How to autowire a component in a dependency/external jar in Spring?

Question

I have a Spring Boot project and I can't get components from an external jar to be autowired. When I try to, I got a org.springframework.beans.factory.NoSuchBeanDefinitionException saying that can't find a bean with that name available.

I tried some solutions found in similar questions, like these ones:

How to autowire @service from external Jar in Spring

Spring Boot @autowired does not work, classes in different package

How can I @Autowire a spring bean that was created from an external jar?

..but still can't managed it to work.

Here is an example of what I'm trying to accomplish:

Here is boot class in the Spring Boot project spring-project-example

package com.springdi.example;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;

import com.dependency.example.DependencyBasePackageClass;
import com.dependency.example.somepackage.SomeBean;

@SpringBootApplication
@ComponentScan(basePackages = {"com.springdi.example"}, basePackageClasses = DependencyBasePackageClass.class)
public class SpringProjectExampleApplication {

    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(SpringProjectExampleApplication.class, args);

        String beanName = SomeBean.class.getName();
        System.out.printf("%s can be autowired: %s\n", beanName, String.valueOf(context.containsBean(beanName)).toUpperCase());
    }
}

It's just a simple Spring Boot project checking if it is possible to autowire a component present in the dependency jar.

Here is the component in the jar (dependency-example-1.0.0.jar)

package com.dependency.example.somepackage;

import org.springframework.stereotype.Component;

@Component
public class SomeBean {

    public void someMethod() {
        System.out.println("Some process...");
    }
}

And here is the base package class of this same jar

package com.dependency.example;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

/**
 * Just a class to serve as the root for component
 * scanning in "com.dependency.example" and its sub-packages
 */
@Configuration
@ComponentScan
public class DependencyBasePackageClass {

}

I've already tried @Import(DependencyBasePackageClass.class) in SpringProjectExampleApplication and @ComponentScan with basePackages and basePackageClasses, but no success.

I also tried using @SpringBootApplication(scanBasePackageClasses = {SpringProjectExampleApplication.class, DependencyBasePackageClass.class})

and the not type safe @SpringBootApplication(scanBasePackages = {"com.springdi.example", "com.dependency.example"}).

@Configuration @ComponentScan({"com.dependency.example"}) also fails, context.containsBean("com.dependency.example.somepackage.SomeBean") still returns false.

This jar is included in classpath and in the pom.xml as a dependency

<dependencies>
    <!-- other dependencies -->

    <dependency>
        <groupId>com.rbaggio</groupId>
        <artifactId>dependency-example</artifactId>
        <version>1.0.0</version>
        <scope>system</scope>
        <systemPath>${basedir}/lib/dependency-example-1.0.0.jar</systemPath>
    </dependency>
</dependencies>

Could it be the location of the jar, the way it is included or some extra configuration needed?

I'd appreciate any help! Thanks in advance.

Answer 1

Okey some basic things, you have mixed up your packages a bit.

@SpringBootApplication will scan all classes in packages below the class this is annotated on. This annotation is an alias for @EnableAutoConfiguration, @Configuration and @ComponentScan means that @ComponentScan(basePackages = {"com.springdi.example"}, basePackageClasses = DependencyBasePackageClass.class) is not needed.

com.springdi.example     // class with @SpringBootApplication annotation
         |
         |
         |
com.springdi.example.*    // Will find all @Service, @Component, @Configuration
                          // in subpackages below the @SpringBootApplication 
                          // annotation

You can read more about the annotation here SpringBootApplication

Since your other annotated classes are NOT in the same package structure as the @SpringBootApplication you need to define all the places you want to scan for annotations.

@SpringBootApplication(scanBasePackages = {"com.springdi.example", "com.dependency.example"})

will probably include all the packages that you want to scan through.