How does Spring Boot handle distributed transactions?

Spring Boot distributed transaction processing

A distributed transaction is one that spans multiple databases or services, and it needs to ensure that all participants process the transaction in a consistent manner. In microservice architecture, it is very important to implement distributed transactions since each service has its own database. In this article, we will describe how to implement distributed transaction processing in a Spring Boot application.

What is a distributed transaction?

In a traditional monolithic application, transactions are usually processed in one database. However, in a microservices architecture, each service has its own database, so transactions spanning multiple services and databases become more complicated. A distributed transaction is one that spans multiple databases or services, and it needs to ensure that all participants process the transaction in a consistent manner.

In distributed transactions, the following four ACID properties need to be ensured:

• Atomicity: The entire transaction must be executed as an atomic operation, either all succeed, or all fail and roll back.
• Consistency: At the end of a transaction, the state of all participants should be consistent.
• Isolation: Each transaction appears to execute in a separate environment, even if they execute concurrently.
• Durability: Once a transaction completes, its results should be permanently stored in the system.

Spring Boot distributed transaction processing mechanism

In a Spring Boot application, we can use the transaction manager of the Spring framework to handle distributed transactions. Spring provides two transaction managers:

• JtaTransactionManager: Used to manage Java Transaction API (JTA) transactions.
• DataSourceTransactionManager: used to manage local transactions.

In distributed transactions, we use JtaTransactionManager to manage transactions. The JTA transaction manager supports XA transactions, a distributed transaction protocol used to ensure that transactions across multiple databases or services are processed in a consistent manner.

Below we will introduce how to implement distributed transaction processing in Spring Boot applications.

Implement distributed transaction processing

To implement distributed transaction processing, you need to perform the following steps:

1. add dependencies

pom.xmlAdd the following dependencies to the file :

    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jta-atomikos</artifactId>
</dependency>

This dependency will add Atomikos JTA Transaction Manager and Spring Boot's JTA support.

2. Configure data source

application.ymlAdd the datasource configuration in the file :

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/db1
    username: username
    password: password
    driver-class-name: com.mysql.jdbc.Driver

mybatis:
  mapper-locations: classpath:mapper/*.xml

This configuration will configure a MySQL database data source. You can change it according to your needs.

3. Configure the Atomikos transaction manager

application.ymlAdd the configuration of Atomikos transaction manager in the file :

spring:
  jta:
    atomikos:
      datasource:
        xa-data-source-class-name: com.mysql.jdbc.jdbc2.optional.MysqlXADataSource
        unique-resource-name: db1
        xa-properties:
          user: username
          password: password
          URL: jdbc:mysql://localhost:3306/db1
      min-pool-size: 1
      max-pool-size: 5
      max-lifetime: 20000
      borrow-connection-timeout:5000
      default-transaction-timeout: 60

In the configuration above, we use xa-data-source-class-namean XA datasource with MySQL specified. We also define some pooling and timeout parameters.

4. Configure MyBatis

application.ymlAdd MyBatis configuration to the file :

mybatis:
  configuration:
    map-underscore-to-camel-case: true
  type-aliases-package: com.example.demo.domain

In the above configuration, we enabled the underscore-to-camel case naming rule of MyBatis, and specified the package path of the entity class.

5. Define entity class

Define an entity class, for example:

public class User {
    
    

    private Long id;
    private String name;
    private Integer age;

    // getters and setters
}

6. Define the Mapper interface

Define the Mapper interface, for example:

public interface UserMapper {
    
    

    @Insert("INSERT INTO user(name, age) VALUES(#{name}, #{age})")
    void insert(User user);
}

7. Define business layer services

Define a business layer service such as:

@Service
@Transactional
public class UserServiceImpl implements UserService {
    
    

    private final UserMapper userMapper;

    public UserServiceImpl(UserMapper, userMapper);
    }

    @Override
    public void addUser(User user) {
    
    
        userMapper.insert(user);
    }
}

In the above code, we @Transactionalmarked UserServiceImplthe class with annotations, indicating that all methods of this class are transactional. We also injected UserMapperand addUsercalled its insertmethod in the method.

8. Define the controller

Define a controller such as:

@RestController
public class UserController {
    
    

    private final UserService userService;

    public UserController(UserService userService) {
    
    
        this.userService = userService;
    }

    @PostMapping("/user")
    public void addUser(@RequestBody User user) {
    
    
        userService.addUser(user);
    }
}

In the above code, we injected UserServiceand addUsercalled its addUsermethod in the method.

Now that we have configured all the components of distributed transaction processing, we can test our application.

Test distributed transaction processing

In order to test distributed transaction processing, we can use tools such as Postman or curl /userto send POST requests to the interface.

POST http://localhost:8080/user
Content-Type: application/json
{
    "name":"John",
    "age": 30
}

If everything worked, you should see the following response:

HTTP/1.1 200 OK

At the same time, you can check in the MySQL database whether a new user record was successfully inserted.

Summarize

In this article, we covered how to implement distributed transaction processing in a Spring Boot application. To implement distributed transaction processing, you need to add Atomikos JTA Transaction Manager and Spring Boot's JTA support dependencies, configure data sources, Atomikos transaction manager and MyBatis, define entity classes, Mapper interfaces, business layer services and controllers. By using distributed transaction processing, you can ensure that multiple services and databases process transactions in a consistent manner, improving application reliability and availability.