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java 过滤器Filter中chain.doFilter()之前和之后代码的执行顺序

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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：

            package
             com.rskd_yswb.lib.filter;


            import javax.servlet.*;
import java.io.IOException;
publicclass HttpRequestAndResponseFilter implements Filter {
    private FilterConfig filterConfig;

    publicvoid destroy() {
    }

    publicvoid doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        resp.setCharacterEncoding(this.filterConfig.getInitParameter("encoding"));
        System.out.println("HttpRequestAndResponseFilterBefore");
        chain.doFilter(req, resp);
        System.out.println("HttpRequestAndResponseFilterAfter");
    }

    publicvoid init(FilterConfig config) throws ServletException {
        this.filterConfig = config;
    }

}

过滤器二：

            package
             com.rskd_yswb.lib.filter;


            import javax.servlet.*;
import java.io.IOException;


publicclass Test2Filter implements Filter {
    publicvoid destroy() {
    }

    publicvoid doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        System.out.println("Test2FilterBefore");
        chain.doFilter(req, resp);
        System.out.println("Test2FilterAfter");
    }

    publicvoid init(FilterConfig config) throws ServletException {

    }

}

 

要执行的servlet:

            package
             com.rskd_yswb.servelt;


            import
             com.rskd_yswb.javabean.db.ConsumerEntity;

            import
             com.rskd_yswb.lib.db.DBConnection;

            import
             com.rskd_yswb.lib.db.GenerateSqlStatement;

            import
             com.rskd_yswb.lib.freemarker.FreeMarker;

            import
             freemarker.template.Template;

            import
             freemarker.template.TemplateException;

            import
             org.apache.commons.dbutils.QueryRunner;

            import
             org.apache.commons.dbutils.handlers.BeanMapHandler;

            import
             org.apache.logging.log4j.LogManager;

            import
             org.apache.logging.log4j.Logger;


            import
             javax.servlet.annotation.WebServlet;

            import
             java.io.IOException;

            import
             java.io.Writer;

            import
             java.sql.Connection;

            import
             java.util.HashMap;

            import
             java.util.Map;



            public
            class IndexServlet extends javax.servlet.http.HttpServlet {
    privatestatic Logger logger = LogManager.getLogger(IndexServlet.class);

    protectedvoid doPost(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
        doGet(request, response);
    }

    protectedvoid doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
        String sql = new GenerateSqlStatement().select("*").from("consumer").get();
        try {
            Map<String, ConsumerEntity> consumer = new QueryRunner().query(DBConnection.getConnection(), sql, new BeanMapHandler<String, ConsumerEntity>(ConsumerEntity.class, "username"));
        } catch (Exception e) {
            logger.debug("IndexServlet Error:" + e.getMessage());
        }
        Map<String, Object> root = new HashMap<String, Object>();
        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：

            <
            web-app
            >
            <
            filter
            >
            <
            filter-name
            >HttpRequestAndResponseFilter</filter-name><filter-class>com.rskd_yswb.lib.filter.HttpRequestAndResponseFilter</filter-class><init-param><param-name>encoding</param-name><param-value>utf8</param-value></init-param></filter><filter><filter-name>Test2Filter</filter-name><filter-class>com.rskd_yswb.lib.filter.Test2Filter</filter-class></filter><filter-mapping><filter-name>HttpRequestAndResponseFilter</filter-name><url-pattern>/*</url-pattern></filter-mapping><filter-mapping><filter-name>Test2Filter</filter-name><url-pattern>/*</url-pattern></filter-mapping><servlet><servlet-name>IndexServlet</servlet-name><servlet-class>com.rskd_yswb.servelt.IndexServlet</servlet-class></servlet><servlet-mapping><servlet-name>IndexServlet</servlet-name><url-pattern>/index</url-pattern></servlet-mapping><servlet-mapping><servlet-name>IndexServlet</servlet-name><url-pattern></url-pattern></servlet-mapping></web-app>

 

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

 

原文：http://www.cnblogs.com/zouyitangzaishuo/p/5995099.html

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