Pre-Filter：

@Component
public class FirstFilter extends ZuulFilter {

    private Logger logger = LoggerFactory.getLogger(FirstFilter.class);

    @Override
    public String filterType() {
        /*
        pre：可以在請求被路由之前調(diào)用
        route：在路由請求時候被調(diào)用
        post：在route和error過濾器之后被調(diào)用
        error：處理請求時發(fā)生錯誤時被調(diào)用
        * */
        // 前置過濾器
        return FilterConstants.PRE_TYPE;
    }

    @Override
    public int filterOrder() {
        //// 優(yōu)先級為0，數(shù)字越大，優(yōu)先級越低
        return 0;
    }
    @Override
    public boolean shouldFilter() {
        RequestContext ctx = RequestContext.getCurrentContext();
        HttpServletRequest request = ctx.getRequest();
        //只過濾OPTIONS 請求
        if(request.getMethod().equals(RequestMethod.OPTIONS.name())){
            return true;
        }

        return false;
    }

    @Override
    public Object run() {
        logger.debug("*****************FirstFilter run start*****************");
        RequestContext ctx = RequestContext.getCurrentContext();
        HttpServletResponse response = ctx.getResponse();
        HttpServletRequest request = ctx.getRequest();
        response.setHeader("Access-Control-Allow-Origin",request.getHeader("Origin"));
        response.setHeader("Access-Control-Allow-Credentials","true");
        response.setHeader("Access-Control-Allow-Headers","authorization, content-type");
        response.setHeader("Access-Control-Allow-Methods","POST,GET");
        response.setHeader("Access-Control-Expose-Headers","X-forwared-port, X-forwarded-host");
        response.setHeader("Vary","Origin,Access-Control-Request-Method,Access-Control-Request-Headers");
        //不再路由
        ctx.setSendZuulResponse(false);
        ctx.setResponseStatusCode(200);
        logger.debug("*****************FirstFilter run end*****************");
        return null;
    }
}

Pre-Filter 用來處理預(yù)處理OPTIONS請求，當發(fā)現(xiàn)是OPTIONS請求的時候，給出跨域響應(yīng)頭，并且不對其進行zuul路由，直接返回成功（200）, 給前端服務(wù)允許跨域

post-Filter ：

@Component
public class PostFilter extends ZuulFilter {

    private Logger logger = LoggerFactory.getLogger(PostFilter.class);

    @Override
    public String filterType() {
        /*
        pre：可以在請求被路由之前調(diào)用
        route：在路由請求時候被調(diào)用
        post：在route和error過濾器之后被調(diào)用
        error：處理請求時發(fā)生錯誤時被調(diào)用
        * */
        // 前置過濾器
        return FilterConstants.POST_TYPE;
    }

    @Override
    public int filterOrder() {
        //// 優(yōu)先級為0，數(shù)字越大，優(yōu)先級越低
        return 2;
    }
    @Override
    public boolean shouldFilter() {
        RequestContext ctx = RequestContext.getCurrentContext();
        HttpServletRequest request = ctx.getRequest();
        //過濾各種POST請求
        if(request.getMethod().equals(RequestMethod.OPTIONS.name())){
            return false;
        }
        return true;
    }

    @Override
    public Object run() {
        logger.debug("*****************PostFilter run start*****************");
        RequestContext ctx = RequestContext.getCurrentContext();
        HttpServletResponse response = ctx.getResponse();
        HttpServletRequest request = ctx.getRequest();
        response.setHeader("Access-Control-Allow-Origin",request.getHeader("Origin"));
        response.setHeader("Access-Control-Allow-Credentials","true");
        response.setHeader("Access-Control-Expose-Headers","X-forwared-port, X-forwarded-host");
        response.setHeader("Vary","Origin,Access-Control-Request-Method,Access-Control-Request-Headers");
        //允許繼續(xù)路由
        ctx.setSendZuulResponse(true);
        ctx.setResponseStatusCode(200);
        logger.debug("*****************PostFilter run end*****************");
        return null;
    }
}

Post-Filter 用來處理 預(yù)處理OPTIONS以外的請求，對于正常的請求，不但要給出跨域請求頭，還需要允許請求進行路由（否則你的請求到這兒就結(jié)束啦），然后返回狀態(tài)碼200。（emmmm……這里要不要返回200，我覺得可能還要想一想……）

按照以上方式配置的話，方法一出現(xiàn)的問題，就得到了解決。服務(wù)A能夠正常請求服務(wù)B了

雖然是正常實現(xiàn)了需求，但是感覺還是存在很多疑惑，希望大家看到的話，能給我指出不足。一起討論！