Exception in yml binding to nested java object

Question

Facing the below exception when trying to map the yml in the nested java object, is any one also facing the exception, please suggest:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'alias': Could not bind properties to Alias (prefix=alias, ignoreInvalidFields=false, ignoreUnknownFields=true, ignoreNestedProperties=false); nested exception is java.lang.NullPointerException at org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor.postProcessBeforeInitialization(ConfigurationPropertiesBindingPostProcessor.java:352) at org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor.postProcessBeforeInitialization(ConfigurationPropertiesBindingPostProcessor.java:303) at org.springframework.cloud.context.properties.ConfigurationPropertiesRebinder.rebind(ConfigurationPropertiesRebinder.java:100)

Caused by: java.lang.**NullPointerException**: null

application-alias.yml

alias:
    name:
      -
        x: 123
      -
        x: 321 



Alias.java

    @Configuration
    @ConfigurationProperties(prefix = "alias")
    public class Alias {

        private List<PropA> name = null;
        public Alias() {}
        public List<PropA> getName() {
            return name;
        }
        public void setName(List<PropA> name) {
            this.name = name;
        }
    }

AliasResolverImpl.java

    @Component
    @EnableConfigurationProperties
    public class AliasResolverImplBack implements MapperInterface {

        @Autowired
        Alias aliases;

        @Override
        public List<Entity> resolve(List<Entity> request) throws AliasException {
            System.out.println("In impl : "+aliases.toString());
            return null;
        }
    }

ApplicationConfig.java

    @SpringBootApplication(scanBasePackages = "com.ie.naukri.services.mnj.lookupService")

    @EnableAutoConfiguration(exclude = { DataSourceAutoConfiguration.class })

    @EnableConfigurationProperties
    public class ApplicationConfig {

        @Bean
        public RestTemplate restTemplate() {
            return new RestTemplate();
        }
        public static void main(final String[] args) {
            SpringApplication.run(ApplicationConfig.class, args);
            final ApplicationContext applicationContext = SpringApplication.run(ApplicationConfig.class, args);
            applicationContext.getBean(AliasResolverImpl.class).resolve(null);
        }
    }

PropA.java



     @Configuration
    @ConfigurationProperties(prefix="alias.name")
    public class PropA {

        private int x=0;

        public int getX() {
            return x;
        }
        public void setX(int x) {
            this.x = x;
        }
        @Override
        public String toString() {
            return "PropA [x=" + x + "]";
        }
    }

Answer 1

This should work

@Configuration
@ConfigurationProperties(prefix = "alias")
public class Alias {

        private List<PropA> name = null;
        public Alias() {}
        public List<PropA> getName() {
            return name;
        }
        public void setName(List<PropA> name) {
            this.name = name;
        }
    }  

And remove these lines from PropA class

@Configuration
@ConfigurationProperties(prefix="alias.name") 

Your PropA class should be just

public class PropA {

  private int x=0;

  public int getX() {
    return x;
  }
  public void setX(int x) {
    this.x = x;
  }
  @Override
  public String toString() {
    return "PropA [x=" + x + "]";
  }
}