过滤器（Filter）解决跨域问题

桃扇骨 2022-03-01 17:50 921阅读 0赞

最近在做一个项目，前端资源与服务端单独部署。遇到一个跨域问题，常见的跨域问题可以通过jsonp方式解决。下面介绍另一种解决方式：  
服务端环境：spring + dubbo + tomcat  
第一步：在WEB-INF目录下添加一个crossdomain.xml文件，内容如下：

<cross-domain-policy>
    <allow-access-from domain="*"/>
    </cross-domain-policy>

表示web服务器允许任何domain的请求。  
第二步：  
在web.xml中添加一个新的过滤器Filter--crossDomainFilter。

<?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0">
      <display-name>Archetype CreatedWeb Application</display-name>
      <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath*:spring-main.xml</param-value>
      </context-param>
      <context-param>
        <param-name>timeoutMinutes</param-name>
        <param-value>120</param-value>
      </context-param>
      <filter>
        <filter-name>encodingFilter</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
        <init-param>
          <param-name>encoding</param-name>
          <param-value>UTF-8</param-value>
        </init-param>
        <init-param>
          <param-name>forceEncoding</param-name>
          <param-value>true</param-value>
        </init-param>
      </filter>
      <filter-mapping>
        <filter-name>encodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
      </filter-mapping>
      <filter>
      <filter-name>crossDomainFilter</filter-name>
        <filter-class>com.*.resource.web.utils.CrossDomainFilter</filter-class>
        <init-param>
            <param-name>file</param-name>
            <param-value>/WEB-INF/web-config.properties</param-value>
        </init-param>
      </filter>
      <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
      </listener>
      <servlet>
        <servlet-name>dispatcher</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
          <param-name>contextConfigLocation</param-name>
          <param-value>classpath*:springmvc-servlet.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
      </servlet>
      <servlet-mapping>
        <servlet-name>dispatcher</servlet-name>
        <url-pattern>*.do</url-pattern>
      </servlet-mapping>
      <filter-mapping>
        <filter-name>crossDomainFilter</filter-name>
        <url-pattern>*.do</url-pattern>
      </filter-mapping>
      <session-config>
        <session-timeout>120</session-timeout>
      </session-config>
      <welcome-file-list>
        <welcome-file>index.html</welcome-file>
      </welcome-file-list>
    </web-app>

crossDomainFilter中增加crossDomain方法：

package com.*.resource.web.utils;
    
    import java.io.FileInputStream;
    import java.io.IOException;
    import java.util.Properties;
    
    import javax.servlet.Filter;
    import javax.servlet.FilterChain;
    import javax.servlet.FilterConfig;
    import javax.servlet.ServletContext;
    import javax.servlet.ServletException;
    import javax.servlet.ServletRequest;
    import javax.servlet.ServletResponse;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import org.apache.commons.lang.exception.ExceptionUtils;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.context.ApplicationContext;
    import org.springframework.web.context.support.WebApplicationContextUtils;
    
    /**
     *
     * @author 
     * @date
     */
    public class CrossDomainFilter implements Filter {
    
        private static final Logger log = LoggerFactory.getLogger(CrossDomainFilter.class);
    
        private Properties pp = new Properties();
    
        private FilterConfig config;
    
        private String allowDomain = "http://allow.com";
    
        @Override
        public void destroy() {
            pp = null;
            this.config = null;
        }
    
        @Override
        public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
                throws IOException, ServletException {
    
            HttpServletRequest req = (HttpServletRequest) request;
            HttpServletResponse resp = (HttpServletResponse) response;
    
            // 得到请求的uri和url
            String reqUri = req.getRequestURI();
            String reqUrl = req.getRequestURL().toString();
            log.info(" reqUri:{} ,reqUrl:{} ", reqUri, reqUrl);
    
            // 跨域处理
            this.crossDomain(req, resp, reqUrl);
            chain.doFilter(req, resp);
    
        }
    
        @Override
        public void init(FilterConfig config) throws ServletException {
    
        }
    
        /**
         * 处理跨域问题
         */
        private void crossDomain(HttpServletRequest request, HttpServletResponse response, String url) {
            response.setHeader("Content-type", "text/html;charset=UTF-8");
            response.setCharacterEncoding("UTF-8");
            response.setHeader("Access-Control-Allow-Credentials", "true");
    
            log.info("REFERER:{}", request.getHeader("REFERER"));
            String referer = request.getHeader("REFERER");
            String reqRefererDomain = "";
            if (referer != null && referer.length() > referer.indexOf(".com") + 4) {
                reqRefererDomain = referer.substring(0, referer.indexOf(".com") + 4);
                log.info("reqRefererDomain:{}", reqRefererDomain);
                if (reqRefererDomain.equals(allowDomain)) {
                    response.setHeader("Access-Control-Allow-Origin", allowDomain );
                }
            }
    
            response.setHeader("Access-Control-Allow-Credentials", "true");
            response.setHeader("Access-Control-Allow-Methods", "GET, POST, OPTIONS");
            response.setHeader("Access-Control-Allow-Headers",
                    "Origin, No-Cache, X-Requested-With, If-Modified-Since, Pragma, Last-Modified, Cache-Control, Expires, Content-Type, X-E4M-With");
    
        }
    
    }

解决跨域的关键：

response.setHeader("Access-Control-Allow-Origin", allowDomain );

from [https://segmentfault.com/a/1190000009512081][https_segmentfault.com_a_1190000009512081]

[https_segmentfault.com_a_1190000009512081]: https://segmentfault.com/a/1190000009512081