4

我正在尝试做的,利用 gSOAP:

  1. 在 XML 模式中定义数据结构
  2. 使用 wsdl2h 和 soapcpp2 生成代表这些结构的 C++ 类
  3. 从 C++ 读取和写入 XML 中的这些结构

请注意,此时我没有使用 Web 服务,我只是对 XML 数据绑定感兴趣。

如果我的课程看起来像:

类基{ ... }

Der1 类:公共基础 { .. }

Der2 类:公共基础 { ... }

然后我可以使用以下方法序列化 Base 对象(实际上可能是派生类型之一):

std::ofstream myFile;
myFile.open("output.out");
ctx.os = &myFile; 

Der1 obj; // or Der2 obj...
// ... populate obj

if (soap_write_Base(ctx, dynamic_cast<Base*>(&obj)) == SOAP_OK)
{ 
  std::cout << "message serialized" << std::endl;
} else 
{
  soap_print_fault(ctx, stderr);
}

并使用反序列化:

std::ifstream myFile;
myFile.open("output.out");

ctx.is = &myFile;
Der1 obj;

if (soap_read_Der1(ctx, &obj) == SOAP_OK)
{
  std::cout << "message deserialized" << std::endl;
  printMessage(msg); //debug
} else 
{
  soap_print_fault(ctx, stderr);
}

其中 ctx 是指向soap上下文的指针,声明为:

soap* ctx = soap_new2(SOAP_XML_STRICT, SOAP_XML_INDENT);

代码的其他地方。

谁能告诉我如何更改上面的反序列化代码以便能够在不预先知道它是 Der1、Der2 还是 Base 对象的情况下读取对象?

谢谢!

4

1 回答 1

1

您需要做几件事。

首先,构建您的 C++ 对象,以便它们派生自xsd__anyType(上的-p选项wsdl2h

当你编译你的代码时,定义WITH_NO_IO这样WITH_NO_HTTP你就不会得到默认的 gSoap HTTP 和 IO 调用。

然后,创建一个Serializer类(请原谅关于 XML 的咆哮):

#pragma once
#include <memory>

namespace MyLib
{
    class SerializerImpl;
    class xsd__anyType;
    class Serializer
    {
        std::shared_ptr<SerializerImpl> ser;
    public:
        Serializer();
        Serializer(Serializer const &) = default;
        Serializer(Serializer &&o) : ser(std::forward<Serializer>(o).ser) { }
        ~Serializer() = default;

        Serializer &operator=(Serializer const& rhs) = default;
        Serializer &operator=(Serializer && rhs)
        {
            ser = std::forward<Serializer>(rhs).ser;
            return *this;
        }

        // Serialize 'value' into 'out'.
        void Serialize(xsd__anyType const &value, std::ostream &out);

        // Returns a shared pointer to the xsd_anyType that comes in 'in'.
        // The shared_ptr returned contains a custom deleter because gSoap ties
        // allocated values to the gSoap context used to deserialize it in the
        // first place. I think that was an attempt at adding some kind of
        // garbage collection so one didn't have to worry about deleting it except,
        // of course, that fails if you get rid of the context prior to the
        // end of the life of the deserialized value. Nobody does XML C++ bindings
        // right. XML sucks and C++ doesn't and it is hard to translate suck to 
        // non-suck.
        std::shared_ptr<xsd__anyType> Deserialize(std::istream &in);
    };
}

实现看起来像:

