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Spring - Using basePackageClasses Attribute of @ComponentScan

[Last Updated: Jun 11, 2021]

@ComponentScan#basePackageClasses is a type-safe alternative to basePackages() for specifying the packages to scan for annotated components. The whole package of each class specified will be scanned.

Spring recommends to create a special no-op marker class or interface in each package that serves no purpose other than being referenced by this attribute.

Example

Creating beans in package com.logicbig.example.service

package com.logicbig.example.service;

import org.springframework.stereotype.Service;

@Service
public class RetailOrderService {

  public void placeOrder(String item) {
      System.out.printf("Retail order placed. Item: %s%n", item);
  }
}
package com.logicbig.example.service;

import org.springframework.stereotype.Service;

@Service
public class WholeSaleOrderService {

  public void placeOrder(String item, int quantity) {
      if (quantity < 10) {
          throw new IllegalArgumentException(
                  "Quantity must be more than 10  for a wholesale order");
      }
      System.out.printf("Wholesale order placed. Item: %s Quantity: %s%n", item, quantity);
  }
}

Creating beans in package com.logicbig.example.client

package com.logicbig.example.client;

import com.logicbig.example.service.RetailOrderService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component
public class Consumer {
  @Autowired
  private RetailOrderService orderService;

  public void buySomething() {
      orderService.placeOrder("Laptop");
  }
}
package com.logicbig.example.client;

import com.logicbig.example.service.WholeSaleOrderService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component
public class Wholesaler {
  @Autowired
  private WholeSaleOrderService wholeSaleOrderService;

  public void buySomethingInBulk() {
      wholeSaleOrderService.placeOrder("Car", 100);
  }
}

Creating marker interface in both packages

package com.logicbig.example.service;

public interface OnlineOrderService {
}
package com.logicbig.example.client;

public interface OnlineOrderClient {
}

Main class

package com.logicbig.example.app;

import com.logicbig.example.client.Consumer;
import com.logicbig.example.client.OnlineOrderClient;
import com.logicbig.example.client.Wholesaler;
import com.logicbig.example.service.OnlineOrderService;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan(basePackageClasses = {OnlineOrderClient.class, OnlineOrderService.class})
public class OnlineOrderApp {

  public static void main(String... strings) {
      AnnotationConfigApplicationContext context =
              new AnnotationConfigApplicationContext(OnlineOrderApp.class);
      System.out.println("-- Spring container started and is ready --");
      Consumer consumer = context.getBean(Consumer.class);
      consumer.buySomething();

      Wholesaler wholesaler = context.getBean(Wholesaler.class);
      wholesaler.buySomethingInBulk();
  }
}

Output

-- Spring container started and is ready --
Retail order placed. Item: Laptop
Wholesale order placed. Item: Car Quantity: 100

In above example if we don't create and specify special marker interfaces in each packages and just specify bean classes for basePackageClasses, that will work too and will produce the same output:

@Configuration
@ComponentScan(basePackageClasses = {RetailOrderService.class, Consumer.class})
public class OnlineOrderApp {
 ...
}

Example Project

Dependencies and Technologies Used:

  • spring-context 5.3.8: Spring Context. Version Compatibility: 3.2.9.RELEASE - 5.3.8 Version List
    ×

    Version compatibilities of spring-context with this example:

