Getting exception expected single matching bean but found 2

Question

Please see the below code:

interface X {

    void method();
}

@Service("Y-Impl")
class Y implements X{
  
        void method{
        
        }
    }

@Service("Z-Impl")
class Z extends Y implements X {
    void method{

    }

}

@Controller
class TestClass {

    @Autowired
    @Qualifier("Y-Impl")
    private X x1;

    @Autowired
    @Qualifier("Z-Impl")
    private X x2;

}

Here I am getting error Error creating bean with name 'X': Unsatisfied dependency expressed through field 'x1'; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'X' available: expected single matching bean but found 2: "Y-Impl","Z-Impl"

Please let me know why I am getting this error even if I am using @Qualifier

NB: This particular question does not exist pls dont mark this as a duplicate

Smutje Smutje · Accepted Answer · 2020-10-29T13:34:56

The following works on my machine without a problem, I added a few methods to prove the correct injection:

X.java

package org.example;

public interface X {

    void method();
}

Y.java

package org.example;

import org.springframework.stereotype.Service;

@Service("Y-Impl")
public class Y implements X {

    public void method() {
        System.out.println("Y");
    }
}

Z.java

package org.example;

import org.springframework.stereotype.Service;

@Service("Z-Impl")
public class Z extends Y implements X {

    public void method() {
        System.out.println("Z");
    }
}

TestClass.java

package org.example;

import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;

@Service
public class TestClass {

    private final X x1;

    private final X x2;

    public TestClass(@Qualifier("Y-Impl") X x1, @Qualifier("Z-Impl") X x2) {
        this.x1 = x1;
        this.x2 = x2;
    }

    public void print() {
        x1.method();
        x2.method();
    }
}

AppStartupRunner.java

package org.example;

import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.stereotype.Component;

@Component
public class AppStartupRunner implements ApplicationRunner {

    private final TestClass testClass;

    public AppStartupRunner(TestClass testClass) {
        this.testClass = testClass;
    }

    @Override
    public void run(ApplicationArguments args) {
        testClass.print();
    }
}

=> Result:

Y
Z

Edit:

For the sake of completeness here the rest of my test project

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 http://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>2.3.3.RELEASE</version>
        <relativePath/>
    </parent>
    <groupId>org.example</groupId>
    <artifactId>SpringBoot</artifactId>
    <version>1.0-SNAPSHOT</version>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>
</project>

Application.java

package org.example;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}