解决跨域问题

跨域问题的产生

• 访问协议不一致
• 访问地址（ip）不一致
• 端口号不一致

解决方案

• 接口类加@CrossOrigin注解允许跨域

@CrossOrigin并不是万能的，有时候遇到加了还会遇到跨域问题，eg：

has been blocked by CORS policy: Request [header](https://so.csdn.net/so/search?q=header&spm=1001.2101.3001.7020) field token is not allowed by Access-Control-Allow-Headers in preflight response.

可以自定义过滤器解决：

package com.yl.common.common.util.filter;

import org.springframework.stereotype.Component;

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

/**
 * 跨域问题过滤器
 *
 * @author Y-wee
 */
@Component
public class SimpleCORSFilter implements Filter {
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletResponse res = (HttpServletResponse) response;
        res.setHeader("Access-Control-Allow-Origin", "*");
        res.setHeader("Access-Control-Allow-Credentials", "true");
        res.setHeader("Access-Control-Allow-Headers", "token");

        chain.doFilter(request, response);
    }

    @Override
    public void init(FilterConfig filterConfig) {
    }

    @Override
    public void destroy() {
    }

}

参考文档：

https://blog.csdn.net/qq_40886696/article/details/108393026