头文件：
#include "json/json.h" // 当前目录下
使用：
char *str = "
{\"abc\": 123, \"wds\": 12.3, \"qwe\": \"ddd\", \"bool0\": false, \"bool1\": true, \"arr\";
编译注意：需要加上
-ljson 库。
1.声明json对象
struct json_object *my_obj;
2.将符合json格式的字符串构造为一个json对象
my_obj =
json_tokener_parse(str);
printf("1-tokener parse: %s\n", json_object_to_json_string(my_obj));
3.在对象里用key值去找，然后删除它的key:value
json_object_object_del(my_obj, "abc");
printf("2-tokener parse: %s\n", json_object_to_json_string(my_obj));
4.在对象里用key值去找，获取它的value值
struct json_object *ret_obj;
ret_obj =
json_object_object_get(my_obj, "wds"); // key == "wds"
printf("obj_get-wds:%s\n", json_object_to_json_string(ret_obj));
5.在json_object_object_get引用一次，将json对象的引用计数减1,子对象引用计数为0时释放所占用内存
json_object_put(ret_obj);
6.获取不同的json数据类型，int.double.string.array.object
struct json_object *val =
json_object_new_int(18542);
7.将key:value加入到对象my_obj中
json_object_object_add(my_obj, "wds", val);
printf("3-object add: %s\n", json_object_to_json_string(my_obj));
json_object_put(val); // 参考第5.
8.输出结果
printf("get string:%s\n",
json_object_get_string(my_obj));
printf("get lh:%d\n",
json_object_get_object(my_obj));
printf("get int:%d\n",
json_object_get_int(my_obj));
// 这个接口函数，包含很多数据类型(array, int, string, object)组成json包，socket传输，为上层提供数据，便于展示。
make_a_common_json_string();
json_object_put(my_obj); // 参考第5.
9.接口函数
void make_a_common_json_string()
{
printf("####################################\n");
int i=0;
struct json_object *obj_all = json_object_new_object();
struct json_object *obj_info = json_object_new_object();
struct json_object *obj_work = json_object_new_object();
struct json_object *obj_life = json_object_new_object();
struct json_object *arr_month_grade =
json_object_new_array();
for(i=1; i<13; i++){
struct json_object *obj_int = json_object_new_int(i);
json_object_array_add(arr_month_grade, obj_int);
}
json_object_object_add(obj_work, "position", json_object_new_string("programmer"));
json_object_object_add(obj_work, "department", json_object_new_string("make code"));
json_object_object_add(obj_work, "address", json_object_new_string("BJ.3.103"));
json_object_object_add(obj_work, "mounth_grade", arr_month_grade);
json_object_object_add(obj_info, "Work", obj_work);
json_object_object_add(obj_life, "Name", json_object_new_string("DS.wen"));
json_object_object_add(obj_life, "Age", json_object_new_int(24.34));
json_object_object_add(obj_life, "M-O", json_object_new_string("Male"));
json_object_object_add(obj_info, "Life", obj_life);
json_object_object_add(obj_all,"W.DS_Info", obj_info);
printf("all_string:%s\n", json_object_to_json_string(obj_all));
json_object_put(obj_all);
return ;
}
>>输出结果：
/*************************************打印结果********************************************/
1-tokener parse: { "abc": 123, "wds": 12.300000, "qwe": "ddd", "bool0": false, "bool1": true, "arr": [ 12, 3, 0, 5, null ] }
2-tokener parse: { "wds": 12.300000, "qwe": "ddd", "bool0": false, "bool1": true, "arr": [ 12, 3, 0, 5, null ] }
obj_get-wds:12.300000
3-object add: { "wds": 18542, "qwe": "ddd", "bool0": false, "bool1": true, "arr": [ 12, 3, 0, 5, null ] }
get string:{ "wds": 18542, "qwe": "ddd", "bool0": false, "bool1": true, "arr": [ 12, 3, 0, 5, null ] }
get lh:26383664
get int:0
####################################
all_string:{ "W.DS_Info": { "Work": { "position": "programmer", "department": "make code", "address": "BJ.3.103", "mounth_grade": [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 ] }, "Life": { "Name": "DS.wen", "Age": 24, "M-O": "Male" } } }
/***************************************************************************************/
JSON对象的生成
Json对象的类型：
json_type_object, “名称/值”对的集合
Json对象的值类型
json_type_boolean,
json_type_double,
json_type_int,
json_type_array, “值”的集合
json_type_string
structjson_object *json_object_new_object();
说明：
创建个空的json_type_object类型JSON对象。
struct json_object *json_object_new_boolean(boolean b);
说明：
创建个json_type_boolean值类型json对象
boolean json_object_get_boolean(structjson_object *obj);
说明：
从json对象中boolean值类型得到boolean值
同样：
structjson_object* json_object_new_int(int i)
intjson_object_get_int(struct json_object *this)
structjson_object* json_object_new_double(double d)
doublejson_object_get_double(struct json_object *this)
structjson_object* json_object_new_string(char *s)
char*json_object_get_string(struct json_object *this)
structjson_object *json_object_new_array();
说明：
创建个空的json_type_array类型JSON数组值对象。
structjson_object *json_tokener_parse(char *str);
说明：
由str里的JSON字符串生成JSON对象，str是son_object_to_json_string() 生成的。
参数：
str – json字符串
structjson_object *json_object_object_get(struct json_object * json,char *name);
说明：
从json中按名字取一个对象。
参数：
json – json对象
name - json域名字
3.2 JSON对象的释放
struct json_object * *json_object_get(struct json_object * this)
说明：
增加对象引用计数。使用c库最关心的是内存谁来分配, 谁来释放. jsonc的内存管理方式, 是基于引用计数的内存树(链), 如果把一个struct json_object 对象a, add到另一个对象b上, 就不用显式的释放(json_object_put) a了, 相当于把a挂到了b的对象树上, 释放b的时候, 就会释放a. 当a即add到b上, 又add到对象c上时会导致a被释放两次(double free), 这时可以增加a的引用计数(调用函数json_object_get(a)), 这时如果先释放b, 后释放c, 当释放b时, 并不会真正的释放a, 而是减少a的引用计数为1, 然后释放c时, 才真正释放a.
参数：
this – json对象
Void json_object_put(struct json_object *this)
说明：
减少对象引用次数一次，当减少到0就释放（free）资源
参数：
this – json对象
样例片段：
my_string =json_object_new_string("\t");
/*输出 my_string= */ \t(table键)
printf("my_string=%s\n",json_object_get_string(my_string));
/*转换json格式字符串输出my_string.to_string()="\t"*/
printf("my_string.to_string()=%s\n",json_object_to_json_string(my_string));
/*释放资源*/
json_object_put(my_string);
3.3 JSON对象的操作
Int json_object_is_type(structjson_object * this, enum json_type type)
说明：
检查json_object是json的某个类型
参数：
this:json_object 实例
type:json_type_boolean,json_type_double, json_type_int, json_type_object,json_type_array, json_type_string
enum json_type json_object_get_type(struct json_object * this )
说明：
得到json_object的类型。
参数：
this – json对象
char * json_object_to_json_string(structjson_object * this)
说明：
将json_object内容转换json格式字符串，其中可能含有转义符。
参数：
this – json对象
返回值：
Json格式字符串
void json_object_object_add(structjson_object* obj, char *key, struct json_object *val);
说明：
添加个对象域到json对象中
参数：
Obj – json对象
key – 域名字
val – json值对象
void json_object_object_del(structjson_object* obj, char *key);
说明：
删除key值json对象
参数：
ob j – json对象
key – 域名字
int json_object_array_length(structjson_object *obj);
说明：
得到json对象数组的长度。
参数：
ob j – json数组值对象
extern int json_object_array_add(struct json_object*obj,
struct json_object *val);
说明：
添加一元素在json对象数组末端
参数：
ob j – json数组值对象
val – json值对象
*
int json_object_array_put_idx(structjson_object *obj, int idx,
struct json_object *val);
说明：
在指定的json对象数组下标插入或替换一个json对象元素。
参数：
ob j – json数组值对象
val – json值对象
idx– 数组下标
struct json_object *json_object_array_get_idx(struct json_object * json_array,int i);
说明：
从数组中，按下标取JSON值对象。
参数：
json_array– json 数组类型对象
i– 数组下标位置
定义宏 json_object_object_foreach(obj,key,val)
说明：
遍历json对象的key和值 （key, val默认参数不变）
样例片段：
/*创建个空json对象值数组类型*/
my_array = json_object_new_array();
/*添加json值类型到数组中*/
json_object_array_add(my_array,json_object_new_int(1));
json_object_array_add(my_array,json_object_new_int(2));
json_object_array_add(my_array, json_object_new_int(3));
json_object_array_put_idx(my_array, 4,json_object_new_int(5));
printf("my_array=\n");
for(i=0; i <json_object_array_length(my_array); i++) {
struct json_object *obj =json_object_array_get_idx(my_array, i);
printf("\t[%d]=%s\n", i,json_object_to_json_string(obj));
}
printf("my_array.to_string()=%s\n",json_object_to_json_string(my_array));
my_object = json_object_new_object();
/*添加json名称和值到json对象集合中*/
json_object_object_add(my_object,"abc", json_object_new_int(12));
json_object_object_add(my_object,"foo", json_object_new_string("bar"));
json_object_object_add(my_object,"bool0", json_object_new_boolean(0));
json_object_object_add(my_object,"bool1", json_object_new_boolean(1));
json_object_object_add(my_object,"baz", json_object_new_string("bang"));
/*同样的key 添加会替换掉*/
json_object_object_add(my_object,"baz", json_object_new_string("fark"));
json_object_object_del(my_object,"baz");
/*添加数组集合到json对象中*/
json_object_object_add(my_object, "arr",my_array);
printf("my_object=\n");
/*遍历json对象集合*/
json_object_object_foreach(my_object, key,val) {
printf("\t%s: %s\n", key,json_object_to_json_string(val));
}
json_object_put(my_object);
4. JSON实例开发
4.1 样例1
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>
#include "json.h"
int main(int argc, char **argv)
{
struct json_tokener *tok;
struct json_object *my_string, *my_int, *my_object, *my_array;
struct json_object *new_obj;
inti;
my_string = json_object_new_string("\t");
/*输出 my_string= */
printf("my_string=%s\n", json_object_get_string(my_string));
/*转换json格式字符串 输出my_string.to_string()="\t"*/
printf("my_string.to_string()=%s\n",json_object_to_json_string(my_string));
/*释放资源*/
json_object_put(my_string);
