org.springframework.beans.factory.NoSuchBeanDefinitionException

The org.springframework.beans.factory.NoSuchBeanDefinitionException is a common exception that can occur when working with the Spring Framework. This exception is thrown when the Spring Application Context is unable to find a bean that has been requested by the application. In this blog post, we will take a look at the causes of this exception and how to fix it with an example code.



Causes

  • The bean requested is not defined in the Spring Configuration file.
  • The bean requested is not defined in the classpath.
  • The bean requested is defined in the configuration file but is not enabled.


Example Code

Consider the following example, where we are trying to autowire a bean named “exampleBean” that is not defined in the Spring Configuration file.

@Autowired
private ExampleBean exampleBean;

In this case, the NoSuchBeanDefinitionException will be thrown at runtime because the “exampleBean” is not defined in the configuration file.



Solution 1

To fix this issue, we need to define the “exampleBean” in the configuration file.

@Configuration
public class ExampleConfig {
    @Bean
    public ExampleBean exampleBean() {
        return new ExampleBean();
    }
}

In the above code, we have defined a new bean “exampleBean” using the @Bean annotation. Now, when the application tries to autowire the “exampleBean”, it will find it in the configuration file and the exception will not be thrown.



Solution 2

Another cause of this exception can be a misspelled bean name.

@Autowired
private ExamplBean exampleBean;

In this case, the exception will be thrown as the bean name ‘ExamplBean’ is not defined in the configuration file.



Solution 3

Another cause of this exception can be when you are trying to autowire a bean that is defined in the configuration file but is not enabled.

@Configuration
public class ExampleConfig {
    @Bean(name = "exampleBean")
    @ConditionalOnProperty(name = "example.bean.enabled", havingValue = "false")
    public ExampleBean exampleBean() {
        return new ExampleBean();
    }
}

In the above code, we have defined the “exampleBean” but it will only be enabled if the property “example.bean.enabled” is set to “true” in the application.properties file. If the property is set to “false” or not defined in the properties file, the bean will not be enabled, and the NoSuchBeanDefinitionException will be thrown when trying to autowire it.

@Autowired
private ExampleBean exampleBean;

To fix this issue, we need to enable the bean by setting the property “example.bean.enabled” to “true” in the application.properties file.

example.bean.enabled=true

Another way to fix this issue is to remove the @ConditionalOnProperty annotation from the @Bean definition, and this way, the bean will always be enabled.

Additionally, when working with multiple configurations, sometimes it’s possible that a bean is defined in one configuration but not in another. In such scenarios, it is important to check all configurations and ensure that the requested bean is defined in all of them.



Summary

In summary, the org.springframework.beans.factory.NoSuchBeanDefinitionException can occur for several reasons, including but not limited to: the bean requested is not defined in the Spring Configuration file, the bean requested is not defined in the classpath, or the bean requested is defined in the configuration file but is not enabled. To fix this exception, it is important to check the configuration files and ensure that the requested bean is defined and enabled.



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