app", "myService", "user", userId))  // visible in SHOW TRANSACTIONS
    .build();
session.executeRead(tx -> { /* ... */ }, config);

Explicit Transactions

Use when work spans multiple methods or requires external coordination. Not auto-retried.

java

try (var session = driver.session(SessionConfig.builder().withDatabase("neo4j").build())) {
    var tx = session.beginTransaction();
    try {
        doPartA(tx);
        doPartB(tx);
        tx.commit();
    } catch (Exception e) {
        try { tx.rollback(); } catch (Exception rb) { e.addSuppressed(rb); }
        throw e;
    }
}

tx.rollback()

is a network call — wrap in its own try/catch and use

addSuppressed

so the original exception is not lost.

Commit uncertainty: if

tx.commit()

throws

ServiceUnavailableException

, the commit may or may not have succeeded. Design writes as idempotent (

MERGE

+ unique constraints) so retrying is safe.

Choose explicit vs managed:

Auto-retry needed →
```
executeRead
```
/
```
executeWrite
```
Work spans multiple methods → explicit (pass
```
tx
```
as parameter)
Coordinating with external I/O → explicit (commit only after I/O succeeds)

Error Handling

java

try {
    driver.executableQuery("...").execute();
} catch (ServiceUnavailableException e) {
    // No servers — check connection
} catch (SessionExpiredException e) {
    // Server closed session — open new one
} catch (TransientException e) {
    // Managed txns retry automatically; explicit txns need manual retry
} catch (Neo4jException e) {
    // Cypher/constraint error — e.code() gives GQL status code
}

Managed transactions auto-retry

TransientException

— no catch needed.

Data Types & Value Extraction

Cypher type	Java accessor
`Integer`	`value.asLong()` / `value.asInt()`
`Float`	`value.asDouble()`
`String`	`value.asString()`
`Boolean`	`value.asBoolean()`
`List`	`value.asList()`
`Map`	`value.asMap()`
`Node`	`value.asNode()`
`Relationship`	`value.asRelationship()`
`Date`	`value.asLocalDate()`
`DateTime`	`value.asZonedDateTime()`

java

var record = result.records().get(0);
String name = record.get("name").asString();
long age    = record.get("age").asLong();

var node = record.get("p").asNode();
String label = node.labels().iterator().next();
Map<String,Object> props = node.asMap();

Null safety — two distinct cases

Situation	`record.get(key)`	`.asString()`
Key present, value non-null	the value	returns string
Key present, value is graph null	`Value` where `.isNull()` = true	throws `Uncoercible`
Key absent (typo / not projected)	`Value.NULL` sentinel	throws `NoSuchElementException`

java

// Graph null — use default overload (safe only if key is always projected):
String city = record.get("city").asString("Unknown");

// Absent key — check containsKey first:
if (record.containsKey("city") && !record.get("city").isNull()) {
    String city = record.get("city").asString();
}

Object Mapping

Map query results to Java records/classes directly — eliminates manual accessor calls.

java

// Domain record — field names match RETURN aliases (case-sensitive)
public record Person(String name, long age) {}

// Map single record
var person = driver.executableQuery("MATCH (p:Person {name: $name}) RETURN p.name AS name, p.age AS age")
    .withParameters(Map.of("name", "Alice"))
    .withConfig(QueryConfig.builder().withDatabase("neo4j").build())
    .execute()
    .records()
    .stream()
    .map(r -> r.get("name").asString())   // or: r.as(Person.class) — see note
    .findFirst()
    .orElseThrow();

// Using .as(Person.class) — maps RETURN keys to record fields by name
var person2 = driver.executableQuery("""
        MATCH (p:Person {name: $name})
        RETURN p.name AS name, p.age AS age
        """)
    .withParameters(Map.of("name", "Tom Hanks"))
    .withConfig(QueryConfig.builder().withDatabase("neo4j").build())
    .execute()
    .records()
    .stream()
    .map(record -> record.get("p").as(Person.class))
    .findFirst()
    .orElseThrow(() -> new RuntimeException("Person not found"));

Nested mapping — return a map projection and include

COLLECT {}

for lists:

java

public record Movie(String title, List<Person> actors) {}

var movieCypher = """
    MATCH (movie:Movie)
    LIMIT 1
    RETURN movie {
        .title,
        actors: COLLECT {
            MATCH (actor:Person)-[:ACTED_IN]->(movie)
            RETURN actor
        }
    }
    """;

var movie = driver.executableQuery(movieCypher)
    .withConfig(QueryConfig.builder().withDatabase("neo4j").build())
    .execute()
    .records()
    .stream()
    .map(r -> r.get("movie").as(Movie.class))
    .findFirst()
    .orElseThrow();

Only mapped properties defined in the record are populated — extra properties returned by Cypher are ignored.

