optimize api

src/main/java/com/qiniu/storage/Api.java

@@ -398,6 +398,10 @@ public static class Request implements Cloneable {
          * @param urlPrefix 请求的 urlPrefix， scheme + host
          */
         protected Request(String urlPrefix) {
+            if (StringUtils.isNullOrEmpty(urlPrefix)) {
+                return;
+            }
+
             try {
                 URL url = new URL(urlPrefix);
                 this.scheme = url.getProtocol();
@@ -628,6 +632,15 @@ public StringMap getHeader() throws QiniuException {
             return header;
         }
 
+        /**
+         * 构造 header 信息，如果需要设置请求体，子类需要重写
+         *
+         * @throws QiniuException 组装 header 时的异常，一般为缺失必要参数的异常
+         */
+        protected void buildHeader() throws QiniuException {
+
+        }
+
         /**
          * 获取 URL
          *
@@ -798,6 +811,7 @@ boolean canRetry() {
         protected void prepareToRequest() throws QiniuException {
             buildPath();
             buildQuery();
+            buildHeader();
             buildBodyInfo();
         }
 
@@ -1046,14 +1060,18 @@ protected RequestBody get() {
                     }
 
                     final MultipartBody.Builder b = new MultipartBody.Builder();
-                    b.addFormDataPart(name, fileName, body);
-
-                    fields.forEach(new StringMap.Consumer() {
-                        @Override
-                        public void accept(String key, Object value) {
-                            b.addFormDataPart(key, value.toString());
-                        }
-                    });
+                    if (StringUtils.isNullOrEmpty(name)) {
+                        b.addFormDataPart(name, fileName, body);
+                    }
+
+                    if (fields != null) {
+                        fields.forEach(new StringMap.Consumer() {
+                            @Override
+                            public void accept(String key, Object value) {
+                                b.addFormDataPart(key, value.toString());
+                            }
+                        });
+                    }
 
                     b.setType(MediaType.parse("multipart/form-data"));
 

src/main/java/com/qiniu/storage/ApiInterceptorRetryHosts.java

@@ -37,9 +37,14 @@ Api.Response intercept(Api.Request request, Api.Handler handler) throws QiniuExc
         }
 
         String reqHost = request.getHost();
-        String firstHost = hostProvider.provider();
-        if (!hostProvider.isHostValid(reqHost) && !StringUtils.isNullOrEmpty(firstHost)) {
-            request.setHost(firstHost);
+        if (!hostProvider.isHostValid(reqHost)) {
+            // 支持不配置默认的 host，未配置则从 provider 中获取
+            String firstHost = hostProvider.provider();
+            if (!StringUtils.isNullOrEmpty(firstHost)) {
+                request.setHost(firstHost);
+            } else {
+                throw QiniuException.unrecoverable("no host provide");
+            }
         }
 
         if (retryMax == 0) {