利用BOOST，解释JSON

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首先从最简单的JSON脚本开始；

假设JSON脚本是：{"userId":"123456","userName":"Alex","company":"HugenessHard"}

这可能是最简单的JSON脚本，再简单就没办法说明问题了。

注：C++中双引号需加入转意符

#include <iostream>#include <boost/property_tree/ptree.hpp>#include <boost/property_tree/json_parser.hpp>#include <string>int main(int argc, char** argv){//NO.1 {"userId":"123456","userName":"Alex","company":"HugenessHard"}using namespace std;using namespace boost;using namespace boost::property_tree;ptree pt;string strJson = "{\"userId\":\"123456\",\"userName\":\"Alex\",\"company\":\"HugenessHard\"}";stringstream stream;stream << strJson;read_json(stream, pt);try{cout << "UserId:" << pt.get<string>("userId") << endl;cout << "UserName:" << pt.get<string>("userName") << endl;cout << "UserCompany:" << pt.get<string>("company") << endl;}catch (std::exception ex){cout << ex.what();}cin.get();return 0;}

输出结果：

UserId:123456

UserName:Alex

UserCompany:HugenessHard

--------------------------完美分割-----------------------------

假设上面的JSON脚本再加个子窜，client

JSON脚本将是：{"userId":"123456","userName":"Alex","company":"HugenessHard","client":[{"clientId":"1111","cname":"Mike","company":"Mikecompany"},{"clientId":"1111","cname":"Jack","company":"Jackcompany"}]}

注：为了简化程序，我就不加try/catch块了，现实中应catch异常，以防读取不存在的节点。

#include <iostream>#include <boost/property_tree/ptree.hpp>#include <boost/property_tree/json_parser.hpp>#include <string>int main(int argc, char** argv){//NO.2 {"userId":"123456","userName":"Alex","company":"HugenessHard","client":[{"clientId":"Mike","company":"Mikecompany"},{"clientId":"Jack","company":"Jackcompany"}]}using namespace std;using namespace boost;using namespace boost::property_tree;ptree pt, pt2;string strJson = "{\"userId\":\"123456\",\"userName\":\"Alex\",\"company\":\"HugenessHard\",\"client\":[{\"clientId\":\"1111\",\"cname\":\"Mike\",\"company\":\"Mikecompany\"},{\"clientId\":\"2222\",\"cname\":\"Jack\",\"company\":\"Jackcompany\"}]}";stringstream stream;stream << strJson;read_json(stream, pt);cout << "UserId:" << pt.get<string>("userId") << endl;cout << "UserName:" << pt.get<string>("userName") << endl;cout << "UserCompany:" << pt.get<string>("company") << endl;pt2 = pt.get_child("client");cout << "----Client----" << endl;for (ptree::iterator it = pt2.begin(); it != pt2.end(); ++it){cout << "ClientId:" << it->second.get<string>("clientId") << endl;cout << "ClientName:" << it->second.get<string>("cname") << endl;cout << "ClientCompany:" << it->second.get<string>("company") << endl;}cin.get();return 0;}

输出结果：

UserId:123456

UserName:Alex

UserCompany:HugenessHard

----Client----

ClientId:1111

ClientName:Mike

ClientCompany:Mikecompany

ClientId:2222

ClientName:Jack

ClientCompany:Jackcompany
总结：

ptree以JSON中的一对大括号为界为一个ptree对象

ptree的JSON对象中同样可以包括子对象，如例中的client节点，就是个子对象

client节点中存有2个客户信息。就需要用ptree的迭代器ptree::iterator，逐个读取子对象。

在读取节点时，应使和try块捕获异常。例如我们读取不存在的节点“age”

则会抛出异常 “No such node (age)”

另外，如果需要用宽字符集，可直接用wstring,wstringstream,wptree分别代替（类型名前加w）

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