Performance Patterns

Always specify database — omitting triggers home-db round-trip on every call.

Route reads to replicas —

RoutingControl.READ

QueryConfig

or use

executeRead

Batch writes with
UNWIND
— pass

List<Map<String,Object>>

(plain maps only; custom objects fail):

java

List<Map<String, Object>> rows = people.stream()
    .map(p -> Map.<String, Object>of("name", p.name(), "age", p.age()))
    .toList();

driver.executableQuery("UNWIND $items AS item MERGE (p:Person {name: item.name}) SET p.age = item.age")
    .withParameters(Map.of("items", rows))
    .withConfig(QueryConfig.builder().withDatabase("neo4j").build())
    .execute();

Allowed leaf types in parameter maps:

String

Long

Integer

Short

Byte

Double

Float

Boolean

List<?>

Map<String,?>

null

. Custom objects and

LocalDate

must be converted first.

Group writes in one transaction — one

executeWrite

with a loop, not one

executeWrite

per iteration.

Connection pool — default 100 connections. Tune if exhausted:

java

Config.builder()
    .withMaxConnectionPoolSize(50)
    .withConnectionAcquisitionTimeout(30, TimeUnit.SECONDS)
    .build()

Common Errors

Mistake	Fix
String-interpolate Cypher params	`.withParameters(Map.of(...))` always
Omit database name	Set in `QueryConfig` / `SessionConfig` every time
New `Driver` per request	Create once at startup; share everywhere
Share `Session` across threads	One session per request/thread
Return `Result` from tx callback	Collect to `List` / `Map` inside callback
Leave `Result` open before next `tx.run()`	Consume before next call
Side effects in managed tx callback	Move outside — callback may retry
Pass custom objects to UNWIND params	Convert to `List<Map<String,Object>>`
`asString()` on graph null	`.asString("default")` or check `.isNull()`
`asString()` on absent key	`containsKey()` before optional access
Naked `tx.rollback()` in catch	Wrap in try/catch; use `addSuppressed`
Assume `commit()` failure = no commit	Commit uncertainty — design writes idempotent
Block inside async callback ( `.join()` )	Chain with `thenCompose`
Skip session close in async error path	`exceptionallyCompose` to close then re-throw
One transaction per write in loop	Batch with `UNWIND` or group in one callback
`executeWrite` for a read	Use `executeRead` — routes to replica

References

Load on demand:

references/async-reactive.md — full async
```
CompletableFuture
```
patterns, reactive
```
RxSession
```
with
```
Flux.usingWhen
```
, deadlock avoidance
references/advanced-config.md — full
```
Config.builder()
```
options, TLS, notification filtering, session-level auth, user impersonation, cross-session bookmarks, spatial types (Values.point/WGS-84/Cartesian)

Docs:

Java Driver manual: https://neo4j.com/docs/java-manual/current/
API reference: https://neo4j.com/docs/api/java-driver/current/

Checklist

One
```
Driver
```
instance created at startup; closed on shutdown
```
verifyConnectivity()
```
called after driver creation
Database name specified in every
```
QueryConfig
```
/
```
SessionConfig
```
Parameters used (never string-interpolated Cypher)
```
Result
```
consumed inside managed transaction callback
No side effects inside
```
executeRead/Write
```
callbacks
Sessions closed via try-with-resources
Async sessions closed in both success and error paths (
```
exceptionallyCompose
```
)
```
ServiceUnavailableException
```
on commit handled as commit-uncertain
```
UNWIND
```
params are
```
List<Map<String,Object>>
```
(no custom objects)
```
containsKey()
```
checked before accessing optional result columns

neo4j-driver-java-skill

NPX Install

Tags

SKILL.md Content

When to Use

When NOT to Use

Dependency

Maven

Gradle

Environment Variables

Driver Lifecycle

Choosing the Right API

`executableQuery`
— Default

Managed Transactions (
`executeRead`
/
`executeWrite`
)

Result must be consumed INSIDE the callback

Callback rules

TransactionConfig — timeouts & metadata

Explicit Transactions

Error Handling

Data Types & Value Extraction

Null safety — two distinct cases

Object Mapping

Performance Patterns

Common Errors

References

Checklist

neo4j-driver-java-skill

NPX Install

Tags

SKILL.md Content

When to Use

When NOT to Use

Dependency

Maven

Gradle

Environment Variables

Driver Lifecycle

Choosing the Right API

executableQuery — Default

Managed Transactions (executeRead / executeWrite)

Result must be consumed INSIDE the callback

Callback rules

TransactionConfig — timeouts & metadata

Explicit Transactions

Error Handling

Data Types & Value Extraction

Null safety — two distinct cases

Object Mapping

Performance Patterns

Common Errors

References

Checklist

`executableQuery`
— Default

Managed Transactions (
`executeRead`
/
`executeWrite`
)