效果如圖：

首先定義攔截器：

package star.july.filter;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;public class FilterDemo implements Filter{public void init(FilterConfig filterConfig) throws ServletException {}public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {//訪問servlet前首先訪問攔截器System.out.println("1、攔截請求資源");//執行放行,在此條語句前為攔截請求資源，之后為攔截響應資源chain.doFilter(request, response);System.out.println("3、攔截響應資源");}public void destroy() {}}

然后創建servlet文件：

package star.july.web;import java.io.IOException;import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;public class FilterServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {System.out.println("2、接收資源");}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

最后是對攔截器Filter的xml配置：

<filter><filter-name>FilterDemo</filter-name><filter-class>star.july.filter.FilterDemo</filter-class> </filter> <filter-mapping><filter-name>FilterDemo</filter-name><!-- url要跟攔截的servlet的一致 --><url-pattern>/FilterServlet</url-pattern> </filter-mapping>

總結

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