SpringBoot中的过滤器和拦截器的实现

一、过滤器    

SpringBoot中使用过滤器不需要在web.xml中配置filter，只需要添加注解@WebFilter同时实现Filter接口

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;

import org.springframework.stereotype.Component;

@Component
@WebFilter(urlPatterns = "/*", filterName = "test")
public class TestFilter implements Filter {

	@Override
	public void init(FilterConfig arg0) throws ServletException {
		System.out.println("过滤器初始化");
	}

	@Override
	public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
			throws IOException, ServletException {
		System.out.printf("过滤器实现");
		System.out.println(((HttpServletRequest) servletRequest).getRequestURI());
		filterChain.doFilter(servletRequest, servletResponse);
	}

	@Override
	public void destroy() {
		System.out.println("过滤器销毁了");
	}

}

启动项目后查看日志：

INFO 6780 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'characterEncodingFilter' to: [/*]
INFO 6780 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
INFO 6780 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'httpPutFormContentFilter' to: [/*]
INFO 6780 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'requestContextFilter' to: [/*]
INFO 6780 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'webStatFilter' to urls: [/*]
INFO 6780 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'testFilter' to: [/*]
过滤器初始化

可以看到过滤器已经被初始化了，接下来再访问一下

日志：过滤器实现/test

说明过滤器已经正常执行（刚开始发现被调用了两次，第二次url打印的是/favicon.ico，这是浏览器在请求网站图标）

二、拦截器

首先创建拦截器实现HandlerInterceptor

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

/**
 * 拦截器
 */
public class MyInterceptor implements HandlerInterceptor{
	 //在请求处理之前进行调用（Controller方法调用之前
    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        System.out.printf("preHandle被调用\n");
        return true;   
    }

    //请求处理之后进行调用，但是在视图被渲染之前（Controller方法调用之后）
    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle被调用\n");
    }

    //在整个请求结束之后被调用，也就是在DispatcherServlet 渲染了对应的视图之后执行（主要是用于进行资源清理工作）
    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
        System.out.println("afterCompletion被调用\n");
    }
}

然后创建一个配置类，用于注册拦截器

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {

	/**
	 * 注册拦截器
	 */
	@Override
	public void addInterceptors(InterceptorRegistry registry) {
		registry.addInterceptor(new MyInterceptor()).addPathPatterns("/**").excludePathPatterns("/a.do");
	}
	
	
}

addPathPatterns和excludePathPatterns可以分别指定要拦截的请求和排除的请求，参数也可以是一个List<String>

好了，访问一下

需要注意的是，拦截器是基于spring的，且只有通过DispatcherServlet的请求才能被拦截。