SpringMVC的Filter和Interceptor
Filter和Interceptor的执行顺序
1. Filter.init()
2. Filter.doFilter()之前
3. HandlerInterceptor.preHandle()
4. Controller方法执行
5. HandlerInterceptor.postHandle()
6. DispatcherServlet视图渲染
7. HandlerInterceptor.afterCompletion()
8. Filter.doFilter()之后
9. Filter.destroy()
Filter和Interceptor的区别
1. Filter是基于函数回调（doFilter()方法）的，而Interceptor则是基于Java反射的（AOP思想）。
2. Filter依赖于Servlet容器，而Interceptor不依赖于Servlet容器。
3. Filter对几乎所有的请求起作用，而Interceptor只能对action请求起作用。
4. Interceptor可以访问Action的上下文，值栈里的对象，而Filter不能。
5. 在action的生命周期里，Interceptor可以被多次调用，Servlet容器在实例化Filter后只调用一次Filter.init()
The servlet container calls the init method exactly once after instantiating the filter.
Filter的使用:
@WebFilter(filterName = "filterOne", urlPatterns = {"/*"})
public class FilterOne implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
System.out.println("init");
}
@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
System.out.println("===========before doFilter");
filterChain.doFilter(servletRequest, servletResponse);
System.out.println("===========after doFilter");
}
@Override
public void destroy() {
System.out.println("destroy");
}
}
给你的配置类（或者启动类）加上
@ServletComponentScan("路径")
或者
@Configuration
public class FilterConfig {
@Bean
public FilterRegistrationBean filterRegistrationBean(){
FilterRegistrationBean bean = new FilterRegistrationBean();
bean.setFilter(new FilterTwo());
bean.addUrlPatterns("/*");
return bean;
}
}
Interceptor的使用
public class MyInterceptor implements HandlerInterceptor {
// 如果拦截器要使用容器里的bean的话，要先把拦截器注入到容器
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
System.out.println("preHandle");
if (...) {
return true;
}
return false;
}
@Override
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) {
System.out.println("postHandle");
}
@Override
public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
System.out.println("afterCompletion");
}
}
@Configuration
public class WebConfig implements WebMvcConfigurer {
@Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(currentLimitingInterceptor())
.addPathPatterns("/*");
}
}