CAS实现SSO，解决AJAX请求跨域系列问题

场景及问题描述：

项目为前后端分离，后台项目使用Spring Boot框架整合了CAS Client。前端发起ajax请求到CAS Client，被CAS Filter拦截器重定向到CAS Server，出现CORS跨域问题 。

 

错误信息：

Chrome F12完整错误信息：

Failed to load [CAS client地址]: Redirect from '[CAS client地址]' to '[CAS server地址]' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin '[前端地址]' is therefore not allowed access.

Chrome F12关键错误信息：

 No 'Access-Control-Allow-Origin' header is present on the requested resource

 

解决方案：

1、CAS Client中定义一个跨域Filter，注意：跨域Filter优先级必须要高于CAS FIlter，否则请求会先被CAS Filter先行执行，加跨域Filter则无意义。这里优先级设定为@Order(value=0)，高于CAS FIlter。

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletResponse;

import org.springframework.context.annotation.Configuration;
import org.springframework.core.annotation.Order;

import java.io.IOException;

@Configuration
@Order(value=0)
@WebFilter(filterName = "CorsFilterConfig", urlPatterns = "/*")
public class CorsFilterConfig implements Filter {

  @Override
  public void init(FilterConfig filterConfig) throws ServletException {
  	System.out.println("===============CorsFilterConfig执行=================");
  }

  @Override
  public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse,
      FilterChain filterChain) throws IOException, ServletException {
    HttpServletResponse res = (HttpServletResponse) servletResponse;
    res.setHeader("Access-Control-Allow-Origin", "*");
    res.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE, PUT");
    res.setHeader("Access-Control-Max-Age", "1728000");
    res.setHeader("Access-Control-Allow-Headers",
        "Authentication, Authorization, content-type, Accept, x-requested-with, Cache-Control");
    filterChain.doFilter(servletRequest, res);
  }

  @Override
  public void destroy() {}
  
}

2、CAS Server项目下找到web.xml，进行跨域Filter配置，但是需要下载java-property-utils和cors-filter jar包，放到lib下

    CORS
    com.thetransactioncompany.cors.CORSFilter
    
     cors.allowOrigin
        *
    
    
     cors.supportedMethods
        GET, POST, HEAD, PUT, DELETE
    
    
     cors.supportedHeaders
        Accept, Origin, X-Requested-With, Content-Type, Last-Modified
    
    
        cors.exposedHeaders
        Set-Cookie
    
    
        cors.supportsCredentials
        true
    


    CORS
    /*

注意：如果只进行第1步对CAS Client跨域配置，不进行第2步对CAS Server跨域配置，则会出现以下错误信息：

Failed to load [CAS server地址?service=url]: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access.

 

找了几篇CORS相关文章，感谢作者分享精神：

http://www.ruanyifeng.com/blog/2016/04/same-origin-policy.html

http://www.ruanyifeng.com/blog/2016/04/cors.html

https://www.cnblogs.com/keyi/p/6726089.html