說明

首先我們看下 Conditional注解

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Conditional {
    Class<? extends Condition>[] value();
}

可以看出，需要使用Conditional注解必須實(shí)現(xiàn)Condition接口。

@FunctionalInterface
public interface Condition {
    boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata);
}

Demo

@Data
public class Test{
    private String id="@Bean";
}

@Data
public class Test2{
    private String id="@Conditional";
}

public class TestCondition implements Condition {
    @Override
    public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
  // 條件判斷
        return false;
    }
}

/**
注冊(cè)bean
*/
@Configuration
public class TestConfiguration {
    @Bean
    @Conditional(TestCondition.class)
    public Test test() {
        return new Test();
    }

    @Bean
    @Conditional(TestCondition.class)
    public Test2 test2() {
        return new Test2();
    }
}