Consider defining a bean of type '[3rd party dependency]' in your configuration

Florian Published at Dev

Florian

I have a Maven project which has approximately the following structure:

project
|--.mvn
|--target
|--backend
|  |--main
|  |  |--src/main/java/com.project
|  |  |  |--controllers
|  |  |  |  |RestController.java
|  |  |  |ProjectApplicationMain.java
|  |  |--src/main/resources
|  |  |  |application.yaml
|  |  |--target
|  |  |pom.xml
|pom.xml

Dependencies are defined in the pom.xml file that is in the root directory of the whole project and pom.xml files of the sub-modules simply use

<relativePath>../../pom.xml</relativePath>

I wish to use dependencies defined in the pom.xml in the RestController.java class, but I am getting the following error when trying to compile the code:

Parameter 0 of constructor in com.project.controllers.RestController required a bean of type 'aClassFromTheDependency' that could not be found.

Action:
Consider defining a bean of type 'aClassFromTheDependency' in your configuration.

The RestController.java class looks approximately as follows:

@RestController
@RequestMapping("/api")
public class RestController {
  private final AClassFromTheDependency aClassFromTheDependency;

@Autowired
public RestController(AClassFromTheDependency aClassFromTheDependency) {
    this.aClassFromTheDependency = aClassFromTheDependency;
  }

  @GetMapping("/make-request")
  public ResponseDTO someApi() {
    final ResponseDTO response = new ResponseDTO();
    response.setResponse(aClassFromTheDependency.aMethodFromTheDependency());
    return response;
  }
}

Additionally, the ProjectApplicationMain.java looks like this:

@SpringBootApplication(exclude = {SecurityAutoConfiguration.class})
@EnableConfigurationProperties({
  FileStorageProperties.class
})
@ComponentScan(basePackages = {"com.project"})
@EnableJpaRepositories(basePackages = {"com.project"})
@EntityScan(basePackages = {"com.project"})
@EnableCaching
public class ProjectApplicationMain {

  public static void main(String[] args) {
    SpringApplication.run(ProjectApplicationMain.class, args);
  }
}

Any ideas what seems to be the case here that I simply cannot create an instance of the dependency's class and use its methods?

Alexander Ivanchenko

In order to create a bean defined in a third party library (any other class that is not your custom one, like standard classes from the JDK) you can create a method annotated with @Bean inside your configuration class.

@Configuration
public class MyConfig {
    @Bean
    AClassFromTheDependency aClassFromTheDependency() {
        
        return AClassFromTheDependency.getInstance();
    }
}

Note

That's not the best practice to search components in each and every package of your project.
You can't place annotation on the third party classes, hence such problem can't be resolved via @ComponentScan.

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