This tutorial shows you how build a simple Java application with CockroachDB and the Hibernate ORM.
We recommend using Java versions 8+ with CockroachDB.
For a sample app and tutorial that uses Spring Data JPA (Hibernate) and CockroachDB, see Build a Spring App with CockroachDB and JPA.
For another use of Hibernate with CockroachDB, see our examples-orms
repository.
Step 1. Start CockroachDB
Create a free cluster
- If you haven't already, sign up for a CockroachDB Cloud account.
- Log in to your CockroachDB Cloud account.
- On the Clusters page, click Create Cluster.
- On the Create your cluster page, select Serverless.
Click Create cluster.
Your cluster will be created in a few seconds and the Create SQL user dialog will display.
Create a SQL user
The Create SQL user dialog allows you to create a new SQL user and password.
- Enter a username in the SQL user field or use the one provided by default.
- Click Generate & save password.
- Copy the generated password and save it in a secure location.
Click Next.
Currently, all new users are created with full privileges. For more information and to change the default settings, see [Manage SQL users on a cluster.
Get the connection information
The Connect to cluster dialog shows information about how to connect to your cluster.
- Select Parameters only from the Select option dropdown.
- Copy the connection information for each parameter displayed and save it in a secure location.
- If you haven't already, download the CockroachDB binary.
Run the
cockroach start-single-node
command:$ cockroach start-single-node --advertise-addr 'localhost' --insecure
This starts an insecure, single-node cluster.
Take note of the following connection information in the SQL shell welcome text:
CockroachDB node starting at 2021-08-30 17:25:30.06524 +0000 UTC (took 4.3s) build: CCL v21.1.6 @ 2021/07/20 15:33:43 (go1.15.11) webui: http://localhost:8080 sql: postgresql://root@localhost:26257?sslmode=disable
You'll use the
sql
connection string to connect to the cluster later in this tutorial.
The --insecure
flag used in this tutorial is intended for non-production testing only. To run CockroachDB in production, use a secure cluster instead.
Step 2. Get the sample code
Clone the example-app-java-hibernate
repo to your machine:
git clone https://github.com/cockroachlabs/example-app-java-hibernate/
The version of the CockroachDB Hibernate dialect in hibernate.cfg.xml
corresponds to a version of CockroachDB. For more information, see Install Client Drivers: Hibernate.
Step 3. Run the code
The sample code in this tutorial (Sample.java
) uses Hibernate to map Java methods to SQL operations. The code performs the following operations, which roughly correspond to method calls in the Sample
class:
- Creates an
accounts
table as specified by theAccount
mapping class. - Inserts rows into the table with the
addAccounts()
method. - Transfers money from one account to another with the
transferFunds()
method. - Prints out account balances before and after the transfer with the
getAccountBalance()
method.
In addition, the code shows a pattern for automatically handling transaction retries by wrapping transactions in a higher-order function named runTransaction()
. It also includes a method for testing the retry handling logic (Sample.forceRetryLogic()
), which will be run if you set the FORCE_RETRY
variable to true
.
It does all of the above using the practices we recommend for using Hibernate (and the underlying JDBC connection) with CockroachDB, which are listed in the Recommended Practices section below.
package com.cockroachlabs;
import java.io.Serializable;
import java.math.BigDecimal;
import java.util.Random;
import java.util.function.Function;
import jakarta.persistence.Column;
import jakarta.persistence.Entity;
import jakarta.persistence.Id;
import jakarta.persistence.Table;
import org.hibernate.JDBCException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
public class Sample implements Serializable {
private static final Random RAND = new Random();
private static final boolean FORCE_RETRY = false;
private static final String RETRY_SQL_STATE = "40001";
private static final int MAX_ATTEMPT_COUNT = 6;
private static Function<Session, BigDecimal> addAccounts() throws JDBCException {
Function<Session, BigDecimal> f = s -> {
BigDecimal rv = new BigDecimal(0);
try {
s.save(new Account(1, 1000));
s.save(new Account(2, 250));
s.save(new Account(3, 314159));
rv = BigDecimal.valueOf(1);
System.out.printf("APP: addAccounts() --> %.2f\n", rv);
} catch (JDBCException e) {
throw e;
}
return rv;
};
return f;
}
private static Function<Session, BigDecimal> transferFunds(long fromId, long toId, BigDecimal amount) throws JDBCException {
Function<Session, BigDecimal> f = s -> {
BigDecimal rv = new BigDecimal(0);
try {
Account fromAccount = (Account) s.get(Account.class, fromId);
Account toAccount = (Account) s.get(Account.class, toId);
if (!(amount.compareTo(fromAccount.getBalance()) > 0)) {
fromAccount.balance = fromAccount.balance.subtract(amount);
toAccount.balance = toAccount.balance.add(amount);
s.save(fromAccount);
s.save(toAccount);
rv = amount;
System.out.printf("APP: transferFunds(%d, %d, %.2f) --> %.2f\n", fromId, toId, amount, rv);
}
} catch (JDBCException e) {
throw e;
}
return rv;
};
return f;
}
// Test our retry handling logic if FORCE_RETRY is true. This
// method is only used to test the retry logic. It is not
// intended for production code.
