What is the method of spring automatic assembly?

Spring automatic assembly methods: 1. XML-based configuration; 2. Annotation-based automatic assembly; 3. Java configuration; 4. Conditional annotations; 5. Profile annotations; 6. Event-driven automatic assembly; 7. Customized automatic assembly strategy; 8. Lazy loading; 9. Component scanning; 10. Environment-related configuration; 11. Combination of automatic assembly and XML configuration; 12. Customized BeanPostProcessor and BeanFactoryPostProcessor; 13. Attribute-driven configuration, etc.

The operating system for this tutorial: Windows 10 system, DELL G3 computer.

The Spring framework provides a variety of automatic assembly methods, allowing developers to manage objects and their dependencies more conveniently. The following are several common methods of Spring autowiring:

1. XML-based configuration:

• The autowire attribute of the element: By setting The autowire attribute is "byName", "byType" or "constructor". Spring can automatically wire the bean based on its name, type or constructor parameters.
• element: Through the element, developers can define aspects and specify on which methods these aspects are applied.

2. Annotation-based autowiring:

• @Autowired: This annotation tells the Spring container to connect to the annotated field, constructor or The beans corresponding to the method parameters are automatically assembled. If no matching bean is found, an exception will be thrown.
• @Resource: This is an annotation provided by Java EE and can also be used in Spring. It is similar to @Autowired but allows matching by name.
• @Qualifier: When there are multiple beans of the same type, you can use the @Qualifier annotation to specify the bean to be injected.
• @PostConstruct and @PreDestroy: These two annotations are used to specify the methods to be called after dependency injection is completed, and are often used for resource initialization and cleanup.

3. Java configuration:

• @Configuration: This is an annotation indicating that the class is used as a configuration class.
• @Bean: This annotation is used on a method, indicating that the method will return an object, which should be registered as a bean in the Spring application context.
• @ComponentScan: This annotation tells the Spring container to scan the specified package for components, configurations and namespaces.

4. Conditional annotations: For example, @ConditionalOnClass, @ConditionalOnProperty, etc. These annotations allow beans to be created and registered only when certain conditions are met.

5. Profile annotation: Use @Profile to limit a bean to a specific configuration file. This bean will only be created when the corresponding profile is activated.

6. Event-driven automatic assembly: Spring container publishes many events, such as ContextRefreshedEvent, etc. Beans that listen to these events can implement automatic assembly.

7. Customized automatic assembly strategy: If the default automatic assembly strategy cannot meet the needs, developers can customize an automatic assembly strategy. This usually involves implementing the ApplicationContextAware interface or overriding the BeanFactory's getBean() method.

8. Lazy Initialization: By default, the Spring container will initialize and return all singleton beans immediately. But sometimes for performance reasons, developers may want to delay bean initialization. For this purpose, you can use the @Lazy annotation, so that the corresponding bean will not be initialized until it is accessed for the first time.

9. Component Scanning: Through configuration or annotations (such as @ComponentScan), the Spring container can automatically scan the specified package to find and register components, configurations and namespaces.

10. Environment-related configuration: According to different environments (such as development, testing, production), developers can define different configuration files and decide which one to load by setting different properties. Configuration files to implement automatic assembly strategies in different environments.

11. Combination of autowiring and XML configuration: Although Spring recommends using Java configuration and annotations to manage beans, in some cases, using XML configuration in combination with annotations can make things better. becomes simpler. For example, you can define a bean in XML and then reference it via @Autowired in Java code.

12. Customized BeanPostProcessor and BeanFactoryPostProcessor: By implementing these interfaces, developers can customize the logic for processing the bean life cycle and configuration. For example, the bean definition can be modified or enhanced in a custom BeanPostProcessor.

13. Property-driven configuration: In Spring Boot, you can use @PropertySource, @Value and other annotations to inject external properties (such as application.properties) into the bean.

14. Conditional annotations and conditional classes: Using these features in combination, you can decide whether to create a bean or use a specific implementation based on runtime conditions.

15. Externalized configuration and Profile: Using externalized configuration (such as application.properties), you can easily use different configuration values ​​​​in different environments or enable/disable certain Function.

16. Event-driven automatic assembly: Spring container publishes many events, such as ContextRefreshedEvent, etc. Beans that listen to these events can implement automatic assembly.

17. Mixed use of Java-based configuration and XML: In large projects, developers may want to continue to use XML for certain configurations, while using Java configuration and annotations to simplify other parts. development work.

18. Customized BeanPostProcessor and BeanFactoryPostProcessor: By implementing these interfaces, developers can customize the logic for processing the bean life cycle and configuration.

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