Spring Boot 3: spring.factories

About

In Spring Boot 3, the traditional META-INF/spring.factories mechanism was replaced by a new metadata-based system using:

• META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports (for auto-configuration)

• META-INF/spring/org.springframework.boot folder with structured metadata files for other use cases

Why the Change ?

• Modularity: Split metadata per feature rather than one bulky file

• Better performance: Optimized classpath scanning

• Clarity: Easier to understand and manage for different framework extension points

• Native image compatibility: Improves behavior in GraalVM and AOT (Ahead-of-Time) contexts

Replacing EnableAutoConfiguration

Old Way (Spring Boot 2):

propertiesCopyEdit# spring.factories
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.example.autoconfig.MyAutoConfiguration

New Way (Spring Boot 3):

Create the file:

META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports

Add your class:

com.example.autoconfig.MyAutoConfiguration

Java Class:

@Configuration
@ConditionalOnClass(name = "com.example.MyService")
public class MyAutoConfiguration {

    @Bean
    public MyService myService() {
        return new MyService();
    }
}

This is now the standard way to register auto-configuration classes in Spring Boot 3.

ApplicationContextInitializer, EnvironmentPostProcessor, RunListener

These are not moved to a new system. They still use spring.factories, even in Spring Boot 3.

So, for the following types, we still use META-INF/spring.factories:

Still supported in Spring Boot 3 via spring.factories:

Interface/Class	Description
ApplicationContextInitializer	Modify application context before refresh
EnvironmentPostProcessor	Add/override environment properties
ApplicationListener	Hook into Spring event lifecycle
SpringApplicationRunListener	Listen to Spring Boot startup phases

Example:

# META-INF/spring.factories
org.springframework.boot.env.EnvironmentPostProcessor=\
com.example.env.MyEnvPostProcessor

public class MyEnvPostProcessor implements EnvironmentPostProcessor {
    public void postProcessEnvironment(ConfigurableEnvironment env, SpringApplication app) {
        env.getSystemProperties().put("env.source", "custom");
    }
}

Comparison

Feature	Spring Boot 2 (Old)	Spring Boot 3 (New)
Auto Configuration	spring.factories with EnableAutoConfiguration key	AutoConfiguration.imports file
Initializers	spring.factories	still spring.factories
Listeners	spring.factories	still spring.factories
Env Post Processor	spring.factories	still spring.factories
Lifecycle Hooks	spring.factories	still spring.factories