How to use Dynamic Datasource to configure multiple data sources in SpringBoot

Functional features:

1. Supports data source grouping, suitable for a variety of scenarios, pure multi-database, read-write separation, one master, multiple slaves, mixed mode.

2. Supports startup without data source and supports configuration of lazy startup data source (3.3.2).

3. Support database sensitive configuration information encryption ENC().

4. Supports independent initialization of table structure schema and database database for each database.

5. Supports custom annotations and needs to inherit DS (3.2.0).

6. Provides fast integration for Druid, Mybatis-Plus, P6sy, Jndi.

7. Simplify the configuration of Druid and HikariCp and provide global parameter configuration. Configure once and use it globally.

8. Provide custom data source solutions.

9. Provides a solution for dynamically adding and removing data sources after the project is started.

10. Provides a pure read-write separation solution in the Mybatis environment.

11. Provides a method to parse the data source scheme, using SpEL dynamic parameters. Built-in spel, session, header, support customization.

12. Supports nested switching of multi-layer data sources. (ServiceA >>> ServiceB >>> ServiceC).

13. Provides solutions, precautions and examples for integrating third-party libraries such as shiro, sharding-jdbc, quartz, etc.

14. Provides a distributed transaction solution based on seata. Attachment: Native spring transactions are not supported.

15. Provides local multi-data source transaction solutions. Attachment: Native spring transactions (3.3.1) are not supported.

Our article mainly implements the separation of reading and writing, and a one-master, multiple-slave environment.

• The main database recommends only performing INSERT, UPDATE, and DELETE operations.

• It is recommended to only perform SELECT operations from the database.

1. Prepare the database

Main database: PiaoDB

## Slave database 1: PiaoDB2

Slave database 2: PiaoDB3

2. Import POM file

Introducing dynamic-datasource-spring-boot-starter.

    com.baomidou
    dynamic-datasource-spring-boot-starter
    3.3.2

3. Edit the configuration file

We configured a master library and two slave libraries.

• The "header" of all data sources separated by underscore _ in the configuration file is the name of the group. Data sources with the same group name will be placed under one group.

• The default data source name is master, which we can modify through spring.datasource.dynamic.primary.

spring:
  datasource:
    dynamic:
      primary: master #设置默认的数据源或者数据源组,默认值即为master
      strict: false #设置严格模式,默认false不启动. 启动后在未匹配到指定数据源时候会抛出异常,不启动则使用默认数据源.
      datasource:
        master:
          url: jdbc:mysql://localhost:3306/PiaoDB?serverTimezone=Asia/Shanghai
          username: root
          password: root
          driver-class-name: com.mysql.jdbc.Driver # 3.2.0开始支持SPI可省略此配置
        slave_1:
          url: jdbc:mysql://localhost:3306/PiaoDB2?serverTimezone=Asia/Shanghai
          username: root
          password: root
          driver-class-name: com.mysql.jdbc.Driver
        slave_2:
          url: jdbc:mysql://localhost:3306/PiaoDB3?serverTimezone=Asia/Shanghai
          username: root
          password: root
          driver-class-name: com.mysql.jdbc.Driver

Because we are using the Alibaba database connection pool Druid, we need to exclude the native Druid quick configuration class.

Other third-party integration address: Druid integration

@SpringBootApplication(exclude = DruidDataSourceAutoConfigure.class)
public class Application {

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

Some springBoot versions may not be able to be excluded and can be excluded in the following ways.

spring:
  autoconfigure:
    exclude: com.alibaba.druid.spring.boot.autoconfigure.DruidDataSourceAutoConfigure

In addition to configuring one master and multiple slaves, we can also configure it.

# 多主多从                      纯粹多库（记得设置primary）                   混合配置
spring:                               spring:                               spring:
  datasource:                           datasource:                           datasource:
    dynamic:                              dynamic:                              dynamic:
      datasource:                           datasource:                           datasource:
        master_1:                             mysql:                                master:
        master_2:                             oracle:                               slave_1:
        slave_1:                              sqlserver:                            slave_2:
        slave_2:                              postgresql:                           oracle_1:
        slave_3:                              h3:                                   oracle_2:

4. Write code

Use @DS to switch data sources. @DS can be annotated on methods and classes. If both exist, method annotations take precedence over class annotations. It is strongly recommended to annotate the service implementation or mapper interface method.

• @DS("xxx") specifies the data source xxx, where xxx can be a group name or the name of a specific library. If it is a group name, the load balancing algorithm is used when switching. If the specified group name or library does not exist, the default data source (main library) will be automatically used

• If there is no @DS, the default data source (main library) will be used

• If @DS is set but a group or library is not specified, a slave library is selected based on the DynamicDataSourceStrategy strategy. Default load balancing policy.

##1. Write Controller

@RestController
@RequiredArgsConstructor
@RequestMapping("/demo")
public class DemoController {

    private final DemoService demoService;

    @GetMapping("/add")
    public String add() {
        return demoService.add(null) + "";
    }

    @GetMapping("/selectGoodsInfo")
    public List selectGoodsInfo(){
        return demoService.selectGoodsInfo();
    }

    @GetMapping("/selectMasterGoodsInfo")
    public List selectMasterGoodsInfo(){
        return demoService.selectMasterGoodsInfo();
    }

}

2. Write Service

public interface DemoService {

    boolean add(GoodsInfo param);

    List selectGoodsInfo();

    List selectMasterGoodsInfo();

}

@Service
@RequiredArgsConstructor
public class DemoServiceImpl implements DemoService {

    private final DemoMapper demoMapper;

    @DS("master")
    @Override
    public boolean add(GoodsInfo param) {
        param = new GoodsInfo();
        param.setGname("1200元秒杀华为Pad");
        param.setGnum(100);

        return demoMapper.insertGoodsInfo(param);
    }

    @DS("slave")
    @Override
    public List selectGoodsInfo() {
        return demoMapper.selectGoodsInfo();
    }

    @DS("master")
    @Override
    public List selectMasterGoodsInfo() {
        return demoMapper.selectGoodsInfo();
    }

}

3. Write Mapper

@Mapper
public interface DemoMapper {

    boolean insertGoodsInfo(GoodsInfo param);

    List selectGoodsInfo();

}

    
        select * from t_goods_info
    

    
        insert into t_goods_info (gname, gnum, gcreatetime)
            values (#{gname}, #{gnum}, now());
    

5. Verification results

1. Request to add a new interface (add data to the main database): 127.0.0.1:8086/demo/add

2. Request to query the main database data Interface: 127.0.0.1:8086/demo/selectMasterGoodsInfo

3. Request slave data interface (load balancing):

First request:

Second request:

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