跨域问题

最新推荐文章于 2025-06-05 02:16:04 发布

thedevilisme888

最新推荐文章于 2025-06-05 02:16:04 发布

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本文链接：https://blog.youkuaiyun.com/thedevilisme888/article/details/116860355

本文探讨了浏览器的跨域问题及其报错信息，详细解释了什么是跨域，即协议、域名或端口不一致导致的访问限制。同时，提出了两种解决方案：添加过滤器或服务器端配置以允许跨域请求。同源策略作为保障安全的机制，要求完全匹配的协议、域名和端口才能被视为同源，否则将触发跨域限制。

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1.跨域问题报错信息：

Access to XMLHttpRequest at 'http://localhost:8080/smallU/user?method=login' from origin 'null' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.
localhost:8080/smallU/user?method=login:1 Failed to load resource: net::ERR_FAILED
axios-0.18.0.js:8 Uncaught (in promise) Error: Network Error
    at e.exports (axios-0.18.0.js:8)
    at XMLHttpRequest.l.onerror (axios-0.18.0.js:8)
DevTools failed to load SourceMap: Could not load content for file:///D:/develop/frontEnd/smallU_back/vue/axios.min.map: System error: net::ERR_FILE_NOT_FOUND

在这里插入图片描述

2.问题解决

添加一个过滤器，代码如下：

package com.ujiuye.web.filter;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebFilter(filterName = "FilterA", urlPatterns = "/*")
public class FilterA implements Filter {
    public void destroy() {
    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        HttpServletResponse response = (HttpServletResponse) resp;
        HttpServletRequest request = (HttpServletRequest) req;

        // 不使用*，自动适配跨域域名，避免携带Cookie时失效
        String origin = request.getHeader("Origin");
        response.setHeader("Access-Control-Allow-Origin", origin);

        // 自适应所有自定义头
        String headers = request.getHeader("Access-Control-Request-Headers");
        response.setHeader("Access-Control-Allow-Headers", headers);
        response.setHeader("Access-Control-Expose-Headers", headers);

        // 允许跨域的请求方法类型
        response.setHeader("Access-Control-Allow-Methods", "*");
        // 预检命令（OPTIONS）缓存时间，单位：秒
        response.setHeader("Access-Control-Max-Age", "3600");
        // 明确许可客户端发送Cookie，不允许删除字段即可
        response.setHeader("Access-Control-Allow-Credentials", "true");


        chain.doFilter(req, resp);
    }

    public void init(FilterConfig config) throws ServletException {

    }

}