has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource

问题的报错信息是：has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. 这个错误通常在进行跨域请求时出现。跨域请求是指在一个域下的页面请求另一个域下的资源，由于同源策略的限制，浏览器会阻止这样的请求。具体错误信息说明了请求中缺少了Access-Control-Allow-Origin请求头，导致请求被阻止。解决这个问题的方法是在服务端的响应中添加Access-Control-Allow-Origin请求头，并设置合适的值来允许跨域请求。如果是简单的跨域请求，可以在相应的请求路径映射的方法中通过设置response的头部信息来添加Access-Control-Allow-Origin请求头，比如：

@GetMapping("/{type}")
public ResponseData queryByType(@PathVariable String type, HttpServletResponse response){
    response.setHeader("Access-Control-Allow-Origin","*");
    return picService.queryByType(type);
}

这样设置后，浏览器就会允许来自任意域的请求访问该资源了。同时，还可以根据需求设置其他的头部信息，如Access-Control-Max-Age、Access-Control-Allow-Headers和Access-Control-Allow-Credentials等。希望这个解决方法可以帮助到您。<span class="em">1</span><span class="em">2</span><span class="em">3</span>
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