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Partner – Microsoft – NPI EA (cat = Baeldung)
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Azure Container Apps is a fully managed serverless container service that enables you to build and deploy modern, cloud-native Java applications and microservices at scale. It offers a simplified developer experience while providing the flexibility and portability of containers.

Of course, Azure Container Apps has really solid support for our ecosystem, from a number of build options, managed Java components, native metrics, dynamic logger, and quite a bit more.

To learn more about Java features on Azure Container Apps, visit the documentation page.

You can also ask questions and leave feedback on the Azure Container Apps GitHub page.

Partner – Microsoft – NPI EA (cat= Spring Boot)
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Azure Container Apps is a fully managed serverless container service that enables you to build and deploy modern, cloud-native Java applications and microservices at scale. It offers a simplified developer experience while providing the flexibility and portability of containers.

Of course, Azure Container Apps has really solid support for our ecosystem, from a number of build options, managed Java components, native metrics, dynamic logger, and quite a bit more.

To learn more about Java features on Azure Container Apps, you can get started over on the documentation page.

And, you can also ask questions and leave feedback on the Azure Container Apps GitHub page.

Partner – Orkes – NPI EA (cat=Spring)
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Modern software architecture is often broken. Slow delivery leads to missed opportunities, innovation is stalled due to architectural complexities, and engineering resources are exceedingly expensive.

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Partner – Orkes – NPI EA (tag=Microservices)
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Modern software architecture is often broken. Slow delivery leads to missed opportunities, innovation is stalled due to architectural complexities, and engineering resources are exceedingly expensive.

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With Orkes Conductor managed through Orkes Cloud, developers can focus on building mission critical applications without worrying about infrastructure maintenance to meet goals and, simply put, taking new products live faster and reducing total cost of ownership.

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Since its introduction in Java 8, the Stream API has become a staple of Java development. The basic operations like iterating, filtering, mapping sequences of elements are deceptively simple to use.

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To get a better understanding on how Streams work and how to combine them with other language features, check out our guide to Java Streams:

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Explore Spring Boot 3 and Spring 6 in-depth through building a full REST API with the framework:

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Course – LSD – NPI EA (tag=Spring Data JPA)
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Spring Data JPA is a great way to handle the complexity of JPA with the powerful simplicity of Spring Boot.

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End-to-end testing is a very useful method to make sure that your application works as intended. This highlights issues in the overall functionality of the software, that the unit and integration test stages may miss.

Playwright is an easy-to-use, but powerful tool that automates end-to-end testing, and supports all modern browsers and platforms.

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1. Overview

The typical scenario for a Spring Boot application is to store data in a single relational database. But we sometimes need to access multiple databases.

In this tutorial, we’ll learn how to configure and use multiple data sources with Spring Boot.

To find out how to deal with a single data source, check out our introduction to Spring Data JPA.

Further reading:

A Guide to JPA with Spring

Setup JPA with Spring - how to set up the EntityManager factory and use the raw JPA APIs.

Introduction to Spring Data JDBC

A quick and practical guide to Spring Data JDBC.

Configuring a DataSource Programmatically in Spring Boot

Learn how to configure a Spring Boot DataSource programmatically, thereby side-stepping Spring Boot's automatic DataSource configuration algorithm.

2. Default Behavior

Let’s remember what declaring a data source in Spring Boot looks like in application.yml:

spring:
  datasource:
    url: ...
    username: ...
    password: ...
    driverClassname: ...

Internally, Spring maps these settings to an instance of org.springframework.boot.autoconfigure.jdbc.DataSourceProperties.

Let’s take a look into the implementation:

@ConfigurationProperties(prefix = "spring.datasource")
public class DataSourceProperties implements BeanClassLoaderAware, InitializingBean {

    // ...

    /**
     * Fully qualified name of the JDBC driver. Auto-detected based on the URL by default.
     */
    private String driverClassName;

    /**
     * JDBC URL of the database.
     */
    private String url;

    /**
     * Login username of the database.
     */
    private String username;

    /**
     * Login password of the database.
     */
    private String password;

    // ...

}

We should point out the @ConfigurationProperties annotation that maps the properties of the configuration to the Java object automatically.

