Issue
I am working with spring boot tutorial about @Autowired and @Primary annotation
Below you can find my main class
package com.example.springtest;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import service.Animal;
@SpringBootApplication
public class SpringtestApplication {
@Autowired
private Animal animal;
public static void main(String[] args) {
SpringApplication.run(SpringtestApplication.class, args);
}
}
Animal interface (the interface that i should autowired)
package service;
public interface Animal {
String characteristics();
}
Dog class (the primary implementation of Animal interface)
package service;
import org.springframework.context.annotation.Primary;
import org.springframework.stereotype.Service;
@Primary
@Service
public class Dog implements Animal {
@Override
public String characteristics() {
return "Bark";
}
}
Cat class (the second implementation of Animal interface)
package service;
import org.springframework.stereotype.Service;
@Service
public class Cat implements Animal {
@Override
public String characteristics() {
return "Meow";
}
}
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.3.1.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>springtest</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>springtest</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
When I run the app there is a problem with injection of animal and I get following error:
***************************
APPLICATION FAILED TO START
***************************
Description:
Field animal in com.example.springtest.SpringtestApplication required a bean of type 'service.Animal' that could not be found.
The injection point has the following annotations:
- @org.springframework.beans.factory.annotation.Autowired(required=true)
Action:
Consider defining a bean of type 'service.Animal' in your configuration.
What could be the reason that Spring cannot do the autowiring?
Solution
You need to add to your main class a @ComponentScan annotation, telling it to scan the package of the services, otherwise it will not initialize these beans
Answered By - Nir Levy
Answer Checked By - Marilyn (JavaFixing Volunteer)
