在 servlet 中启用 CORS

Question

我在 servlet doPost 方法中使用此标头方法来启用 CORS。虽然我在获取 api 时在我的 Reactjs 应用程序中遇到 CORS 错误。这里出现reactjs错误（错误：已被CORS策略阻止：对预检请求的响应未通过访问控制检查：请求的资源上不存在“Access-Control-Allow-Origin”标头。如果不透明的响应为您提供服务如果需要，请将请求的模式设置为“no-cors”以在禁用 CORS 的情况下获取资源。）

    response.addHeader("Access-Control-Allow-Origin", "*");
    response.addHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, PUT, DELETE, HEAD");
    response.addHeader("Access-Control-Allow-Headers", "X-PINGOTHER, Origin, X-Requested-With, Content-Type, Accept");
    response.addHeader("Access-Control-Max-Age", "1728000");

在 tomcat web.xml 中，我添加了下面给出的一堆代码。如何更改多个客户端的参数值而不是tomcat 中的固定 URL（如http://localhost:3000 ）？

<filter>
<filter-name>CorsFilter</filter-name>
<filter-class>org.apache.catalina.filters.CorsFilter</filter-class>
<init-param>
<param-name>cors.allowed.origins</param-name>
<param-value>http://localhost:3000</param-value>
  **(How I can change param-value for multiple client instead of fixed URL)**
</init-param>
<init-param>
<param-name>cors.allowed.methods</param-name>
<param-value>GET,POST,HEAD,OPTIONS,PUT</param-value>
  </init-param>
    <init-param>
     <param-name>cors.allowed.headers</param-name>
     <param-value>Content-Type,X-Requested-With,accept,Origin,Access- 
      Control-Request-Method,Access-Control-Request-Headers</param-value>
  </init-param>
  <init-param>
      <param-name>cors.exposed.headers</param-name>
      <param-value>Access-Control-Allow-Origin,Access-Control-Allow- 
         Credentials</param-value>
  </init-param>
  <init-param>
     <param-name>cors.support.credentials</param-name>
     <param-value>true</param-value>
  </init-param>
  <init-param>
  <param-name>cors.preflight.maxage</param-name>
  <param-value>1800</param-value>
  </init-param>
  </filter>
  <filter-mapping>
  <filter-name>CorsFilter</filter-name>
  <url-pattern>/*</url-pattern>
  </filter-mapping>

Answer 1

对于不同的前端应用程序和后端，它会有所不同......对于 Emberjs，请在相应的 doGet 或 doPost 方法中添加此行。

> response.addHeader("Access-Control-Allow-Origin", "http://localhost:4200");

（或者）

> response.addHeader("Access-Control-Allow-Origin", "*"); (for all hosts)

对于 Tomcat 的 web.xml 配置，请遵循我下面提到的这些步骤！..

https://tomcat.apache.org/tomcat-7.0-doc/config/filter.html#:~:text=The%20filter%20class%20name%20for%20the%20CORS%20Filter%20is%20org，catalina。

对于多个客户端 URL，只需通过逗号分隔来放置所有 URL

<filter>
  <filter-name>CorsFilter</filter-name>
  <filter-class>org.apache.catalina.filters.CorsFilter</filter-class>
  <init-param>
    <param-name>cors.allowed.origins</param-name>
    <param-value> http://localhost:4200, http://localhost:3000 </param-value>
  </init-param>
</filter>