详解SpringCloud Zuul过滤器返回值拦截

public class AuthResponseFilter extends AbstractZuulFilter {

 private static final String RESPONSE_KEY_TOKEN = "token";
 @Value("${system.config.authFilter.authUrl}")
 private String authUrl;
 @Value("${system.config.authFilter.tokenKey}")
 private String tokenKey = RESPONSE_KEY_TOKEN;

 @Autowired
 private AuthApi authApi;

 @Override
 public boolean shouldFilter() {
  RequestContext context = getCurrentContext();
  return StringUtils.equals(context.getRequest().getRequestURI().toString(), authUrl);
 }

 @Override
 public Object run() {

  try {
   RequestContext context = getCurrentContext();

   InputStream stream = context.getResponseDataStream();
   String body = StreamUtils.copyToString(stream, Charset.forName("UTF-8"));

   if (StringUtils.isNotBlank(body)) {
    Gson gson = new Gson();
    @SuppressWarnings("unchecked")
    Map<String, String> result = gson.fromJson(body, Map.class);
    if (StringUtils.isNotBlank(result.get(tokenKey))) {
     AuthModel authResult = authApi.encodeToken(result.get(tokenKey));
     if (authResult.getStatus() != HttpServletResponse.SC_OK) {
      throw new IllegalArgumentException(authResult.getErrMsg());
     }
     String accessToken = authResult.getToken();
     result.put(tokenKey, accessToken);
    }
    body = gson.toJson(result);
   }
   context.setResponseBody(body);
  } catch (IOException e) {
   rethrowRuntimeException(e);
  }
  return null;
 }

 @Override
 public String filterType() {
  return FilterConstants.POST_TYPE;
 }

 @Override
 public int filterOrder() {
  return FilterConstants.SEND_RESPONSE_FILTER_ORDER - 2;
 }

}

@Override
 public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
  try {
   init((HttpServletRequest) servletRequest, (HttpServletResponse) servletResponse);
   try {
    preRouting();
   } catch (ZuulException e) {
    error(e);
    postRouting();
    return;
   }

   // Only forward onto to the chain if a zuul response is not being sent
   if (!RequestContext.getCurrentContext().sendZuulResponse()) {
    filterChain.doFilter(servletRequest, servletResponse);
    return;
   }

   try {
    routing();
   } catch (ZuulException e) {
    error(e);
    postRouting();
    return;
   }
   try {
    postRouting();
   } catch (ZuulException e) {
    error(e);
    return;
   }
  } catch (Throwable e) {
   error(new ZuulException(e, 500, "UNCAUGHT_EXCEPTION_FROM_FILTER_" + e.getClass().getName()));
  } finally {
   RequestContext.getCurrentContext().unset();
  }
 }

  // Only forward onto to the chain if a zuul response is not being sent
   if (!RequestContext.getCurrentContext().sendZuulResponse()) {
    filterChain.doFilter(servletRequest, servletResponse);
    return;
   }