C++下最好的json库必然是MiloYip大神写的rapidjson库啦~ 连cocos2dx官方都把这个库集成进去了
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"}'
2rapidjson读写测试
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; }
输出的json:
{ "author": "tashaxing","number": [ 0,1,2 ],"language": { "language1": "C++","language2": "java" },"information": [ { "hobby": "drawing" },{ "height": 1.71 } ] }