Spring Boot configure and use two data sources

Question

How can I configure and use two data sources?

For example, here is what I have for the first data source:

application.properties

#first db
spring.datasource.url = [url]
spring.datasource.username = [username]
spring.datasource.password = [password]
spring.datasource.driverClassName = oracle.jdbc.OracleDriver
#second db ...

Application class

@SpringBootApplication
public class SampleApplication
{
 public static void main(String[] args) {
 SpringApplication.run(SampleApplication.class, args);
 }
}

How do I modify application.properties to add another data source? How do I autowire it to be used by a different repository?

• dbaltor: The 2nd answer most voted below (from @Surasin) used to be a good one if you don't need distributed transactions across both dbs. But ChainedTransactionManager has been deprecated. Anyone landing here in 2023 looking for a robust solution for distributed transactions must read this answer stackoverflow.com/a/71392118/7066647

Answer 1

Here you go.

Add in your application.properties file:

#first db
spring.datasource.url = [url]
spring.datasource.username = [username]
spring.datasource.password = [password]
spring.datasource.driverClassName = oracle.jdbc.OracleDriver
#second db ...
spring.secondDatasource.url = [url]
spring.secondDatasource.username = [username]
spring.secondDatasource.password = [password]
spring.secondDatasource.driverClassName = oracle.jdbc.OracleDriver

Add in any class annotated with @Configuration the following methods:

@Bean
@Primary
@ConfigurationProperties(prefix="spring.datasource")
public DataSource primaryDataSource() {
 return DataSourceBuilder.create().build();
}
@Bean
@ConfigurationProperties(prefix="spring.secondDatasource")
public DataSource secondaryDataSource() {
 return DataSourceBuilder.create().build();
}

• K. Siva Prasad Reddy: Take a look at baeldung.com/spring-data-jpa-multiple-databases which describes the same what you are looking for.
• Dai Kaixian: Sometimes you may need to assign datasource, transactionManager, and SqlSessionFactory as primary all.
• Matexon: @K. Siva Prasad Reddy OK but I have 2 different JPARepositories - how does Spring Boot know which DataSource to use? Every JPARepository shoudl use different database
• K. Siva Prasad Reddy: @Matley This blog post javadevjournal.com/spring-boot/… might be what you are looking for.
• harsha kumar Reddy: will this work if one is oracle db and another is hsql. its not working for me

Answer 2

Update 2022年05月29日 with Spring Boot 1.5.8.RELEASE which should work with Spring Boot 2.x

Most answers do not provide how to use them (as datasource itself and as transaction), only how to config them.

Moreover you should know how to commit/rollback transactions of both datasources at the same time.

You can see the runnable example and some explanation in https://github.com/surasint/surasint-examples/tree/master/spring-boot-jdbi/10_spring-boot-two-databases (see what you can try in README.txt)

I copied some code here.

First you have to set application.properties like this

#Database
database1.datasource.url=jdbc:mysql://localhost/testdb
database1.datasource.username=root
database1.datasource.password=root
database1.datasource.driver-class-name=com.mysql.jdbc.Driver
database2.datasource.url=jdbc:mysql://localhost/testdb2
database2.datasource.username=root
database2.datasource.password=root
database2.datasource.driver-class-name=com.mysql.jdbc.Driver

Then define them as providers (@Bean) like this:

@Bean(name = "datasource1")
@ConfigurationProperties("database1.datasource")
@Primary
public DataSource dataSource(){
 return DataSourceBuilder.create().build();
}
@Bean(name = "datasource2")
@ConfigurationProperties("database2.datasource")
public DataSource dataSource2(){
 return DataSourceBuilder.create().build();
}

Note that I have @Bean(name="datasource1") and @Bean(name="datasource2"), then you can use it when we need datasource as @Qualifier("datasource1") and @Qualifier("datasource2") , for example

@Qualifier("datasource1")
@Autowired
private DataSource dataSource;

If you do care about transaction, you have to define DataSourceTransactionManager for both of them, like this:

