一文了解Spring中拦截器的原理与使用

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

@Component
public class EasyLogControllerInterceptor implements HandlerInterceptor {
 
    /**
     * 在controller调用之前执行
     */
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
            throws Exception {
        System.out.println(request.getRequestURI()+"开始执行");
        return true;
    }
 
    /**
     * 在controller调用中执行
     */
    public void postHandle(
            HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)
            throws Exception {
    }
 
    /**
     * 在controller调用后执行
     */
    public void afterCompletion(
            HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
            throws Exception {
        System.out.println(request.getRequestURI()+"执行结束");
    }
 
}

@RestController
public class TestController {
 
    @GetMapping("/hello")
    public Map<String,String> hello(){
        Map<String,String> response=new HashMap<>();
        response.put("msg","hello");
        return response;
    }
 
}

@Configuration
public class IntercepterConfig implements WebMvcConfigurer {
 
    @Autowired
    private EasyLogControllerInterceptor easyLogControllerInterceptor;
 
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        //addPathPatterns用于添加拦截路径
        //excludePathPatterns用于添加不拦截的路径
        registry.addInterceptor(easyLogControllerInterceptor).addPathPatterns("/hello");
 
    }
 
 
    //此方法用于配置静态资源路径
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/**").addResourceLocations("classpath:/my/");
    }
}

public abstract class HandlerInterceptorAdapter implements HandlerInterceptor {  
  
 
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)  
        throws Exception {  
        return true;  
    }  
 
    public void postHandle(  
            HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)  
            throws Exception {  
    }  
  
 
    public void afterCompletion(  
            HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)  
            throws Exception {  
    }  
  
}  

protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {  
        HttpServletRequest processedRequest = request;  
        HandlerExecutionChain mappedHandler = null;  
        int interceptorIndex = -1;  
  
        try {  
            ModelAndView mv;  
            boolean errorView = false;  
  
            try {  
                processedRequest = checkMultipart(request);  
  
                // Determine handler for the current request.  
                mappedHandler = getHandler(processedRequest, false);  
                if (mappedHandler == null || mappedHandler.getHandler() == null) {  
                    noHandlerFound(processedRequest, response);  
                    return;  
                }  
  
                // Determine handler adapter for the current request.  
                HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());  
  
                // Process last-modified header, if supported by the handler.  
                String method = request.getMethod();  
                boolean isGet = "GET".equals(method);  
                if (isGet || "HEAD".equals(method)) {  
                    long lastModified = ha.getLastModified(request, mappedHandler.getHandler());  
                    if (logger.isDebugEnabled()) {  
                        String requestUri = urlPathHelper.getRequestUri(request);  
                        logger.debug("Last-Modified value for [" + requestUri + "] is: " + lastModified);  
                    }  
                    if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {  
                        return;  
                    }  
                }  
  
                // Apply preHandle methods of registered interceptors.  
                HandlerInterceptor[] interceptors = mappedHandler.getInterceptors();  
                if (interceptors != null) {  
                    for (int i = 0; i < interceptors.length; i++) {  
                        HandlerInterceptor interceptor = interceptors[i];  
                        if (!interceptor.preHandle(processedRequest, response, mappedHandler.getHandler())) {  
                            triggerAfterCompletion(mappedHandler, interceptorIndex, processedRequest, response, null);  
                            return;  
                        }  
                        interceptorIndex = i;  
                    }  
                }  
  
                // Actually invoke the handler.  
                mv = ha.handle(processedRequest, response, mappedHandler.getHandler());  
  
                // Do we need view name translation?  
                if (mv != null && !mv.hasView()) {  
                    mv.setViewName(getDefaultViewName(request));  
                }  
  
                // Apply postHandle methods of registered interceptors.  
                if (interceptors != null) {  
                    for (int i = interceptors.length - 1; i >= 0; i--) {  
                        HandlerInterceptor interceptor = interceptors[i];  
                        interceptor.postHandle(processedRequest, response, mappedHandler.getHandler(), mv);  
                    }  
                }  
            }  
            catch (ModelAndViewDefiningException ex) {  
                logger.debug("ModelAndViewDefiningException encountered", ex);  
                mv = ex.getModelAndView();  
            }  
            catch (Exception ex) {  
                Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null);  
                mv = processHandlerException(processedRequest, response, handler, ex);  
                errorView = (mv != null);  
            }  
  
            // Did the handler return a view to render?  
            if (mv != null && !mv.wasCleared()) {  
                render(mv, processedRequest, response);  
                if (errorView) {  
                    WebUtils.clearErrorRequestAttributes(request);  
                }  
            }  
            else {  
                if (logger.isDebugEnabled()) {  
                    logger.debug("Null ModelAndView returned to DispatcherServlet with name '" + getServletName() +  
                            "': assuming HandlerAdapter completed request handling");  
                }  
            }  
  
            // Trigger after-completion for successful outcome.  
            triggerAfterCompletion(mappedHandler, interceptorIndex, processedRequest, response, null);  
        }  
  
        catch (Exception ex) {  
            // Trigger after-completion for thrown exception.  
            triggerAfterCompletion(mappedHandler, interceptorIndex, processedRequest, response, ex);  
            throw ex;  
        }  
        catch (Error err) {  
            ServletException ex = new NestedServletException("Handler processing failed", err);  
            // Trigger after-completion for thrown exception.  
            triggerAfterCompletion(mappedHandler, interceptorIndex, processedRequest, response, ex);  
            throw ex;  
        }  
  
        finally {  
            // Clean up any resources used by a multipart request.  
            if (processedRequest != request) {  
                cleanupMultipart(processedRequest);  
            }  
        }  
    }