CAS實現SSO，解決AJAX請求跨域系列問題

場景及問題描述：

項目爲前後端分離，後臺項目使用Spring Boot框架整合了CAS Client。前端發起ajax請求到CAS Client，被CAS Filter攔截器重定向到CAS Server，出現CORS跨域問題 。

 

錯誤信息：

Chrome F12完整錯誤信息：

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關鍵錯誤信息：

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

 

解決方案：

1、CAS Client中定義一個跨域Filter，注意：跨域Filter優先級必須要高於CAS FIlter，否則請求會先被CAS Filter先行執行，加跨域Filter則無意義。這裏優先級設定爲@Order(value=0)，高於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執行=================");
  }

  @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項目下找到web.xml，進行跨域Filter配置，但是需要下載java-property-utils和cors-filter jar包，放到lib下

<filter>
    <filter-name>CORS</filter-name>
    <filter-class>com.thetransactioncompany.cors.CORSFilter</filter-class>
    <init-param>
     <param-name>cors.allowOrigin</param-name>
        <param-value>*</param-value>
    </init-param>
    <init-param>
     <param-name>cors.supportedMethods</param-name>
        <param-value>GET, POST, HEAD, PUT, DELETE</param-value>
    </init-param>
    <init-param>
     <param-name>cors.supportedHeaders</param-name>
        <param-value>Accept, Origin, X-Requested-With, Content-Type, Last-Modified</param-value>
    </init-param>
    <init-param>
        <param-name>cors.exposedHeaders</param-name>
        <param-value>Set-Cookie</param-value>
    </init-param>
    <init-param>
        <param-name>cors.supportsCredentials</param-name>
        <param-value>true</param-value>
    </init-param>
</filter>
<filter-mapping>
    <filter-name>CORS</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

注意：如果只進行第1步對CAS Client跨域配置，不進行第2步對CAS Server跨域配置，則會出現以下錯誤信息：

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.

 

找了幾篇CORS相關文章，感謝作者分享精神：

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