SpringBoot AnnotationUtils工具类的使用实例详解

import java.lang.annotation.*;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface PayCode {

    // 支付方法的业务code
    String payCode();
	
    // 支付方法的名称
    String name();
}

import java.lang.annotation.*;

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD})
public @interface PayOrder {

    int value() default 0;
}

import java.lang.annotation.*;
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD})
public @interface Version {

    String value() default "0";
}

@PayCode(payCode = "alia", name = "支付宝支付")
@Component
public class AliaPay {

    @PayOrder(value = 1)
    public void pay() {
        System.out.println("===发起支付宝支付1===");
    }
}

@PayCode(payCode = "jingdong", name = "京东支付")
@Component
public class JingDongPay {

    @Version(value = "1.1")
    public String version;

    @PayOrder(value = 20)
    public void pay() {
        System.out.println("===发起京东支付===");
    }
}

import org.springframework.boot.CommandLineRunner;
import org.springframework.util.ReflectionUtils;
@Component
public class ZTestController implements CommandLineRunner {
    @Resource
    private AliaPay aliaPay;
	@Resource
    private JingDongPay jingDongPay;

    @Override
    public void run(String... args) throws Exception {

        // ⏹原生Java的方式获类上的注解
        PayCode aliPay = aliaPay.getClass().getAnnotation(PayCode.class);
        System.out.println(aliPay);
        // @com.example.jmw.common.annotation.PayCode(payCode=alia, name=支付宝支付)
		
		 // ⏹原生Java的方式获取属性上的注解
        Field versionField = ReflectionUtils.findField(jingDongPay.getClass(), "version");
        Version version = versionField.getAnnotation(Version.class);
    }
}

// AnnotationUtils的方式获取指定类上的注解
import org.springframework.core.annotation.AnnotationUtils;

PayCode aliPay = AnnotationUtils.findAnnotation(aliaPay.getClass(), PayCode.class);

import org.springframework.util.ReflectionUtils;
import org.springframework.core.annotation.AnnotationUtils;

// 通过反射获取aliaPay对象上的pay方法的Method对象
Method payMethod = ReflectionUtils.findMethod(aliaPay.getClass(), "pay");
// 获取方法上的注解
PayOrder payOrder = AnnotationUtils.findAnnotation(payMethod, PayOrder.class);

// AnnotationUtils的方式获取指定类上的注解
PayCode aliPayAnnotation = AnnotationUtils.findAnnotation(aliaPay.getClass(), PayCode.class);
// 获取注解上指定的值
Object payCode = AnnotationUtils.getValue(aliPayAnnotation, "payCode");

// 获取注解上所有的属性值
PayCode aliPay = AnnotationUtils.findAnnotation(aliaPay.getClass(), PayCode.class);
Map<String, Object> annotationAttributes = AnnotationUtils.getAnnotationAttributes(aliPay);