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.
Before you begin
- Install CockroachDB.
- Start up a secure or insecure local cluster.
- Choose the instructions that correspond to whether your cluster is secure or insecure:
Step 1. Install the Gradle build tool
This tutorial uses the Gradle build tool to get all dependencies for your application, including Hibernate.
To install Gradle on Mac, run the following command:
$ brew install gradle
To install Gradle on a Debian-based Linux distribution like Ubuntu:
$ apt-get install gradle
To install Gradle on a Red Hat-based Linux distribution like Fedora:
$ dnf install gradle
For other ways to install Gradle, see its official documentation.
Step 2. Create the maxroach
user and bank
database
Start the built-in SQL shell:
$ cockroach sql --certs-dir=certs
In the SQL shell, issue the following statements to create the maxroach
user and bank
database:
> CREATE USER IF NOT EXISTS maxroach;
> CREATE DATABASE bank;
Give the maxroach
user the necessary permissions:
> GRANT ALL ON DATABASE bank TO maxroach;
Exit the SQL shell:
> \q
Step 3. Generate a certificate for the maxroach
user
Create a certificate and key for the maxroach
user by running the following command. The code samples will run as this user.
You can pass the --also-generate-pkcs8-key
flag to generate a key in PKCS#8 format, which is the standard key encoding format in Java. In this case, the generated PKCS8 key will be named client.maxroach.key.pk8
.
$ cockroach cert create-client maxroach --certs-dir=certs --ca-key=my-safe-directory/ca.key --also-generate-pkcs8-key
Step 4. Run the Java code
The code below uses Hibernate to map Java methods to SQL operations. It perform the following steps which roughly correspond to method calls in the Sample
class.
- Create an
accounts
table in thebank
database as specified by the HibernateAccount
class. - Inserts rows into the table using
session.save(new Account(int id, int balance))
(seeSample.addAccounts()
). - Transfer money from one account to another, printing out account balances before and after the transfer (see
transferFunds(long fromId, long toId, long amount)
). - Print out account balances before and after the transfer (see
Sample.getAccountBalance(long id)
).
In addition, the code shows a pattern for automatically handling transaction retries by wrapping transactions in a higher-order function Sample.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.
To run it:
Download and extract hibernate-basic-sample.tgz. The settings in
hibernate.cfg.xml
specify how to connect to the database.Note: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.Compile and run the code using
build.gradle
, which will also download the dependencies.$ gradle run
To clone a version of the code below that connects to insecure clusters, run the command below. Note that you will need to edit the connection string to use the certificates that you generated when you set up your secure cluster.
git clone https://github.com/cockroachlabs/example-app-java-hibernate/
The contents of Sample.java
:
package com.cockroachlabs;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.JDBCException;
import org.hibernate.cfg.Configuration;
import java.util.*;
import java.util.function.Function;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
public class Sample {
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;
// Account is our model, which corresponds to the "accounts" database table.
@Entity
@Table(name="accounts")
public static class Account {
@Id
@Column(name="id")
public long id;
public long getId() {
return id;
}
@Column(name="balance")
public long balance;
public long getBalance() {
return balance;
}
public void setBalance(long newBalance) {
this.balance = newBalance;
}
// Convenience constructor.
public Account(int id, int balance) {
this.id = id;
this.balance = balance;
}
// Hibernate needs a default (no-arg) constructor to create model objects.
public Account() {}
}
private static Function<Session, Long> addAccounts() throws JDBCException{
Function<Session, Long> f = s -> {
long rv = 0;
try {
s.save(new Account(1, 1000));
s.save(new Account(2, 250));
s.save(new Account(3, 314159));
rv = 1;
System.out.printf("APP: addAccounts() --> %d\n", rv);
} catch (JDBCException e) {
throw e;
}
return rv;
};
return f;
}
private static Function<Session, Long> transferFunds(long fromId, long toId, long amount) throws JDBCException{
Function<Session, Long> f = s -> {
long rv = 0;
try {
Account fromAccount = (Account) s.get(Account.class, fromId);
Account toAccount = (Account) s.get(Account.class, toId);
if (!(amount > fromAccount.getBalance())) {
fromAccount.balance -= amount;
toAccount.balance += amount;
s.save(fromAccount);
s.save(toAccount);
rv = amount;
System.out.printf("APP: transferFunds(%d, %d, %d) --> %d\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, Long> forceRetryLogic() throws JDBCException {
Function<Session, Long> f = s -> {
long rv = -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, Long> getAccountBalance(long id) throws JDBCException{
Function<Session, Long> f = s -> {
long balance;
try {
Account account = s.get(Account.class, id);
balance = account.getBalance();
System.out.printf("APP: getAccountBalance(%d) --> %d\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 do not have to duplicate it in
// various places.
private static long runTransaction(Session session, Function<Session, Long> fn) {
long rv = 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 != -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 = -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;
long transferAmount = 100;
if (FORCE_RETRY) {
System.out.printf("APP: About to test retry logic in 'runTransaction'\n");
runTransaction(session, forceRetryLogic());
} else {
runTransaction(session, addAccounts());
long fromBalance = runTransaction(session, getAccountBalance(fromAccountId));
long toBalance = runTransaction(session, getAccountBalance(toAccountId));
if (fromBalance != -1 && toBalance != -1) {
// Success!
