How can I create a Spring 5 component index?

Spring 5 Has added a new feature to improve startup performance of large applications.

it creates a list of component candidates at compilation time.

In this mode, all modules of the application must use this mechanism as, when the ApplicationContext detects such index, it will automatically use it rather than scanning the classpath.

To generate the index, we just need to add below dependency to each module

Maven:

<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context-indexer</artifactId>
        <version>5.0.3.RELEASE</version>
        <optional>true</optional>
    </dependency>
</dependencies>

Gradle

dependencies {
    compileOnly("org.springframework:spring-context-indexer:5.0.3.RELEASE")
}

This process will generate a META-INF/spring.components file that is going to be included in the jar.

Reference : 1.10.9. Generating an index of candidate components

The META-INF/spring.components files are generated by an annotation processor library called spring-context-indexer. If you add this library as "annotation processor path" to the maven-compiler-plugin, the files will be generated automatically at build time:

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-compiler-plugin</artifactId>
  <configuration>
    <annotationProcessorPaths>
      <path>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context-indexer</artifactId>
        <version>5.0.6.RELEASE</version>
      </path>
    </annotationProcessorPaths>
    ...
  </configuration>
</plugin>

This setup requires maven-compiler-plugin version 3.5 or greater.

See also: https://maven.apache.org/plugins/maven-compiler-plugin/compile-mojo.html#annotationProcessorPaths