How to resolve 'org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type ...' - using stereotype Annotations and using @Configuration, @Bean Annotation

"At the end of the day, it doesn't really matter whether you use XML, annotation or Java configuration. It's important that beans are known to application context." - Tomasz Nurkiewicz

Hello everyone, in this article, we will learn how to resolve
org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.knf.dev.demo.account.HelloManager' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: 

Using:

1. Stereotype Annotations.
2. @Configuration, @Bean Annotation.




Before going to the example just a quick overview of NoSuchBeanDefinitionException@Configuration annotation, @Bean annotation, and @Component annotation(Stereotype annotation).


NoSuchBeanDefinitionException:

The 'org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.knf.dev.demo.account.HelloManager' available: expected at least 1 bean which qualifies as autowire candidate....' will be thrown when the bean is not available or defined while auto-wired in another class. If the bean is not available when the spring boot bean is annotated by @Autowired from the spring boot ApplicationContext, this exception will be thrown from the application.


@Configuration:

The @Configuration annotation is a part of the spring core framework. The @Configuration is a marker annotation which denotes that a class declares one or more @Bean methods and may be processed by the Spring container to engender bean definitions and service requests for those beans at runtime.


@Bean:

The @Bean annotation is a part of the spring core framework. The  @Bean annotation tells that a method produces a bean to be managed by the Spring container. 


@Component:

The @Component annotation is utilized to denote a class as a Component. It signifies that Spring will autodetect these classes for dependency injection when annotation-predicated configuration and classpath scanning is utilized.

@ComponentScan:

The @ComponentScan annotation provides a mechanism to identify Spring bean candidates explicitly. If the application is a Spring Boot application, then all the packages under the package containing the Spring Boot application class will be covered by an implicit component scan.

**Important Notes**

  • The @ComponentScan annotation provides a mechanism to identify Spring bean candidates explicitly. If the application is a Spring Boot application, then all the packages under the package containing the Spring Boot application class will be covered by an implicit component scan.
  • Spring Boot’s @SpringBootApplication annotation implies the @Configuration, @ComponentScan, and @EnableAutoConfiguration annotations.
  • The process of searching the classpath for classes that should contribute to the application context is called component scanning. 
  • The  @SpringBootApplication annotation implies the @Configuration, @ComponentScan, and @EnableAutoConfiguration annotations. 
  • By default, the @ComponentScan annotation will scan for components in the current package and all its sub-packages. So if your application doesn’t have a varying package structure then there is no need for explicit component scanning.


Spring Boot Example 1: Reproduce the issue,

Hello.java:

public class Hello {

private String message;

public String getMessage() {
return message;
}

public void setMessage(String message) {
this.message = message;
}

public Hello(String message) {
super();
this.message = message;
}

public Hello() {
super();
}
}


HelloManager.java:

public interface HelloManager {

public Hello hello();
}


HelloManagerImpl.java:

public class HelloManagerImpl implements HelloManager {

@Override
public Hello hello() {
Hello hello = new Hello("Hello Spring!");
return hello;
}
}

HelloConfig.java:

public class HelloConfig {

public HelloManager helloWorld() {
return new HelloManagerImpl();
}
}


Spring Boot Main Driver:

@SpringBootApplication
public class DemoApplication implements CommandLineRunner {

private static final Logger LOG =
LoggerFactory.getLogger(DemoApplication.class);

@Autowired
private HelloManager HelloManager;

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

@Override
public void run(String... args) throws Exception {
String hello = HelloManager.hello().getMessage();
LOG.info(hello);

}
}
Spring Boot’s @SpringBootApplication annotation implies the @Configuration, @ComponentScan, and @EnableAutoConfiguration annotations.

Exception:

Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'demoApplication': Unsatisfied dependency expressed through field 'HelloManager'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.knf.dev.demo.account.HelloManager' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
2022-05-01 01:11:38.364  INFO 23309 --- [           main] ConditionEvaluationReportLoggingListener : 

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2022-05-01 01:11:39.078 ERROR 23309 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 

***************************
APPLICATION FAILED TO START
***************************

Description:

Field HelloManager in com.knf.dev.demo.account.DemoApplication required a bean of type 'com.knf.dev.demo.account.HelloManager' that could not be found.

The injection point has the following annotations:
        - @org.springframework.beans.factory.annotation.Autowired(required=true)


Action:

Consider defining a bean of type 'com.knf.dev.demo.account.HelloManager' in your configuration.


Solution: Using @Configuration and @Bean

@Configuration
public class HelloConfig {

@Bean
public HelloManager helloWorld() {
return new HelloManagerImpl();
}
}
Here we have a @Configuration class that we can use to create and use beans within the application context. @Bean is used to mark a method as one that creates a bean and Spring will then add it to the context for us.


Console Output:

Hello Spring!




Spring Boot Example 2: Reproduce the issue,

Hello.java:

public class Hello {

private String message;

public String getMessage() {
return message;
}

public void setMessage(String message) {
this.message = message;
}

public Hello(String message) {
super();
this.message = message;
}

public Hello() {
super();
}
}


HelloManager.java:

public interface HelloManager {

public Hello hello();
}


HelloManagerImpl.java:

public class HelloManagerImpl implements HelloManager {

@Override
public Hello hello() {
Hello hello = new Hello("Hello Spring!");
return hello;
}
}


Spring Boot Main Driver:

@SpringBootApplication
public class DemoApplication implements CommandLineRunner {

private static final Logger LOG =
LoggerFactory.getLogger(DemoApplication.class);

@Autowired
private HelloManager HelloManager;

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

@Override
public void run(String... args) throws Exception {
String hello = HelloManager.hello().getMessage();
LOG.info(hello);

}
}


Exception:

Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'demoApplication': Unsatisfied dependency expressed through field 'HelloManager'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.knf.dev.demo.account.HelloManager' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
2022-05-01 01:32:57.447  INFO 6535 --- [           main] ConditionEvaluationReportLoggingListener : 

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2022-05-01 01:32:57.571 ERROR 6535 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 

***************************
APPLICATION FAILED TO START
***************************

Description:

Field HelloManager in com.knf.dev.demo.account.DemoApplication required a bean of type 'com.knf.dev.demo.account.HelloManager' that could not be found.

The injection point has the following annotations:
        - @org.springframework.beans.factory.annotation.Autowired(required=true)


Action:

Consider defining a bean of type 'com.knf.dev.demo.account.HelloManager' in your configuration.


Solution: Using stereotype annotation

@Component //or other stereotype annotations
public class HelloManagerImpl implements HelloManager {

@Override
public Hello hello() {

Hello hello = new Hello("Hello Spring!");
return hello;
}
}
Mark HelloManagerImpl with @Component annotation.


Console Output:

 Hello Spring!

When to use What?

@Component Preferable for component scanning and automatic wiring.
Sometimes @Component is not an option. 
For example, You want to wire components from 3rd-party libraries but you don't have the source code so you can't annotate its classes with @Component, so automatic configuration is not possible.
The @Bean annotation returns an object that spring should register as a bean in the application context. The body of the method bears the logic responsible for engendering the instance.

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