spring boot中的条件装配bean的实现

public interface CalculateService {

  /**
   * 从多个整数 sum 求和
   * @param values 多个整数
   * @return sum 累加值
   */
  Integer sum(Integer... values);
}

@Profile("Java7")
@Service
public class Java7CalculateService implements CalculateService {

  @Override
  public Integer sum(Integer... values) {
    System.out.println("Java 7 for 循环实现 ");
    int sum = 0;
    for (int i = 0; i < values.length; i++) {
      sum += values[i];
    }
    return sum;
  }

}

@Profile("Java8")
@Service
public class Java8CalculateService implements CalculateService {

  @Override
  public Integer sum(Integer... values) {
    System.out.println("Java 8 Lambda 实现");
    int sum = Stream.of(values).reduce(0, Integer::sum);
    return sum;
  }

  public static void main(String[] args) {
    CalculateService calculateService = new Java8CalculateService();
    System.out.println(calculateService.sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10));
  }

}

@SpringBootApplication(scanBasePackages = "com.service")
public class CalculateServiceBootstrap {

  public static void main(String[] args) {
    ConfigurableApplicationContext context = new SpringApplicationBuilder(CalculateServiceBootstrap.class)
        .web(WebApplicationType.NONE)
        .profiles("Java8")
        .run(args);

    // CalculateService Bean 是否存在
    CalculateService calculateService = context.getBean(CalculateService.class);

    System.out.println("calculateService.sum(1...10) : " +
        calculateService.sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10));

    // 关闭上下文
    context.close();
  }
}

/**
 * Java 系统属性 条件判断
 *
 */
@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.TYPE, ElementType.METHOD })
@Documented
@Conditional(OnSystemPropertyCondition.class)
public @interface ConditionalOnSystemProperty {

  /**
   * Java 系统属性名称
   * @return
   */
  String name();

  /**
   * Java 系统属性值
   * @return
   */
  String value();
}

/**
 * 系统属性条件判断
 *
 */
public class OnSystemPropertyCondition implements Condition {

  @Override
  public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {

    Map<String, Object> attributes = metadata.getAnnotationAttributes(ConditionalOnSystemProperty.class.getName());

    String propertyName = String.valueOf(attributes.get("name"));

    String propertyValue = String.valueOf(attributes.get("value"));

    String javaPropertyValue = System.getProperty(propertyName);

    return propertyValue.equals(javaPropertyValue);
  }
}

public class ConditionalOnSystemPropertyBootstrap {

  @Bean
  @ConditionalOnSystemProperty(name = "user.name", value = "yanghongxing")
  public String helloWorld() {
    return "Hello,World Honson";
  }

  public static void main(String[] args) {
    ConfigurableApplicationContext context = new SpringApplicationBuilder(ConditionalOnSystemPropertyBootstrap.class)
        .web(WebApplicationType.NONE)
        .run(args);
    // 通过名称和类型获取 helloWorld Bean
    String helloWorld = context.getBean("helloWorld", String.class);

    System.out.println("helloWorld Bean : " + helloWorld);

    // 关闭上下文
    context.close();
  }
}