RestTemplate可以自定義重試次數

/**
         * 重試處理
         * 默認是重試3次
         */
        //禁用重試(參數：retryCount、requestSentRetryEnabled)
        HttpRequestRetryHandler requestRetryHandler = new DefaultHttpRequestRetryHandler(0, false);
        //自定義重試策略
        HttpRequestRetryHandler myRetryHandler = new HttpRequestRetryHandler() {
 
            public boolean retryRequest(IOException exception, int executionCount, HttpContext context) {
                //Do not retry if over max retry count
                if (executionCount >= 3) {
                    return false;
                }
                //Timeout
                if (exception instanceof InterruptedIOException) {
                    return false;
                }
                //Unknown host
                if (exception instanceof UnknownHostException) {
                    return false;
                }
                //Connection refused
                if (exception instanceof ConnectTimeoutException) {
                    return false;
                }
                //SSL handshake exception
                if (exception instanceof SSLException) {
                    return false;
                }
                
                HttpClientContext clientContext = HttpClientContext.adapt(context);
                HttpRequest request = clientContext.getRequest();
                boolean idempotent = !(request instanceof HttpEntityEnclosingRequest);
                //Retry if the request is considered idempotent
                //如果請求類型不是HttpEntityEnclosingRequest，被認為是冪等的，那么就重試
                //HttpEntityEnclosingRequest指的是有請求體的request，比HttpRequest多一個Entity屬性
                //而常用的GET請求是沒有請求體的，POST、PUT都是有請求體的
                //Rest一般用GET請求獲取數據，故冪等，POST用於新增數據，故不冪等
                if (idempotent) {
                    return true;
                }
                
                return false;
            }
        };