@Bean(name="tm1")
@Autowired
@Primary
DataSourceTransactionManager tm1(@Qualifier ("datasource1") DataSource datasource) {
 DataSourceTransactionManager txm = new DataSourceTransactionManager(datasource);
 return txm;
}
@Bean(name="tm2")
@Autowired
DataSourceTransactionManager tm2(@Qualifier ("datasource2") DataSource datasource) {
 DataSourceTransactionManager txm = new DataSourceTransactionManager(datasource);
 return txm;
}

Then you can use it like

@Transactional //this will use the first datasource because it is @primary

or

@Transactional("tm2")

The most important part, which you will hardly find an example in anywhere: if you want a method to commit/rollback transactions of both databases, you need ChainedTransactionManager for tm1 and tm2 , like this:

@Bean(name = "chainedTransactionManager")
public ChainedTransactionManager getChainedTransactionManager(@Qualifier ("tm1") DataSourceTransactionManager tm1, @Qualifier ("tm2") DataSourceTransactionManager tm2){
 return new ChainedTransactionManager(tm1, tm2);
}

To use it, add this annotation in a method @Transactional(value="chainedTransactionManager") for example

@Transactional(value="chainedTransactionManager")
public void insertAll() {
 UserBean test = new UserBean();
 test.setUsername("username" + new Date().getTime());
 userDao.insert(test);
 userDao2.insert(test);
}

This should be enough. See example and detail in the link above.

• Arun Sudhakaran: Hi @Surasin Tancharoen, we are trying to keep two data sources with same data so that if one fails, the application will run on the other data source. Will be above approach be fine?
• Raja Anbazhagan: @ArunSudhakaran No. This solution will not work as a backup. If you are looking for high availability, then most databases already have configurations to run multiple databases with a single virtual IP. try that instead.
• Avec: Link surasint.com/spring-boot-with-multiple-databases-example does not work anymore.

Answer 3

Refer the official documentation

---

Creating more than one data source works same as creating the first one. You might want to mark one of them as @Primary if you are using the default auto-configuration for JDBC or JPA (then that one will be picked up by any @Autowired injections).

@Bean
@Primary
@ConfigurationProperties(prefix="datasource.primary")
public DataSource primaryDataSource() {
 return DataSourceBuilder.create().build();
}
@Bean
@ConfigurationProperties(prefix="datasource.secondary")
public DataSource secondaryDataSource() {
 return DataSourceBuilder.create().build();
}

• Manoj Shrestha: Thank you for the link to the official documentation on this.
• Даяна Димитрова: Hi, what about if I want to use not the primary database, how should I tell JPA which one to pick? Because I try to use this approach but I have an error for no such table in primary database (the table is not in the primary, but in the secondary).
• mzzzzb: LInk to official documentation spring boot 3 docs.spring.io/spring-boot/how-to/…

Answer 4

I also had to setup connection to 2 datasources from Spring Boot application, and it was not easy - the solution mentioned in the Spring Boot documentation didn't work. After a long digging through the internet I made it work and the main idea was taken from this article and bunch of other places.

The following solution is written in Kotlin and works with Spring Boot 2.1.3 and Hibernate Core 5.3.7. Main issue was that it was not enough just to setup different DataSource configs, but it was also necessary to configure EntityManagerFactory and TransactionManager for both databases.

Here is config for the first (Primary) database:

