@Component public class MyFilter implements Filter { // 堆代码 duidaima.com @Override public void init(FilterConfig filterConfig) throws ServletException { System.out.println("Filter 前置"); } @Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { System.out.println("Filter 处理中"); filterChain.doFilter(servletRequest, servletResponse); } @Override public void destroy() { System.out.println("Filter 后置"); } }2、拦截器 (Interceptor)
@Component public class MyInterceptor implements HandlerInterceptor { @Override public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { System.out.println("Interceptor 前置"); return true; } @Override public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception { System.out.println("Interceptor 处理中"); } @Override public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception { System.out.println("Interceptor 后置"); } }将自定义好的拦截器处理类进行注册,并通过addPathPatterns、excludePathPatterns等属性设置需要拦截或需要排除的 URL。
@Configuration public class MyMvcConfig implements WebMvcConfigurer { @Override public void addInterceptors(InterceptorRegistry registry) { registry.addInterceptor(new MyInterceptor()).addPathPatterns("/**"); registry.addInterceptor(new MyInterceptor1()).addPathPatterns("/**"); } }我们不一样
public interface FilterChain { void doFilter(ServletRequest var1, ServletResponse var2) throws IOException, ServletException; }
ApplicationFilterChain里面能拿到我们自定义的xxxFilter类,在其内部回调方法doFilter()里调用各个自定义xxxFilter过滤器,并执行 doFilter() 方法。
public final class ApplicationFilterChain implements FilterChain { @Override public void doFilter(ServletRequest request, ServletResponse response) { ...//省略 internalDoFilter(request,response); } private void internalDoFilter(ServletRequest request, ServletResponse response){ if (pos < n) { //获取第pos个filter ApplicationFilterConfig filterConfig = filters[pos++]; Filter filter = filterConfig.getFilter(); ... filter.doFilter(request, response, this); } } }而每个xxxFilter 会先执行自身的 doFilter() 过滤逻辑,最后在执行结束前会执行filterChain.doFilter(servletRequest, servletResponse),也就是回调ApplicationFilterChain的doFilter() 方法,以此循环执行实现函数回调。
@Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { filterChain.doFilter(servletRequest, servletResponse); }2、使用范围不同
@Controller @RequestMapping() public class Test { @RequestMapping("/test1") @ResponseBody public String test1(String a) { System.out.println("我是controller"); return null; } }项目启动过程中发现,过滤器的init()方法,随着容器的启动进行了初始化。
Filter 处理中 Interceptor 前置 Interceptor 处理中 Interceptor 后置 Filter 处理中过滤器Filter执行了两次,拦截器Interceptor只执行了一次。这是因为过滤器几乎可以对所有进入容器的请求起作用,而拦截器只会对Controller中请求或访问static目录下的资源请求起作用。
@Component public class TestServiceImpl implements TestService { @Override public void a() { System.out.println("我是方法A"); } }过滤器中注入service,发起请求测试一下 ,日志正常打印出“我是方法A”。
@Autowired private TestService testService; @Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { System.out.println("Filter 处理中"); testService.a(); filterChain.doFilter(servletRequest, servletResponse); }Filter 处理中
@Configuration public class MyMvcConfig implements WebMvcConfigurer { @Bean public MyInterceptor getMyInterceptor(){ System.out.println("注入了MyInterceptor"); return new MyInterceptor(); } @Override public void addInterceptors(InterceptorRegistry registry) { registry.addInterceptor(getMyInterceptor()).addPathPatterns("/**"); } }6、控制执行顺序不同
@Order(Ordered.HIGHEST_PRECEDENCE) @Component public class MyFilter2 implements Filter {拦截器默认的执行顺序,就是它的注册顺序,也可以通过Order手动设置控制,值越小越先执行。
@Override public void addInterceptors(InterceptorRegistry registry) { registry.addInterceptor(new MyInterceptor2()).addPathPatterns("/**").order(2); registry.addInterceptor(new MyInterceptor1()).addPathPatterns("/**").order(1); registry.addInterceptor(new MyInterceptor()).addPathPatterns("/**").order(3); }看到输出结果发现,先声明的拦截器 preHandle() 方法先执行,而postHandle()方法反而会后执行。postHandle() 方法被调用的顺序跟 preHandle() 居然是相反的!如果实际开发中严格要求执行顺序,那就需要特别注意这一点。
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception { try { ........... try { // 获取可以执行当前Handler的适配器 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()) { logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified); } if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) { return; } } // 注意: 执行Interceptor中PreHandle()方法 if (!mappedHandler.applyPreHandle(processedRequest, response)) { return; } // 注意:执行Handle【包括我们的业务逻辑,当抛出异常时会被Try、catch到】 mv = ha.handle(processedRequest, response, mappedHandler.getHandler()); if (asyncManager.isConcurrentHandlingStarted()) { return; } applyDefaultViewName(processedRequest, mv); // 注意:执行Interceptor中PostHandle 方法【抛出异常时无法执行】 mappedHandler.applyPostHandle(processedRequest, response, mv); } } ........... }看看两个方法applyPreHandle()、applyPostHandle()具体是如何被调用的,就明白为什么postHandle()、preHandle() 执行顺序是相反的了。
boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception { HandlerInterceptor[] interceptors = this.getInterceptors(); if(!ObjectUtils.isEmpty(interceptors)) { for(int i = 0; i < interceptors.length; this.interceptorIndex = i++) { HandlerInterceptor interceptor = interceptors[i]; if(!interceptor.preHandle(request, response, this.handler)) { this.triggerAfterCompletion(request, response, (Exception)null); return false; } } } return true; } void applyPostHandle(HttpServletRequest request, HttpServletResponse response, @Nullable ModelAndView mv) throws Exception { HandlerInterceptor[] interceptors = this.getInterceptors(); if(!ObjectUtils.isEmpty(interceptors)) { for(int i = interceptors.length - 1; i >= 0; --i) { HandlerInterceptor interceptor = interceptors[i]; interceptor.postHandle(request, response, this.handler, mv); } } }发现两个方法中在调用拦截器数组 HandlerInterceptor[] 时,循环的顺序竟然是相反的。。。,导致postHandle()、preHandle() 方法执行的顺序相反。