以下 均是实例，没有进行原理说明，建议单独百度看原理一起食用

（也可以看guide哥的全方位的springBoot：https://github.com/Snailclimb/springboot-guide）

1. springBoot 解决跨域

@Configuration
public class CorsConfig implements WebMvcConfigurer {@Overridepublic void addCorsMappings(CorsRegistry registry) {registry.addMapping("/**").allowedOrigins("*").allowCredentials(true).allowedMethods("GET", "POST", "PUT", "DELETE", "OPTIONS").maxAge(3600);}
}

2. springBoot开启异步:

           @EnableAsync

（注意比如A调用B方法， 那么B 要异步：是public 方法且和A不在同类下，否则不能走代理；）

// 1.first step @EnableAsync :开启异步
@EnableAsync  
@SpringBootApplication
public class Application {public static void main(String[] args) {SpringApplication.run(Application.class, args);}
}// 2.second step -> b方法 : @Async 使用异步
@Async
public void syncBatteries(List<BatteryDTO> batteryDTOs) {batteryDTOs.forEach(s -> scooterService.syncBattery(s));
}// 3.third step -> 配置async 开启线程池的配置
@Configuration
public class AsyncConfig {@Beanpublic Executor asyncExecutor() {ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();executor.setCorePoolSize(4);executor.setMaxPoolSize(8);executor.setQueueCapacity(200);executor.setThreadNamePrefix("LocustTask-");executor.initialize();return executor;}
}

）

3.spring的重试机制：

         @EnableRetry

 （使用场景：比如我们接入三方接口，有的需要重试逻辑 （注意事项和2的一样， 非同类方法且public））

// 1. first step  -> @EnableRetry：开启重试
@EnableRetry 
@SpringBootApplication
public class Application {public static void main(String[] args) {SpringApplication.run(Application.class, args);}}// 2. second step -> 使用重试 抛出的异常会被相应的value 中的RetryException.class捕捉，并开启重试，此例中最多重试三次，每1s后重试一次，不叠加时间 （multiplier = 1）@Retryable(value = RetryException.class, maxAttempts = 3, backoff = @Backoff(delay = 1000, multiplier = 1))public  String request(Constant.DockingPlat platform, HttpData httpData){if(处理失败){throw new RetryException("xxx");}}// 3. second step -> 恢复机制
@Recover
public void recover(RetryException e) {e.printStackTrace();log.error("xxx！");
}

4. springBoot过滤器：filter

   1. 方式一 ：基于自定义 + 配置添加

//1. first step ->  自定义过滤器：实现filter方法
public class XssFilter implements Filter {@Overridepublic void init(FilterConfig config) throws ServletException {}public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)throws IOException, ServletException {XssHttpServletRequestWrapper xssRequest = new XssHttpServletRequestWrapper((HttpServletRequest) request);chain.doFilter(xssRequest, response);}@Overridepublic void destroy() {}}//2. second step ->  将自定义的过滤器添加进来：并设置范围
public class FilterConfig {@Beanpublic FilterRegistrationBean xssFilterRegistration() {FilterRegistrationBean registration = new FilterRegistrationBean();registration.setDispatcherTypes(DispatcherType.REQUEST);registration.setFilter(new XssFilter()); //自定义xss过滤器添加进来registration.addUrlPatterns("/*");registration.setName("xssFilter");registration.setOrder(Integer.MAX_VALUE);return registration;}
}

2. 方式二 -> 基于 @WebFilter

// 1. first step -> 开启包扫描
@SpringBootApplication
@ServletComponentScan(basePackages = "com.example.demo.filter")
public class DemoApplication {public static void main(String[] args) {SpringApplication.run(DemoApplication.class, args);}
}// 2. second step -> 自定义过滤器 业务处理
@Slf4j
@WebFilter(filterName = "myFilter1", urlPatterns = "/*")
public class MyFilter1 implements Filter {@Overridepublic void init(FilterConfig filterConfig) throws ServletException {log.info(filterConfig.getFilterName() + " init");}@Overridepublic void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) {log.info("myFilter1 begin");try {log.info("业务方法执行");chain.doFilter(request, response);} catch (Exception e) {log.error("error!", e);}log.info("myFilter1 end");}@Overridepublic void destroy() {}
}