System.out.printf("APP: getAccountBalance(%d) --> %d\n", fromAccountId, fromBalance);
System.out.printf("APP: getAccountBalance(%d) --> %d\n", toAccountId, toBalance);
}
// Transfer $100 from account 1 to account 2
long transferResult = runTransaction(session, transferFunds(fromAccountId, toAccountId, transferAmount));
if (transferResult != -1) {
// Success!
System.out.printf("APP: transferFunds(%d, %d, %d) --> %d \n", fromAccountId, toAccountId, transferAmount, transferResult);
long fromBalanceAfter = runTransaction(session, getAccountBalance(fromAccountId));
long toBalanceAfter = runTransaction(session, getAccountBalance(toAccountId));
if (fromBalanceAfter != -1 && toBalanceAfter != -1) {
// Success!
System.out.printf("APP: getAccountBalance(%d) --> %d\n", fromAccountId, fromBalanceAfter);
System.out.printf("APP: getAccountBalance(%d) --> %d\n", toAccountId, toBalanceAfter);
}
}
}
} finally {
sessionFactory.close();
}
}
}
Toward the end of the output, you should see:
APP: BEGIN;
APP: addAccounts() --> 1
APP: COMMIT;
APP: BEGIN;
APP: getAccountBalance(1) --> 1000
APP: COMMIT;
APP: BEGIN;
APP: getAccountBalance(2) --> 250
APP: COMMIT;
APP: getAccountBalance(1) --> 1000
APP: getAccountBalance(2) --> 250
APP: BEGIN;
APP: transferFunds(1, 2, 100) --> 100
APP: COMMIT;
APP: transferFunds(1, 2, 100) --> 100
APP: BEGIN;
APP: getAccountBalance(1) --> 900
APP: COMMIT;
APP: BEGIN;
APP: getAccountBalance(2) --> 350
APP: COMMIT;
APP: getAccountBalance(1) --> 900
APP: getAccountBalance(2) --> 350
To verify that the account balances were updated successfully, start the built-in SQL client:
$ cockroach sql --certs-dir=certs
To check the account balances, issue the following statement:
SELECT id, balance FROM accounts;
id | balance
+----+---------+
1 | 900
2 | 350
3 | 314159
(3 rows)
Step 2. Create the maxroach
user and bank
database
Start the built-in SQL shell:
$ cockroach sql --insecure
In the SQL shell, issue the following statements to create the maxroach
user and bank
database:
> CREATE USER IF NOT EXISTS maxroach;
> CREATE DATABASE bank;
Give the maxroach
user the necessary permissions:
> GRANT ALL ON DATABASE bank TO maxroach;
Exit the SQL shell:
> \q
Step 3. Run the Java code
The code below uses Hibernate to map Java methods to SQL operations. It perform the following steps which roughly correspond to method calls in the Sample
class.
- Create an
accounts
table in thebank
database as specified by the HibernateAccount
class. - Inserts rows into the table using
session.save(new Account(int id, int balance))
(seeSample.addAccounts()
). - Transfer money from one account to another, printing out account balances before and after the transfer (see
transferFunds(long fromId, long toId, long amount)
). - Print out account balances before and after the transfer (see
Sample.getAccountBalance(long id)
).
In addition, the code shows a pattern for automatically handling transaction retries by wrapping transactions in a higher-order function Sample.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.
To run it:
Clone the
example-app-java-hibernate
repo to your machine:git clone https://github.com/cockroachlabs/example-app-java-hibernate/
Compile and run the code using
build.gradle
, which will also download the dependencies.$ gradle run
The contents of Sample.java
:
package com.cockroachlabs;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.JDBCException;
import org.hibernate.cfg.Configuration;
import java.util.*;
import java.util.function.Function;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
public class Sample {
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;
// Account is our model, which corresponds to the "accounts" database table.