@Configuration
@EnableJpaRepositories(
 entityManagerFactoryRef = "firstDbEntityManagerFactory",
 transactionManagerRef = "firstDbTransactionManager",
 basePackages = ["org.path.to.firstDb.domain"]
)
@EnableTransactionManagement
class FirstDbConfig {
 @Bean
 @Primary
 @ConfigurationProperties(prefix = "spring.datasource.firstDb")
 fun firstDbDataSource(): DataSource {
 return DataSourceBuilder.create().build()
 }
 @Primary
 @Bean(name = ["firstDbEntityManagerFactory"])
 fun firstDbEntityManagerFactory(
 builder: EntityManagerFactoryBuilder,
 @Qualifier("firstDbDataSource") dataSource: DataSource
 ): LocalContainerEntityManagerFactoryBean {
 return builder
 .dataSource(dataSource)
 .packages(SomeEntity::class.java)
 .persistenceUnit("firstDb")
 // Following is the optional configuration for naming strategy
 .properties(
 singletonMap(
 "hibernate.naming.physical-strategy",
 "org.hibernate.boot.model.naming.PhysicalNamingStrategyStandardImpl"
 )
 )
 .build()
 }
 @Primary
 @Bean(name = ["firstDbTransactionManager"])
 fun firstDbTransactionManager(
 @Qualifier("firstDbEntityManagerFactory") firstDbEntityManagerFactory: EntityManagerFactory
 ): PlatformTransactionManager {
 return JpaTransactionManager(firstDbEntityManagerFactory)
 }
}

And this is config for second database:

@Configuration
@EnableJpaRepositories(
 entityManagerFactoryRef = "secondDbEntityManagerFactory",
 transactionManagerRef = "secondDbTransactionManager",
 basePackages = ["org.path.to.secondDb.domain"]
)
@EnableTransactionManagement
class SecondDbConfig {
 @Bean
 @ConfigurationProperties("spring.datasource.secondDb")
 fun secondDbDataSource(): DataSource {
 return DataSourceBuilder.create().build()
 }
 @Bean(name = ["secondDbEntityManagerFactory"])
 fun secondDbEntityManagerFactory(
 builder: EntityManagerFactoryBuilder,
 @Qualifier("secondDbDataSource") dataSource: DataSource
 ): LocalContainerEntityManagerFactoryBean {
 return builder
 .dataSource(dataSource)
 .packages(EntityFromSecondDb::class.java)
 .persistenceUnit("secondDb")
 .build()
 }
 @Bean(name = ["secondDbTransactionManager"])
 fun secondDbTransactionManager(
 @Qualifier("secondDbEntityManagerFactory") secondDbEntityManagerFactory: EntityManagerFactory
 ): PlatformTransactionManager {
 return JpaTransactionManager(secondDbEntityManagerFactory)
 }
}

The properties for datasources are like this:

spring.datasource.firstDb.jdbc-url=
spring.datasource.firstDb.username=
spring.datasource.firstDb.password=
spring.datasource.secondDb.jdbc-url=
spring.datasource.secondDb.username=
spring.datasource.secondDb.password=

Issue with properties was that I had to define jdbc-url instead of url because otherwise I had an exception.

p.s. Also you might have different naming schemes in your databases, which was the case for me. Since Hibernate 5 does not support all previous naming schemes, I had to use solution from this answer - maybe it will also help someone as well.

• rvit34: I had problems with entity and table naming. And it's helped me along with your answer: mapOf("hibernate.physical_naming_strategy" to "org.springframework.boot.orm.jpa.hibernate.SpringPhysicalNamingStrategy", "hibernate.implicit_naming_strategy" to "org.springframework.boot.orm.jpa.hibernate.SpringImplicitNamingStrategy" )
• Galley: I replace url with jdbcUrl, it works, thank you

Answer 5

# Here '1stDB' is the database name
spring.datasource.url=jdbc:mysql://localhost/A
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
 
 
# Here '2ndDB' is the database name
spring.second-datasourcee.url=jdbc:mysql://localhost/B
spring.second-datasource.username=root
spring.second-datasource.password=root
spring.second-datasource.driver-class-name=com.mysql.jdbc.Driver

@Bean
@Primary
@ConfigurationProperties(prefix = "spring.datasource")
public DataSource firstDataSource() {
 return DataSourceBuilder.create().build();
}
 
@Bean
@ConfigurationProperties(prefix = "spring.second-datasource")
public DataSource secondDataSource() {
 return DataSourceBuilder.create().build();
}

