springboot的过滤器拦截器AOP和异常处理器

前言

过滤器、拦截器、AOP、异常处理器是搭建系统框架时，经常用到的部分，异常处理器的作用很明显，就是处理接口执行过程中的异常，而过滤器、拦截器和AOP的作用就很丰富了，日志记录、性能监控、安全认证等等可以向上抽取的功能组件，均可以用他们来实现。

过滤器

创建过滤器

使用@WebFilter注解，创建过滤器，代码如下：

package com.example.demo.filter;

import org.springframework.stereotype.Component;

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

@WebFilter(filterName = "demoFilter",urlPatterns = "/demo/hello")
@Component
public class DemoFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("过滤器创建");
    }

    @Override
    public void destroy() {
        System.out.println("过滤器销毁");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        try {
            System.out.println("过滤请求开始");
            filterChain.doFilter(servletRequest, servletResponse);
            System.out.println("过滤请求结束");
        }catch (Exception e){
            System.out.println("过滤器捕获异常");
            throw e;
        }
    }
}

拦截器

创建拦截器

实现HandlerInterceptor接口，创建拦截器，代码如下：

package com.example.demo.interceptor;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class DemoInterceptor implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("拦截请求--进入Controller前");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("拦截请求--Controller中方法执行完");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        if (ex != null){
            System.out.println("拦截器判断存在异常，但不能处理异常");
        }
        System.out.println("拦截请求--视图渲染完成后");
    }
}

配置拦截器

继承WebMvcConfigurationSupport类，配置拦截器，代码如下：

package com.example.demo.interceptor;

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;

@Configuration
public class DemoInterceptorConfig extends WebMvcConfigurationSupport {

    @Override
    protected void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new DemoInterceptor()).addPathPatterns("/demo/hello");
        super.addInterceptors(registry);
    }
}

AOP

创建AOP

使用@Aspect注解，创建AOP切面类，代码如下：

package com.example.demo.aop;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.springframework.stereotype.Component;

/**
 * AOP切面
 * @author Neo
 */
@Aspect
@Component
public class DemoAop {

    /**
     * 切点
     */
    @Pointcut("@annotation(org.springframework.web.bind.annotation.GetMapping)")
    public void getMapping() {}

    /**
     * 环绕通知
     * @param pjp
     * @return
     * @throws Throwable
     */
    @Around("getMapping()")
    public Object around(ProceedingJoinPoint pjp) throws Throwable {
        try {
            System.out.println("切面请求开始");
            Object object = pjp.proceed();
            System.out.println("切面请求结束");
            return object;
        }catch (Exception e){
            System.out.println("切面捕获到异常");
            throw e;
        }
    }
}

异常处理器

创建异常处理器

使用@RestControllerAdvice注解，创建异常处理器，代码如下：

package com.example.demo.exception;

import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;

@RestControllerAdvice
public class DemoException {

    @ExceptionHandler
    public Object demoException(Exception e) throws Exception{
        System.out.println("全局异常处理器捕获到异常");
        throw e;
    }
}

测试请求的执行过程

创建接口

代码如下：

package com.example.demo.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/demo")
public class DemoController {

    @GetMapping(value = "/hello")
    public String hello(){

        System.out.println("执行方法");

//        int a = 1/0;

        return "hello world!";

    }

}

发送请求

测试1–正常请求：


测试2–发生异常：