private static Function<Session, BigDecimal> forceRetryLogic() throws JDBCException {
Function<Session, BigDecimal> f = s -> {
BigDecimal rv = new BigDecimal(-1);
try {
System.out.printf("APP: testRetryLogic: BEFORE EXCEPTION\n");
s.createNativeQuery("SELECT crdb_internal.force_retry('1s')").executeUpdate();
} catch (JDBCException e) {
System.out.printf("APP: testRetryLogic: AFTER EXCEPTION\n");
throw e;
}
return rv;
};
return f;
}
private static Function<Session, BigDecimal> getAccountBalance(long id) throws JDBCException {
Function<Session, BigDecimal> f = s -> {
BigDecimal balance;
try {
Account account = s.get(Account.class, id);
balance = account.getBalance();
System.out.printf("APP: getAccountBalance(%d) --> %.2f\n", id, balance);
} catch (JDBCException e) {
throw e;
}
return balance;
};
return f;
}
// Run SQL code in a way that automatically handles the
// transaction retry logic so we don't have to duplicate it in
// various places.
private static BigDecimal runTransaction(Session session, Function<Session, BigDecimal> fn) {
BigDecimal rv = new BigDecimal(0);
int attemptCount = 0;
while (attemptCount < MAX_ATTEMPT_COUNT) {
attemptCount++;
if (attemptCount > 1) {
System.out.printf("APP: Entering retry loop again, iteration %d\n", attemptCount);
}
Transaction txn = session.beginTransaction();
System.out.printf("APP: BEGIN;\n");
if (attemptCount == MAX_ATTEMPT_COUNT) {
String err = String.format("hit max of %s attempts, aborting", MAX_ATTEMPT_COUNT);
throw new RuntimeException(err);
}
// This block is only used to test the retry logic.
// It is not necessary in production code. See also
// the method 'testRetryLogic()'.
if (FORCE_RETRY) {
session.createNativeQuery("SELECT now()").list();
}
try {
rv = fn.apply(session);
if (!rv.equals(-1)) {
txn.commit();
System.out.printf("APP: COMMIT;\n");
break;
}
} catch (JDBCException e) {
if (RETRY_SQL_STATE.equals(e.getSQLState())) {
// Since this is a transaction retry error, we
// roll back the transaction and sleep a little
// before trying again. Each time through the
// loop we sleep for a little longer than the last
// time (A.K.A. exponential backoff).
System.out.printf("APP: retryable exception occurred:\n sql state = [%s]\n message = [%s]\n retry counter = %s\n", e.getSQLState(), e.getMessage(), attemptCount);
System.out.printf("APP: ROLLBACK;\n");
txn.rollback();
int sleepMillis = (int) (Math.pow(2, attemptCount) * 100) + RAND.nextInt(100);
System.out.printf("APP: Hit 40001 transaction retry error, sleeping %s milliseconds\n", sleepMillis);
try {
Thread.sleep(sleepMillis);
} catch (InterruptedException ignored) {
// no-op
}
rv = BigDecimal.valueOf(-1);
} else {
throw e;
}
}
}
return rv;
}
public static void main(String[] args) {
// Create a SessionFactory based on our hibernate.cfg.xml configuration
// file, which defines how to connect to the database.
SessionFactory sessionFactory
= new Configuration()
.configure("hibernate.cfg.xml")
.addAnnotatedClass(Account.class)
.buildSessionFactory();
try (Session session = sessionFactory.openSession()) {
long fromAccountId = 1;
long toAccountId = 2;
BigDecimal transferAmount = BigDecimal.valueOf(100);
if (FORCE_RETRY) {
System.out.printf("APP: About to test retry logic in 'runTransaction'\n");
runTransaction(session, forceRetryLogic());
} else {
runTransaction(session, addAccounts());
BigDecimal fromBalance = runTransaction(session, getAccountBalance(fromAccountId));
BigDecimal toBalance = runTransaction(session, getAccountBalance(toAccountId));
if (!fromBalance.equals(-1) && !toBalance.equals(-1)) {
// Success!
