已被CORS策略阻止：請求的資源上沒有'Access-Control-Allow-Origin'標頭 (使用Access-Control-Allow-Origin解決跨域)

問題：已被CORS策略阻止：請求的資源上沒有'Access-Control-Allow-Origin'標頭（跨域請求失敗）

解決方法：使用過濾器設置Access-Control-Allow-Origin解決跨域請求

第一步： 建立過濾器

package com.ljw.filter;
 
import java.io.IOException;
 
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletResponse;
 
public class SimpleCORSFilter implements Filter {
 
	@Override
	public void destroy() {
 
	}
 
	@Override
	public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
		HttpServletResponse response = (HttpServletResponse) res;  
		// 指定容許其餘域名訪問 
		response.setHeader("Access-Control-Allow-Origin", "*"); // 容許全部
		// response.setHeader("Access-Control-Allow-Origin", "http://127.0.0.1, http://locahost"); // 容許白名單IP
		// 響應類型
		response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");  
		// 預檢請求的結果緩存60分鐘
		response.setHeader("Access-Control-Max-Age", "3600");  
		// 響應頭設置 
		response.setHeader("Access-Control-Allow-Headers", "x-requested-with");  
		chain.doFilter(req, res);  
	}
 
	@Override
	public void init(FilterConfig arg0) throws ServletException {
 
	}
}

第二步：web.xml 配置過濾器

<filter>  
    <filter-name>cors</filter-name>  
    <filter-class>com.ljw.filter.SimpleCORSFilter</filter-class>  
  </filter>  
  <filter-mapping>  
    <filter-name>cors</filter-name>  
    <url-pattern>/*</url-pattern>  
  </filter-mapping>

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原文連接：https://blog.csdn.net/qq_39726772/article/details/88973362