4. springBoot拦截器：intercepter

public class LogInterceptor extends HandlerInterceptorAdapter {@Overridepublic boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)throws Exception {long startTime = System.currentTimeMillis();System.out.println("\n-------- LogInterception.preHandle --- ");System.out.println("Request URL: " + request.getRequestURL());System.out.println("Start Time: " + System.currentTimeMillis());request.setAttribute("startTime", startTime);return true;}@Overridepublic void postHandle(HttpServletRequest request, HttpServletResponse response, //Object handler, ModelAndView modelAndView) throws Exception {System.out.println("\n-------- LogInterception.postHandle --- ");System.out.println("Request URL: " + request.getRequestURL());// You can add attributes in the modelAndView// and use that in the view page}@Overridepublic void afterCompletion(HttpServletRequest request, HttpServletResponse response, //Object handler, Exception ex) throws Exception {System.out.println("\n-------- LogInterception.afterCompletion --- ");long startTime = (Long) request.getAttribute("startTime");long endTime = System.currentTimeMillis();System.out.println("Request URL: " + request.getRequestURL());System.out.println("End Time: " + endTime);System.out.println("Time Taken: " + (endTime - startTime));}}

5. springBoot全局异常处理

// 1. first step -> 定义全局异常类方法 继承 RuntimeException 
public class RRException extends RuntimeException {private static final long serialVersionUID = 1L;private String msg;private int code = 500;public RRException(String msg) {super(msg);this.msg = msg;}
}// 2. second step -> @RestControllerAdvice
@RestControllerAdvice
public class RRExceptionHandler {private Logger logger = LoggerFactory.getLogger(getClass());/*** 处理自定义异常*/@SysLog("异常记录") //这个是我自己的逻辑不用关心：日志记录的自定义注解@ExceptionHandler(RRException.class)public R handleRRException(RRException e){R r = new R();r.put("code", e.getCode());r.put("msg", e.getMessage());logger.error(e.getMessage(), e); // 这个是我自己的逻辑 不用关心ThreadLocalUtils.remove(); // 这个是我自己的逻辑 不用关心：异常后清理所有的信息，防止回收问题导致内存溢出return r;}
}// 3.third step -> 抛出异常后会被全局拦截器拦截并 响应给前端 提示public <T> T getConfigObject(String key, Class<T> clazz) {String value = getValue(key);if(StringUtils.isNotBlank(value)){return new Gson().fromJson(value, clazz);}try {return clazz.newInstance();} catch (Exception e) {throw new RRException("获取参数失败"); // 这样前端就会接收到500 ，和msg的错误信息}}

6. springBoot 中的threadLocal使用： 

    1. 如果你a方法调用b 方法 比如： a -> b->c->d .. 方法调用链很长，但是 传参的话很不便利哪里 你可以再a方法中使用如
在d方法中取出

// 1 first step: 设置threadLocal
public R appLogin(String phone, String code) {SysUserEntity patrolUser = (SysUserEntity) r.get("result");ThreadLocalUtils.set("loginUser",patrolUser); //  当前登陆用户的信息 -> 方便后面使用 b(); 一系列的方法调用ThreadLocalUtils.remove("loginUser");// 清理threadLocal-> 回收return R.ok().put("result", ecLoginResultDTO);
}// 2 second step -> 使用 threadlocal b方法： 
public void b(){SysUserEntity loginUser = ThreadLocalUtils.get("loginUser");
}// 3 third step -> 清理threadLocal1. 在拦截器清理2. 使用完成后就清理3. 全局异常处理器清理// 4 fourth step -> advice 建议： 当然也可以利用 threadLocal 或者拦截器 ，请求进来的时候根据token，获取用户存入，请求结束后再拦截器清理掉

