How to centralize the Entity, Mapper, and Service of the business module into the Common module in Spring Cloud Alibaba?

Best practices for centrally managing public modules Entity, Mapper, and Service in Spring Cloud Alibaba

When building a microservice architecture using Spring Cloud Alibaba, it is crucial to organize your code structure properly. This article discusses how to integrate the Entity, Mapper, and Service components of multiple business modules into a common module (Common module), and resolve possible conflicts and problems, ultimately improving code reusability and maintainability.

Project structure:

Suppose the project contains the following modules:

1. common module: includes Entity, Mapper, Service interface and implementation classes, database connection configuration, unified exception handling, Redis JSON serialization, unified response result encapsulation, Swagger configuration, MyBatis Plus configuration, CORS configuration and other common components.
2. Merchant module (merchant terminal): contains controller, calls the Service in the common module to process business logic and provides an API interface to the outside world.
3. supply module (supplier): Similar to the merchant module, it contains controller and business logic, and also relies on the common module.

Problems and solutions:

When starting the merchant module, a javax.management.InstanceAlreadyExistsException error appears, which is usually related to Spring Boot Admin conflicts, and may also be related to incorrect package scanning configurations. The solution is as follows:

1. Precise package scanning configuration: In the startup class of each business module (merchant and supply), use @ComponentScan to accurately specify the package path to scan. Avoid using wildcards * , only scan the controls of the business module itself, and rely on components in the common module. For example, the start class of the merchant module:

    @SpringBootApplication
   @ComponentScan(basePackages = "com.quanneng.merchant") // Scan only the components under the merchant module @MapperScan("com.quanneng.common.mapper") // Scan the mapper interface separately public class MerchantApiApplication {
       // ...
   }

2. Avoid Spring Boot Admin conflicts: If Spring Boot Admin is used, make sure it is configured correctly and does not conflict with other components. Check the configuration of Spring Boot Admin to make sure the name of the application it monitors is unique. If the problem persists, you can temporarily disable Spring Boot Admin to check whether it is a conflict caused by it.

3. Mapper interface scanning: Use the @MapperScan annotation to scan the Mapper interface under the common module separately to avoid conflicts with the Mapper interface of other modules. Ensure that the package path specified by @MapperScan is accurate.

4. Dependency management of public components: Ensure that all public components dependencies in common modules are correctly declared and that the version is compatible with other modules.

5. Modular design: Design the common module as a separate module and package it into a Spring Boot Starter. In this way, other modules only need to rely on this Starter to easily use the components in the common module, avoiding the complexity of package scanning configuration.

Improvement suggestions:

• Use Spring Boot Starter: Package common modules into a Spring Boot Starter to simplify dependency management and configuration.
• Unified exception handling: Implement a unified exception handling mechanism in common module and use it in all modules.
• Unified response results: Define a unified response result format in the common module to improve the consistency of the API interface.
• Modular principle: Follow the modular design principle, separate public components from business components, and improve the maintainability and reusability of code.

Through the above steps, you can effectively concentrate Entity, Mapper, and Service components into the common module and avoid potential conflicts. Accurate package scanning configuration and modular design are key to solving such problems. If you still encounter problems, please check the log information to find out the specific cause of the error.

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