• Amir Keshavarz: Not working for me. And saying this: Error creating bean with name 'dataSourceScriptDatabaseInitializer' defined in class path resource [org/springframework/boot/autoconfigure/sql/init/DataSourceInitializationConfiguration.class]: Invocation of init method failed; nested exception is java.lang.IllegalArgumentException: jdbcUrl is required with driverClassName.
• user9802118: @AmirKeshavarz my answer might be a little ... to late, but you have to modify the datasource.url to datasource.jdbc-url and it will work

Answer 6

Here is the Complete solution

#First Datasource (DB1)
db1.datasource.url: url
db1.datasource.username:user
db1.datasource.password:password
#Second Datasource (DB2)
db2.datasource.url:url
db2.datasource.username:user
db2.datasource.password:password

Since we are going to get access two different databases (db1, db2), we need to configure each data source configuration separately like:

public class DB1_DataSource {
@Autowired
private Environment env;
@Bean
@Primary
public LocalContainerEntityManagerFactoryBean db1EntityManager() {
 LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
 em.setDataSource(db1Datasource());
 em.setPersistenceUnitName("db1EntityManager");
 HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
 em.setJpaVendorAdapter(vendorAdapter);
 HashMap<string, object=""> properties = new HashMap<>();
 properties.put("hibernate.dialect",
 env.getProperty("hibernate.dialect"));
 properties.put("hibernate.show-sql",
 env.getProperty("jdbc.show-sql"));
 em.setJpaPropertyMap(properties);
 return em;
}
@Primary
@Bean
public DataSource db1Datasource() {
 DriverManagerDataSource dataSource
 = new DriverManagerDataSource();
 dataSource.setDriverClassName(
 env.getProperty("jdbc.driver-class-name"));
 dataSource.setUrl(env.getProperty("db1.datasource.url"));
 dataSource.setUsername(env.getProperty("db1.datasource.username"));
 dataSource.setPassword(env.getProperty("db1.datasource.password"));
 return dataSource;
}
@Primary
@Bean
public PlatformTransactionManager db1TransactionManager() {
 JpaTransactionManager transactionManager
 = new JpaTransactionManager();
 transactionManager.setEntityManagerFactory(
 db1EntityManager().getObject());
 return transactionManager;
}
}

Second Datasource :

public class DB2_DataSource {
@Autowired
private Environment env;
@Bean
public LocalContainerEntityManagerFactoryBean db2EntityManager() {
 LocalContainerEntityManagerFactoryBean em
 = new LocalContainerEntityManagerFactoryBean();
 em.setDataSource(db2Datasource());
 em.setPersistenceUnitName("db2EntityManager");
 HibernateJpaVendorAdapter vendorAdapter
 = new HibernateJpaVendorAdapter();
 em.setJpaVendorAdapter(vendorAdapter);
 HashMap<string, object=""> properties = new HashMap<>();
 properties.put("hibernate.dialect",
 env.getProperty("hibernate.dialect"));
 properties.put("hibernate.show-sql",
 env.getProperty("jdbc.show-sql"));
 em.setJpaPropertyMap(properties);
 return em;
}
@Bean
public DataSource db2Datasource() {
 DriverManagerDataSource dataSource
 = new DriverManagerDataSource();
 dataSource.setDriverClassName(
 env.getProperty("jdbc.driver-class-name"));
 dataSource.setUrl(env.getProperty("db2.datasource.url"));
 dataSource.setUsername(env.getProperty("db2.datasource.username"));
 dataSource.setPassword(env.getProperty("db2.datasource.password"));
 return dataSource;
}
@Bean
public PlatformTransactionManager db2TransactionManager() {
 JpaTransactionManager transactionManager
 = new JpaTransactionManager();
 transactionManager.setEntityManagerFactory(
 db2EntityManager().getObject());
 return transactionManager;
}
}

Here you can find the complete Example on my blog : Spring Boot with Multiple DataSource Configuration

• Rohit Chaurasiya: this code will not run how 2 @primary annotation work together in same db.
• im_infamous: indeed, but this code mentions important part with manual properties setting instead of plain and simple return DataSourceBuilder.create().build(); which is apparently not working, hence my upvote goes here
• pixel: what if your 2 databases are from different vendor? How do you set hibernate dialect in that case?

