Java拦截器的小例子

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效果如图：

首先定义拦截器：

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 {//访问servlet前首先访问拦截器System.out.println("1、拦截请求资源");//执行放行,在此条语句前为拦截请求资源，之后为拦截响应资源chain.doFilter(request, response);System.out.println("3、拦截响应资源");}public void destroy() {}}

然后创建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、接收资源");}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

最后是对拦截器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要跟拦截的servlet的一致 --><url-pattern>/FilterServlet</url-pattern></filter-mapping>

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