请帮助我将派生类反序列化为基类指针。我附上完整的源代码示例。
request.hpp(无配对 cpp 文件)
#ifndef REQUEST_HPP
#define REQUEST_HPP
#include <memory>
#include <string>
#include <boost/archive/xml_oarchive.hpp>
#include <boost/archive/xml_iarchive.hpp>
namespace demo {
namespace common {
class request {
public:
static const int INVALID_ID = -42;
request()
: id_(INVALID_ID), timestamp_(0), source_ip_("unknown") {};
request(int id, long timestamp, const std::string& source_ip)
: id_(id), timestamp_(timestamp), source_ip_(source_ip) {};
virtual ~request() {};
int id() const { return id_; }
long timestamp() const { return timestamp_; }
std::string source_ip() const { return source_ip_; }
protected:
int id_;
long timestamp_;
std::string source_ip_;
private:
friend class boost::serialization::access;
template<class Archive>
void serialize(Archive& ar, const unsigned version) {
ar & BOOST_SERIALIZATION_NVP(id_);
ar & BOOST_SERIALIZATION_NVP(timestamp_);
ar & BOOST_SERIALIZATION_NVP(source_ip_);
}
};
typedef std::shared_ptr<request> request_ptr;
}
};
#endif
command.hpp(派生类)
#ifndef COMMAND_HPP
#define COMMAND_HPP
#include <memory>
#include <string>
#include <boost/serialization/export.hpp>
#include <demo/common/request.hpp>
namespace demo {
namespace common {
class command : public request {
public:
command(): name_("untitled") {};
explicit command(const std::string& name) : name_(name) {};
virtual ~command() {};
virtual void execute();
std::string name() const { return name_; }
protected:
std::string name_;
private:
friend class boost::serialization::access;
template<class Archive>
void serialize(Archive& ar, const unsigned version) {
ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(request);
ar & BOOST_SERIALIZATION_NVP(name_);
}
};
typedef std::shared_ptr<command> command_ptr;
}
};
BOOST_CLASS_EXPORT_KEY(demo::common::command)
#endif
命令.cpp
#include "command.hpp"
#include <iostream>
BOOST_CLASS_EXPORT_IMPLEMENT(demo::common::command)
namespace demo {
namespace common {
void command::execute() {
std::cout << " I am '" + name_ +"' and I am executing..." << std::endl;
}
}
};
序列化器.hpp
#ifndef SERIALIZER_HPP
#define SERIALIZER_HPP
#include <sstream>
#include <string>
/* classes to serialize */
#include <demo/common/request.hpp>
#include <demo/common/command.hpp>
namespace demo {
namespace common {
class serializer {
public:
serializer() : {};
template<typename T>
std::string serialize(const T& t){
std::stringstream stream;
boost::archive::xml_oarchive archive(stream);
archive << BOOST_SERIALIZATION_NVP(t);
std::string serialized = stream.str();
return serialized;
}
template<typename T>
void deserialize(const std::string& serialized, T& t) {
std::stringstream stream(serialized);
boost::archive::xml_iarchive archive(stream);
archive >> BOOST_SERIALIZATION_NVP(t);
}
};
}
}
#endif
示例用法
#include <iostream>
#include <demo/common/serializer.hpp>
#include <demo/common/command.hpp>
using namespace std;
using namespace demo::common;
int main(){
serializer serializer_;
command r("123"); // <-- (1) my desired way of declaring
//request* r = new command("123"); <-- (2) replacing with this makes all work!
//command* r = new command("123"); <-- (3) replacing with this crashes the app, like (1)
std::string s = serializer_.serialize(r);
std::cout << s << std::endl;
request* rr = nullptr;
serializer_.deserialize(s, rr); //this throws an exception
command* rrr = dynamic_cast<command*>(rr);
rrr->execute();
}
我以为我做了所有需要做的事情,在任何类导出之前包含文件,所有默认构造函数初始化成员..
请注意,可序列化类和序列化器被编译为 lib 文件。然后该库在两个子项目中使用,这两个子项目可以访问 header 并链接该库。他们使用这些类相互通信,通过网络发送序列化对象。
为什么我无法将派生类反序列化为基类指针? 我正在使用 Boost 1.51 和 VC11。
最佳答案
问题:
我发现关于 Boost::serialization 导致我出现问题的两个主要问题如下:
- 堆栈上的对象与堆上的对象混合的序列化/反序列化。例如,如果您从堆栈上的对象序列化,然后尝试反序列化为指针(例如调用您的 load_construct_data<> ) 可能会出现异常。与相反的情况相同。
- 未正确链接导出内容。例如,如果您创建序列化模板/类并将它们放入 .lib 中,则导出可能无法正确链接/公开。这适用于链接到共享对象/DLL,然后使用它。
解决方案:
对于#1,我发现制定始终对指针进行序列化/反序列化的规则是最简单的。即使堆栈上的对象也可以在序列化时使用临时指针以允许此规则。例如:
// serialize
MyObject myobj;
std::ostringstream oss;
boost::archive::text_oarchive oa(oss);
MyObject* myObjPtr = &myObj;
oa << myObjPtr; // this is different than oa << myObj!!
std::string serialized = oss.str();
// deserialize
MyObject* myNewObjPtr;
std::stringstream iss(serialized);
boost::archive::text_iarchive ia(iss);
ia >> myNewObjPtr; // invokes new, don't forget to delete (or use smart ptrs!!!)
对于#2,只需创建一个包含所有导出的 .cpp 文件。将此 CPP 直接链接到您的模块中。换句话说,您将拥有一个带有一堆 BOOST_CLASS_EXPORT_IMPLMENT() 的 .cpp:
BOOST_CLASS_EXPORT_IMPLEMENT(MyObject);
// ...
更完整的示例:
下面是一个更完整的示例,显示了一些使用非侵入式模板的序列化技巧。侵入式成员方法将非常相似:
MyObject.h
// Can be broken into MyObject.h, MyObject.cpp, MyObjectSerialization.h for example as well.
// This stuff can live in your .lib
#include <boost/serialization/export.hpp>
#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
// assume this class contains GetSomeMember() returning SomeMemberType
class MyObject { /* ... */ };
BOOST_CLASS_EXPORT_KEY(MyObject);
namespace boost { namespace serialization {
template<class Archive>
void serialize(Archive& ar, MyObject& myObj, const unsigned int version)
{
ar & myObj.m_someMember;
}
template<class Archive>
inline void save_construct_data(Archive& ar, const MyObject* myObj, const unsigned int version)
{
ar & boost::serialization::make_nvp("SomeMemberType", static_cast<const SomeMemberType&>(myObj->GetSomeMember()));
}
template<class Archive>
inline void load_construct_data(Archive& ar, MyObject* myObj, const unsigned int version)
{
SomeMemberType t;
ar & boost::serialization::make_nvp("SomeMemberType", t);
::new(myObj)MyObject(t);
}
} } // end boost::serialization ns
MyObjectExports.cpp
// This file must be explicitly linked into your module(s) that use serialization.
// This means your executable or shared module/DLLs
#include <boost/serialization/export.hpp>
#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
#include "MyObject.h"
BOOST_CLASS_EXPORT_IMPLEMENT(MyObject);
关于c++ - Boost 将派生类反序列化为基类指针,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/13089884/