Answer 7

My requirement was slightly different but used two data sources.

I have used two data sources for same JPA entities from same package. One for executing DDL at the server startup to create/update tables and another one is for DML at runtime.

The DDL connection should be closed after DDL statements are executed, to prevent further usage of super user previlleges anywhere in the code.

Properties

spring.datasource.url=jdbc:postgresql://Host:port
ddl.user=ddluser
ddl.password=ddlpassword
dml.user=dmluser
dml.password=dmlpassword
spring.datasource.driver-class-name=org.postgresql.Driver

Data source config classes

//1st Config class for DDL Data source

 public class DatabaseDDLConfig {
 @Bean
 public LocalContainerEntityManagerFactoryBean ddlEntityManagerFactoryBean() {
 LocalContainerEntityManagerFactoryBean entityManagerFactoryBean = new LocalContainerEntityManagerFactoryBean();
 PersistenceProvider persistenceProvider = new 
 org.hibernate.jpa.HibernatePersistenceProvider();
 entityManagerFactoryBean.setDataSource(ddlDataSource());
 entityManagerFactoryBean.setPackagesToScan(new String[] { 
 "com.test.two.data.sources"});
 HibernateJpaVendorAdapter vendorAdapter = new 
 HibernateJpaVendorAdapter();
 entityManagerFactoryBean.setJpaVendorAdapter(vendorAdapter);
 HashMap<String, Object> properties = new HashMap<>();
 properties.put("hibernate.dialect", 
 "org.hibernate.dialect.PostgreSQLDialect");
 properties.put("hibernate.physical_naming_strategy", 
 "org.springframework.boot.orm.jpa.hibernate.
 SpringPhysicalNamingStrategy");
 properties.put("hibernate.implicit_naming_strategy", 
 "org.springframework.boot.orm.jpa.hibernate.
 SpringImplicitNamingStrategy");
 properties.put("hibernate.hbm2ddl.auto", "update");
 entityManagerFactoryBean.setJpaPropertyMap(properties);
 entityManagerFactoryBean.setPersistenceUnitName("ddl.config");
 entityManagerFactoryBean.setPersistenceProvider(persistenceProvider);
 return entityManagerFactoryBean;
 }
 @Bean
 public DataSource ddlDataSource() {
 DriverManagerDataSource dataSource = new DriverManagerDataSource();
 dataSource.setDriverClassName(env.getProperty("spring.datasource.driver-class-name"));
 dataSource.setUrl(env.getProperty("spring.datasource.url"));
 dataSource.setUsername(env.getProperty("ddl.user");
 dataSource.setPassword(env.getProperty("ddl.password"));
 return dataSource;
 }
 @Bean
 public PlatformTransactionManager ddlTransactionManager() {
 JpaTransactionManager transactionManager = new JpaTransactionManager();
 transactionManager.setEntityManagerFactory(ddlEntityManagerFactoryBean().getObject());
 return transactionManager;
 }
}

//2nd Config class for DML Data source

public class DatabaseDMLConfig {
 @Bean
 @Primary
 public LocalContainerEntityManagerFactoryBean dmlEntityManagerFactoryBean() {
 LocalContainerEntityManagerFactoryBean entityManagerFactoryBean = new LocalContainerEntityManagerFactoryBean();
 PersistenceProvider persistenceProvider = new org.hibernate.jpa.HibernatePersistenceProvider();
 entityManagerFactoryBean.setDataSource(dmlDataSource());
 entityManagerFactoryBean.setPackagesToScan(new String[] { "com.test.two.data.sources" });
 JpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
 entityManagerFactoryBean.setJpaVendorAdapter(vendorAdapter);
 entityManagerFactoryBean.setJpaProperties(defineJpaProperties());
 entityManagerFactoryBean.setPersistenceUnitName("dml.config");
 entityManagerFactoryBean.setPersistenceProvider(persistenceProvider);
 return entityManagerFactoryBean;
 }
 @Bean
 @Primary
 public DataSource dmlDataSource() {
 DriverManagerDataSource dataSource = new DriverManagerDataSource();
 dataSource.setDriverClassName(env.getProperty("spring.datasource.driver-class-name"));
 dataSource.setUrl(envt.getProperty("spring.datasource.url"));
 dataSource.setUsername("dml.user");
 dataSource.setPassword("dml.password");
 return dataSource;
 }
 @Bean
 @Primary
 public PlatformTransactionManager dmlTransactionManager() {
 JpaTransactionManager transactionManager = new JpaTransactionManager();
 transactionManager.setEntityManagerFactory(dmlEntityManagerFactoryBean().getObject());
 return transactionManager;
 }
 }

