Protobuf 的快速使用（四）

Protobuf 还常⽤于通讯协议、服务端数据交换场景。那么在这个⽰例中，我们将实现⼀个⽹络版本的通讯录，模拟实现客⼾端与服务端的交互，通过 Protobuf 来实现各端之间的协议序列化。需求如下：

客⼾端可以选择对通讯录进⾏以下操作：

• 新增⼀个联系⼈
• 删除⼀个联系⼈
• 查询通讯录列表
• 查询⼀个联系⼈的详细信息

为了将代码简化，我们只具体实现新增联系人的功能， 服务端则相应提供增删查能⼒，并需要持久化通讯录（为了将代码简化， 这里只是将收到的需求序列化后打印出来），客⼾端、服务端间的交互数据使⽤ Protobuf 来完成。

搭建 Httplib 库

Httplib 库：cpp-httplib 是个开源库，是⼀个c++封装的http库，使⽤这个库可以在linux、 windows平台下完成http客⼾端、http服务端的搭建。使⽤起来⾮常⽅便，只需要包含头⽂件 httplib.h 即可。编译程序时，需要带上 -lpthread 选项。

源码库地址： https://github.com/yhirose/cpp-httplib

完整代码

protocol.proto

syntax="proto3";
package protocol;message Response
{string uid = 1; bool success = 2;// 返回结果string error_desc = 3;// 错误描述
}message AddContactRequest
{string name = 1;int32 age=2;message Phone{string number = 1;// 电话号码enum PhoneType{MP = 0;// 移动电话TEL = 1;// 固定电话}PhoneType type = 2;}repeated Phone phone =3;
}

将代码补充好后编译一下

protoc --cpp_out=. protocol.proto

之后就在当前文件夹出现 protocol.pb.h 和 protocol.pb.cc 文件，还需要记得添加下载的 httplib.h 文件。

ContactsException.h

定义抛异常的类

#include <string>
class ContactsException
{
public:ContactsException(std::string str = "problem"): message(str){}std::string what() const{return message;}private:std::string message;
};

client.cc

#include <iostream>
#include "httplib.h"
#include "ContactsException.h"
#include "protocol.pb.h"
using namespace std;const string server_ip = "127.0.0.1";
const int server_port = 8080;
void menu()
{std::cout << "-----------------------------------------------------" << std::endl<< "--------------- 请选择对通讯录的操作 ----------------" << std::endl<< "------------------ 1、新增联系⼈ --------------------" << std::endl<< "------------------ 2、删除联系⼈ --------------------" << std::endl<< "------------------ 3、查看联系⼈列表 ----------------" << std::endl<< "------------------ 4、查看联系⼈详细信息 ------------" << std::endl<< "------------------ 0、退出 --------------------------" << std::endl<< "-----------------------------------------------------" << std::endl;
}void buildAddContactRequest(protocol::AddContactRequest *req)
{cout << "-------------新增联系⼈-------------" << endl;cout << "请输⼊联系⼈姓名: ";string name;getline(cin, name);req->set_name(name);cout << "请输⼊联系⼈年龄: ";int age;cin >> age;req->set_age(age);cin.ignore(256, '\n');for (int i = 1;; i++){cout << "请输⼊联系⼈电话" << i << "(只输⼊回⻋完成电话新增):";string numbers;getline(cin, numbers);if (numbers.empty())break;auto phone = req->add_phone();phone->set_number(numbers);cout << "选择此电话类型（1.移动电话 2.固定电话）:";int type;cin >> type;cin.ignore(256, '\n');switch (type){case 1:phone->set_type(protocol::AddContactRequest_Phone_PhoneType::AddContactRequest_Phone_PhoneType_MP);break;case 2:phone->set_type(protocol::AddContactRequest_Phone_PhoneType::AddContactRequest_Phone_PhoneType_TEL);break;default:cout << "非法选择，使用默认值！" << endl;break;}}
}
void addContact()
{httplib::Client client(server_ip, server_port);// 构造requestprotocol::AddContactRequest req;buildAddContactRequest(&req);// 序列化requeststring req_str;if (!req.SerializeToString(&req_str)){throw ContactsException("AddContactRequest序列化失败!");}// 发起post调用httplib::Result res = client.Post("/contacts/add", req_str, "application/protobuf");if (!res){string err_desc = "/contacts/add 链接失败!错误信息: " + httplib::to_string(res.error());throw ContactsException(err_desc);}// 反序列化responseprotocol::Response rsp;bool parse = rsp.ParseFromString(res->body);if (res->status != 200 && parse == false){string err_desc = "/contacts/add 调用失败,返回状态码为: " +to_string(res->status) + "(" + res->reason + ")";throw ContactsException(err_desc);}else if (res->status != 200){string err_desc = "/contacts/add 调用失败,返回状态码为: " +to_string(res->status) + "(" + res->reason + "),错误原因: " + rsp.error_desc();throw ContactsException(err_desc);}else if (rsp.success() == false){string err_desc = "/contacts/add 结果异常,异常原因: " + rsp.error_desc();throw ContactsException(err_desc);}// 结果打印cout << "新增联系人成功，联系人ID: " << rsp.uid() << endl;
}
int main()
{enum OPTION{QUIT = 0,ADD,DEL,FIND_ALL,FIND_ONE};while (true){menu();cout << "--->请选择: ";int choose;cin >> choose;cin.ignore(256, '\n');try{switch (choose){case OPTION::QUIT:cout << "程序退出!" << endl;return 0;case OPTION::ADD:cout << "新增联系人--->" << endl;addContact();break;case OPTION::DEL:cout << "删除联系人--->" << endl;break;case OPTION::FIND_ALL:cout << "查看联系⼈列表--->" << endl;break;case OPTION::FIND_ONE:cout << "查看联系⼈详细信息--->" << endl;break;default:cout << "选择错误，请重新选择!" << endl;break;}}catch (const ContactsException &e){cout << "操作通讯录时发生异常，异常信息为: " << e.what() << endl;}}return 0;
}

