Java自定义注解的实现

Java自定义注解的实现,总共三步(eg.@RandomlyThrowsException)：

1.首先编写一个自定义注解@RandomlyThrowsException

package com.github.prontera;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

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

2.编写自定义注解@RandomlyThrowsException的实现

package com.github.prontera.aspect;

import com.github.prontera.config.ManualExceptionProperties;
import com.github.prontera.exception.ManualException;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.springframework.core.Ordered;

import java.security.SecureRandom;
import java.util.Random;

@Aspect
public class ManualExceptionAspect implements Ordered {
    private final int order;
    private final ManualExceptionProperties properties;
    private static final Random RANDOM = new SecureRandom();

    public ManualExceptionAspect(int order, ManualExceptionProperties properties) {
        this.order = order;
        this.properties = properties;
    }

    @Around("@annotation(com.github.prontera.RandomlyThrowsException)")
    public Object aroundMethod(ProceedingJoinPoint joinPoint) throws Throwable {
        if (properties.isEnabled()) {
            if (RANDOM.nextInt(100) % properties.getFactor() == 0) {
                throw new ManualException("manual exception");
            }
        }
        return joinPoint.proceed();
    }

    @Override
    public int getOrder() {
        return order;
    }
}

3.使用自定义注解@RandomlyThrowsException

    @Delay
    @RandomlyThrowsException
    @ApiOperation(value = "下单", notes = "生成预订单")
    @RequestMapping(value = "/orders", method = RequestMethod.POST)
    public ObjectDataResponse placeOrder(@Valid @RequestBody PlaceOrderRequest request, BindingResult result) {
        return orderService.placeOrder(request);
    }