//Usage of DDL data sources in code.

public class DDLServiceAtStartup {
//Import persistence unit ddl.config for ddl purpose.
@PersistenceUnit(unitName = "ddl.config")
private EntityManagerFactory entityManagerFactory;
public void executeDDLQueries() throws ContentServiceSystemError {
 try {
 EntityManager entityManager = entityManagerFactory.createEntityManager();
 entityManager.getTransaction().begin();
 entityManager.createNativeQuery("query to create/update table").executeUpdate();
 entityManager.flush();
 entityManager.getTransaction().commit();
 entityManager.close();
 //Close the ddl data source to avoid from further use in code.
 entityManagerFactory.close();
 } catch(Exception ex) {}
}

//Usage of DML data source in code.

public class DDLServiceAtStartup {
 @PersistenceUnit(unitName = "dml.config")
 private EntityManagerFactory entityManagerFactory;
 public void createRecord(User user) {
 userDao.save(user);
 }
}

Answer 8

@Primary annotation when used against a method like below works good if the two data sources are on the same db location/server.

@Bean(name = "datasource1")
@ConfigurationProperties("database1.datasource")
@Primary
public DataSource dataSource(){
 return DataSourceBuilder.create().build();
}
@Bean(name = "datasource2")
@ConfigurationProperties("database2.datasource")
public DataSource dataSource2(){
 return DataSourceBuilder.create().build();
}

If the data sources are on different servers its better to use @Component along with @Primary annotation. The following code snippet works well on two different data sources at different locations

database1.datasource.url = jdbc:mysql://127.0.0.1:3306/db1
database1.datasource.username = root
database1.datasource.password = mysql
database1.datasource.driver-class-name=com.mysql.jdbc.Driver
database2.datasource1.url = jdbc:mysql://192.168.113.51:3306/db2
database2.datasource1.username = root
database2.datasource1.password = mysql
database2.datasource1.driver-class-name=com.mysql.jdbc.Driver
@Configuration
@Primary
@Component
@ComponentScan("com.db1.bean")
class DBConfiguration1{
 @Bean("db1Ds")
 @ConfigurationProperties(prefix="database1.datasource")
 public DataSource primaryDataSource() {
 return DataSourceBuilder.create().build();
 }
}
@Configuration
@Component
@ComponentScan("com.db2.bean")
class DBConfiguration2{
 @Bean("db2Ds")
 @ConfigurationProperties(prefix="database2.datasource1")
 public DataSource primaryDataSource() {
 return DataSourceBuilder.create().build();
 }
}

Answer 9

I used mybatis - springboot 2.0 tech stack, solution:

