Spring构造器自动注入报错：多个同类型Parrot Bean冲突

我正在通过《Spring Start Here》学习Spring框架，已在Spring上下文中注册了两个Parrot类的Bean（parrot1和parrot2），尝试通过构造器自动将parrot2注入到Person类中，但持续收到报错：

"Unsatisfied dependency expressed through constructor parameter 0: No qualifying bean of type 'beans.Parrot' available: expected single matching bean but found 2: parrot1,parrot2"

原本以为构造器参数名与bean名称匹配就不会有问题，尝试使用@Qualifier注解后仍出现相同错误。相关代码及错误信息如下：

相关代码 #

配置类（ProjectConfig.java） #

package config;

import beans.Parrot;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;


@Configuration
@ComponentScan(basePackages = "beans")
public class ProjectConfig {

    @Bean
    public Parrot parrot1() {
        Parrot p = new Parrot();
        p.setName("Koko");
        return p;
    }

    @Bean
    public Parrot parrot2() {
        Parrot p = new Parrot();
        p.setName("Miki");
        return p;
    }
}

Parrot类（Parrot.java） #

package beans;

public class Parrot {
    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "Parrot : " + name;
    }
}

Person类（Person.java） #

package beans;

import org.springframework.stereotype.Component;

@Component
public class Person {
    private String name = "Ella";

    private final Parrot parrot;

    public Person(Parrot parrot2) {
        this.parrot = parrot2;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Parrot getParrot() {
        return parrot;
    }
}

主类（Main.java） #

package main;

import beans.Person;
import config.ProjectConfig;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class Main {
    public static void main(String[] args) {
        var context = new AnnotationConfigApplicationContext(ProjectConfig.class);

        Person p = context.getBean(Person.class);

        System.out.println("Person's name: " + p.getName());
        System.out.println("Person's parrot: " + p.getParrot());
    }
}

错误信息 #

Unsatisfied dependency expressed through constructor parameter 0: No qualifying bean of type 'beans.Parrot' available: expected single matching bean but found 2: parrot1,parrot2
Exception in thread "main" org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'person' defined in file [C:\Users\Ian36\IdeaProjects\BENAS\target\classes\beans\Person.class]: Unsatisfied dependency expressed through constructor parameter 0: No qualifying bean of type 'beans.Parrot' available: expected single matching bean but found 2: parrot1,parrot2
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:802)
    at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:241)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1354)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1191)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:561)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:521)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:325)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:323)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:975)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:960)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:625)
    at org.springframework.context.annotation.AnnotationConfigApplicationContext.<init>(AnnotationConfigApplicationContext.java:93)
    at main.Main.main(Main.java:9)
Caused by: org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'beans.Parrot' available: expected single matching bean but found 2: parrot1,parrot2
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveNotUnique(DependencyDescriptor.java:218)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1420)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1353)
    at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:911)
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:789)
    ... 14 more

Process finished with exit code 1

解决方案 #

方法1：正确使用@Qualifier注解 #

你之前的@Qualifier可能未正确添加到构造器参数上，需要在参数前标注@Qualifier("parrot2")，并确保导入对应的包。修改后的Person类代码如下：

package beans;

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

@Component
public class Person {
    private String name = "Ella";

    private final Parrot parrot;

    public Person(@Qualifier("parrot2") Parrot parrot2) {
        this.parrot = parrot2;
    }

    // getter、setter和toString方法保持不变
}

方法2：开启编译参数保留构造器参数名 #

Spring支持通过构造器参数名匹配Bean名称，但前提是编译时保留了参数名信息。如果使用Java 8+，需要在编译配置中添加-parameters参数，让Spring能识别到参数名parrot2。

Maven配置示例（pom.xml）：

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.8.1</version>
            <configuration>
                <source>11</source> <!-- 替换为你的Java版本 -->
                <target>11</target>
                <compilerArgs>
                    <arg>-parameters</arg>
                </compilerArgs>
            </configuration>
        </plugin>
    </plugins>
</build>

方法3：标记其中一个Bean为@Primary #

如果parrot2是多数场景下默认需要注入的Bean，可以在其@Bean注解上添加@Primary，让Spring优先选择该Bean：

package config;

import beans.Parrot;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;

@Configuration
@ComponentScan(basePackages = "beans")
public class ProjectConfig {

    @Bean
    public Parrot parrot1() {
        Parrot p = new Parrot();
        p.setName("Koko");
        return p;
    }

    @Primary
    @Bean
    public Parrot parrot2() {
        Parrot p = new Parrot();
        p.setName("Miki");
        return p;
    }
}

内容的提问来源于stack exchange，提问作者Ian