Interceptors and filters

contrast

1 Filters can only be called once during container initialization , and action In cycle , Interceptors can be called multiple times .

2 Filters work on all requests , Interceptors can only be used to action Work .

3 Filter cannot access context , Stack objects .

4 Filters depend on servlet Containers

5 Filters are based on function callbacks , Interceptors are based on java Reflection .

6 The filter cannot get ioc Container of bean, Interceptors can , Intercept injection service, You can call the business logic .

Execution order

filter–interceptor.preHandle–handler–interceptor.postHandle–interceptor.afterCompletion–filter

Interceptor

@Component
public class SampleInterceptor implements HandlerInterceptor {
    

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
    

        System.out.println("\n Has entered the interceptor ");
        return true;

        //return HandlerInterceptor.super.preHandle(request, response, handler);
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
    

        System.out.println(" The controller is finished ");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
    
        System.out.println(" Get the results "+response);
        System.out.println(" End of request \n");
    }
}

Configuration class

public class InterceptorConfig implements WebMvcConfigurer {
    

    @Autowired
    SampleInterceptor sampleInterceptor;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
    
        registry.addInterceptor(sampleInterceptor).addPathPatterns("*/**").excludePathPatterns("/**/LoginController/**","/**/error")
                .excludePathPatterns("/error");
        WebMvcConfigurer.super.addInterceptors(registry);
    }
}

Interceptor scenario

Section oriented programming , Functions that conform to crosscutting concerns can be used in interceptors

Login authentication

Authority verification

logging Log request operations , Count the requested visits .

Handle cookie

Performance monitoring , Monitoring processing time .

Execution sequence considerations

First define the interceptor and then execute .

You can also use order Method to set the execution order , The smaller the value, the earlier to execute .

filter

servlet A component of , Before users access a resource , Filter access requests and responses .

principle

Based on function callbacks , A filter instance can only be called once during container initialization .

Different from interceptors

Can't get ioc Container of bean

Filter>>interceptor>>controllerAdvice>>aspect>>controller

Implement filter methods

Annotation mode

@Order(2)
@WebFilter(filterName = "sampleFilterAnnotation",urlPatterns = {
    "/study/interfaces/v1/user/*"})
public class SampleFilterAnnotation implements Filter {
    
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    
        System.out.println(" initialization filter");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
    
        System.out.println(" What to do before entering the filter ");
        filterChain.doFilter(servletRequest,servletResponse);
        System.out.println(" Process the returned response");
    }

    @Override
    public void destroy() {
    
        System.out.println(" The filter is destroyed ");
    }
}

The parameters above , To baidu .

Last

After configuring the above , You need to add a scan package annotation to the startup class , Turn on package scanning .

The use of tools is fast , In what scene , How do you use it? , This is what we need to think about .