7. springBoot中自定义注解进行，异常记录

（注意try catch 和 开启异步 提高响应速度和不影响主业务的使用，建议重要方法加上日志，避免开启代理 还是会耗时）

// 1.first step  -> 自定义注解
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface SysLog {String value() default "";
}// 2.second step  -> @Aspect：开启切面 
@Aspect
@Component
@Slf4j
public class SysLogAspect {@Autowiredprivate SysLogService sysLogService;@Pointcut("@annotation(com.immotor.common.annotation.SysLog)") //切点public void logPointCut() { }@Around("logPointCut()")//环绕(处理前后逻辑) 处理public Object around(ProceedingJoinPoint point) throws Throwable { long beginTime = System.currentTimeMillis();//执行方法Object result = point.proceed();//执行时长(毫秒)long time = System.currentTimeMillis() - beginTime;//保存日志sysLogService.saveSysLog(point, String.valueOf(time), result);return result;}}// 3.third step -> 记录日志方法 ：开启异步，和异常处理@Async@Override@Transactional(propagation= Propagation.NOT_SUPPORTED)public void saveSysLog(ProceedingJoinPoint joinPoint, String time, Object result)  {MethodSignature signature = (MethodSignature) joinPoint.getSignature();Method method = signature.getMethod();SysLogEntity sysLog = new SysLogEntity();SysLog syslog = method.getAnnotation(SysLog.class);if(syslog != null){//注解上的描述sysLog.setOperation(syslog.value());}//请求的方法名String className = joinPoint.getTarget().getClass().getName();String methodName = signature.getName();sysLog.setMethod(className + "." + methodName + "()");//请求的参数try{Object[] args = joinPoint.getArgs();String params = new Gson().toJson(args);if (params.length() < Constant.LogMaxLength){sysLog.setParams(params);}else{sysLog.setParams(params.substring(0,Constant.LogMaxLength-1));log.warn("日志参数太长无法保存");}}catch (Exception e){log.info("没有获取参数！");}// 请求的结果try {String resultStr = (String) result;if (resultStr.length() < Constant.LogMaxLength){sysLog.setResults(resultStr); //获取响应结果}else{sysLog.setResults(resultStr.substring(0,Constant.LogMaxLength-1));log.warn("日志响应太长无法保存");}String username = ((SysUserEntity) SecurityUtils.getSubject().getPrincipal()).getUsername(); // 操作人姓名sysLog.setUsername(username);HttpServletRequest request = HttpContextUtils.getHttpServletRequest(); //idsysLog.setIp(IPUtils.getIpAddr(request));} catch (Throwable throwable) {log.info("没有获取到响应结果！");}sysLog.setTime(time);sysLog.setCreateDate(new Date());this.save(sysLog);}4. fourth step : sql ddl
CREATE TABLE `sys_log` (`ad` int(11) NOT NULL AUTO_INCREMENT COMMENT '自增主键',`id` varchar(50) NOT NULL,`username` varchar(50) DEFAULT NULL COMMENT '用户名',`operation` varchar(50) DEFAULT NULL COMMENT '用户操作',`type` varchar(255) DEFAULT '方法日志' COMMENT '日志类型： , 异常日志',`method` varchar(200) DEFAULT NULL COMMENT '请求方法',`params` varchar(10000) DEFAULT NULL COMMENT '请求参数',`results` varchar(5000) DEFAULT NULL COMMENT '响应结果',`status` int(11) DEFAULT '1' COMMENT '执行状态：1成功； 0失败',`time` varchar(20) DEFAULT NULL COMMENT '执行时长(毫秒)',`ip` varchar(64) DEFAULT NULL COMMENT 'IP地址',`create_date` timestamp NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',PRIMARY KEY (`ad`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=32263 DEFAULT CHARSET=utf8mb4 COMMENT='系统日志';