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rapidjson生成复杂的json串

{"name":"jack",//常规的"age":18,"sub":["a","b"],//value是数组"elp":[ {"a":"A","b":"B"},//value是一个数组且里面每个元素又是一个json格式{"c":"C","d":"D"},]
}

//#include "rapidjson/stringbuffer.h"
//#include "rapidjson/writer.h"#include <rapidjson/document.h>
#include <rapidjson/prettywriter.h>
#include <rapidjson/stringbuffer.h>#include <iostream>std::string build_json_msg(){rapidjson::Document doc;//生成DOM元素doc.SetObject();rapidjson::Document::AllocatorType& allocator = doc.GetAllocator();//生成一个分配器//构建键值对doc.AddMember("name","jack",allocator);doc.AddMember("age",18,allocator);//====构建数组元素====["1","2"]rapidjson::Value array_sub(rapidjson::kArrayType);//创建一个数组类型对象array_sub.PushBack("a",allocator);array_sub.PushBack("b",allocator);//================doc.AddMember("sub",array_sub,allocator);//====构建数组object===[{"1":2,},{}]rapidjson::Value array_json(rapidjson::kArrayType);rapidjson::Value obj(rapidjson::kObjectType);//每一个数组里面是一个json格式obj.AddMember("a","A",allocator);obj.AddMember("b","B",allocator);array_json.PushBack(obj,allocator);rapidjson::Value obj1(rapidjson::kObjectType);//每一个数组里面是一个json格式obj1.AddMember("c","C",allocator);obj1.AddMember("d","D",allocator);array_json.PushBack(obj1,allocator);
//            array_json.PushBack(obj1,allocator);doc.AddMember("elp",array_json,allocator);rapidjson::StringBuffer s;rapidjson::Writer<rapidjson::StringBuffer> writer(s);doc.Accept(writer);return std::string(s.GetString());}int main()
{std::string str_json = build_json_msg();std::cout<<str_json<<std::endl;std::cout<<"hello world"<<std::endl;return 0;
}

我用的qt,其中.pro如下：

QT -= guiCONFIG += c++11 console
CONFIG -= app_bundle# The following define makes your compiler emit warnings if you use
# any feature of Qt which as been marked deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0SOURCES += main.cppINCLUDEPATH += /data_2/project_202009/project/3rdparty/

程序跑起来打印如下：

{"name":"jack","age":18,"sub":["a","b"],"elp":[{"a":"A","b":"B"},{"c":"C","d":"D"}]}
hello world
按 <RETURN> 来关闭窗口...

在网站json.cn可以格式化显示json：

{"name":"jack","age":18,"sub":["a","b"],"elp":[{"a":"A","b":"B"},{"c":"C","d":"D"}]
}

在生成的时候我们需要几个十分重要的对象，Document、AllocatorType。刚开始的三行代码是比较固定的，先申明一个doc和一个分配器。

rapidjson::Document doc;//生成DOM元素
doc.SetObject();
rapidjson::Document::AllocatorType& allocator = doc.GetAllocator();//生成一个分配器

我们添加json元素主要通过doc.AddMember(key,value,分配器)的形式来生成。如果json格式很简单，那么代码也很简单，如下：

doc.AddMember("name","jack",allocator);
doc.AddMember("age",18,allocator);

但是，如果涉及到数组。就需要注意一下。首先，我们需要创建一个数组类型的对象。然后把数组里面的内容PushBack进去。最后同样通过doc.AddMember()添加进去。但是value却变成了array_sub.说明AddMember()的第二个参数，不仅可以是值还可以是对象。

rapidjson::Value array_sub(rapidjson::kArrayType);//创建一个数组类型对象array_sub.PushBack("a",allocator);array_sub.PushBack("b",allocator);//================
doc.AddMember("sub",array_sub,allocator);

同样，如果数组里面是json串，该怎么办呢？其实写法按着上面的逻辑来，看上面的代码，只不过把‘a’换成object类型的。具体写法如下：

//====构建数组object===[{"1":2,},{}]rapidjson::Value array_json(rapidjson::kArrayType);rapidjson::Value obj(rapidjson::kObjectType);//每一个数组里面是一个json格式obj.AddMember("a","A",allocator);obj.AddMember("b","B",allocator);array_json.PushBack(obj,allocator);rapidjson::Value obj1(rapidjson::kObjectType);//每一个数组里面是一个json格式obj1.AddMember("c","C",allocator);obj1.AddMember("d","D",allocator);array_json.PushBack(obj1,allocator);array_json.PushBack(obj1,allocator);doc.AddMember("elp",array_json,allocator);

读写json参考链接：https://www.cnblogs.com/fnlingnzb-learner/p/10334988.html