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Spring Framework - @ComponentScan Examples

Spring Framework 

import com.logicbig.example.bean.MyPrototypeBean;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan("com.logicbig.example.bean")
public class AppConfig {

    public static void main(String... strings) {
        AnnotationConfigApplicationContext context =
                new AnnotationConfigApplicationContext(AppConfig.class);
        System.out.println("-- Spring container started and is ready --");
        MyPrototypeBean bean = context.getBean(MyPrototypeBean.class);
        bean.doSomething();
    }
}
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@Configuration
@ComponentScan(basePackageClasses = MySingletonBean.class)
public class AppConfig {

    @Bean
    @Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
    public MyPrototypeBean prototypeBean() {
        return new MyPrototypeBean();
    }

    public static void main(String[] args) throws InterruptedException {
        AnnotationConfigApplicationContext context =
                new AnnotationConfigApplicationContext(AppConfig.class);

        MySingletonBean bean = context.getBean(MySingletonBean.class);
        bean.showMessage();

        Thread.sleep(1000);

        bean = context.getBean(MySingletonBean.class);
        bean.showMessage();
    }
}
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@Configuration
@ComponentScan
public class AppRunner {

    public static void main(String... strings) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(AppRunner.class);
        OrderServiceClient bean = context.getBean(OrderServiceClient.class);
        bean.showPendingOrderDetails();
    }
}
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This example shows that classes annotated with @Component can register new beans using @Bean annotation on their methods, but such methods will not be CGLIB enhance proxies. 

import org.springframework.context.annotation.*;
import org.springframework.stereotype.Component;

@Configuration
@ComponentScan(basePackageClasses = ScanFactoryComponentExample.class, useDefaultFilters = false,
                    includeFilters = {@ComponentScan.Filter(
                                        type = FilterType.ASSIGNABLE_TYPE,
                                        value = ScanFactoryComponentExample.TestBean.class)})
public class ScanFactoryComponentExample {

    public static void main (String[] args) {
        AnnotationConfigApplicationContext context =
                            new AnnotationConfigApplicationContext(
                                                ScanFactoryComponentExample.class);
        MyBean bean = context.getBean(MyBean.class);
        System.out.println(bean);

        //accessing multiple times
        bean = context.getBean(MyBean.class);
        System.out.println(bean);

        /*this will return a new instance because @Component methods are not
        * CGLIB proxied*/
        TestBean testBean = context.getBean(TestBean.class);
        System.out.println(testBean.myBean());
    }

    @Component
     static class TestBean {
        @Bean
        public MyBean myBean () {
            return new MyBean();
        }
    }
}

Output

com.logicbig.example.MyBean@1c95649a
com.logicbig.example.MyBean@1c95649a
com.logicbig.example.MyBean@373137a0
Original Post

This example shows that classes annotated with @Configuration will be scanned as well, if they are in scan path. 

import org.springframework.context.annotation.*;

@Configuration
@ComponentScan(basePackageClasses = ScanConfigurationExample.class, useDefaultFilters = false,
                    includeFilters = {@ComponentScan.Filter(
                                        type = FilterType.ASSIGNABLE_TYPE,
                                        value = ScanConfigurationExample.TestBean.class)})
public class ScanConfigurationExample {

    public static void main (String[] args) {
        AnnotationConfigApplicationContext context =
                            new AnnotationConfigApplicationContext(
                                                ScanConfigurationExample.class);
        MyBean bean = context.getBean(MyBean.class);
        System.out.println(bean);

        //accessing multiple times
        bean = context.getBean(MyBean.class);
        System.out.println(bean);

        /*this will return same instance because @Configuration classes even in scan path will be
        * CGLIB proxied*/
        TestBean testBean = context.getBean(TestBean.class);
        System.out.println(testBean.myBean());
    }

    @Configuration
    static class TestBean {
        @Bean
        public MyBean myBean () {
            return new MyBean();
        }
    }
}

Output

com.logicbig.example.MyBean@28e5716a
com.logicbig.example.MyBean@28e5716a
com.logicbig.example.MyBean@28e5716a
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@Configuration
@ComponentScan({"com.logicbig.example.scan"})
public class ConstBasedDIWithScan {

    @Bean
    public OrderService orderService() {
        return new OrderService();
    }

    public static void main(String... strings) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(
                ConstBasedDIWithScan.class);
        OrderServiceClient bean = context.getBean(OrderServiceClient.class);
        bean.showPendingOrderDetails();
    }

    @Component
    public static class OrderServiceClient {

        private OrderService orderService;

        @Autowired
        OrderServiceClient(OrderService orderService) {
            this.orderService = orderService;
        }

        public void showPendingOrderDetails() {
            System.out.println(orderService.getOrderDetails("500"));
        }
    }
}
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@Configuration
@ComponentScan
public class AppRunner {
    private Greeter greeter;

    public AppRunner(Greeter greeter) {
        this.greeter = greeter;
    }

    public static void main(String... strings) {
        AnnotationConfigApplicationContext context =
                new AnnotationConfigApplicationContext(AppRunner.class);

        AppRunner appRunner = context.getBean(AppRunner.class);
        appRunner.greeter.greet("Joe");
    }
}
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import com.logicbig.example.client.Buyer;
import com.logicbig.example.client.Wholesaler;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan(basePackages = {"com.logicbig.example.client","com.logicbig.example.service"})
public class OnlineOrderApp {

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

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

}
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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();
    }
}
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import com.logicbig.example.client.RetailBuyer;
import com.logicbig.example.client.Wholesaler;
import com.logicbig.example.service.WholeSaleOrderService;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.FilterType;

@Configuration
@ComponentScan(basePackages = "com.logicbig.example.client;com.logicbig.example.service",
        excludeFilters = @ComponentScan.Filter(
                type = FilterType.ASSIGNABLE_TYPE,
                classes = {WholeSaleOrderService.class, Wholesaler.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 --");
        RetailBuyer retailBuyer = context.getBean(RetailBuyer.class);
        retailBuyer.buySomething();

        boolean wholeSaleOrderServiceRegistered =
                context.containsBean("wholeSaleOrderService");
        System.out.println("wholeSaleOrderService registered: "+ wholeSaleOrderServiceRegistered);
    }
}
Original Post
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.FilterType;

@Configuration
@ComponentScan(includeFilters = @ComponentScan.Filter(
        type = FilterType.ASSIGNABLE_TYPE, classes = {OrderService.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 --");
        Buyer buyer = context.getBean(Buyer.class);
        buyer.buySomething();
    }
}
Original Post




import com.logicbig.example.client.RetailBuyer;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.FilterType;

@Configuration
@ComponentScan(basePackages = "com.logicbig.example.client;com.logicbig.example.service",
        excludeFilters = @ComponentScan.Filter(
                type = FilterType.ANNOTATION,
                classes = ExcludeFromScan.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 --");
        RetailBuyer retailBuyer = context.getBean(RetailBuyer.class);
        retailBuyer.buySomething();

        boolean wholeSaleOrderServiceRegistered =
                context.containsBean("wholeSaleOrderService");
        System.out.println("WholeSaleOrderService registered: " + wholeSaleOrderServiceRegistered);


        boolean wholesaler =
                context.containsBean("wholesaler");
        System.out.println("Wholesaler registered: " + wholesaler);
    }
}
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import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.FilterType;

@Configuration
@ComponentScan(includeFilters = @ComponentScan.Filter(
        type = FilterType.ANNOTATION, classes = {IncludeInScan.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 --");
        Buyer buyer = context.getBean(Buyer.class);
        buyer.buySomething();
    }
}
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See Also