server.cc

#include <iostream>
#include "httplib.h"
#include "ContactsException.h"
#include "protocol.pb.h"
using namespace std;unsigned int random_char()
{// ⽤于随机数引擎获得随机种⼦random_device rd;// mt19937是c++11新特性，它是⼀种随机数算法，⽤法与rand()函数类似，但是mt19937具有速度快，周期⻓的特点// 作⽤是⽣成伪随机数mt19937 gen(rd());// 随机⽣成⼀个整数i 范围[0, 255]uniform_int_distribution<> dis(0, 255);return dis(gen);
}
// ⽣成 UUID （通⽤唯⼀标识符）
string generate_hex(const unsigned int len)
{stringstream ss;// ⽣成 len 个16进制随机数，将其拼接⽽成for (auto i = 0; i < len; i++){const auto rc = random_char();stringstream hexstream;hexstream << hex << rc;auto hex = hexstream.str();ss << (hex.length() < 2 ? '0' + hex : hex);}return ss.str();
}
void printContact(const protocol::AddContactRequest &proto_req)
{cout << "联系⼈姓名: " << proto_req.name() << endl;cout << "联系⼈年龄: " << proto_req.age() << endl;int j = 1;for (auto phone : proto_req.phone()){cout << "联系⼈电话" << j++ << ": " << phone.number();cout << " (" << phone.PhoneType_Name(phone.type()) << ")" << endl;}
}
int main()
{cout << "服务启动..." << endl;httplib::Server server;server.Post("/contacts/add", [](const httplib::Request &req, httplib::Response &rsp){cout << "收到post请求!" << endl;protocol::AddContactRequest proto_req;protocol::Response proto_rsp;try{// 反序列化req，取出req的bodyif(!proto_req.ParseFromString(req.body)){throw ContactsException("AddContactRequest反序列化失败");}// 新增联系人，持久化到文件或打印printContact(proto_req);// 构造proto_rspproto_rsp.set_success(true);proto_rsp.set_uid(generate_hex(10));// 序列化proto_rsp,构造rsp的bodystring rsp_str;if(!proto_rsp.SerializeToString(&rsp_str)){throw ContactsException("Response序列化失败");}rsp.status=200;rsp.body=rsp_str;rsp.set_header("Content-Type","application/protobuf");}catch (const ContactsException &e){//返回异常的rsprsp.status=500;proto_rsp.set_success(false);proto_rsp.set_error_desc(e.what());string rsp_str;if(proto_rsp.SerializeToString(&rsp_str)){rsp.body=rsp_str;rsp.set_header("Content-Type","application/protobuf");}cout<<"/contacts/add 发生异常，异常信息: "<<e.what()<<endl;} });// 绑定端口server.listen("0.0.0.0", 8080);return 0;
}

makefile

.PHONY:all
all:server clientserver:server.cc protocol.pb.ccg++ -o $@ $^ -std=c++17 -lpthread -lprotobuf
client:client.cc protocol.pb.ccg++ -o $@ $^ -std=c++17 -lpthread -lprotobuf.PHONY:clean
clean:rm -f server client