3. Extending the Defaults

So, to use multiple data sources, we need to declare multiple beans with different mappings within Spring’s application context.

We can do this by using configuration classes:

@Configuration
public class TodoDatasourceConfiguration {

    @Bean
    @ConfigurationProperties("spring.datasource.todos")
    public DataSourceProperties todosDataSourceProperties() {
        return new DataSourceProperties();
    }
}

@Configuration
public class TopicDatasourceConfiguration {

    @Bean
    @ConfigurationProperties("spring.datasource.topics")
    public DataSourceProperties topicsDataSourceProperties() {
        return new DataSourceProperties();
    }

}

The configuration for the data sources must look like this:

spring:
  datasource:
    todos:
      url: ...
      username: ...
      password: ...
      driverClassName: ...
    topics:
      url: ...
      username: ...
      password: ...
      driverClassName: ...

Then we can create the data sources by using the DataSourceProperties objects:

@Bean
public DataSource todosDataSource() {
    return todosDataSourceProperties()
      .initializeDataSourceBuilder()
      .build();
}

@Bean
public DataSource topicsDataSource() {
    return topicsDataSourceProperties()
      .initializeDataSourceBuilder()
      .build();
}

4. Spring Data JDBC

When using Spring Data JDBC, we also need to configure one instance of JdbcTemplate for each DataSource:

@Bean
public JdbcTemplate todosJdbcTemplate(@Qualifier("todosDataSource") DataSource dataSource) {
    return new JdbcTemplate(dataSource);
}

@Bean
public JdbcTemplate topicsJdbcTemplate(@Qualifier("topicsDataSource") DataSource dataSource) {
    return new JdbcTemplate(dataSource);
}

We can then use them also by specifying a @Qualifier:

@Autowired
@Qualifier("topicsJdbcTemplate")
JdbcTemplate jdbcTemplate;

5. Spring Data JPA

When using Spring Data JPA, we want to use repositories like the following, where Todo is the entity:

public interface TodoRepository extends JpaRepository<Todo, Long> {}

So, we need to declare EntityManager factories for each data source:

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
  basePackageClasses = Todo.class,
  entityManagerFactoryRef = "todosEntityManagerFactory",
  transactionManagerRef = "todosTransactionManager"
)
public class TodoJpaConfiguration {

    @Bean
    public LocalContainerEntityManagerFactoryBean todosEntityManagerFactory(
      @Qualifier("todosDataSource") DataSource dataSource,
      EntityManagerFactoryBuilder builder) {
        return builder
          .dataSource(dataSource)
          .packages(Todo.class)
          .build();
    }

    @Bean
    public PlatformTransactionManager todosTransactionManager(
      @Qualifier("todosEntityManagerFactory") LocalContainerEntityManagerFactoryBean todosEntityManagerFactory) {
        return new JpaTransactionManager(Objects.requireNonNull(todosEntityManagerFactory.getObject()));
    }

}

Let’s look at a few restrictions that we should be aware of.

We need to split the packages to allow one @EnableJpaRepositories for each data source.

Unfortunately, to get EntityManagerFactoryBuilder injected, we need to declare one of the data sources as @Primary.

This is because EntityManagerFactoryBuilder is declared in org.springframework.boot.autoconfigure.orm.jpa.JpaBaseConfiguration, and this class needs a single data source injected. Usually, some parts of the framework might not expect multiple data sources configured.

6. Configure Hikari Connection Pool

If we want to configure Hikari, we just need to add an @ConfigurationProperties to the data source definition:

@Bean
@ConfigurationProperties("spring.datasource.todos.hikari")
public DataSource todosDataSource() {
    return todosDataSourceProperties()
      .initializeDataSourceBuilder()
      .build();
}

Then we can insert the following lines into the application.properties file:

spring.datasource.todos.hikari.connectionTimeout=30000 
spring.datasource.todos.hikari.idleTimeout=600000 
spring.datasource.todos.hikari.maxLifetime=1800000 

7. Conclusion

In this article, we learned how to configure multiple data sources with Spring Boot.

We saw that we need some configuration and that there might be pitfalls when deviating from the standard but that it is possible in the end.

