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;
//濾器設定

public class DomainFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
}

@Override
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
    HttpServletResponse response = (HttpServletResponse) res;
    response.setHeader("Access-Control-Allow-Origin", "*");
    response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");
    response.setHeader("Access-Control-Max-Age", "3600");
    response.addHeader("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
    chain.doFilter(req, res);
}

@Override
public void destroy() {

}
 

}

//spring boot過濾器設定
@Bean
public FilterRegistrationBean filterRegistrationBean() {
FilterRegistrationBean registrationBean = new FilterRegistrationBean();
DomainFilter domainFilter = new DomainFilter();
registrationBean.setFilter(domainFilter);
List urlPatterns = new ArrayList();
urlPatterns.add(“/*”);
registrationBean.setUrlPatterns(urlPatterns);
return registrationBean;
}

如果上面還不行可再往下再配置
tomcat中的配置(這個是把前端html頁面放入)
在tomcat 下載cors-filter-1.7.1.jar 和 java-property-utils-1.9.1.jar兩個jar包放到 lib目錄下
並在conf目錄下的web.xml中加入配置

<!-- 實現跨域   (filter配置放在其它所有filter的上面)-->
    <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>