rapidjson使用

爱被打了一巴掌 2022-05-17 07:09 171阅读 0赞

一，字符串json封装及及解析的实例

#include "rapidjson/document.h"
    #include "rapidjson/prettywriter.h"  
    #include "rapidjson/writer.h"
    #include "rapidjson/stringbuffer.h"
    #include <iostream>
    using namespace rapidjson;
    using namespace std;
    int main() 
    {
    
    //一，转json格式
        //1,获取Document对象
        Document doc;  
        doc.SetObject();    //key-value 相当与map
        //doc.Setvalue();        //数组型 相当与vector
        Document::AllocatorType &allocator=doc.GetAllocator(); //获取分配器
    
        //2，给doc对象赋值
        doc.AddMember("name","张山",allocator);
        
        //添加数组型数据
        Value array1(kArrayType);
        for(int i=0;i<3;i++)  
        {  
            Value int_object(kObjectType);  
            int_object.SetInt(i);  
            array1.PushBack(int_object,allocator);  
        }
        
        doc.AddMember("number",array1,allocator);
    
        //3，将doc对象的值写入字符串
        StringBuffer buffer;  
        //PrettyWriter<StringBuffer> writer(buffer);  //PrettyWriter是格式化的json，如果是Writer则是换行空格压缩后的json  
        Writer<StringBuffer> writer(buffer);
        doc.Accept(writer); 
    
        cout<<buffer.GetString()<<endl;
    
    //二，解析json格式
        //1，将json格式字符串转换
        string readdate;
        readdate = buffer.GetString();
        Document document;  
        document.Parse<0>(readdate.c_str());  
        
        //2,取出自己想要的值
        Value &node1=document["name"];  
        cout<<"name:"<<node1.GetString()<<endl; 
    
        Value &node2=document["number"];  
        cout<<"number: "<<endl;  
        if(node2.IsArray())  
        {  
            for(int i=0;i<node2.Size();i++)  
                cout<<'\t'<<node2[i].GetInt()<<endl;  
        }  
    
        return 0;
    }

二，文件json封装及解析的实例

**1 两个问题**

（1）标准json和非标准json：

标准json要求键必须都是双引号的字符串，而非标准json可以单引号。

例如：

\{a : 'abc'\}

\{'a' : 'abc'\}

\{a : "abc"\}

\{"a" : "abc"\}

只有第4个是标准json

（2）json中的\[\]与\{\}:

在 JSON 里 \[\] 是 Array \{\} 是Ojbect   
  
\[\] Array 的key 是 int  从0算起  
\{\} 的key 是 string   
  
var a= Array();   
a\[a.length\] = '3';   
a\[a.length\] = '4';   
a\[a.length\] = '5';   
  
a toJSON 后 ='\["3", "4", "5"\]'   
  
var a = new Object();   
  
a\['test1'\] = '3';   
a\['test2'\] = '4';   
a\['test3'\] = '5';   
  
a toJSON 后 = '\{"test1":"3", "test2":"4", "test3":"5"\}'

**2 rapidjson读写[测试][Link 1]**

下载rapidjson库，解压后关联到工程。

代码：

#include <iostream>  
    #include <string>  
    #include <fstream>  
    //包含rapidjson必要头文件,rapidjson文件夹拷贝到工程目录，或者设置include路径，或者加入到工程树  
    #include "rapidjson/document.h"  
    #include "rapidjson/filestream.h"  
    #include "rapidjson/prettywriter.h"  
    #include "rapidjson/stringbuffer.h"  
    using namespace std;  
    using namespace rapidjson;  //引入rapidjson命名空间  
      
    //写json文件  
    void json_write()  
    {  
        Document doc;  
        doc.SetObject();  
        Document::AllocatorType &allocator=doc.GetAllocator(); //获取分配器  
        //1.添加字符串对象  
        doc.AddMember("author","tashaxing",allocator);   
        //2.添加数组对象  
        Value array1(kArrayType);  
        for(int i=0;i<3;i++)  
        {  
            Value int_object(kObjectType);  
            int_object.SetInt(i);  
            array1.PushBack(int_object,allocator);  
        }  
        doc.AddMember("number",array1,allocator);  
        //3.添加复合对象  
        Value object(kObjectType);  
        object.AddMember("language1","C++",allocator);  
        object.AddMember("language2","java",allocator);  
        doc.AddMember("language",object,allocator);  
        //4.添加对象数组和复合对象的组合  
        Value array2(kArrayType);  
        Value object1(kObjectType);  
        object1.AddMember("hobby","drawing",allocator);  
        array2.PushBack(object1,allocator);  
        Value object2(kObjectType);  
        object2.AddMember("height",1.71,allocator);  
        array2.PushBack(object2,allocator);  
        doc.AddMember("information",array2,allocator);  
        StringBuffer buffer;  
        PrettyWriter<StringBuffer> pretty_writer(buffer);  //PrettyWriter是格式化的json，如果是Writer则是换行空格压缩后的json  
        doc.Accept(pretty_writer);  
        //打印到屏幕  
        cout<<"the json output:"<<endl;  
        cout<<buffer.GetString()<<endl;  
        //输出到文件  
        ofstream fout;  
        fout.open("test");    //可以使绝对和相对路径，用\\隔开目录，test, test.json, test.txt 都行，不局限于文件格式后缀，只要是文本文档  
        fout<<buffer.GetString();  
        fout.close();  
    }  
      
    //读json文件  
    void json_read()  
    {  
        cout<<"the json read:"<<endl;  
        ifstream fin;  
        fin.open("test");  
        string str;  
        string str_in="";  
        while(getline(fin,str))    //一行一行地读到字符串str_in中  
        {  
            str_in=str_in+str+'\n';  
        }  
        //解析并打印出来  
        Document document;  
        document.Parse<0>(str_in.c_str());  
      
        Value &node1=document["author"];  
        cout<<"author: "<<node1.GetString()<<endl;  
      
        Value &node2=document["number"];  
        cout<<"number: "<<endl;  
        if(node2.IsArray())  
        {  
            for(int i=0;i<node2.Size();i++)  
                cout<<'\t'<<node2[i].GetInt()<<endl;  
        }  
      
        Value &node3=document["language"];  
        cout<<"language: "<<endl;  
        Value &tmp=node3["language1"];  
        cout<<'\t'<<"language1: "<<tmp.GetString()<<endl;  
        tmp=node3["language2"];  
        cout<<'\t'<<"language2: "<<tmp.GetString()<<endl;  
      
        Value &node4=document["information"];  
        cout<<"information: "<<endl;  
        if(node4.IsArray())  
        {  
            int i=0;  
            Value &data=node4[i];   //注意，此处下表索引只能用变量，不能用常量，例如node[0]编译错误  
            cout<<'\t'<<"hobby: "<<data["hobby"].GetString()<<endl;  
            i=1;  
            data=node4[i];  
            cout<<'\t'<<"height: "<<data["height"].GetDouble()<<endl;  
        }  
      
    }  
    int main(int argc,char **argv)  
    {  
        //写、读 测试  
        json_write();  
        json_read();  
        return 0;  
    }

[Link 1]: http://lib.csdn.net/base/softwaretest