关于java:过滤器拦截器入门看这一篇就够了

理论我的项目开发过程中，必定有这样的需要：

1. 记录每个rest申请消耗的工夫，入参，出参
2. 某些申请须要判断是否有权限，某些申请是不须要权限也能够运行的

这个需要太广泛了。明天咱们就一起来学习这个需要的两种实现形式：

1. 拦截器
2. 过滤器

拦截器

话不多说，咱们上代码，新建日志拦截器：

@Component
public class LogInterceptor implements HandlerInterceptor {
    //在申请rest接口之前调用
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("申请url："+request.getRequestURL());
        Map<String, String[]> parameterMap = request.getParameterMap();
        Enumeration<String> parameterNames = request.getParameterNames();

        System.out.println("申请参数：");
        while (parameterNames.hasMoreElements()) {
            String name = (String) parameterNames.nextElement();
            String value = request.getParameter(name);
            System.out.println(name+"==>"+value);
        }

        //假如参数a传递的如果是1的话，是不非法的申请，不持续往下执行
        if("1".equals(request.getParameter("a"))){
            return false;
        }
        return true;//如果返回false则不会持续往下执行，不会真正的进入到controller
    }

    //申请解决之后进行调用，然而在视图被渲染之前（Controller办法调用之后）
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle is called...");
    }

    //在整个申请完结之后被调用
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion is called...");
    }
}

在WebMvcConfigurer中注册该拦截器，并通知spring哪些门路须要拦挡，哪些门路不须要拦挡

@Configuration
public class InterceperConfig implements WebMvcConfigurer {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        //增加拦截器
        InterceptorRegistration interceptorRegistration = registry.addInterceptor(new LogInterceptor() {
        });
        //如下的门路不拦挡，多个门路用逗号分隔
        interceptorRegistration.excludePathPatterns("/demo/test2");
        //拦挡如下门路
        interceptorRegistration.addPathPatterns("/**");
    }
}

好了，拦截器就做完了，so easy。上面咱们写个controller来测试下吧！

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

    @GetMapping("test1")
    public String test1(){
        System.out.println("rest.test1 is called");
        return "test1";
    }

    @GetMapping("test2")
    public String test2(){
        System.out.println("rest.test2 is called");
        return "test2";
    }

    @GetMapping("test3")
    public String test3(@RequestParam("a")String a){
        System.out.println("rest.test3 is called");
        return "test3";
    }
}

测试的后果根本能够预期到

1. demo/test1 和 demo/test3会被拦挡，进拦截器
2. demo/test2 不会进拦截器
3. demo/test3?a=1 这个申请会进拦截器，然而进不了controller。

过滤器

@WebFilter(urlPatterns = "/*", filterName = "LogFilter")
public class LogFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("logfilter.init is called...");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("filter中打印的申请参数：");
        Enumeration<String> parameterNames = servletRequest.getParameterNames();
        while (parameterNames.hasMoreElements()) {
            String key = parameterNames.nextElement();
            String value = servletRequest.getParameter(key);
            System.out.println(key+"==>"+value);
        }

        long bgn = System.currentTimeMillis();
        //肯定要调用链式调用传递，否则也进不了controller
        filterChain.doFilter(servletRequest,servletResponse);
        long end = System.currentTimeMillis();
        System.out.println("filter中记录耗时："+(end-bgn)+"ms");
    }

    @Override
    public void destroy() {
        System.out.println("logfilter.destroy is called...");
    }
}

留神：@WebFilter这个注解是Servlet3.0的标准，并不是Spring boot提供的。除了这个注解以外，咱们还需在配置类中加另外一个注解：@ServletComponetScan，指定扫描的包。

总结

拦截器、过滤器执行程序，默认先执行过滤器，再执行拦截器。

如果过滤器有多个会依据过滤器的名词依照A-Z的排序先后执行。这是因为@WebFilter这个注解不反对执行程序。当然你也能够通过写一个配置文件解决。

@Configuration
public class WebConfig {

    @Bean
    public FilterRegistrationBean reqResFilter1() {
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
        LogFilter logFilter = new LogFilter();
        filterRegistrationBean.setFilter(logFilter);
        filterRegistrationBean.addUrlPatterns("/demo/test1","/demo/test3");//配置过滤规定
        filterRegistrationBean.addInitParameter("name","spingboot");//设置init参数
        filterRegistrationBean.setName("logFilter");//设置过滤器名称
        filterRegistrationBean.setOrder(2);//执行秩序

        return filterRegistrationBean;
    }

    @Bean
    public FilterRegistrationBean reqResFilter() {
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
        Log1Filter log1Filter = new Log1Filter();
        filterRegistrationBean.setFilter(log1Filter);
        filterRegistrationBean.addUrlPatterns("*");//配置过滤规定
        filterRegistrationBean.setName("Log1Filter");//设置过滤器名称
        filterRegistrationBean.setOrder(1);//执行秩序
        
        return filterRegistrationBean;
    }
}

更多java原创浏览：https://javawu.com/