spring中的切面类实践

目标功能：自定义一个在方法执行前后做日志记录的切面方法，需要考虑到方法执行成功与失败的情况，并记录方法名与意义与参数。

自定义的切面类需要配套一个自定义注解执行

import java.lang.annotation.*;

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD,ElementType.TYPE})
@Documented
public @interface LogRec {
    String value() default ""; // 接口名称描述
}

切面类的类层面

@Aspect
@Component
public class LogRecordAspect {
    private static final Logger logger = LoggerFactory.getLogger(LogRecordAspect.class);

    @Autowired
    private SystemService systemService;

    @Pointcut("@annotation(com.example.config.aspect.LogRec)")
    public void logRecMethods() { }
    ...
}

类里面环绕目标方法的增强方法

    /**
     * 环绕通知并记录日志
     * @param joinPoint
     * @param logRec
     * @return
     * @throws Throwable
     */
    @Around("logRecMethods() && @annotation(logRec)")
    public Object logAround(ProceedingJoinPoint joinPoint, LogRec logRec) throws Throwable {
        long startTime = System.currentTimeMillis();

        // 获取注解值
        String methodDesc = logRec.value();
        Object result = null;
        Object logRes = null;

        try {
            // 获取 request
            HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes()).getRequest();

            // 执行原方法
            result = joinPoint.proceed();
            logRes = result;
            //logRes可以用来做额外处理，保留最终返回的result的完整性，避免误修改
            //正常日志记录
            ...
            return result;
        } catch (Exception e) {
            //异常日志记录
            logger.error("接口调用异常：{}", e.getMessage(), e);
            throw e;
        } finally {
            //收尾代码
            ...
        }
    }

起初考虑不全时，只想到before和after，这里也记录一下。特别提示：这俩和around不能共存。

    @Before("logRecMethods() && @annotation(logRec)")
    public void logBefore(JoinPoint joinPoint,LogRec logRec){
        String methodName = joinPoint.getSignature().getName();
        String methodParams = logRec.value();
        String interfaceName = joinPoint.getTarget().getClass().getName();
        logger.info("【"+interfaceName+"】"+methodName+"("+methodParams+")");
        Object[] args = joinPoint.getArgs();
        for (Object arg : args){
            if (arg instanceof HttpServletRequest){
                HttpServletRequest request = (HttpServletRequest) arg;
                systemService.writeReqLog(request,methodParams+"：开始执行");
            }
        }
    }

    @After("logRecMethods() && @annotation(logRec)")
    public void logAfter(JoinPoint joinPoint,LogRec logRec){
        String methodName = joinPoint.getSignature().getName();
        String methodParams = logRec.value();;
        String interfaceName = joinPoint.getTarget().getClass().getName();
        logger.info("【"+interfaceName+"】"+methodName+"("+methodParams+")");
        Object[] args = joinPoint.getArgs();
        for (Object arg : args){
            if (arg instanceof HttpServletRequest){
                HttpServletRequest request = (HttpServletRequest) arg;
                systemService.writeReqLog(request,methodParams+"：结束执行");
            }
        }
    }

除了环绕方法，还有出现异常时的处理方法

    /**
     * 异常通知：记录失败日志
     */
    @AfterThrowing(pointcut = "logRecMethods()", throwing = "ex")
    public void logAfterThrowing(JoinPoint joinPoint, Throwable ex) {
        String methodName = joinPoint.getSignature().getName();
        String methodParams = ex.getMessage();
        String interfaceName = joinPoint.getTarget().getClass().getName();
        logger.info("【"+interfaceName+"】"+methodName+"("+methodParams+")");
        Object[] args = joinPoint.getArgs();
        for (Object arg : args){
            if (arg instanceof HttpServletRequest){
                HttpServletRequest request = (HttpServletRequest) arg;
                systemService.writeReqLog(request,"发生异常："+ex.getMessage());
            }
        }
    }