过滤器拦截到响应url的请求后会先执行doFilter()方法中chain.doFilter()之前的代码，然后执行下一个过滤器或者servelt。紧接着执行chain.doFilter()之后的代码。

一下为两个过滤器的执行顺序：

过滤器一：

packagecom.rskd_yswb.lib.filter;import javax.servlet.*;importjava.io.IOException;

public class HttpRequestAndResponseFilter implementsFilter {privateFilterConfig filterConfig;public voiddestroy() {

}public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throwsServletException, IOException {

resp.setCharacterEncoding(this.filterConfig.getInitParameter("encoding"));

System.out.println("HttpRequestAndResponseFilterBefore");

chain.doFilter(req, resp);

System.out.println("HttpRequestAndResponseFilterAfter");

}public void init(FilterConfig config) throwsServletException {this.filterConfig =config;

}

}

过滤器二：

packagecom.rskd_yswb.lib.filter;import javax.servlet.*;importjava.io.IOException;public class Test2Filter implementsFilter {public voiddestroy() {

}public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throwsServletException, IOException {

System.out.println("Test2FilterBefore");

chain.doFilter(req, resp);

System.out.println("Test2FilterAfter");

}public void init(FilterConfig config) throwsServletException {

}

}

要执行的servlet:

packagecom.rskd_yswb.servelt;importcom.rskd_yswb.javabean.db.ConsumerEntity;importcom.rskd_yswb.lib.db.DBConnection;importcom.rskd_yswb.lib.db.GenerateSqlStatement;importcom.rskd_yswb.lib.freemarker.FreeMarker;importfreemarker.template.Template;importfreemarker.template.TemplateException;importorg.apache.commons.dbutils.QueryRunner;importorg.apache.commons.dbutils.handlers.BeanMapHandler;importorg.apache.logging.log4j.LogManager;importorg.apache.logging.log4j.Logger;importjavax.servlet.annotation.WebServlet;importjava.io.IOException;importjava.io.Writer;importjava.sql.Connection;importjava.util.HashMap;importjava.util.Map;public class IndexServlet extendsjavax.servlet.http.HttpServlet {private static Logger logger = LogManager.getLogger(IndexServlet.class);protected void doPost(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throwsjavax.servlet.ServletException, IOException {

doGet(request, response);

}protected void doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throwsjavax.servlet.ServletException, IOException {

String sql= new GenerateSqlStatement().select("*").from("consumer").get();try{

Map consumer = new QueryRunner().query(DBConnection.getConnection(), sql, new BeanMapHandler(ConsumerEntity.class, "username"));

}catch(Exception e) {

logger.debug("IndexServlet Error:" +e.getMessage());

}

Map root = new HashMap();try{

FreeMarker.getFreemarker().getTemplate("index.ftl").process(root, response.getWriter());

System.out.println("请求处理中");

}catch(TemplateException e) {

logger.debug("IndexServlet Error:" +e.getMessage());

}

}

}

web.xml配置内容如下：

HttpRequestAndResponseFilter

com.rskd_yswb.lib.filter.HttpRequestAndResponseFilter

encoding

utf8

Test2Filter

com.rskd_yswb.lib.filter.Test2Filter

HttpRequestAndResponseFilter

/*

Test2Filter

/*

IndexServlet

com.rskd_yswb.servelt.IndexServlet

IndexServlet

/index

IndexServlet

filter的执行顺序如同web.xml中的配置的顺序，在浏览器输入http://localhost:8080/index 控制台将打印如下内容：

HttpRequestAndResponseFilterBefore

Test2FilterBefore

请求处理中

Test2FilterAfter

HttpRequestAndResponseFilterAfter