Run your own transactions

// import org.neo4j.driver.SessionConfig

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

// import java.util.Map
// import org.neo4j.driver.SessionConfig

try (var session = driver.session(SessionConfig.builder().withDatabase("neo4j").build())) {  (1)
    var people = session.executeRead(tx -> {  (2)
        var result = tx.run("""
        MATCH (p:Person) WHERE p.name STARTS WITH $filter  (3)
        RETURN p.name AS name ORDER BY name
        """, Map.of("filter", "Al"));
        return result.list();  // return a list of Record objects (4)
    });
    people.forEach(person -> {
        System.out.println(person);
    });
    // further tx.run() calls will execute within the same transaction
}

package demo;

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

import org.neo4j.driver.AuthTokens;
import org.neo4j.driver.GraphDatabase;
import org.neo4j.driver.QueryConfig;
import org.neo4j.driver.Record;
import org.neo4j.driver.RoutingControl;
import org.neo4j.driver.SessionConfig;
import org.neo4j.driver.TransactionContext;
import org.neo4j.driver.exceptions.NoSuchRecordException;

public class App {

    // Create & employ 100 people to 10 different organizations
    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))) {
            try (var session = driver.session(SessionConfig.builder().withDatabase("neo4j").build())) {
                for (int i=0; i<100; i++) {
                    String name = String.format("Thor%d", i);

                    try {
                        String orgId = session.executeWrite(tx -> employPersonTx(tx, name));
                        System.out.printf("User %s added to organization %s.%n", name, orgId);
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                    }
                }
            }
        }
    }

    static String employPersonTx(TransactionContext tx, String name) {
        final int employeeThreshold = 10;

        // Create new Person node with given name, if not exists already
        tx.run("MERGE (p:Person {name: $name})", Map.of("name", name));

        // Obtain most recent organization ID and the number of people linked to it
        var result = tx.run("""
            MATCH (o:Organization)
            RETURN o.id AS id, COUNT{(p:Person)-[r:WORKS_FOR]->(o)} AS employeesN
            ORDER BY o.createdDate DESC
            LIMIT 1
            """);

        Record org = null;
        String orgId = null;
        int employeesN = 0;
        try {
            org = result.single();
            orgId = org.get("id").asString();
            employeesN = org.get("employeesN").asInt();
        } catch (NoSuchRecordException e) {
            // The query is guaranteed to return <= 1 results, so if.single() throws, it means there's none.
            // If no organization exists, create one and add Person to it
            orgId = createOrganization(tx);
            System.out.printf("No orgs available, created %s.%n", orgId);
        }

        // If org does not have too many employees, add this Person to it
        if (employeesN < employeeThreshold) {
            addPersonToOrganization(tx, name, orgId);
            // If the above throws, the transaction will roll back
            // -> not even Person is created!

        // Otherwise, create a new Organization and link Person to it
        } else {
            orgId = createOrganization(tx);
            System.out.printf("Latest org is full, created %s.%n", orgId);
            addPersonToOrganization(tx, name, orgId);
            // If any of the above throws, the transaction will roll back
            // -> not even Person is created!
        }

        return orgId;  // Organization ID to which the new Person ends up in
    }

    static String createOrganization(TransactionContext tx) {
        var result = tx.run("""
            CREATE (o:Organization {id: randomuuid(), createdDate: datetime()})
            RETURN o.id AS id
        """);
        var org = result.single();
        var orgId = org.get("id").asString();
        return orgId;
    }

    static void addPersonToOrganization(TransactionContext tx, String personName, String orgId) {
        tx.run("""
            MATCH (o:Organization {id: $orgId})
            MATCH (p:Person {name: $name})
            MERGE (p)-[:WORKS_FOR]->(o)
            """, Map.of("orgId", orgId, "name", personName)
        );
    }
}

try (var session = driver.session(SessionConfig.builder().withDatabase("neo4j").build())) {
    try (Transaction tx = session.beginTransaction()) {
        // use tx.run() to run queries
        //     tx.commit() to commit the transaction
        //     tx.rollback() to rollback the transaction
    }
}

package demo;

import java.util.Map;
import java.util.List;
import java.util.Arrays;

import org.neo4j.driver.AuthTokens;
import org.neo4j.driver.Driver;
import org.neo4j.driver.GraphDatabase;
import org.neo4j.driver.QueryConfig;
import org.neo4j.driver.Record;
import org.neo4j.driver.SessionConfig;
import org.neo4j.driver.Transaction;

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))) {
            driver.verifyConnectivity();

            String customerId = createCustomer(driver);
            int otherBankId = 42;
            transferToOtherBank(driver, customerId, otherBankId, 999);
        }
    }

    static String createCustomer(Driver driver) {
        var result = driver.executableQuery("""
            MERGE (c:Customer {id: randomUUID(), balance: 1000})
            RETURN c.id AS id
            """)
            .withConfig(QueryConfig.builder().withDatabase("neo4j").build())
            .execute();
        return result.records().get(0).get("id").asString();
    }

    static void transferToOtherBank(Driver driver, String customerId, int otherBankId, float amount) {
        try (var session = driver.session(SessionConfig.builder().withDatabase("neo4j").build())) {
            try (var tx = session.beginTransaction()) {
                if (! customerBalanceCheck(tx, customerId, amount)) {
                    System.out.printf("Customer %s doesn't have enough funds.%n", customerId);
                    return;  // give up
                }

                otherBankTransferApi(customerId, otherBankId, amount);
                // Now the money has been transferred => can't rollback anymore
                // (cannot rollback external services interactions)

                try {
                    decreaseCustomerBalance(tx, customerId, amount);
                    tx.commit();
                    System.out.printf("Transferred %f to %s.%n", amount, customerId);
                } catch (Exception e) {
                    requestInspection(customerId, otherBankId, amount, e);
                    throw new RuntimeException(e.getMessage());
                }
            }
        }
    }

    static boolean customerBalanceCheck(Transaction tx, String customerId, float amount) {
        var result = tx.run("""
            MATCH (c:Customer {id: $id})
            RETURN c.balance >= $amount AS sufficient
            """, Map.of("id", customerId, "amount", amount));
        var record = result.single();
        return record.get("sufficient").asBoolean();
    }

    static void otherBankTransferApi(String customerId, int otherBankId, float amount) {
        // make some API call to other bank
    }

    static void decreaseCustomerBalance(Transaction tx, String customerId, float amount) {
        tx.run("""
            MATCH (c:Customer {id: $id})
            SET c.balance = c.balance - $amount
            """, Map.of("id", customerId, "amount", amount));
    }

    static void requestInspection(String customerId, int otherBankId, float amount, Exception e) {
        // manual cleanup required; log this or similar
        System.out.printf("WARNING: transaction rolled back due to exception: %s.%n", e.getMessage());
        System.out.printf("customerId: %s, otherBankId: %d, amount: %f.%n", customerId, otherBankId, amount);
    }
}

// import java.time.Duration
// import org.neo4j.driver.SessionConfig
// import org.neo4j.driver.TransactionConfig

try (var session = driver.session(SessionConfig.builder().withDatabase("neo4j").build())) {
    var people = session.executeRead(tx -> {
        var result = tx.run("MATCH (p:Person) RETURN p");
        return result.list();  // return a list of Record objects
    }, TransactionConfig.builder()
        .withTimeout(Duration.ofSeconds(5))  // mark-line
        .withMetadata(Map.of("appName", "peopleTracker"))  // mark-line
        .build()
    );
    people.forEach(person -> System.out.println(person));
}

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

// session usage

session.close();