    • 3.2.9.RELEASE
    • 3.2.10.RELEASE
    • 3.2.11.RELEASE
    • 3.2.12.RELEASE
    • 3.2.13.RELEASE
    • 3.2.14.RELEASE
    • 3.2.15.RELEASE
    • 3.2.16.RELEASE
    • 3.2.17.RELEASE
    • 3.2.18.RELEASE
    • 4.0.0.RELEASE
    • 4.0.1.RELEASE
    • 4.0.2.RELEASE
    • 4.0.3.RELEASE
    • 4.0.4.RELEASE
    • 4.0.5.RELEASE
    • 4.0.6.RELEASE
    • 4.0.7.RELEASE
    • 4.0.8.RELEASE
    • 4.0.9.RELEASE
    • 4.1.0.RELEASE
    • 4.1.1.RELEASE
    • 4.1.2.RELEASE
    • 4.1.3.RELEASE
    • 4.1.4.RELEASE
    • 4.1.5.RELEASE
    • 4.1.6.RELEASE
    • 4.1.7.RELEASE
    • 4.1.8.RELEASE
    • 4.1.9.RELEASE
    • 4.2.0.RELEASE
    • 4.2.1.RELEASE
    • 4.2.2.RELEASE
    • 4.2.3.RELEASE
    • 4.2.4.RELEASE
    • 4.2.5.RELEASE
    • 4.2.6.RELEASE
    • 4.2.7.RELEASE
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    • 4.2.9.RELEASE
    • 4.3.0.RELEASE
    • 4.3.1.RELEASE
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    • 4.3.5.RELEASE
    • 4.3.6.RELEASE
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    • 4.3.9.RELEASE
    • 4.3.10.RELEASE
    • 4.3.11.RELEASE
    • 4.3.12.RELEASE
    • 4.3.13.RELEASE
    • 4.3.14.RELEASE
    • 4.3.15.RELEASE
    • 4.3.16.RELEASE
    • 4.3.17.RELEASE
    • 4.3.18.RELEASE
    • 4.3.19.RELEASE
    • 4.3.20.RELEASE
    • 4.3.21.RELEASE
    • 4.3.22.RELEASE
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    • 4.3.29.RELEASE
    • 4.3.30.RELEASE
    • 5.0.0.RELEASE
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    • 5.0.5.RELEASE
    • 5.0.6.RELEASE
    • 5.0.7.RELEASE
    • 5.0.8.RELEASE
    • 5.0.9.RELEASE
    • 5.0.10.RELEASE
    • 5.0.11.RELEASE
    • 5.0.12.RELEASE
    • 5.0.13.RELEASE
    • 5.0.14.RELEASE
    • 5.0.15.RELEASE
    • 5.0.16.RELEASE
    • 5.0.17.RELEASE
    • 5.0.18.RELEASE
    • 5.0.19.RELEASE
    • 5.0.20.RELEASE
    • 5.1.0.RELEASE
    • 5.1.1.RELEASE
    • 5.1.2.RELEASE
    • 5.1.3.RELEASE
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    • 5.1.5.RELEASE
    • 5.1.6.RELEASE
    • 5.1.7.RELEASE
    • 5.1.8.RELEASE
    • 5.1.9.RELEASE
    • 5.1.10.RELEASE
    • 5.1.11.RELEASE
    • 5.1.12.RELEASE
    • 5.1.13.RELEASE
    • 5.1.14.RELEASE
    • 5.1.15.RELEASE
    • 5.1.16.RELEASE
    • 5.1.17.RELEASE
    • 5.1.18.RELEASE
    • 5.1.19.RELEASE
    • 5.1.20.RELEASE
    • 5.2.0.RELEASE
    • 5.2.1.RELEASE
    • 5.2.2.RELEASE
    • 5.2.3.RELEASE
    • 5.2.4.RELEASE
    • 5.2.5.RELEASE
    • 5.2.6.RELEASE
    • 5.2.7.RELEASE
    • 5.2.8.RELEASE
    • 5.2.9.RELEASE
    • 5.2.10.RELEASE
    • 5.2.11.RELEASE
    • 5.2.12.RELEASE
    • 5.2.13.RELEASE
    • 5.2.14.RELEASE
    • 5.2.15.RELEASE
    • 5.2.15.RELEASE
    • 5.3.0
    • 5.3.1
    • 5.3.2
    • 5.3.3
    • 5.3.4
    • 5.3.5
    • 5.3.6
    • 5.3.7
    • 5.3.8

    Versions in green have been tested.

  • JDK 8
  • Maven 3.8.1

@ComponentScan#basePackageClasses Example Select All Download
  • spring-component-scanning-base-package-classes-attribute
    • src
      • main
        • java
          • com
            • logicbig
              • example
                • app
                  • OnlineOrderApp.java
                  • client
                  • service

    See Also