#include "MyLibH.h"
#include "stdsoap2.h"
#include "Serializer.h"

namespace MyLib
{
    static int fsend(struct soap* ctx, char const *buf, size_t len)
    {
        if (!ctx->os)
        {
            throw std::logic_error("soap.fsend the struct soap 'os' member must be set.");
        }

        ctx->os->write(buf, len);
        return SOAP_OK;
    }

    static size_t frecv(struct soap* ctx, char* buf, size_t len)
    {
        if (!ctx->is)
        {
            throw std::logic_error("soap.fsend the struct soap 'is' member must be set.");
        }

        ctx->is->read(buf, len);
        return ctx->is->gcount();
    }

    static SOAP_SOCKET fopen(struct soap*, const char*, const char*, int)
    {
        throw std::logic_error("soap.fopen not implemented for Serializer.");
    }

    static int fclose(struct soap *ctx)
    {
        return SOAP_OK;
    }

    static int fclosesocket(struct soap*, SOAP_SOCKET)
    {
        throw std::logic_error("soap.fclosesocket not implemented for Serializer.");
    }

    static int fshutdownsocket(struct soap*, SOAP_SOCKET, int)
    {
        throw std::logic_error("soap.fshutdownsocket not implemented for Serializer.");
    }

    static SOAP_SOCKET faccept(struct soap*, SOAP_SOCKET, struct sockaddr*, int *n)
    {
        throw std::logic_error("soap.faccept not implemented for Serializer.");
    }


    class SerializerImpl
    {
        struct soap mutable soap;
    public:
        SerializerImpl();
        ~SerializerImpl();
        struct soap *ctx() const { return &soap; }
    };

    SerializerImpl::SerializerImpl()
    {
        soap_init(&soap);

        // compiled with WITH_NOIO so set these function pointers
        soap.fsend = fsend;
        soap.frecv = frecv;
        soap.fopen = fopen;
        soap.fclose = fclose;
        soap.fclosesocket = fclosesocket;
        soap.fshutdownsocket = fshutdownsocket;
        soap.fpoll = nullptr;
        soap.faccept = faccept;

        // Set input/output mode
        soap_imode(&soap, SOAP_ENC_XML);
        soap_set_omode(&soap, SOAP_XML_INDENT);
    }


    SerializerImpl::~SerializerImpl()
    {
        // remove deserialized class instances (C++ objects)
        soap_destroy(&soap);

        // clean up and remove deserialized data 
        soap_end(&soap);

        // detach context (last use and no longer in scope)
        soap_done(&soap);
    }

    Serializer::Serializer() : ser(std::make_shared<SerializerImpl>())
    {
    }

    void Serializer::Serialize(xsd__anyType const& value, std::ostream &out)
    {
        soap_begin(ser->ctx());
        ser->ctx()->is = &in;
        soap_free_temp(ser->ctx());
        int type;
        int err;
        char errbuf[200];
        if ((err = soap_begin_recv(ser->ctx())) != SOAP_OK)
        {
            _snprintf_s(
                errbuf, 
                sizeof(errbuf), 
                _TRUNCATE, 
                "Serializer::Deserialize failed soap_begin_recv: %d", 
                err);
            errbuf[sizeof(errbuf) - 1] = 0;
            throw std::exception(errbuf);
        }

        // Create a deleter for the element returned from 'soap_getelement()'
        auto serializerImpl = this->ser;
        auto deleteElement = [serializerImpl](void *toDelete)
        {
            soap_dealloc(serializerImpl->ctx(), toDelete);
        };

        // parse the XML into an element
        std::unique_ptr<void, decltype(deleteElement)>
            res(soap_getelement(ser->ctx(), &type), deleteElement);
        if (!res)
        {
            // populate ser->ctx()->msgbuf with more detailed information
            soap_set_fault(ser->ctx());
            if (ser->ctx()->msgbuf)
            {
                _snprintf_s(
                    errbuf, 
                    sizeof(errbuf), 
                    _TRUNCATE, 
                    "Serializer::Deserialize failed soap_getelement: %s",
                    ser->ctx()->msgbuf);
            }
            else
            {
                _snprintf_s(
                    errbuf, 
                    sizeof(errbuf), 
                    _TRUNCATE, 
                    "Serializer::Deserialize failed soap_getelement: %d",
                    ser->ctx()->error);
            }

            errbuf[sizeof(errbuf) - 1] = 0;
            throw std::exception(errbuf);
        }

