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jsoncpp安装与使用 cmake安装 升级g++ gcc支持c++11

  来了新公司之后,现在的json解析真的很难用,举个例子,假如想删除一个对象,要重新生成,去掉要删除的,其余的要组装上。很怀念之前用的jsoncpp,想引进来,就研究一下。

 下载和安装

  下载

    从github,直接搜jsoncpp就能搜到,第一个就是,懒得搜直接给你地址:https://github.com/open-source-parsers/jsoncpp

  安装

    python amalgamate.py

    然后执行

    cmake CMakeLists.txt

    没有安装cmake,可以参考这篇博客:https://www.cnblogs.com/liudw-0215/p/9877290.html

    新版cmake对gcc版本,用的centos6.5,是需要升级的,可以参考这篇博客:https://blog.csdn.net/centnetHY/article/details/81284657,但升级gcc,比较耗时。

    然后再执行

    make 

    如果想把头文件和库安装到系统目录,就执行

    make install

    

    使用

    序列化新旧接口

    代码如下:

    

#include "json/json.h"
#include <iostream>
/** \brief Write a Value object to a string.
 * Example Usage:
 * $g++ stringWrite.cpp -ljsoncpp -std=c++11 -o stringWrite
 * $./stringWrite
 * {
 *     "action" : "run",
 *     "data" :
 *     {
 *         "number" : 1
 *     }
 * }
 */
int main() {
  Json::Value root;
  Json::Value data;
  constexpr bool shouldUseOldWay = false;
  root["action"] = "run";
  data["number"] = 1;
  root["data"] = data;

  if (shouldUseOldWay) {
    Json::FastWriter writer;
    const std::string json_file = writer.write(root);
    std::cout << json_file << std::endl;
  } else {
    Json::StreamWriterBuilder builder;
    const std::string json_file = Json::writeString(builder, root);
    std::cout << json_file << std::endl;
  }
  return EXIT_SUCCESS;
}
stringWrite.cpp

      

    会警告,is deprecated: Use StreamWriterBuilder instead [-Wdeprecated-declarations],因为这旧的接口,如果不想报警告,可以在代码最上面加上下面代码:    

#if defined(__GNUC__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
#elif defined(_MSC_VER)
#pragma warning(disable : 4996)
#endif

  代码如下:

    

#if defined(__GNUC__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
#elif defined(_MSC_VER)
#pragma warning(disable : 4996)
#endif

#include "json/json.h"
#include <iostream>
/** \brief Write a Value object to a string.
 *  * Example Usage:
 *  * $g++ stringWrite.cpp -ljsoncpp -std=c++11 -o stringWrite
 *  * $./stringWrite
 *  * {
 *  *     "action" : "run",
 *  *     "data" :
 *  *     {
 *  *         "number" : 1
 *  *     }
 *  * }
 *  */
int main() {
    Json::Value root;
    Json::Value data;
    constexpr bool shouldUseOldWay = false;
    root["action"] = "run";
    data["number"] = 1;
    root["data"] = data;

    if (shouldUseOldWay) {
        Json::FastWriter writer;
        const std::string json_file = writer.write(root);
        std::cout << json_file << std::endl;
    } else {
        Json::StreamWriterBuilder builder;
        const std::string json_file = Json::writeString(builder, root);
        std::cout << json_file << std::endl;
    }
    return EXIT_SUCCESS;
}
stringWrite.cpp

 

    反序列化新旧接口

    

#include "json/json.h"
#include <iostream>
/**
 * \brief Parse a raw string into Value object using the CharReaderBuilder
 * class, or the legacy Reader class.
 * Example Usage:
 * $g++ readFromString.cpp -ljsoncpp -std=c++11 -o readFromString
 * $./readFromString
 * colin
 * 20
 */
int main() {
  const std::string rawJson = R"({"Age": 20, "Name": "colin"})";
  const auto rawJsonLength = static_cast<int>(rawJson.length());
  constexpr bool shouldUseOldWay = false;
  JSONCPP_STRING err;
  Json::Value root;

  if (shouldUseOldWay) {
    Json::Reader reader;
    reader.parse(rawJson, root);
  } else {
    Json::CharReaderBuilder builder;
    const std::unique_ptr<Json::CharReader> reader(builder.newCharReader());
    if (!reader->parse(rawJson.c_str(), rawJson.c_str() + rawJsonLength, &root,
                       &err)) {
      std::cout << "error" << std::endl;
      return EXIT_FAILURE;
    }
  }
  const std::string name = root["Name"].asString();
  const int age = root["Age"].asInt();

  std::cout << name << std::endl;
  std::cout << age << std::endl;
  return EXIT_SUCCESS;
}
readFromString.cpp

 

  

posted on 2020-08-28 17:08  逆袭之路666  阅读(92)  评论(0编辑  收藏

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