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Spring Framework - @Bean Examples

Spring Framework 

This example shows how to use @Bean annotation 

import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class AppConfig {

    @Bean
    Calculator calculator() {
        return new Calculator();
    }

    public static void main(String[] args) {
        AnnotationConfigApplicationContext context =
                new AnnotationConfigApplicationContext(AppConfig.class);
        Calculator calculator = context.getBean(Calculator.class);
        int sum = calculator.sum(5, 7);
        System.out.println(sum);
    }
}
public class Calculator {

    public int sum(int x, int y) {
        return x + y;
    }
}
Original Post




Using @Bean annotation's element 'autowire' with value Autowire.NO. This is actually redundant as it's the default autowiring mode. 

import org.springframework.beans.factory.annotation.Autowire;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

public class AutowireNoExample {

    public static void main (String[] args) {
        AnnotationConfigApplicationContext context = new
                            AnnotationConfigApplicationContext(Config.class);
        ClientBean bean = context.getBean(ClientBean.class);
        bean.doSomething();
    }

    @Configuration
    public static class Config {

        @Bean(autowire = Autowire.NO)
        public ClientBean clientBean () {
            return new ClientBean();
        }

        @Bean
        public ServiceBean serviceBean () {
            return new ServiceBean("Service bean 1");
        }
    }

    private static class ClientBean {
        @Autowired
        private ServiceBean serviceBean;

        public void doSomething () {
            System.out.println(serviceBean.getMsg());
        }
    }

    private static class ServiceBean {
        private String msg;

        public ServiceBean (String msg) {
            this.msg = msg;
        }

        public String getMsg () {
            return msg;
        }
    }
}

Output

Service bean 1
Original Post




Using @Bean annotation's element 'autowire' with value Autowire.BY_TYPE. @Bean can only be used on methods or another annotation definitions. They are typically used on the methods of a @Configuration class to register bean to Spring context. 

import org.springframework.beans.factory.annotation.Autowire;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

public class AutowireByType {

    public static void main (String[] args) {
        AnnotationConfigApplicationContext context = new
                            AnnotationConfigApplicationContext(Config.class);
        ClientBean bean = context.getBean(ClientBean.class);
        bean.doSomething();
    }

    @Configuration
    public static class Config {

        @Bean(autowire = Autowire.BY_TYPE)
        public ClientBean clientBean () {
            return new ClientBean();
        }

        @Bean
        public ServiceBean serviceBean1 () {
            return new ServiceBean("Service bean 1");
        }
    }

    private static class ClientBean {
        private ServiceBean serviceBean;

        public void setServiceBean (ServiceBean serviceBean) {
            this.serviceBean = serviceBean;
        }

        public void doSomething () {
            System.out.println(serviceBean.getMsg());
        }
    }

    private static class ServiceBean {
        private String msg;

        public ServiceBean (String msg) {
            this.msg = msg;
        }

        public String getMsg () {
            return msg;
        }
    }
}

Output

Service bean 1
Original Post

See Also