Java工具的使用

缓存-SpringCache

1.启动类添加注解@EnableCaching

2.方法上使用注解 

注解	功能	说明	参数
@Cacheable	查询缓存	没有缓存数据，就调用方法，存入返回值	cacheNames = "user::token", key = "#id"
@CachePut	添加缓存	调用方法，存入返回值	cacheNames = "user::token", key = "#result.id"
@CacheEvict	删除缓存	——	cacheNames = "user::token", key = "#id"

定时任务-SpringTask(不能分布式)

1.启动类添加注解@EnableScheduling

2.编写定时任务

@Component
public class SpringTask {
    /**
     *定时任务
     */
    @Scheduled(cron = "0/5 * * * * ?")
    public void  scheduleTask(){
        System.out.println("==========RunTask==========");
    }
}

过滤器-Filter

1.启动类添加注解@ServletComponentScan，开启对Servlet组件的支持。

2.编写过滤器，实现Filter接口，可以只实现doFilter方法

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;

@WebFilter(urlPatterns = "/*")
public class DemoFilter implements Filter {
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        System.out.println("放行前处理：" + request);
        chain.doFilter(request,response); //放行请求
        System.out.println("放行后处理：" + request);
    }
}

拦截器-Interceptor

1.定义拦截器，实现HandlerInterceptor接口

@Component
public class DemoInterceptor implements HandlerInterceptor {
    @Override    //资源调用前运行
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("========preHandle========");
        return true;    //是否放行
    }

    @Override    //资源调用后运行
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("========postHandle========");
        HandlerInterceptor.super.postHandle(request, response, handler, modelAndView);
    }

    @Override   //视图渲染后，最后运行
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("========afterCompletion========");
        HandlerInterceptor.super.afterCompletion(request, response, handler, ex);
    }
}

2.定义配置类，注册拦截器，实现WebMvcConfigurer接口

@Configuration
public class DemoConfig implements WebMvcConfigurer {
    private DemoInterceptor demoInterceptor;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(demoInterceptor)   //注册拦截器
                .addPathPatterns("/**")  //拦截哪些
                .excludePathPatterns("/login")  //不拦截哪些
        ;
    }
}

全局异常处理器

使用注解@RestControllerAdvice和@ExceptionHandler

@RestControllerAdvice
public class GlobalExceptionHandler {
    @ExceptionHandler(RuntimeException.class)  //处理异常的类型
    public String ex(Exception ex){
        ex.printStackTrace();
        return "操作失败";
    }
}

切面-SpringAop

1.导入依赖

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-aop</artifactId>
</dependency>

2.定义切入点表达式，使用@Pointcut注解确认切入点

切入点表达式：execution根据方法匹配，@annotation根据注解匹配，需要在目标程序上使用注解

• execution(访问修饰符  返回值  包名.类名.方法名(方法参数)  throws 异常)
• @annotation(注解)

    @Pointcut("execution(* com.example.demo.*.*(..) throws Exception)")
    private void key(){}

    @Pointcut("@annotation(com.example.demo.DemoAspect.MyLog)")
    private void key2(){}

3.编写AOP程序，使用@Around等注解指定切入点

    对于@Around，获取连接点只能使用ProceedingJoinPoint，对于其它四种，只能使用JoinPoint，它是前者的父类

• @Around：环绕通知
• @Before：前置通知
• @After：后置通知
• @AfterReturning：返回后通知
• @AfterReturning：异常后通知

@Order(1) //排序
@Aspect
@Component
public class DemoAspect {
    @Around("key()")  //指定切入点，key()也可直接替换为切入点表达式
    public Object recordTime(ProceedingJoinPoint point) throws Throwable {
        // 打印方法信息
        String className = point.getTarget().getClass().getName();
        String methodName = point.getSignature().getName();
        Object[] args = point.getArgs();
        System.out.println("类名："+className+"方法名："+methodName+"参数："+ Arrays.toString(args));

        Object result = point.proceed();//执行无参方法
//        Object result = point.proceed(args); //执行有参方法
        return result;
    }
}