SpringBoot [SpringBoot] springboot auto-assembly principles

What is automated assembly

Auto-Configuration is one of the core features of the Spring Boot framework.It automatically configures and assembles the various components required by a Spring application by scanning the application's classpath and dependencies. In traditional Spring applications , developers need to manually configure a large number of beans , such as data sources , transaction managers , view resolvers and so on. These configuration processes are cumbersome and error-prone , increasing the difficulty and cost of development . Spring Boot’s auto-assembly mechanism can automatically complete these configuration processes , so that developers can focus more on the implementation of business logic . Spring Boot’s auto-assembly accomplishes the following goals:

• Simplified configuration: Spring Boot’s auto-assembly can automatically configure the required components according to the needs and conditions of the application, avoiding the tedious manual configuration process.
• Reduced errors: Since automated assembly is based on conditionalized configuration, it avoids errors and omissions that occur during manual configuration.
• Improved efficiency: Automated assembly can improve development efficiency and reduce development time and costs.
• Enhanced Maintainability: Automated assembly allows for a more standardized and standardized configuration of applications, improving maintainability and scalability.

In short, auto-assembly is an important feature of Spring Boot , by automatically configuring and assembling the required components , so that developers can focus more on the implementation of business logic , improve development efficiency , reduce the possibility of error , and enhance the maintainability and scalability of the application .

SpringBoot auto-assembly

When we use Spring Boot to develop applications , do not need to manually configure many tedious details , but through automatic assembly to simplify the configuration process . The following will analyze the principles and mechanisms of Spring Boot auto-assembly in detail:

• Conditional Annotation (Conditional Annotation): Spring Boot uses conditional annotations to determine whether auto-configuration is required. Conditional annotations are based on the evaluation of conditions, according to certain conditions to determine the need for auto-configuration. Common conditional annotations include @ConditionalOnClass, @ConditionalOnMissingBean, @ConditionalOnProperty and so on.
• Auto-assembly startup process: During the Spring Boot startup process, the application’s classpath and dependencies are scanned and the results of the conditional annotations are used to determine whether auto-configuration is required.
• Spring Boot Starter dependencies : Spring Boot provides a series of Starter dependencies , each Starter dependency defines a set of commonly used dependency libraries , such as spring-boot-starter-web, spring-boot-starter-data-jpa and so on. These Starter dependencies are automatically assembled with the required components through an auto-configuration mechanism.
• Auto-Configuration Class: Each Starter dependency contains one or more auto-configuration classes that use conditional annotations to determine whether auto-configuration is required. Auto-configuration classes usually contain @Configuration annotations that define the creation and configuration of various beans.
• Autoconfiguration Prioritization: In multiple autoconfiguration classes, there may be the creation and configuration of beans of the same type.Spring Boot uses autoconfiguration prioritization to determine which autoconfiguration class’s settings will take effect. Generally, the later-loaded configuration class overrides the earlier configuration class. Developers can also override the default autoconfiguration by customizing the configuration.
• Custom Configuration: If an application needs to modify or extend the automatic configuration, it can provide its own configuration classes. This allows you to replace or extend the default behavior in the autoconfiguration by writing custom beans.

Through auto-assembly , Spring Boot can be based on application requirements and conditions , rapid configuration and assembly of the required components , so that developers can focus on business logic without having to pay too much attention to the tedious details of the configuration . At the same time , developers can also customize the configuration as needed , the flexibility to adjust the behavior of auto-configuration . Summary: Spring Boot’s auto-assembly automatically configures and assembles the components required by an application based on conditional judgments and prioritization rules through mechanisms such as conditional annotations, auto-configuration classes, and Starter dependencies. This approach simplifies the configuration process and improves development efficiency , while also retaining the flexibility to allow developers to customize the configuration .

concrete operation

Adding the @SpringBootApplication annotation to the SpringBoot starter class will first auto-assemble the The @SpringBootApplication is actually a composite annotation, and the annotation that really goes to auto-assembly first is @EnableAutoConfiguration The realization of automated assembly relies on 3 core key technologies

• When introducing a starter to start a dependent component, the component must contain a @Configuration configuration class, and in this configuration class, we need to declare the bean objects that need to be assembled into the IOC container through the @Bean annotation.
• This configuration class is placed in the third-party jar package, and then through SpringBoot in the agreement is better than the configuration of such a concept, go to the full path of the configuration class in the classpath:/META-INF/spring.factories file, so SpringBoot can know the third-party jar package inside the location of this configuration class (this step is mainly used in Spring Spring SpringFactoriesLoader to complete). the location of the configuration class (this step is mainly used inside the Spring SpringFactoriesLoader to complete the)
• SpringBoot to get all the third-party jar package declared inside the configuration class, and then through the Spring ImportSelector provides an interface to achieve the dynamic loading of these configuration classes, thus completing the automatic assembly of the

This allows developers to focus more on writing business code and less on business-agnostic configurations.