Spring - Default Auto-wiring mode, Autowire.No Example

[Last Updated: Nov 28, 2020]

This is the default. We have to explicitly use @Autowire annotation at injection point. That means Spring doesn't do automatic wiring in this mode. We have to tell Spring that at what points bean wiring should happen by specifying @Autowired annotation at those points.

On finding @Autowired annotation, Spring attempts to match injection point type with the available registered beans type for a successful injection.

Bean ambiguity

There shouldn't be any conflict (ambiguity), which means there should be no more than one bean instance of the same type registered for a given injection point, otherwise we will have NoUniqueBeanDefinitionException.

Example

package com.logicbig.example;

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

If there are two beans available of the required type then the match is performed based on the bean's name. If no match is found then NoUniqueBeanDefinitionException is thrown.

package com.logicbig.example;

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;

public class AutowireNoExample2 {

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

    public static class Config {

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

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

        @Bean
        public ServiceBean serviceBean2 () {
            return new ServiceBean("Service Bean 2");
        }
    }

    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

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'clientBean': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.logicbig.example.AutowireNoExample2$ServiceBean com.logicbig.example.AutowireNoExample2$ClientBean.serviceBean; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [com.logicbig.example.AutowireNoExample2$ServiceBean] is defined: expected single matching bean but found 2: serviceBean2,serviceBean1
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues (AutowiredAnnotationBeanPostProcessor.java:334)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean (AbstractAutowireCapableBeanFactory.java:1214)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean (AbstractAutowireCapableBeanFactory.java:543)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean (AbstractAutowireCapableBeanFactory.java:482)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject (AbstractBeanFactory.java:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton (DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean (AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean (AbstractBeanFactory.java:197)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons (DefaultListableBeanFactory.java:772)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization (AbstractApplicationContext.java:838)
    at org.springframework.context.support.AbstractApplicationContext.refresh (AbstractApplicationContext.java:537)
    at org.springframework.context.annotation.AnnotationConfigApplicationContext.<init> (AnnotationConfigApplicationContext.java:84)
    at com.logicbig.example.AutowireNoExample2.main (AutowireNoExample2.java:20)
    at sun.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:498)
    at org.codehaus.mojo.exec.ExecJavaMojo$1.run (ExecJavaMojo.java:282)
    at java.lang.Thread.run (Thread.java:748)
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.logicbig.example.AutowireNoExample2$ServiceBean com.logicbig.example.AutowireNoExample2$ClientBean.serviceBean; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [com.logicbig.example.AutowireNoExample2$ServiceBean] is defined: expected single matching bean but found 2: serviceBean2,serviceBean1
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject (AutowiredAnnotationBeanPostProcessor.java:573)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject (InjectionMetadata.java:88)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues (AutowiredAnnotationBeanPostProcessor.java:331)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean (AbstractAutowireCapableBeanFactory.java:1214)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean (AbstractAutowireCapableBeanFactory.java:543)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean (AbstractAutowireCapableBeanFactory.java:482)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject (AbstractBeanFactory.java:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton (DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean (AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean (AbstractBeanFactory.java:197)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons (DefaultListableBeanFactory.java:772)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization (AbstractApplicationContext.java:838)
    at org.springframework.context.support.AbstractApplicationContext.refresh (AbstractApplicationContext.java:537)
    at org.springframework.context.annotation.AnnotationConfigApplicationContext.<init> (AnnotationConfigApplicationContext.java:84)
    at com.logicbig.example.AutowireNoExample2.main (AutowireNoExample2.java:20)
    at sun.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:498)
    at org.codehaus.mojo.exec.ExecJavaMojo$1.run (ExecJavaMojo.java:282)
    at java.lang.Thread.run (Thread.java:748)
Caused by: org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [com.logicbig.example.AutowireNoExample2$ServiceBean] is defined: expected single matching bean but found 2: serviceBean2,serviceBean1
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency (DefaultListableBeanFactory.java:1126)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency (DefaultListableBeanFactory.java:1014)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject (AutowiredAnnotationBeanPostProcessor.java:545)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject (InjectionMetadata.java:88)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues (AutowiredAnnotationBeanPostProcessor.java:331)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean (AbstractAutowireCapableBeanFactory.java:1214)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean (AbstractAutowireCapableBeanFactory.java:543)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean (AbstractAutowireCapableBeanFactory.java:482)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject (AbstractBeanFactory.java:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton (DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean (AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean (AbstractBeanFactory.java:197)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons (DefaultListableBeanFactory.java:772)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization (AbstractApplicationContext.java:838)
    at org.springframework.context.support.AbstractApplicationContext.refresh (AbstractApplicationContext.java:537)
    at org.springframework.context.annotation.AnnotationConfigApplicationContext.<init> (AnnotationConfigApplicationContext.java:84)
    at com.logicbig.example.AutowireNoExample2.main (AutowireNoExample2.java:20)
    at sun.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:498)
    at org.codehaus.mojo.exec.ExecJavaMojo$1.run (ExecJavaMojo.java:282)
    at java.lang.Thread.run (Thread.java:748)

To fix above exception either use bean default name or @Qualifier at the injection point.

Using bean default name

package com.logicbig.example;

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;

public class AutowireNoExample3 {

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

    public static class Config {

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

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

        @Bean
        public ServiceBean serviceBean2 () {
            return new ServiceBean("Service Bean 2");
        }
    }

    private static class ClientBean {
        @Autowired
        private ServiceBean serviceBean2;

        public void doSomething () {
            System.out.println(serviceBean2.getMsg());
        }
    }

    private static class ServiceBean {
        private String msg;

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

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

Output

Service Bean 2

Using @Qualifier annotation

package com.logicbig.example;

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

public class AutowireNoExample4 {

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

    public static class Config {

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

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

        @Bean
        public ServiceBean serviceBean2() {
            return new ServiceBean("Service Bean 2");
        }
    }

    private static class ClientBean {
        @Autowired
        @Qualifier("serviceBean2")
        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 2

Example Project

Dependencies and Technologies Used:

spring-context 4.2.3.RELEASE: Spring Context.
JDK 1.8
Maven 3.6.3

spring-autowire-default-mode

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Download

spring-autowire-default-mode
- src
  - main
    - java
      - com
        logicbig
        example
        
        AutowireNoExample.java
        
        AutowireNoExample2.java
        
        AutowireNoExample3.java
        
        AutowireNoExample4.java
- pom.xml

Spring - Default Auto-wiring mode, Autowire.No Example

Bean ambiguity

Example

Output

Output

Using bean default name

Output

Using @Qualifier annotation

Output

Example Project

See Also