System.out.printf("APP: getAccountBalance(%d) --> %.2f\n", fromAccountId, fromBalance);
System.out.printf("APP: getAccountBalance(%d) --> %.2f\n", toAccountId, toBalance);
}
// Transfer $100 from account 1 to account 2
BigDecimal transferResult = runTransaction(session, transferFunds(fromAccountId, toAccountId, transferAmount));
if (!transferResult.equals(-1)) {
// Success!
System.out.printf("APP: transferFunds(%d, %d, %.2f) --> %.2f \n", fromAccountId, toAccountId, transferAmount, transferResult);
BigDecimal fromBalanceAfter = runTransaction(session, getAccountBalance(fromAccountId));
BigDecimal toBalanceAfter = runTransaction(session, getAccountBalance(toAccountId));
if (!fromBalanceAfter.equals(-1) && !toBalanceAfter.equals(-1)) {
// Success!
System.out.printf("APP: getAccountBalance(%d) --> %.2f\n", fromAccountId, fromBalanceAfter);
System.out.printf("APP: getAccountBalance(%d) --> %.2f\n", toAccountId, toBalanceAfter);
}
}
}
} finally {
sessionFactory.close();
}
}
}
Update the connection configuration
Open src/main/resources/hibernate.cfg.xml
, and set the hibernate.connection.url
, hibernate.connection.username
, and hibernate.connection.password
properties, using the connection information that you obtained from the Cloud Console:
<property name="hibernate.connection.url">jdbc:postgresql://{host}:{port}/defaultdb?options=--cluster%3D{routing-id}&sslmode=verify-full</property>
<property name="hibernate.connection.username">{username}</property>
<property name="hibernate.connection.password">{password}</property>
Run the code
Compile and run the code using gradlew
, which will also download the dependencies:
$ cd example-app-java-hibernate
$ ./gradlew run
Toward the end of the output, you should see:
APP: BEGIN;
APP: addAccounts() --> 1.00
APP: COMMIT;
APP: BEGIN;
APP: getAccountBalance(1) --> 1000.00
APP: COMMIT;
APP: BEGIN;
APP: getAccountBalance(2) --> 250.00
APP: COMMIT;
APP: getAccountBalance(1) --> 1000.00
APP: getAccountBalance(2) --> 250.00
APP: BEGIN;
APP: transferFunds(1, 2, 100.00) --> 100.00
APP: COMMIT;
APP: transferFunds(1, 2, 100.00) --> 100.00
APP: BEGIN;
APP: getAccountBalance(1) --> 900.00
APP: COMMIT;
APP: BEGIN;
APP: getAccountBalance(2) --> 350.00
APP: COMMIT;
APP: getAccountBalance(1) --> 900.00
APP: getAccountBalance(2) --> 350.00
Recommended Practices
Generate PKCS8 keys for client authentication
You can pass the --also-generate-pkcs8-key
flag to cockroach cert
to generate a key in PKCS#8 format, which is the standard key encoding format in Java. For example, if you have the user max
:
$ cockroach cert create-client max --certs-dir=certs --ca-key=my-safe-directory/ca.key --also-generate-pkcs8-key
The generated PKCS8 key will be named client.max.key.pk8
.
CockroachDB Cloud does not yet support certificate-based user authentication.
Use IMPORT
to read in large data sets
If you are trying to get a large data set into CockroachDB all at once (a bulk import), avoid writing client-side code altogether and use the IMPORT
statement instead. It is much faster and more efficient than making a series of INSERT
s and UPDATE
s. It bypasses the SQL layer altogether and writes directly to the storage layer of the database.
For more information about importing data from PostgreSQL, see Migrate from PostgreSQL.
For more information about importing data from MySQL, see Migrate from MySQL.
Use reWriteBatchedInserts
for increased speed
We strongly recommend setting reWriteBatchedInserts=true
; we have seen 2-3x performance improvements with it enabled. From the JDBC connection parameters documentation:
This will change batch inserts from
insert into foo (col1, col2, col3) values (1,2,3)
intoinsert into foo (col1, col2, col3) values (1,2,3), (4,5,6)
this provides 2-3x performance improvement
Retrieve large data sets in chunks using cursors
CockroachDB now supports the PostgreSQL wire-protocol cursors for implicit transactions and explicit transactions executed to completion. This means the PGJDBC driver can use this protocol to stream queries with large result sets. This is much faster than paginating through results in SQL using LIMIT .. OFFSET
.
For instructions showing how to use cursors in your Java code, see Getting results based on a cursor from the PGJDBC documentation.
Note that interleaved execution (partial execution of multiple statements within the same connection and transaction) is not supported when Statement.setFetchSize()
is used.
What's next?
Read more about using the Hibernate ORM, or check out a more realistic implementation of Hibernate with CockroachDB in our examples-orms
repository.
You might also be interested in the following pages: