更多API参考jsoncpp头文件
1 jsoncpp的api简要说明
1,解析(json字符串转为对象)
std::string strDataJson;
Json::Reader JReader;
Json::Value JObject;
if (!JReader.parse(strDataJson, JObject))
{
cerr << "parse json error." << endl;
return bSuccess;
}
2,读取
std::string strMsg = JRec["msg"].asString();
int nRetCode = JRec["ret"]..asInt();
Json::Value JList = JRec["data"]["list"];
int nSize = JList.size();
获取错误信息： JReader.getFormatedErrorMessages()
3,增加或修改
JRoot["stringdata"] = Json::Value("msg");
JRoot["intdata"] = Json::Value(10);
4,删除
JValue.removeMember("toberemove");
5,对象转为字符串
//输出无格式json字符串
Json::FastWriter fast_writer;
strJRecList = fast_writer.write(JRoot);
//格式化之后的json,有回车换行符
std::string strOut = JRoot.toStyledString(）；
转自;http://my.oschina.net/chenleijava/blog/144312
6各种json子类型的使用
(1)json Object
for (Json::ValueIterator iter=groups_config.begin(); iter!=groups_config.end();iter++) {
Json::Value client_dict = (*iter)["clients"];
string topic_recresult = (*iter)["topics"]["recresult"].asString();
string topic_recreq = (*iter)["topics"]["recreq"].asString();
string topic_input = (*iter)["topics"]["input"].asString();
for (Json::ValueIterator client_iter=client_dict.begin(); client_iter != client_dict.end(); ++client_iter) {
string cid = client_iter.key().asString();
// FIXME: create a new customer configuration
CustomerPtr c(new Customer);
c->LoadFromJson(cid, (*client_iter), topic_recresult, topic_recreq, topic_input);
customers[cid] = c;
}
}
2 详细API
</pre><pre code_snippet_id="342950" snippet_file_name="blog_20140513_1_8471295" name="code" class="cpp">class JSONAPI_API JsonValue
{
typedef std::map<std::string, JsonValue*> InnerMap;
typedef std::vector<JsonValue*> InnerVector; public:
JsonValue();
virtual ~JsonValue(); public:
void clear(); //import/export
void parse(const char* jsonString);
JsonString toString();
JsonString toString_styled();
void toFile(const char* filename);
void toFile_styled(const char* filename); //set
void operator=(JsonValue& jval); void operator=(char vInteger);
void operator=(unsigned char vInteger);
void operator=(short vInteger);
void operator=(unsigned short vInteger);
void operator=(long vInteger);
void operator=(unsigned long vInteger);
void operator=(int vInteger);
void operator=(unsigned int vInteger);
void operator=(__int64 vInteger);
void operator=(unsigned __int64 vInteger);
void operator=(float vReal);
void operator=(double vReal);
void operator=(bool vBoolean);
void operator=(const char* vString); int append(JsonValue& jval);
int append(char vInteger);
int append(unsigned char vInteger);
int append(short vInteger);
int append(unsigned short vInteger);
int append(long vInteger);
int append(unsigned long vInteger);
int append(int vInteger);
int append(unsigned int vInteger);
int append(__int64 vInteger);
int append(unsigned __int64 vInteger);
int append(float vReal);
int append(double vReal);
int append(bool vBoolean);
int append(const char* vString); //get
JsonValue& operator [](const char* name);
JsonValue& operator [](unsigned int arrIdx0); //get final value
char getChar();
unsigned char getUChar();
short getShort();
unsigned short getUShort();
long getLong();
unsigned long getULong();
int getInt();
unsigned int getUInt();
__int64 getInt64();
unsigned __int64 getUInt64();
bool getBoolean();
float getFloat();
double getDouble();
const char* getString(); //check
bool isNull();
bool isChar();
bool isUChar();
bool isShort();
bool isUShort();
bool isLong();
bool isULong();
bool isInt();
bool isUInt();
bool isInt64();
bool isUInt64();
bool isBoolean();
bool isFloat();
bool isDouble();
bool isString();
bool isObject();
bool isArray(); protected:
ValueType m_valueType;
union
{
__int64 m_integer;
double m_real;
bool m_boolean;
char* m_string;
InnerMap* m_kv;
InnerVector* m_array;
}m_v; protected:
void setAsObject();
void setAsArray(); friend JValHelper;
};
1.jsoncpp是什么？
jsoncpp是一个使用C++语言来解析json文件的开源库，其项目地址为：http://sourceforge.net/projects/jsoncpp/，属于免费项目，任何人都可以下载使用
2. 编译jsoncpp
jsoncpp文件中提供了vs71的工程文件以及makerelease.py文件，用来编译，里面分为jsontest、lib_json、test_lib_json三个工程，按照自己需要的编译。
注意:如果使用VS默认的编译选项MTd或者MT，在使用json_libmtd.lib的时候可能会出现LNK2038错误(我使用的VS2012 vc110环境)，所以请修改MTD为MDd，MT为MD。
3.使用jsoncpp读JSON文件
如何将lib库添加进VS工程中在此就不赘述了。先看第一个读文件的例
// JSON文件
{"address":[
{"name":"eliteYang", "email":"elite_yang@163.com"},
{"name":"AAA", "email":"aaa@163.com"},
{"name":"BBB", "email":"bbb@163.com"}
]}
/**
* file : jsoncpp_test.cpp
* author : eliteYang
* email : elite_yang@163.com
* blog : http://www.cppfasn.org
* desc : json cpp test
*/ #include <fstream>
#include <string>
#include "jsoncpp/json.h" int _tmain(int argc, _TCHAR* argv[])
{
std::ifstream ifs;
ifs.open("test.json"); Json::Reader reader;
Json::Value root;
if (!reader.parse(ifs, root, false))
{ return -1; } Json::Value add_value = root["address"];
for (int i = 0; i < add_value.size(); ++i)
{
Json::Value temp_value = add_value[i];
std::string strName = temp_value["name"].asString();
std::string strMail = temp_value["email"].asString();
std::cout << "name: " << strName << " email: " << strMail << std::endl; // use value array[index]
//Json::Value temp_value = add_value[i];
//std::string strName = add_value[i]["name"].asString();
//std::string strMail = add_value[i]["email"].asString();
//std::cout << "name: " << strName << " email: " << strMail << std::endl;
} system("Pause"); return 0;
}
结果：
name: eliteYang email: elite_yang@163.com
name: AAA email: aaa@163.com
name: BBB email: bbb@163.com
请按任意键继续. . .
跟我们文件中的数据完全一致。
4.使用JSON写入一块数据
我们继续使用上述文件，在中间加上一块数据。我们插入一个新的{"name": "append", "email": "append@163.com"}
/**
* file : jsoncpp_test.cpp
* author : eliteYang
* email : elite_yang@163.com
* blog : http://www.cppfasn.org
* desc : json cpp test
*/ #include <fstream>
#include <string>
#include "jsoncpp/json.h" int _tmain(int argc, _TCHAR* argv[])
{
std::ifstream ifs;
ifs.open("test.json"); Json::Reader reader;
Json::Value root;
if (!reader.parse(ifs, root, false))
{ return -1; } Json::Value& add_value = root["address"];
Json::Value append_value;
append_value["name"] = "append";
append_value["email"] = "append@163.com";
add_value.append(append_value); for (int i = 0; i < add_value.size(); ++i)
{
Json::Value temp_value = add_value[i];
std::string strName = temp_value["name"].asString();
std::string strMail = temp_value["email"].asString();
std::cout << "name: " << strName << " email: " << strMail << std::endl;
} Json::FastWriter writer;
std::string json_append_file = writer.write(root); std::ofstream ofs;
ofs.open("test_append.json");
ofs << json_append_file; system("Pause"); return 0;
}
结果：
name: eliteYang email: elite_yang@163.com
name: AAA email: aaa@163.com
name: BBB email: bbb@163.com
name: append email: append@163.com
请按任意键继续. . .
