A. c语言 解析json字符串
你好，你用json-c库，编译通过了吗？我是在ubuntu里使用json-c库，但是无法编译通过回，报错 undefined reference to 'json_tokener_parse'，类似的函数答没定义的错误，你是怎么调用的json-c库？请教一下，谢谢！
B. 怎么用C语言获取JSON中的数据
用C语言获取JSON中的数据的方法是使用 CJSON。
以下简单介绍用CJSON的思路及实现：
1）创建json，从json中获取数据。
#nclude <stdio.h>
#include "cJSON.h"
char * makeJson()
{
cJSON * pJsonRoot = NULL;
pJsonRoot = cJSON_CreateObject();
if(NULL == pJsonRoot)
{
//error happend here
return NULL;
}
cJSON_AddStringToObject(pJsonRoot, "hello", "hello world");
cJSON_AddNumberToObject(pJsonRoot, "number", 10010);
cJSON_AddBoolToObject(pJsonRoot, "bool", 1);
cJSON * pSubJson = NULL;
pSubJson = cJSON_CreateObject();
if(NULL == pSubJson)
{
// create object faild, exit
cJSON_Delete(pJsonRoot);
return NULL;
}
cJSON_AddStringToObject(pSubJson, "subjsonobj", "a sub json string");
cJSON_AddItemToObject(pJsonRoot, "subobj", pSubJson);
char * p = cJSON_Print(pJsonRoot);
// else use :
// char * p = cJSON_PrintUnformatted(pJsonRoot);
if(NULL == p)
{
//convert json list to string faild, exit
//because sub json pSubJson han been add to pJsonRoot, so just delete pJsonRoot, if you also delete pSubJson, it will coremp, and error is : double free
cJSON_Delete(pJsonRoot);
return NULL;
}
//free(p);
cJSON_Delete(pJsonRoot);
return p;
}
void parseJson(char * pMsg)
{
if(NULL == pMsg)
{
return;
}
cJSON * pJson = cJSON_Parse(pMsg)；
if(NULL == pJson)
{
// parse faild, return
return ;
}
// get string from json
cJSON * pSub = cJSON_GetObjectItem(pJson, "hello");
if(NULL == pSub)
{
//get object named "hello" faild
}
printf("obj_1 : %s
", pSub->valuestring);
// get number from json
pSub = cJSON_GetObjectItem(pJson, "number");
if(NULL == pSub)
{
//get number from json faild
}
printf("obj_2 : %d
", pSub->valueint);
// get bool from json
pSub = cJSON_GetObjectItem(pJson, "bool");
if(NULL == pSub)
{
// get bool from json faild
}
printf("obj_3 : %d
", pSub->valueint);
// get sub object
pSub = cJSON_GetObjectItem(pJson, "subobj");
if(NULL == pSub)
{
// get sub object faild
}
cJSON * pSubSub = cJSON_GetObjectItem(pSub, "subjsonobj");
if(NULL == pSubSub)
{
// get object from subject object faild
}
printf("sub_obj_1 : %s
", pSubSub->valuestring);
cJSON_Delete(pJson);
}
int main()
{
char * p = makeJson();
if(NULL == p)
{
return 0;
}
printf("%s ", p);
parseJson(p);
free(p);//这里不要忘记释放内存，cJSON_Print()函数或者cJSON_PrintUnformatted（）产生的内存，使用free(char *)进行释放
return 0;
}
2）创建json数组和解析json数组
//创建数组，数组值是另一个JSON的item，这里使用数字作为演示
char * makeArray(int iSize)
{
cJSON * root = cJSON_CreateArray();
if(NULL == root)
{
printf("create json array faild ");
return NULL;
}
int i = 0;
for(i = 0; i < iSize; i++)
{
cJSON_AddNumberToObject(root, "hehe", i);
}
char * out = cJSON_Print(root);
cJSON_Delete(root);
return out;
}
//解析刚刚的CJSON数组
void parseArray(char * pJson)
{
if(NULL == pJson)
{
return ;
}
cJSON * root = NULL;
if((root = cJSON_Parse(pJson)) == NULL)
{
return ;
}
int iSize = cJSON_GetArraySize(root);
for(int iCnt = 0; iCnt < iSize; iCnt++)
{
cJSON * pSub = cJSON_GetArrayItem(root, iCnt);
if(NULL == pSub)
{
continue;
}
int iValue = pSub->valueint;
printf("value[%2d] : [%d] ", iCnt, iValue);
}
cJSON_Delete(root);
return;
}
C. 怎样从java后台获取json字符串并转换为json对象输出
使用json-lib.jar这个工具
public String getJson(Object obj){
JSONObject json;
json = JSONObject.fromObject(obj);
return json.toString();
}
使用jquery来处理json
//转换为json数据 datas可以用ajax从后台获取上面getJson中的内数据
var jsonDatas = eval("(" + datas + ")");
//循环遍历数容据
jQuery.each(jsonDatas, function(item) {
//循环
});
D. JSON对象如何转化为字符串
1 换回字来符串
var myObjectInJSON = myObject.toJSONString();//也没有源这个方法
var jsonStr = JSON.stringify( obj );
var jsonStr = jQuery.stringifyJSON(obj);//没有这个方法，误导我
2 转为json对象
var bToObj=JSON.parse(b);
jQuery.parseJSON(json);
var c='{"name":"Mike","sex":"女","age":"29"}';
var jsonObj=eval("("+c+")");
E. fastjson怎样json转换成字符串
// jackson
private static ObjectMapper om = new ObjectMapper ();
public static String objectToString (Object obj ) throws IOException{
return om.writeValueAsString (obj );
}
@Test
public void test1 () throws IOException {
Map<String, Object> map = new HashMap<String, Object>();
Map<String, String> map2 = new HashMap<String, String>();
map2.put ("name", "1");
map2.put ("age", "12");
map.put ("att", map2 );
List<String> list = new ArrayList<String>();
list.add ("hi");list.add ("hello");
map.put ("list", list );
List<Map<String, String>> confuselist = new ArrayList<Map<String, String>>();
Map<String, String> map3 = new HashMap<String, String>();
map3.put ("name", "1");
map3.put ("age", "12");
confuselist.add (map3 );
confuselist.add (map2 );
map.put ("confuselist", confuselist );
Object array = Array.newInstance (String.class, 10 );
Array.set (array, 0, "a");
Array.set (array, 1, "b");
Array.set (array, 2, "c");
map.put ("array", array );
// 使用 jackson
System.out.println (objectToString (map ));
// 使用 fastJson
System.out.println (JSON.toJSONString (map ));
}
输出：
{"att":{"age":"12","name":"1"},"list":["hi","hello"],"confuselist":[{"age":"12","name":"1"}, {"age":"12","name":"1"}],"array":["a","b","c",null,null,null,null,null,null,null]}
{"att":{"age":"12","name":"1"},"list":["hi","hello"],"confuselist":[{"age":"12","name":"1"},{"$ref":"$.att"}],"array":["a","b","c",null,null,null,null,null,null,null]}
F. c语言怎么解析json字符串
列出了一堆C语言的版JSON库。权
C:
JSON_checker.
