File: depot/addurl/addurl_frontend.h

#ifndef ADDURL_ADDURL_FRONTEND_H_

#define ADDURL_ADDURL_FRONTEND_H_

// Forward-declaration of dependencies.

class AddUrlService;

class HTTPRequest;

class HTTPReply;

// Frontend for the AddUrl system.

// Accepts HTTP requests from web clients,

// and forwards well-formed requests to the backend.

class AddUrlFrontend {

public:

// Constructor which enables injection of an

// AddUrlService dependency.

explicit AddUrlFrontend(AddUrlService* add_url_service);

~AddUrlFrontend;

// Method invoked by our HTTP server when a request arrives

// for the /addurl resource.

void HandleAddUrlFrontendRequest(const HTTPRequest* http_request,

HTTPReply* http_reply);

private:

AddUrlService* add_url_service_;

// Declare copy constructor and operator= private to prohibit

// unintentional copying of instances of this class.

AddUrlFrontend(const AddUrlFrontend&);

AddUrlFrontend& operator=(const AddUrlFrontend& rhs);

};

#endif // ADDURL_ADDURL_FRONTEND_H_

Продолжая определять классы AddUrlFrontend, разработчик создает файл addurl_frontend.cc, в котором описывает класс AddUrlFrontend. Для экономии места мы опустили часть файла.

File: depot/addurl/addurl_frontend.cc

#include "addurl/addurl_frontend.h"

#include "addurl/addurl.pb.h"

#include "path/to/httpqueryparams.h"

// Functions used by HandleAddUrlFrontendRequest below, but

// whose definitions are omitted for brevity.

void ExtractHttpQueryParams(const HTTPRequest* http_request,

HTTPQueryParams* query_params);

void WriteHttp200Reply(HTTPReply* reply);

void WriteHttpReplyWithErrorDetails(

HTTPReply* http_reply, const AddUrlReply& add_url_reply);

// AddUrlFrontend constructor that injects the AddUrlService

// dependency.

AddUrlFrontend::AddUrlFrontend(AddUrlService* add_url_service)

: add_url_service_(add_url_service) {

}

// AddUrlFrontend destructor–there's nothing to do here.

AddUrlFrontend::~AddUrlFrontend {

}

// HandleAddUrlFrontendRequest:

// Handles requests to /addurl by parsing the request,

// dispatching a backend request to an AddUrlService backend,

// and transforming the backend reply into an appropriate

// HTTP reply.

//

// Args:

// http_request–The raw HTTP request received by the server.

// http_reply–The raw HTTP reply to send in response.

void AddUrlFrontend::HandleAddUrlFrontendRequest(

const HTTPRequest* http_request, HTTPReply* http_reply) {

// Extract the query parameters from the raw HTTP request.

HTTPQueryParams query_params;

ExtractHttpQueryParams(http_request, &query_params);

// Get the 'url' and 'comment' query components.

// Default each to an empty string if they were not present

// in http_request.