//application.properties - start
 sp.ds1.jdbc-url=jdbc:mysql://localhost:3306/mydb?useSSL=false
 sp.ds1.username=user
 sp.ds1.password=pwd
 sp.ds1.testWhileIdle=true
 sp.ds1.validationQuery=SELECT 1
 sp.ds1.driverClassName=com.mysql.jdbc.Driver
 sp.ds2.jdbc-url=jdbc:mysql://localhost:4586/mydb?useSSL=false
 sp.ds2.username=user
 sp.ds2.password=pwd
 sp.ds2.testWhileIdle=true
 sp.ds2.validationQuery=SELECT 1
 sp.ds2.driverClassName=com.mysql.jdbc.Driver
//application.properties - end
//configuration class
 @Configuration
 @ComponentScan(basePackages = "com.mypkg")
 public class MultipleDBConfig {
 public static final String SQL_SESSION_FACTORY_NAME_1 = "sqlSessionFactory1";
 public static final String SQL_SESSION_FACTORY_NAME_2 = "sqlSessionFactory2";
 public static final String MAPPERS_PACKAGE_NAME_1 = "com.mypg.mymapper1";
 public static final String MAPPERS_PACKAGE_NAME_2 = "com.mypg.mymapper2";
 @Bean(name = "mysqlDb1")
 @Primary
 @ConfigurationProperties(prefix = "sp.ds1")
 public DataSource dataSource1() {
 System.out.println("db1 datasource");
 return DataSourceBuilder.create().build();
 }
 @Bean(name = "mysqlDb2")
 @ConfigurationProperties(prefix = "sp.ds2")
 public DataSource dataSource2() {
 System.out.println("db2 datasource");
 return DataSourceBuilder.create().build();
 }
 @Bean(name = SQL_SESSION_FACTORY_NAME_1)
 @Primary
 public SqlSessionFactory sqlSessionFactory1(@Qualifier("mysqlDb1") DataSource dataSource1) throws Exception {
 System.out.println("sqlSessionFactory1");
 SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
 sqlSessionFactoryBean.setTypeHandlersPackage(MAPPERS_PACKAGE_NAME_1);
 sqlSessionFactoryBean.setDataSource(dataSource1);
 SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBean.getObject();
 sqlSessionFactory.getConfiguration().setMapUnderscoreToCamelCase(true);
 sqlSessionFactory.getConfiguration().setJdbcTypeForNull(JdbcType.NULL);
 return sqlSessionFactory;
 }
 @Bean(name = SQL_SESSION_FACTORY_NAME_2)
 public SqlSessionFactory sqlSessionFactory2(@Qualifier("mysqlDb2") DataSource dataSource2) throws Exception {
 System.out.println("sqlSessionFactory2");
 SqlSessionFactoryBean diSqlSessionFactoryBean = new SqlSessionFactoryBean();
 diSqlSessionFactoryBean.setTypeHandlersPackage(MAPPERS_PACKAGE_NAME_2);
 diSqlSessionFactoryBean.setDataSource(dataSource2);
 SqlSessionFactory sqlSessionFactory = diSqlSessionFactoryBean.getObject();
 sqlSessionFactory.getConfiguration().setMapUnderscoreToCamelCase(true);
 sqlSessionFactory.getConfiguration().setJdbcTypeForNull(JdbcType.NULL);
 return sqlSessionFactory;
 }
 @Bean
 @Primary
 public MapperScannerConfigurer mapperScannerConfigurer1() {
 System.out.println("mapperScannerConfigurer1");
 MapperScannerConfigurer configurer = new MapperScannerConfigurer();
 configurer.setBasePackage(MAPPERS_PACKAGE_NAME_1);
 configurer.setSqlSessionFactoryBeanName(SQL_SESSION_FACTORY_NAME_1);
 return configurer;
 }
 @Bean
 public MapperScannerConfigurer mapperScannerConfigurer2() {
 System.out.println("mapperScannerConfigurer2");
 MapperScannerConfigurer configurer = new MapperScannerConfigurer();
 configurer.setBasePackage(MAPPERS_PACKAGE_NAME_2);
 configurer.setSqlSessionFactoryBeanName(SQL_SESSION_FACTORY_NAME_2);
 return configurer;
 }
 }

Note : 1)@Primary -> @primary

2)---."jdbc-url" in properties -> After Spring Boot 2.0 migration: jdbcUrl is required with driverClassName

