从 Ignite 中读取 Cassandra 的 Blob答案

【问题标题】：Reading Cassandra's Blob from Ignite从 Ignite 中读取 Cassandra 的 Blob
【发布时间】：2018-10-05 18:05:21
【问题描述】：

我正在尝试从 Ignite 读取 Cassandra 表的内容（充当缓存）。下表如下：：

CREATE TABLE test.epc_table (
    imsi text PRIMARY KEY,
    data blob
)

数据块用于存储 C++ 类对象（类名称为“RtCassEpcTableDataVo”）。

我正在尝试使用下面的c++程序来传递'imsi'的值并获取对应的'data'。

#include "ignite/ignite.h"
#include "ignite/ignition.h"


#include <iostream>
#include<string>

#include "RtCassEpcTableDataVo.hpp"

using namespace ignite;
using namespace cache;
using namespace std;

int main()
{
        IgniteConfiguration cfg;

        cfg.springCfgPath = "/home/ignite/apache-ignite-fabric-2.4.0-bin/config/cassandra-config.xml";

        try
        {
                // Start a node.
                Ignite ignite = Ignition::Start(cfg);
Cache<string,RtCassEpcTableDataVo> cache = ignite.GetCache<std::string, RtCassEpcTableDataVo>("cache1");

cout<<endl<<"Enter IMSI : ";
string l_imsi;
getline(cin>>ws,l_imsi);

RtCassEpcTableDataVo l_blob=cache.Get(l_imsi);
                Ignition::StopAll(false);
        }
        catch (IgniteError& err)
        {
                std::cout << "An error occurred: " << err.GetText() << std::endl;

                return err.GetCode();
        }

        std::cout << std::endl;

