Java Spring 无法创建使用枚举作为构造函数参数的 Bean

Question

我是 Spring 新手，但在搜索了一个多小时后我还没有找到答案。我正在制作一副简单的纸牌，但无法使用两个枚举作为构造函数中的参数来实例化我的 Card 对象。 Spring 可以使用枚举吗？我可以不在配置类中进行硬连线吗？这是我的代码:

@Component
public class Card {

    EnumValue value;
    EnumSuit suit;

    public Card(EnumValue v, EnumSuit s) {
        value = v;
        suit = s;

    }

    public EnumValue getValue() {
        return value;
    }

    public void setValue(EnumValue value) {
        this.value = value;
    }

    public EnumSuit getSuit() {
        return suit;
    }

    public void setSuit(EnumSuit suit) {
        this.suit = suit;
    }

    @Override
    public String toString() {
        return String.format("[%s][%s]", value.getShortName(), suit.getShortName());
    }
}

@Component
public enum EnumValue {
    ACE("A",1), TWO("2", 2), THREE("3", 3), FOUR("4", 4), FIVE("5", 5), SIX("6", 6), SEVEN("7", 7), 
    EIGHT("8", 8), NINE("9", 9), TEN("T", 10), JACK("J", 10), QUEEN("Q", 10), KING("K", 10);

    private String shortName;
    private int points;


    EnumValue(String name, int score){
        shortName = name;
        points = score;
    }


    public String getShortName() {
        return shortName;
    }


    public void setShortName(String shortName) {
        this.shortName = shortName;
    }


    public int getPoints() {
        return points;
    }

    public void setPoints(int points) {
        this.points = points;
    }
}


@Component
public enum EnumSuit {
    CLUBS, DIAMONDS, HEARTS, SPADES;

    public String getShortName() {
        return this.toString().substring(0,1);
    }
}


@Configuration
@ComponentScan(basePackages = "com.betterstuff.learnspring")
public class AppConfig {

    @Bean
    public Card getSampleCard() {
        return new Card(EnumValue.ACE, EnumSuit.CLUBS);
    }
}

public class App {

    public static void main(String[] args) {
        ApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);

        Card obj = (Card) context.getBean(Card.class);

        System.out.println("My Card is: " + obj.toString());

    }

}

我收到错误:

WARNING: Exception encountered during context initialization - cancelling refresh attempt: UnsatisfiedDependencyException: Error creating bean with name 'card' defined in file [...\Card.class]: Unsatisfied dependency expressed through constructor parameter 0; nested exception is NoSuchBeanDefinitionException: No qualifying bean of type 'com...EnumValue' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {}
Exception in thread "main" UnsatisfiedDependencyException: Error creating bean with name 'card' defined in file [...\Card.class]: Unsatisfied dependency expressed through constructor parameter 0; nested exception is NoSuchBeanDefinitionException: No qualifying bean of type 'com...EnumValue' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {}

Answer 1

由于您在 Card 类上注释了 @Component，spring 尝试在应用程序上下文期间创建 bean，并且由于您声明了参数构造函数，因此将没有可用的默认构造函数

public Card(EnumValue v, EnumSuit s) {
    value = v;
    suit = s;

}

因此，从 Card 类中删除 @Component ，并且对于 Enum 类 EnumValue 也存在同样的错误，或者您可以添加默认构造函数或删除 @Component

EnumValue(){
 }