YAJL.
js0n.
LibU.
json-c.
json-parser.
jsonsl.
WJElement.
M's JSON parser.
cJSON.
Jansson.
jsmn.
cson.
parson.
ujson4c.
nxjson.
frozen.
G. C++解析Json字符串问题！
一、从字符串中读取JSON
#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;
//从字符串中读取数据
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、从文件中读取JSON
PersonalInfo.json（一个存储了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;
//从文件中读取
ifstream is;
is.open( "PersonalInfo.json" , ios::binary);
if (reader.parse(is,root))
{
//读取根节点信息
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;
//读取子节点信息
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;
//读取数组信息
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、将信息保存为JSON格式
a.cpp
#include <iostream>
#include <fstream>
#include "json/json.h"
using namespace std;
int main()
{
//根节点
Json::Value root;
//根节点属性
root[ "name" ] = Json::Value( "Tsybius" );
root[ "age" ] = Json::Value(23);
root[ "sex_is_male" ] = Json::Value( true );
//子节点
Json::Value partner;
//子节点属性
partner[ "partner_name" ] = Json::Value( "Galatea" );
partner[ "partner_age" ] = Json::Value(21);
partner[ "partner_sex_is_male" ] = Json::Value( false );
//子节点挂到根节点上
root[ "partner" ] = Json::Value(partner);
//数组形式
root[ "achievement" ].append( "ach1" );
root[ "achievement" ].append( "ach2" );
root[ "achievement" ].append( "ach3" );
//直接输出
cout << "FastWriter:" << endl;
Json::FastWriter fw;
cout << fw.write(root) << endl << endl;
//缩进输出
cout << "StyledWriter:" << endl;
Json::StyledWriter sw;
cout << sw.write(root) << endl << endl;
//输出到文件
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
}
H. 如何把json对象转换成字符串
1.简单的解析json字符串
首先将json字符串转换为json对象，然后再解析json对象，过程如下。
JSONObject jsonObject = JSONObject.fromObject(jsonStr);
[java] view plain
<pre></pre><span style="white-space:pre"></span>
<pre></pre>
根据json中的键得到它的值
String name = jsonObject.getString("name");
int num = jsonObject.getInt("num");
String sex = jsonObject.getString("sex");
int age = jsonObject.getInt("age");
2.将json字符串转换为java对象
同样先将json字符串转换为json对象，再将json对象转换为java对象，如下所示。
JSONObject obj = new JSONObject().fromObject(jsonStr);//将json字符串转换为json对象
将json对象转换为java对象
Person jb = (Person)JSONObject.toBean(obj,Person.class);//将建json对象转换为Person对象
3.将java对象转换为json字符串
先将java对象转换为json对象，在将json对象转换为json字符串
JSONObject json = JSONObject.fromObject(obj);//将java对象转换为json对象
String str = json.toString();//将json对象转换为字符串
完整代码如下：
[java] view plain
package baz.parse;
import java.util.ArrayList;
import java.util.List;
import net.sf.json.JSON;
import net.sf.json.JSONArray;
import net.sf.json.JSONObject;
import net.sf.json.JSONSerializer;
import baz.bean.Person;
public class ParseJson {
private String jsonStr;
public ParseJson() {
}
I. 怎么把json对象转换为json字符串
1 换回字符串
var myObjectInJSON = myObject.toJSONString();//也没有这个方法
var jsonStr = JSON.stringify( obj );
var jsonStr = jQuery.stringifyJSON(obj);//没有这个方法，误导我版
2 转为json对象权
var bToObj=JSON.parse(b);
jQuery.parseJSON(json);
var c='{"name":"Mike","sex":"女","age":"29"}';
var jsonObj=eval("("+c+")");
J. json对象转字符串如何实现
1 换回字符串
var myObjectInJSON = myObject.toJSONString();//也没有这个方法
var jsonStr = JSON.stringify( obj );
var jsonStr = jQuery.stringifyJSON(obj);//没有这个方法，误版导我
2 转为json对象权
var bToObj=JSON.parse(b);
jQuery.parseJSON(json);
var c='{"name":"Mike","sex":"女","age":"29"}';
var jsonObj=eval("("+c+")");