        if ((err = soap_end_recv(ser->ctx())) != SOAP_OK)
        {
            _snprintf_s(
                errbuf, 
                sizeof(errbuf), 
                _TRUNCATE, 
                "Serializer::Deserialize failed soap_end_recv: %d", 
                err);
            errbuf[sizeof(errbuf) - 1] = 0;
            throw std::exception(errbuf);
        }
        // anything that can be cast as an xml_Any gets cast here
        switch (type)
        {
         case SOAP_TYPE_MyLib_ns1__FooType:
         case SOAP_TYPE_MyLib_ns1__BarType:
         case SOAP_TYPE_MyLib_ns1__BazType:
            // In theory, res is a subclass of xsd_anyType, so cast 
            // it here as if it was
            auto anyType = static_cast<xsd__anyType *>(res.release());

            // build a shared pointer with the custom deleter that keeps serializerImpl
            auto ret = std::shared_ptr<xsd__anyType>(anyType, deleteElement);
            return ret;
        }

        _snprintf_s(
            errbuf, 
            sizeof(errbuf), 
            _TRUNCATE, 
            "Serializer::Deserialize failed - "
            "unsupported cast of type %d to xsd__anyType", 
            type);
        errbuf[sizeof(errbuf) - 1] = 0;
        throw std::exception(errbuf);
    }
}

使用这个类,您可以创建一个Serializer ser;then doser.Serialize(myEntity, myOutputStream);auto myEntity = ser.Deserialize(myInputStream);.

Deserialize()您可以在它调用的方法中看到多态反序列化的秘密,该方法soap_getelement()为它可以反序列化的任何类型返回一个 void 指针。然后,如果类型是已知基于 a 的类型xsd__anyType,那么它会shared_ptr<xsd__anyType>使用自定义删除方法强制转换为 a ,该方法保留struct soap上下文,以便它可以以适当的 gSoap 方式删除。转换为的能力xsd__anyType是我们告诉wsdl2h使用选项从该类型派生所有类型的原因-p

请注意,要让它为我工作,我必须创建一些其他功能。wsdl2h用and构建源代码soapcpp2的方式WITH_NOGLOBAL得到了定义。这导致了一些未定义的功能。我通过以下方式进行定义:

#include "MyLib3.nsmap"

SOAP_FMAC3 const char ** SOAP_FMAC4 soap_faultcode(struct soap *soap)
{
    static char const *ret;
    ret = nullptr;
    return &ret;
}

SOAP_FMAC3 const char ** SOAP_FMAC4 soap_faultsubcode(struct soap *soap)
{
    static char const *ret;
    ret = nullptr;
    return &ret;
}

SOAP_FMAC3 const char ** SOAP_FMAC4 soap_faultstring(struct soap *soap)
{
    static char const *ret;
    ret = nullptr;
    return &ret;
}

SOAP_FMAC3 const char ** SOAP_FMAC4 soap_faultdetail(struct soap *soap)
{
    static char const *ret;
    ret = nullptr;
    return &ret;
}

SOAP_FMAC3 const char * SOAP_FMAC4 soap_check_faultsubcode(struct soap *soap)
{
    return nullptr;
}

SOAP_FMAC3 const char * SOAP_FMAC4 soap_check_faultdetail(struct soap *soap)
{
    return nullptr;
}

SOAP_FMAC3 void SOAP_FMAC4 soap_serializefault(struct soap *soap)
{
}

SOAP_FMAC3 void SOAP_FMAC4 soap_serializeheader(struct soap *soap)
{
}

SOAP_FMAC3 int SOAP_FMAC4 soap_putheader(struct soap *soap)
{
    return SOAP_OK;
}

SOAP_FMAC3 int SOAP_FMAC4 soap_getfault(struct soap *soap)
{
    return SOAP_OK;
}

SOAP_FMAC3 int SOAP_FMAC4 soap_putfault(struct soap *soap)
{
    return SOAP_OK;
}

SOAP_FMAC3 int SOAP_FMAC4 soap_getheader(struct soap *soap)
{
    return SOAP_OK;
}
于 2015-06-10T23:30:02.810 回答