Java注解-一文就懂，mysql数据库sql语句面试题

Java注解-一文就懂，mysql数据库sql语句面试题

int period() default 5000

}

定义注解处理器 - 切面

@Aspect

@Component

public class RetryAspect {

private final Logger logger = LoggerFactory.getLogger(this.getClass());

@AfterThrowing(pointcut=(“execution(* com.liziba.web.service.impl.RetryHttpRequestClient.*(…)) && @annotation(com.liziba.web.annotation.Retry)”))

public void tryAgain(JoinPoint point) {

logger.info("------------开始重试------------");

try {

// 获取方法上定义的Retry注解

MethodSignature methodSignature = (MethodSignature) point.getSignature();

Retry retry = methodSignature.getMethod().getAnnotation(Retry.class);

// ThreadLocal做线程隔离 times记录已经重试的次数

Object object = point.getTarget();

Field field = object.getClass().getDeclaredField(“threadLocal”);

field.setAccessible(true);

ThreadLocal> threadLocal = (ThreadLocal

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tring, Object>>) field.get(object);

Map threadLocalMap = threadLocal.get();

AtomicInteger times = (AtomicInteger)threadLocalMap.get(“times”);

// 重试 -1一直循环

if (retry.value() == -1 || (times.intValue() < retry.value())) {

logger.info(“开始重试第”+ index + “次”);

int index = times.incrementAndGet();

MethodInvocationProceedingJoinPoint methodPoint = ((MethodInvocationProceedingJoinPoint) point);

methodPoint.proceed();

} else {

// 数据库服务异常捕获，防止异常中异常导致StackOverFlowError

try {

// ToDo

// 此处可以保存到数据库，做周期性失败重试，重试次数达到阈值后通过消息平台通知到运维及时处理异常任务

// 移除threadLocal，防止线程生命周期过长导致内存泄露

threadLocal.remove();

} catch (Exception e) {

e.printStackTrace();

}

}

} catch (Throwable throwable) {

logger.error(throwable.getMessage(),throwable);

// 失败后继续重试

tryAgain(point);

}

}

}

4.2 日志记录注解

定义注解

@Target(ElementType.METHOD)

@Retention(RetentionPolicy.RUNTIME)

public @interface Log {

String value() default “”;

boolean enable() default true;

LogActionType type() default LogActionType.SELECT;

}

日志类型

public enum LogActionType {

ADD(“新增”),

SELECT(“查询”),

UPDATE(“更新”),

DELETE(“删除”);

private String value;

LogActionType(String value) {

this.value = value;

}

public String getValue() {

return value;

}

public void setValue(String value) {

this.value = value;

}

}

定义注解处理器 - 切面

@Component

@Aspect

@Slf4j

public class LogAspect {

// 保存日志信息服务

private final LogService logService;

// 线程隔离，用于计算每个方法的执行时间

ThreadLocal currentTime = new ThreadLocal<>();

public LogAspect(LogService logService) {

this.logService = logService;

}

@Pointcut("@annotation(com.liziba.annotation.Log)")

public void logPointcut() {

}

@Around(“logPointcut()”)

public Object logAround(ProceedingJoinPoint joinPoint) throws Throwable {

Object result;

// 计算方法 *** 作时间

currentTime.set(System.currentTimeMillis());

result = joinPoint.proceed();

Log log = new Log(“INFO”,System.currentTimeMillis() - currentTime.get());

currentTime.remove();

HttpServletRequest request = RequestHolder.getHttpServletRequest();

// 记录用户名、浏览器信息、ip地址、切入点、日志信息

logService.save(getUsername(), StringUtils.getBrowser(request), StringUtils.getIp(request),joinPoint, log);

return result;

}

@AfterThrowing(pointcut = “logPointcut()”, throwing = “e”)

public void logAfterThrowing(JoinPoint joinPoint, Throwable e) {

Log log = new Log(“ERROR”,System.currentTimeMillis() - currentTime.get());

currentTime.remove();

// 获取日志堆栈信息，并设值

log.setExceptionDetail(ThrowableUtil.getStackTrace(e).getBytes());

HttpServletRequest request = RequestHolder.getHttpServletRequest();

// 记录用户名、浏览器信息、ip地址、切入点、日志信息

logService.save(getUsername(), StringUtils.getBrowser(request), StringUtils.getIp(request), (ProceedingJoinPoint)joinPoint, log);

}

public String getUsername() {

try {

return SecurityUtils.getCurrentUsername();

}catch (Exception e){

return “”;

}

}

}

4.3 限流注解 - redis+lua限流

注解定义

@Target(ElementType.METHOD)

@Retention(RetentionPolicy.RUNTIME)

public @interface Limit {

// 资源名称，用于描述接口功能

String name() default “”;

// 资源 key

String key() default “”;

// key prefix

String prefix() default “”;

// 时间的，单位秒

int period();

// 限制访问次数

int count();

// 限制类型

LimitType limitType() default LimitType.CUSTOMER;

}

注解类型

public enum LimitType {

// 默认

CUSTOMER,

// IP限流

IP

}

定义注解处理器 - 切面

@Aspect

@Component

public class LimitAspect {

// redis用于执行lua脚本

private final RedisTemplate redisTemplate;

private static final Logger logger = LoggerFactory.getLogger(LimitAspect.class);

public LimitAspect(RedisTemplate redisTemplate) {

this.redisTemplate = redisTemplate;

}

@Pointcut("@annotation(com.liziba.annotation.Limit)")

public void pointcut() {

}

@Around(“pointcut()”)

public Object around(ProceedingJoinPoint joinPoint) throws Throwable {

HttpServletRequest request = RequestHolder.getHttpServletRequest();

// 获取方法的Limit注解

MethodSignature signature = (MethodSignature) joinPoint.getSignature();

Method signatureMethod = signature.getMethod();

Limit limit = signatureMethod.getAnnotation(Limit.class);

LimitType limitType = limit.limitType();

String key = limit.key();

if (StringUtils.isEmpty(key)) {

if (limitType == LimitType.IP) {

key = StringUtils.getIp(request);

} else {

key = signatureMethod.getName();

}

}

// 通过方法或者ip 结合资源请求路径定义限流key

ImmutableList keys = ImmutableList.of(StringUtils.join(limit.prefix(), “", key, "”, request.getRequestURI().replaceAll("/","_")));

// Lua限流脚本

String luascript = buildLuascript();

Redisscript redisscript = new DefaultRedisscript<>(luascript, Number.class);