The code backing this article is available on GitHub. Once you're logged in as a Baeldung Pro Member, start learning and coding on the project.
Baeldung Pro – NPI EA (cat = Baeldung)
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Baeldung Pro comes with both absolutely No-Ads as well as finally with Dark Mode, for a clean learning experience:

>> Explore a clean Baeldung

Once the early-adopter seats are all used, the price will go up and stay at $33/year.

Partner – Microsoft – NPI EA (cat = Spring Boot)
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Azure Container Apps is a fully managed serverless container service that enables you to build and deploy modern, cloud-native Java applications and microservices at scale. It offers a simplified developer experience while providing the flexibility and portability of containers.

Of course, Azure Container Apps has really solid support for our ecosystem, from a number of build options, managed Java components, native metrics, dynamic logger, and quite a bit more.

To learn more about Java features on Azure Container Apps, visit the documentation page.

You can also ask questions and leave feedback on the Azure Container Apps GitHub page.

Partner – Orkes – NPI EA (cat = Spring)
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Modern software architecture is often broken. Slow delivery leads to missed opportunities, innovation is stalled due to architectural complexities, and engineering resources are exceedingly expensive.

Orkes is the leading workflow orchestration platform built to enable teams to transform the way they develop, connect, and deploy applications, microservices, AI agents, and more.

With Orkes Conductor managed through Orkes Cloud, developers can focus on building mission critical applications without worrying about infrastructure maintenance to meet goals and, simply put, taking new products live faster and reducing total cost of ownership.

Try a 14-Day Free Trial of Orkes Conductor today.

Partner – Orkes – NPI EA (tag = Microservices)
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Modern software architecture is often broken. Slow delivery leads to missed opportunities, innovation is stalled due to architectural complexities, and engineering resources are exceedingly expensive.

Orkes is the leading workflow orchestration platform built to enable teams to transform the way they develop, connect, and deploy applications, microservices, AI agents, and more.

With Orkes Conductor managed through Orkes Cloud, developers can focus on building mission critical applications without worrying about infrastructure maintenance to meet goals and, simply put, taking new products live faster and reducing total cost of ownership.

Try a 14-Day Free Trial of Orkes Conductor today.

eBook – HTTP Client – NPI EA (cat=HTTP Client-Side)
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The Apache HTTP Client is a very robust library, suitable for both simple and advanced use cases when testing HTTP endpoints. Check out our guide covering basic request and response handling, as well as security, cookies, timeouts, and more:

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eBook – Java Concurrency – NPI EA (cat=Java Concurrency)
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Handling concurrency in an application can be a tricky process with many potential pitfalls. A solid grasp of the fundamentals will go a long way to help minimize these issues.

Get started with understanding multi-threaded applications with our Java Concurrency guide:

>> Download the eBook

eBook – Java Streams – NPI EA (cat=Java Streams)
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Since its introduction in Java 8, the Stream API has become a staple of Java development. The basic operations like iterating, filtering, mapping sequences of elements are deceptively simple to use.

But these can also be overused and fall into some common pitfalls.

To get a better understanding on how Streams work and how to combine them with other language features, check out our guide to Java Streams:

>> Join Pro and download the eBook

eBook – Persistence – NPI EA (cat=Persistence)
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Working on getting your persistence layer right with Spring?

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Course – LS – NPI EA (cat=REST)

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Get started with Spring Boot and with core Spring, through the Learn Spring course:

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Course – Spring Sale 2025 – NPI EA (cat= Baeldung)
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Yes, we're now running our Spring Sale. All Courses are 25% off until 26th May, 2025:

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Partner – Microsoft – NPI (cat=Spring)
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Azure Container Apps is a fully managed serverless container service that enables you to build and deploy modern, cloud-native Java applications and microservices at scale. It offers a simplified developer experience while providing the flexibility and portability of containers.

Of course, Azure Container Apps has really solid support for our ecosystem, from a number of build options, managed Java components, native metrics, dynamic logger, and quite a bit more.

To learn more about Java features on Azure Container Apps, visit the documentation page.

You can also ask questions and leave feedback on the Azure Container Apps GitHub page.

eBook Jackson – NPI EA – 3 (cat = Jackson)
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