Answer 10

declaring a data source in Spring Boot application.properties

spring.datasource.company.url=jdbc:mysql://localhost/company_db?createDatabaseIfNotExist=true&autoReconnect=true&useSSL=false&allowPublicKeyRetrieval=true
spring.datasource.company.username=root
spring.datasource.company.password=root
spring.datasource.company.platform=mysql
spring.datasource.employee.url=jdbc:mysql://localhost/employee_db?createDatabaseIfNotExist=true&autoReconnect=true&useSSL=false&allowPublicKeyRetrieval=true
spring.datasource.employee.username=root
spring.datasource.employee.password=root
spring.datasource.employee.platform=mysql

---

use multiple data sources, we need to declare multiple beans with different mappings within Spring's application context. using a configuration class

---

@Configuration
@EnableJpaRepositories(basePackages = "com.example.multiple.datasources.entity.company",
 entityManagerFactoryRef = "companyEntityManagerFactory",
 transactionManagerRef = "companyTransactionManager")
public class CompanyDataSourceConfiguration {
 @Bean
 @ConfigurationProperties("spring.datasource.company")
 public DataSourceProperties companyDataSourceProperties() {
 return new DataSourceProperties();
 }
 @Bean
 @ConfigurationProperties("spring.datasource.company.configuration")
 public DataSource companyDataSource() {
 return companyDataSourceProperties().initializeDataSourceBuilder()
 .type(HikariDataSource.class).build();
 }
 @Bean(name = "companyEntityManagerFactory")
 public LocalContainerEntityManagerFactoryBean companyEntityManagerFactory(EntityManagerFactoryBuilder builder) {
 return builder.dataSource(companyDataSource()).packages(Company.class).build();
 }
 @Bean
 public PlatformTransactionManager companyTransactionManager(
 final @Qualifier("companyEntityManagerFactory") LocalContainerEntityManagerFactoryBean companyEntityManagerFactory
 ) {
 return new JpaTransactionManager(companyEntityManagerFactory.getObject());
 }
}

---

we need to declare one of the datasources as @Primary. This is because EntityManagerFactoryBuilder is declared in JpaBaseConfiguration and this class need a single data source injected.

---

@Configuration
@EnableJpaRepositories(basePackages = "com.example.multiple.datasources.entity.employee",
 entityManagerFactoryRef = "employeeEntityManagerFactory",
 transactionManagerRef = "employeeTransactionManager")
public class EmployeeDatasourceConfiguration {
 @Bean
 @Primary
 @ConfigurationProperties("spring.datasource.employee")
 public DataSourceProperties employeeDataSourceProperties() {
 return new DataSourceProperties();
 }
 @Bean
 @Primary
 @ConfigurationProperties("spring.datasource.employee.configuration")
 public DataSource employeeDataSource() {
 return employeeDataSourceProperties().initializeDataSourceBuilder().type(HikariDataSource.class).build();
 }
 @Primary
 @Bean("employeeEntityManagerFactory")
 public LocalContainerEntityManagerFactoryBean employeeEntityManagerFactory(EntityManagerFactoryBuilder builder) {
 return builder.dataSource(employeeDataSource()).packages(Employee.class).build();
 }
 @Primary
 @Bean
 public PlatformTransactionManager employeeTransactionManager(
 final @Qualifier("employeeEntityManagerFactory") LocalContainerEntityManagerFactoryBean employeeEntityManagerFactory
 ) {
 return new JpaTransactionManager(employeeEntityManagerFactory.getObject());
 }
}

Answer 11

There are some useful answers here but the official Spring Boot docs also cover this in detail.

For modern Spring Boot (3 at the time of writing):

https://docs.spring.io/spring-boot/how-to/data-access.html#howto.data-access.configure-two-datasources

Official Documentation for Spring Boot 2 for legacy projects:

https://docs.spring.io/spring-boot/docs/2.7.18/reference/html/howto.html#howto.data-access.configure-two-datasources

I know there is a preference for including a sample but I will leave that to other answers as there is too much detail here to copy and paste. I will say that most 3rd party articles are just restating information present in these docs and the Spring Boot docs should be your first stop if you are trying to figure out specific scenarios.