Spring bean not getting Autowired from custom library

Question

I have created by own library(com.custom.mylib) which returns a string like below.

@Component
public class MyLibrary{

    @Value("${str.message}")
    private String message; //This val should come from app which is going to use this lib
    public String readMessage() {
        return message;
    }

I have create a project which is going to use above library. I have included the lib as pom dependency .But when I try to call library method from my app. I get the error below. How to resolve it?

   @Autowired
    private MyLibrary myLibrary;

Consider defining a bean of type 'com.custom.mylog.MyLibrary' in your configuration.

I also have below in application.properties file so that library can pick the value up

str.message=Hello world

can you share your `@Configuration` class? do you component-scan the relevant package? — Nir Levy, Feb 27 '22 at 08:22
I don't have any `@Configuration` class in the app(which is using library) .Its simple app trying to inject the component `Mylibrary`.Main app uses `@SpringBootApplication`.Am i missing something? — Pale Blue Dot, Feb 27 '22 at 08:25
@NirLevyI got the solution it seems.I need to create META-INF file and do `org.springframework.boot.autoconfigure.EnableAutoConfiguration=` as given here https://stackoverflow.com/questions/41815871/spring-boot-autowire-beans-from-library-project — Pale Blue Dot, Feb 27 '22 at 08:43

score 1 · Answer 1 · answered Feb 27 '22 at 09:23

1

I got the solution it seems.I need to create META-INF file and do org.springframework.boot.autoconfigure.EnableAutoConfiguration=<fully_qualified_name_of_configuration_file>

as given here Spring Boot: autowire beans from library project

answered Feb 27 '22 at 09:23

Pale Blue Dot

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score 0 · Answer 2 · answered Feb 27 '22 at 19:10

As it has to be used as a external library, you can instantiate it throught a @Configuration file:

@Configuration
public class AppConfiguration {

    @Bean
    public MyLibrary createMyLibraryInstance() {
        return new MyLibrary();
    }
}

The rule I used is the follow (this is not an universal rule):

In your domain classes (Controller, Service) : use @Autowired in your constructor. It is the recommanded way to inject your dependencies.
You want to use external classes : implements a Java Configuration with @Configuration annotation, to instanciate your external classes as beans.
You want to create custom utilities classes : decorate it with @Component.
When you have more than on implementation, use @Qualifier and define your beans in a @Configuration class.

Spring bean not getting Autowired from custom library

2 Answers2

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