C++解析Json字符串問題！

#include <iostream>

#include "json/json.h"

using namespace std;

int main()

{

//字符串

const char * str =

"{\"praenomen\":\"Gaius\",\"nomen\":\"Julius\",\"cognomen\":\"Caezar\","

"\"born\":-100,\"died\":-44}" ;

Json::Reader reader;

Json::Value root;

//從字符串中讀取數據

if (reader.parse(str,root))

{

string praenomen = root[ "praenomen" ].asString();

string nomen = root[ "nomen" ].asString();

string cognomen = root[ "cognomen" ].asString();

int born = root[ "born" ].asInt();

int died = root[ "died" ].asInt();

cout << praenomen + " " + nomen + " " + cognomen

<< " was born in year " << born

<< ", died in year " << died << endl;

}

return 0;

}

makefile文件

LIB=-L /usr/local/lib/libjson/ -ljson_linux- gcc -4.4.7_libmt

a: a.o

g++ -o a -std=c++0x a.o $(LIB)

a.o: a.cpp

g++ -c a.cpp

clean:

rm -rf a.o a

二、從文件中讀取JSON

PersonalInfo.json（壹個存儲了JSON格式字符串的文件）

{

"name" : "Tsybius" ,

"age" :23,

"sex_is_male" : true ,

"partner" :

{

"partner_name" : "Galatea" ,

"partner_age" :21,

"partner_sex_is_male" : false

},

"achievement" :[ "ach1" , "ach2" , "ach3" ]

}

#include <iostream>

#include <fstream>

#include "json/json.h"

using namespace std;

int main()

{

Json::Reader reader;

Json::Value root;

//從文件中讀取

ifstream is;

is.open( "PersonalInfo.json" , ios::binary);

if (reader.parse(is,root))

{

//讀取根節點信息

string name = root[ "name" ].asString();

int age = root[ "age" ].asInt();

bool sex_is_male = root[ "sex_is_male" ].asBool();

cout << "My name is " << name << endl;

cout << "I'm " << age << " years old" << endl;

cout << "I'm a " << (sex_is_male ? "man" : "woman" ) << endl;

//讀取子節點信息

string partner_name = root[ "partner" ][ "partner_name"].asString();

int partner_age = root[ "partner" ][ "partner_age" ].asInt();

bool partner_sex_is_male = root[ "partner" ]["partner_sex_is_male" ].asBool();

cout << "My partner's name is " << partner_name << endl;

cout << (partner_sex_is_male ? "he" : "she" ) << " is "

<< partner_age << " years old" << endl;

//讀取數組信息

cout << "Here's my achievements:" << endl;

for ( int i = 0; i < root[ "achievement" ].size(); i++)

{

string ach = root[ "achievement" ][i].asString();

cout << ach << '\t' ;

}

cout << endl;

cout << "Reading Complete!" << endl;

}

is.close();

return 0;

}

makefile

LIB=-L /usr/local/lib/libjson/ -ljson_linux- gcc -4.4.7_libmt

a: a.o

g++ -o a -std=c++0x a.o $(LIB)

a.o: a.cpp

g++ -c a.cpp

clean:

rm -rf a.o a

三、將信息保存為JSON格式

a.cpp

#include <iostream>

#include <fstream>

#include "json/json.h"

using namespace std;

int main()

{

//根節點

Json::Value root;

//根節點屬性

root[ "name" ] = Json::Value( "Tsybius" );

root[ "age" ] = Json::Value(23);

root[ "sex_is_male" ] = Json::Value( true );

//子節點

Json::Value partner;

//子節點屬性

partner[ "partner_name" ] = Json::Value( "Galatea" );

partner[ "partner_age" ] = Json::Value(21);

partner[ "partner_sex_is_male" ] = Json::Value( false );

//子節點掛到根節點上

root[ "partner" ] = Json::Value(partner);

//數組形式

root[ "achievement" ].append( "ach1" );

root[ "achievement" ].append( "ach2" );

root[ "achievement" ].append( "ach3" );

//直接輸出

cout << "FastWriter:" << endl;

Json::FastWriter fw;

cout << fw.write(root) << endl << endl;

//縮進輸出

cout << "StyledWriter:" << endl;

Json::StyledWriter sw;

cout << sw.write(root) << endl << endl;

//輸出到文件

ofstream os;

os.open( "PersonalInfo" );

os << sw.write(root);

os.close();

return 0;

}

makefile

LIB=-L /usr/local/lib/libjson/ -ljson_linux- gcc -4.4.7_libmt

a: a.o

g++ -o a -std=c++0x a.o $(LIB)

a.o: a.cpp

g++ -c a.cpp

clean:

rm -rf a.o a

{

"achievement" : [ "ach1" , "ach2" , "ach3" ],

"age" : 23,

"name" : "Tsybius" ,

"partner" : {

"partner_age" : 21,

"partner_name" : "Galatea" ,

"partner_sex_is_male" : false

},

"sex_is_male" : true

}