background

In many applications, you may encounter situations where you need to connect to multiple databases . These databases can be of different types, such as relational and NoSQL databases, or they can be of the same type but contain different data. To handle this situation, we can use dual data sources to manage multiple database connections.

Dual data sources refer to using two or more different database connections in one application at the same time, which can be different types of databases, or the same type but with different data. Using dual data sources makes it easier to manage multiple databases and use the appropriate data source for read and write operations when needed. For example, an application may need to connect a relational database and a NoSQL database to store different types of data. By configuring dual data sources, the application can connect to and operate the two databases at the same time.

So how to configure and use a dual data source in a Spring Boot application? First, we will understand what a dual data source is and why it is needed. Then, we will detail how to configure and implement dual data sources in Spring Boot.

Advantages of dual data sources

The benefits of using dual data sources are as follows:

Flexibility and scalability : Dual data sources allow applications to connect to multiple databases, and data sources can be easily switched according to actual needs. This provides greater flexibility and scalability to accommodate changes in different data storage requirements.
Separation of business logic: By storing different types of data in different data sources, business logic can be better separated and managed. For example, storing relational data in one data source and logs or files in another data source makes business logic clearer and more maintainable.
Performance and load balancing : Using dual data sources can achieve read-write separation and load balancing. For example, routing read operations to one data source and writing operations to another data source improves the performance and throughput of database operations.
Data isolation and security : By using dual data sources, sensitive data and non-sensitive data can be stored in different data sources to achieve data isolation and security. This better protects sensitive data and reduces the risk of data breaches.
Platform independence : The configuration and use of dual data sources is usually independent of specific frameworks and platforms. This means you can use the same dual data source configuration in different applications and environments without modifying or rewriting code.

technology

Configuring dual data sources in a Spring Boot application can use the following techniques:

Spring Boot : A framework for creating standalone, production-grade Spring applications.
Java Persistence API (JPA) : Part of the Java EE specification for data persistence through mapping between objects and relational databases.
HikariCP : A high-performance JDBC connection pool.

usage

add dependencies

pom.xmlFirst, add the necessary dependencies in your Spring Boot project's files. These dependencies include Spring Boot Starter Data JPA, HikariCPand the database driver of your choice.

<dependencies>
  <!-- Spring Boot Starter Data JPA -->
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
  </dependency>

  <!-- HikariCP -->
  <dependency>
    <groupId>com.zaxxer</groupId>
    <artifactId>HikariCP</artifactId>
  </dependency>

  <!-- MySQL驱动程序 -->
  <dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
  </dependency>

  <!-- 可选：其他数据库驱动程序 -->
</dependencies>

Configure data source

application.propertiesConfigure the connection information of the dual data source in the (or application.yml) file . The following example shows how to configure two MySQL data sources:

# 数据源1
spring.datasource.url=jdbc:mysql://localhost:3306/db1
spring.datasource.username=root
spring.datasource.password=123456
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

# 数据源2
datasource2.url=jdbc:mysql://localhost:3306/db2
datasource2.username=root
datasource2.password=123456
datasource2.driver-class-name=com.mysql.cj.jdbc.Driver

Create entity class and repository

Create entity classes and repository interfaces corresponding to each data source. Each entity class and repository interface should be annotated with a different data source.

// 实体类1
@Entity
@Table(name = "table1", schema = "db1")
public class Entity1 {
    
    
  // 实体类定义...
}

// 存储库接口1
@Repository
public interface Repository1 extends JpaRepository<Entity1, Long> {
    
    
  // 存储库方法定义...
}

// 实体类2
@Entity
@Table(name = "table2", schema = "db2")
public class Entity2 {
    
    
  // 实体类定义...
}

// 存储库接口2
@Repository
public interface Repository2 extends JpaRepository<Entity2, Long> {
    
    
  // 存储库方法定义...
}

Configure data sources and entity managers

We need to create two configuration classes, one for each datasource and entity manager.

@Configuration
@EnableJpaRepositories(
    basePackages = "com.example.repository1",
    entityManagerFactoryRef = "entityManagerFactory1",
    transactionManagerRef = "transactionManager1"
)
public class DataSource1Config {
    
    
  // 数据源1的配置...
}

@Configuration
@EnableJpaRepositories(
    basePackages = "com.example.repository2",
    entityManagerFactoryRef = "entityManagerFactory2",
    transactionManagerRef = "transactionManager2"
)
public class DataSource2Config {
    
    
  // 数据源2的配置...
}

Configure Transaction Manager

Finally, we also need to configure a master transaction manager to manage transactions for all data sources.

@Configuration
@EnableTransactionManagement
public class TransactionManagementConfig {
    
    
  @Bean
  public PlatformTransactionManager transactionManager(
      EntityManagerFactory entityManagerFactory1,
      EntityManagerFactory entityManagerFactory2
  ) {
    
    
    JpaTransactionManager jpaTransactionManager = new JpaTransactionManager();
    jpaTransactionManager.setEntityManagerFactory(entityManagerFactory1);
    jpaTransactionManager.setEntityManagerFactory(entityManagerFactory2);
    return jpaTransactionManager;
  }
}

Implement dual data sources

Integrate all the above configurations into the main application. Create a @SpringBootApplicationmain class with annotations and add configuration classes for the two data sources and the transaction manager in it.

@SpringBootApplication
@Import({
    
     DataSource1Config.class, DataSource2Config.class, TransactionManagementConfig.class })
public class DualDataSourceApplication {
    
    
  public static void main(String[] args) {
    
    
    SpringApplication.run(DualDataSourceApplication.class);
  }
}

Steps to configure a dual data source in a Spring Boot application. First, we set up the project by adding the required dependencies. We then configured the connection information for each data source and created entity classes and repository interfaces. Next, we created configuration classes for the data source and entity manager, and configured a main transaction manager. Finally, we consolidate all configurations into the main application.

How to configure dual datasource in Spring Boot?