        return 0;
}

但是，我遇到了编译错误。

In file included from /usr/local/include/ignite/impl/binary/binary_writer_impl.h:32:0,
                 from /usr/local/include/ignite/binary/binary_raw_writer.h:30,
                 from /home/ignite/apache-ignite-fabric-2.4.0-bin/platforms/cpp/core/include/ignite/cache/query/query_scan.h:29,
                 from /home/ignite/apache-ignite-fabric-2.4.0-bin/platforms/cpp/core/include/ignite/impl/cache/cache_impl.h:21,
                 from /home/ignite/apache-ignite-fabric-2.4.0-bin/platforms/cpp/core/include/ignite/impl/ignite_impl.h:27,
                 from /home/ignite/apache-ignite-fabric-2.4.0-bin/platforms/cpp/core/include/ignite/ignite.h:26,
                 from sample.cpp:1:
/usr/local/include/ignite/impl/binary/binary_utils.h: In instantiation of âstatic T ignite::impl::binary::BinaryUtils::GetDefaultValue() [with T = RtCassEpcTableDataVo]â:
/home/ignite/apache-ignite-fabric-2.4.0-bin/platforms/cpp/core/include/ignite/impl/operations.h:349:62:   required from âvoid ignite::impl::Out1Operation<T>::SetNull() [with T = RtCassEpcTableDataVo]â
sample.cpp:72:1:   required from here
/usr/local/include/ignite/impl/binary/binary_utils.h:475:59: error: âGetNullâ is not a member of âignite::binary::BinaryType<RtCassEpcTableDataVo>â
                     ignite::binary::BinaryType<T>::GetNull(res);
                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/local/include/ignite/impl/binary/binary_object_impl.h:31:0,
                 from /usr/local/include/ignite/impl/binary/binary_writer_impl.h:35,
                 from /usr/local/include/ignite/binary/binary_raw_writer.h:30,
                 from /home/ignite/apache-ignite-fabric-2.4.0-bin/platforms/cpp/core/include/ignite/cache/query/query_scan.h:29,
                 from /home/ignite/apache-ignite-fabric-2.4.0-bin/platforms/cpp/core/include/ignite/impl/cache/cache_impl.h:21,
                 from /home/ignite/apache-ignite-fabric-2.4.0-bin/platforms/cpp/core/include/ignite/impl/ignite_impl.h:27,
                 from /home/ignite/apache-ignite-fabric-2.4.0-bin/platforms/cpp/core/include/ignite/ignite.h:26,
                 from sample.cpp:1:
/usr/local/include/ignite/impl/binary/binary_reader_impl.h: In instantiation of âvoid ignite::impl::binary::BinaryReaderImpl::ReadTopObject0(T&) [with T = RtCassEpcTableDataVo]â:
/usr/local/include/ignite/impl/binary/binary_type_impl.h:100:17:   required from âstatic T ignite::binary::ReadHelper<T>::Read(R&) [with R = ignite::impl::binary::BinaryReaderImpl; T = RtCassEpcTableDataVo]â
/usr/local/include/ignite/impl/binary/binary_reader_impl.h:887:63:   required from âT ignite::impl::binary::BinaryReaderImpl::ReadTopObject() [with T = RtCassEpcTableDataVo]â
/home/ignite/apache-ignite-fabric-2.4.0-bin/platforms/cpp/core/include/ignite/impl/operations.h:344:21:   required from âvoid ignite::impl::Out1Operation<T>::ProcessOutput(ignite::impl::binary::BinaryReaderImpl&) [with T = RtCassEpcTableDataVo]â
sample.cpp:72:1:   required from here
/usr/local/include/ignite/impl/binary/binary_reader_impl.h:1001:40: error: âReadâ is not a member of âBType {aka ignite::binary::BinaryType<RtCassEpcTableDataVo>}â
                             BType::Read(reader, res);
                             ~~~~~~~~~~~^~~~~~~~~~~~~
/usr/local/include/ignite/impl/binary/binary_reader_impl.h: In instantiation of âT ignite::impl::binary::BinaryReaderImpl::GetNull() const [with T = RtCassEpcTableDataVo]â:
/usr/local/include/ignite/impl/binary/binary_reader_impl.h:905:45:   required from âvoid ignite::impl::binary::BinaryReaderImpl::ReadTopObject0(T&) [with T = RtCassEpcTableDataVo]â
/usr/local/include/ignite/impl/binary/binary_type_impl.h:100:17:   required from âstatic T ignite::binary::ReadHelper<T>::Read(R&) [with R = ignite::impl::binary::BinaryReaderImpl; T = RtCassEpcTableDataVo]â
/usr/local/include/ignite/impl/binary/binary_reader_impl.h:887:63:   required from âT ignite::impl::binary::BinaryReaderImpl::ReadTopObject() [with T = RtCassEpcTableDataVo]â
/home/ignite/apache-ignite-fabric-2.4.0-bin/platforms/cpp/core/include/ignite/impl/operations.h:344:21:   required from âvoid ignite::impl::Out1Operation<T>::ProcessOutput(ignite::impl::binary::BinaryReaderImpl&) [with T = RtCassEpcTableDataVo]â
sample.cpp:72:1:   required from here
/usr/local/include/ignite/impl/binary/binary_reader_impl.h:1024:59: error: âGetNullâ is not a member of âignite::binary::BinaryType<RtCassEpcTableDataVo>â
                     ignite::binary::BinaryType<T>::GetNull(res);
                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/local/include/ignite/impl/binary/binary_writer_impl.h:30:0,
                 from /usr/local/include/ignite/binary/binary_raw_writer.h:30,
                 from /home/ignite/apache-ignite-fabric-2.4.0-bin/platforms/cpp/core/include/ignite/cache/query/query_scan.h:29,
                 from /home/ignite/apache-ignite-fabric-2.4.0-bin/platforms/cpp/core/include/ignite/impl/cache/cache_impl.h:21,
                 from /home/ignite/apache-ignite-fabric-2.4.0-bin/platforms/cpp/core/include/ignite/impl/ignite_impl.h:27,
                 from /home/ignite/apache-ignite-fabric-2.4.0-bin/platforms/cpp/core/include/ignite/ignite.h:26,
                 from sample.cpp:1:
/usr/local/include/ignite/impl/binary/binary_id_resolver.h: In instantiation of âint32_t ignite::impl::binary::TemplatedBinaryIdResolver<T>::GetTypeId() [with T = RtCassEpcTableDataVo; int32_t = int]â:
sample.cpp:72:1:   required from here
/usr/local/include/ignite/impl/binary/binary_id_resolver.h:88:68: error: âGetTypeIdâ is not a member of âignite::binary::BinaryType<RtCassEpcTableDataVo>â
                     return ignite::binary::BinaryType<T>::GetTypeId();
                            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~
/usr/local/include/ignite/impl/binary/binary_id_resolver.h: In instantiation of âint32_t ignite::impl::binary::TemplatedBinaryIdResolver<T>::GetFieldId(int32_t, const char*) [with T = RtCassEpcTableDataVo; int32_t = int]â:
sample.cpp:72:1:   required from here
/usr/local/include/ignite/impl/binary/binary_id_resolver.h:94:73: error: âGetFieldIdâ is not a member of âignite::binary::BinaryType<RtCassEpcTableDataVo>â
                         return ignite::binary::BinaryType<T>::GetFieldId(name);
                                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~

persistance-settings.xml如下：

<persistence keyspace="test" table="epc_table">
    <keyPersistence class="java.lang.String" strategy="PRIMITIVE" column="imsi"/>
    <valuePersistence column="data" />
</persistence>

我不明白为什么在其他表上使用相同的程序时（在 cpp 和 persistence-setting.xml 中进行了一些小的更改），即

CREATE TABLE test.table2 (
    imsi text PRIMARY KEY,
    data int
)

继续：Integrating Apache Cassandra with Apache Ignite

【问题讨论】：

标签： c++ cassandra ignite cassandra-3.0

【解决方案1】：

您似乎没有为您的类型RtCassEpcTableDataVo 提供BinaryType 模板的特化。如下所示：

class RtCassEpcTableDataVo {
    friend struct ignite::binary::BinaryType<RtCassEpcTableDataVo>;
    ...
}

template<> struct ignite::binary::BinaryType<RtCassEpcTableDataVo> {
  static void Write(BinaryWriter& writer, const RtCassEpcTableDataVo& obj) {
    // writing data
    // writer.Write...("attributename", obj.GetAttribute());
  }    

  static void Read(BinaryReader& reader, RtCassEpcTableDataVo& dst) {
      // reading data
      // dst.attribute = reader.Read...("attributename");
  }

  ...
}

全面的描述和示例可以在这里找到：Object Serialization

【讨论】：