@Entity
@Table(name="accounts")
public static class Account {
@Id
@Column(name="id")
public long id;
public long getId() {
return id;
}
@Column(name="balance")
public long balance;
public long getBalance() {
return balance;
}
public void setBalance(long newBalance) {
this.balance = newBalance;
}
// Convenience constructor.
public Account(int id, int balance) {
this.id = id;
this.balance = balance;
}
// Hibernate needs a default (no-arg) constructor to create model objects.
public Account() {}
}
private static Function<Session, Long> addAccounts() throws JDBCException{
Function<Session, Long> f = s -> {
long rv = 0;
try {
s.save(new Account(1, 1000));
s.save(new Account(2, 250));
s.save(new Account(3, 314159));
rv = 1;
System.out.printf("APP: addAccounts() --> %d\n", rv);
} catch (JDBCException e) {
throw e;
}
return rv;
};
return f;
}
private static Function<Session, Long> transferFunds(long fromId, long toId, long amount) throws JDBCException{
Function<Session, Long> f = s -> {
long rv = 0;
try {
Account fromAccount = (Account) s.get(Account.class, fromId);
Account toAccount = (Account) s.get(Account.class, toId);
if (!(amount > fromAccount.getBalance())) {
fromAccount.balance -= amount;
toAccount.balance += amount;
s.save(fromAccount);
s.save(toAccount);
rv = amount;
System.out.printf("APP: transferFunds(%d, %d, %d) --> %d\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, Long> forceRetryLogic() throws JDBCException {
Function<Session, Long> f = s -> {
long rv = -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, Long> getAccountBalance(long id) throws JDBCException{
Function<Session, Long> f = s -> {
long balance;
try {
Account account = s.get(Account.class, id);
balance = account.getBalance();
System.out.printf("APP: getAccountBalance(%d) --> %d\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 do not have to duplicate it in
// various places.
private static long runTransaction(Session session, Function<Session, Long> fn) {
long rv = 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 != -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 = -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;
long transferAmount = 100;
if (FORCE_RETRY) {
System.out.printf("APP: About to test retry logic in 'runTransaction'\n");
runTransaction(session, forceRetryLogic());
} else {
runTransaction(session, addAccounts());
long fromBalance = runTransaction(session, getAccountBalance(fromAccountId));
long toBalance = runTransaction(session, getAccountBalance(toAccountId));
if (fromBalance != -1 && toBalance != -1) {
// Success!
System.out.printf("APP: getAccountBalance(%d) --> %d\n", fromAccountId, fromBalance);
System.out.printf("APP: getAccountBalance(%d) --> %d\n", toAccountId, toBalance);
}
// Transfer $100 from account 1 to account 2
long transferResult = runTransaction(session, transferFunds(fromAccountId, toAccountId, transferAmount));
if (transferResult != -1) {
// Success!
System.out.printf("APP: transferFunds(%d, %d, %d) --> %d \n", fromAccountId, toAccountId, transferAmount, transferResult);
long fromBalanceAfter = runTransaction(session, getAccountBalance(fromAccountId));
long toBalanceAfter = runTransaction(session, getAccountBalance(toAccountId));
if (fromBalanceAfter != -1 && toBalanceAfter != -1) {
// Success!
System.out.printf("APP: getAccountBalance(%d) --> %d\n", fromAccountId, fromBalanceAfter);
System.out.printf("APP: getAccountBalance(%d) --> %d\n", toAccountId, toBalanceAfter);
}
}
}
} finally {
sessionFactory.close();
}
}
}
Toward the end of the output, you should see:
APP: BEGIN;
APP: addAccounts() --> 1
APP: COMMIT;
APP: BEGIN;
APP: getAccountBalance(1) --> 1000
APP: COMMIT;
APP: BEGIN;
APP: getAccountBalance(2) --> 250
APP: COMMIT;
APP: getAccountBalance(1) --> 1000
APP: getAccountBalance(2) --> 250
APP: BEGIN;
APP: transferFunds(1, 2, 100) --> 100
APP: COMMIT;
APP: transferFunds(1, 2, 100) --> 100
APP: BEGIN;
APP: getAccountBalance(1) --> 900
APP: COMMIT;
APP: BEGIN;
APP: getAccountBalance(2) --> 350
APP: COMMIT;
APP: getAccountBalance(1) --> 900
APP: getAccountBalance(2) --> 350
To verify that the account balances were updated successfully, start the built-in SQL client:
$ cockroach sql --insecure --database=bank
To check the account balances, issue the following statement:
SELECT id, balance FROM accounts;
id | balance
+----+---------+
1 | 900
2 | 350
3 | 314159
(3 rows)
Recommended Practices
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 Postgres, see Migrate from Postgres.
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 Postgres 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: