C/C++|基于http的protobuf服务实现 C

通常webapi实现通过http get/post请求，返回文本型的json，xml等字符串。本文以Tomcat8为web服务器，借助protobuf框架，响应二进制数据。
由于protobuf协议能跨语言，我们可以用java servlet实现服务端，C/C++实现客户端，达到各模块解耦目的。双方需设置ContentType为application/x-protobuf。

1. 准备proto文件

package qwd.kettas; // 请求结构 message CTestReq { optional uint32 ShopId = 1; // 店铺ID }message CProduct { optional uint32 Id = 1; // 商品ID optional bytes Name = 2; // 商品名称 optional double price = 3; // 商品价格 }// 响应结构 message CTestResp { optional int32 Total = 1; // 商品总数 repeated CProduct Product = 2; // 商品数组 }

2. Java Servlet服务

/** * Servlet 服务实现，接收post请求，响应protocol buffer二进制数据 */ protected void service( HttpServletRequest req, HttpServletResponse resp ) throws ServletException, IOException { /* * 注：用in.read() 无数据部分填充0，会导致parseFrom()失败，不可行。 byte[] postBuf = new byte[128]; InputStream in = req.getInputStream(); int len = in.read( postBuf ); */ // protobuf 解析参数 CTestReq tReq = CTestReq.parseFrom( req.getInputStream() ); // InputStream作为参数 int shopid = tReq.getShopId(); // 准备数据 CTestResp.Builder pBuilder = CTestResp.newBuilder(); pBuilder.setTotal(2); // 产品一 CProduct.Builder pProBuild1 = CProduct.newBuilder(); pProBuild1.setId( shopid + 1001 ); pProBuild1.setName( ByteString.copyFrom("小明","UTF-8") ); // 字符串需要通过ByteString转化，最好定义string pProBuild1.setPrice(15.8); pBuilder.addProduct( pProBuild1 ); // 产品二 pProBuild1 = CProduct.newBuilder(); pProBuild1.setId( shopid + 1002 ); pProBuild1.setName( ByteString.copyFrom("小王","UTF-8") ); pProBuild1.setPrice(29.8); pBuilder.addProduct( pProBuild1 ); // reponse CTestResp pResp = pBuilder.build(); System.out.println( "Data: " + pResp.toString() ); // 序列化 byte[] buff = pResp.toByteArray(); // 响应，设置HTTP头部为: application/x-protobuf resp.setContentType("application/x-protobuf"); resp.getOutputStream().write( buff ); // 发送 }

3. 客户端测试

// 数据回调函数 size_t OnWriteData( void* buffer, size_t size, size_t nmemb, void *lpVoid ) { std::string* str = dynamic_cast((std::string *)lpVoid); if ( NULL == str || NULL == buffer ) { return -1; }char* pData = https://www.it610.com/article/(char*)buffer; str->append(pData, size * nmemb); return nmemb; }// curl模拟post请求 void TestCurl() { printf( "\n****************TestCurl*******************\n" ); const char *url = "http://10.14.230.7:8080/protoweb/proto"; CTestReq req; CTestResp resp; string sReq; string sResp; req.set_shopid( 1500 ); // 序列化请求 if ( !req.SerializeToString(&sReq) ) return; curl_slist *m_header = NULL; m_header = curl_slist_append( m_header, "Content-Type: application/x-protobuf" ); // 设置消息头CURL *curl = curl_easy_init(); curl_easy_setopt( curl, CURLOPT_HTTPHEADER, m_header ); // Header curl_easy_setopt( curl, CURLOPT_REFERER, "nginx" ); curl_easy_setopt( curl, CURLOPT_VERBOSE, 1L ); curl_easy_setopt( curl, CURLOPT_URL, url ); curl_easy_setopt( curl, CURLOPT_NOSIGNAL, 1); curl_easy_setopt( curl, CURLOPT_POSTFIELDS, sReq.c_str() ); // Post curl_easy_setopt( curl, CURLOPT_POSTFIELDSIZE, sReq.length() ); curl_easy_setopt( curl, CURLOPT_WRITEFUNCTION, OnWriteData ); curl_easy_setopt( curl, CURLOPT_WRITEDATA, (void*)&sResp ); // Accept dataCURLcode ret = curl_easy_perform( curl ); assert( ret == CURLE_OK ); curl_easy_cleanup( curl ); curl_slist_free_all( m_header ); // 反序列化数据 if ( !resp.ParseFromString(sResp) ) return; printf( "Response: %s\n", resp.DebugString().c_str() ); }

执行结果，curl发起post请求，返回46字节内容：