// test_append.json
{"address":[{"email":"elite_yang@163.com","name":"eliteYang"},{"email":"aaa@163.com","name":"AAA"},{"email":"bbb@163.com","name":"BBB"},{"email":"append@163.com","name":"append"}]}
转自：http://www.cppfans.org/1445.html
一个jsoncpp的例子
使用jsoncpp进行字符串、数字、布尔值和数组的封装与解析。
1）下载jsoncpp的代码库 百度网盘地址 ：http://pan.baidu.com/s/1ntqQhIT
2）解压缩文件 jsoncpp.rar
unzip jsoncpp.rar
3）修改jsoncpp/src/main.cpp文件
vim src/main.cpp
1 #include <string>
2 #include <json/json.h>
3 #include "stdio.h"
4
5 int ReadJson(const std::string &);
6 std::string writeJson();
7
8 int main(int argc, char** argv)
9 {
10 using namespace std;
11
12 std::string strMsg;
13
14 cout<<"--------------------------------"<<endl;
15 strMsg = writeJson();
16 cout<< "json write : " << endl << strMsg << endl;
17 cout<<"--------------------------------"<<endl;
18 cout<< "json read :" << endl;
19 ReadJson(strMsg);
20 cout<<"--------------------------------"<<endl;
21
22 return 0;
23 }
24
25 int ReadJson(const std::string & strValue)
26 {
27 using namespace std;
28
29 Json::Reader reader;
30 Json::Value value;
31
32 if (reader.parse(strValue, value))
33 {
34 //解析json中的对象
35 string out = value["name"].asString();
36 cout << "name : " << out << endl;
37 cout << "number : " << value["number"].asInt() << endl;
38 cout << "value : " << value["value"].asBool() << endl;
39 cout << "no such num : " << value["haha"].asInt() << endl;
40 cout << "no such str : " << value["hehe"].asString() << endl;
41
42 //解析数组对象
43 const Json::Value arrayNum = value["arrnum"];
44 for (unsigned int i = 0; i < arrayNum.size(); i++)
45 {
46 cout << "arrnum[" << i << "] = " << arrayNum[i];
47 }
48 //解析对象数组对象
49 Json::Value arrayObj = value["array"];
50 cout << "array size = " << arrayObj.size() << endl;
51 for(unsigned int i = 0; i < arrayObj.size(); i++)
52 {
53 cout << arrayObj[i];
54 }
55 //从对象数组中找到想要的对象
56 for(unsigned int i = 0; i < arrayObj.size(); i++)
57 {
58 if (arrayObj[i].isMember("string"))
59 {
60 out = arrayObj[i]["string"].asString();
61 std::cout << "string : " << out << std::endl;
62 }
63 }
64 }
65
66 return 0;
67 }
68
69 std::string writeJson()
70 {
71 using namespace std;
72
73 Json::Value root;
74 Json::Value arrayObj;
75 Json::Value item;
76 Json::Value iNum;
77
78 item["string"] = "this is a string";
79 item["number"] = 999;
80 item["aaaaaa"] = "bbbbbb";
81 arrayObj.append(item);
82
83 //直接对jsoncpp对象以数字索引作为下标进行赋值，则自动作为数组
84 iNum[1] = 1;
85 iNum[2] = 2;
86 iNum[3] = 3;
87 iNum[4] = 4;
88 iNum[5] = 5;
89 iNum[6] = 6;
90
91 //增加对象数组
92 root["array"] = arrayObj;
93 //增加字符串
94 root["name"] = "json";
95 //增加数字
96 root["number"] = 666;
97 //增加布尔变量
98 root["value"] = true;
99 //增加数字数组
100 root["arrnum"] = iNum;
101
102 root.toStyledString();
103 string out = root.toStyledString();
104
105 return out;
106 }
4）在目录jsoncpp/ 下执行make命令
jsoncpp$ make
mkdir -p objs/src/json; mkdir -p objs/src;
g++ -c -Wall -Werror -g -I include src/json/json_reader.cpp -o objs/src/json/json_reader.o
g++ -c -Wall -Werror -g -I include src/json/json_value.cpp -o objs/src/json/json_value.o
g++ -c -Wall -Werror -g -I include src/json/json_writer.cpp -o objs/src/json/json_writer.o
g++ -c -Wall -Werror -g -I include src/main.cpp -o objs/src/main.o
g++ objs/src/json/json_reader.o objs/src/json/json_value.o objs/src/json/json_writer.o objs/src/main.o -o main
5)运行jsoncpp/下的main文件
./main
6)运行结果如下
fengbo: jsoncpp$ ./main
--------------------------------
json write :
{
"array" : [
{
"aaaaaa" : "bbbbbb",
"number" : 999,
"string" : "this is a string"
}
],
"arrnum" : [ null, 1, 2, 3, 4, 5, 6 ],
"name" : "json",
"number" : 666,
"value" : true
} --------------------------------
json read :
name : json
number : 666
value : 1
no such num : 0
no such str :
arrnum[0] = null
arrnum[1] = 1
arrnum[2] = 2
arrnum[3] = 3
arrnum[4] = 4
arrnum[5] = 5
arrnum[6] = 6
array size = 1 {
"aaaaaa" : "bbbbbb",
"number" : 999,
"string" : "this is a string"
}
string : this is a string
--------------------------------
作者：风波
mail : fengbohello@qq.com
jsoncpp使用优化：http://www.searchtb.com/2012/11/jsoncpp-optimization.html