my_string = json_object_new_string("\\");
printf("my_string=%s\n", json_object_get_string(my_string));
printf("my_string.to_string()=%s\n", json_object_to_json_string(my_string));
json_object_put(my_string);
my_string = json_object_new_string("foo");
printf("my_string=%s\n", json_object_get_string(my_string));
printf("my_string.to_string()=%s\n",json_object_to_json_string(my_string));
my_int = json_object_new_int(9);
printf("my_int=%d\n", json_object_get_int(my_int));
printf("my_int.to_string()=%s\n",json_object_to_json_string(my_int));
/*创建个空json对象值数组类型*/
my_array = json_object_new_array();
/*添加json值类型到数组中*/
json_object_array_add(my_array, json_object_new_int(1));
json_object_array_add(my_array, json_object_new_int(2));
json_object_array_add(my_array, json_object_new_int(3));
json_object_array_put_idx(my_array, 4, json_object_new_int(5));
printf("my_array=\n");
for(i=0; i < json_object_array_length(my_array); i++) {
struct json_object *obj = json_object_array_get_idx(my_array, i);
printf("\t[%d]=%s\n", i, json_object_to_json_string(obj));
}
printf("my_array.to_string()=%s\n",json_object_to_json_string(my_array));
my_object = json_object_new_object();
/*添加json名称和值到json对象集合中*/
json_object_object_add(my_object, "abc",json_object_new_int(12));
json_object_object_add(my_object, "foo",json_object_new_string("bar"));
json_object_object_add(my_object, "bool0",json_object_new_boolean(0));
json_object_object_add(my_object, "bool1",json_object_new_boolean(1));
json_object_object_add(my_object, "baz",json_object_new_string("bang"));
/*同样的key 添加会替换掉*/
json_object_object_add(my_object, "baz",json_object_new_string("fark"));
json_object_object_del(my_object, "baz");
printf("my_object=\n");
/*遍历json对象集合*/
json_object_object_foreach(my_object, key, val) {
printf("\t%s: %s\n", key, json_object_to_json_string(val));
}
printf("my_object.to_string()=%s\n",json_object_to_json_string(my_object));
/*对些不规则的串做了些解析测试*/
new_obj = json_tokener_parse("\"\003\"");
printf("new_obj.to_string()=%s\n",json_object_to_json_string(new_obj));
json_object_put(new_obj);
new_obj = json_tokener_parse("/* hello */\"foo\"");
printf("new_obj.to_string()=%s\n",json_object_to_json_string(new_obj));
json_object_put(new_obj);
new_obj = json_tokener_parse("// hello\n\"foo\"");
printf("new_obj.to_string()=%s\n",json_object_to_json_string(new_obj));
json_object_put(new_obj);
new_obj =json_tokener_parse("\"\\u0041\\u0042\\u0043\"");
printf("new_obj.to_string()=%s\n", json_object_to_json_string(new_obj));
json_object_put(new_obj);
new_obj = json_tokener_parse("null");
printf("new_obj.to_string()=%s\n",json_object_to_json_string(new_obj));
json_object_put(new_obj);
new_obj = json_tokener_parse("True");
printf("new_obj.to_string()=%s\n",json_object_to_json_string(new_obj));
json_object_put(new_obj);
new_obj = json_tokener_parse("12");
printf("new_obj.to_string()=%s\n",json_object_to_json_string(new_obj));
json_object_put(new_obj);
new_obj = json_tokener_parse("12.3");
/*得到json double类型
printf("new_obj.to_string()=%s\n",json_object_to_json_string(new_obj));
json_object_put(new_obj);
new_obj = json_tokener_parse("[\"\\n\"]");
printf("new_obj.to_string()=%s\n",json_object_to_json_string(new_obj));
json_object_put(new_obj);
new_obj = json_tokener_parse("[\"\\nabc\\n\"]");
printf("new_obj.to_string()=%s\n",json_object_to_json_string(new_obj));
json_object_put(new_obj);
new_obj = json_tokener_parse("[null]");
printf("new_obj.to_string()=%s\n",json_object_to_json_string(new_obj));
json_object_put(new_obj);
new_obj = json_tokener_parse("[]");
printf("new_obj.to_string()=%s\n",json_object_to_json_string(new_obj));
json_object_put(new_obj);
new_obj = json_tokener_parse("[false]");
printf("new_obj.to_string()=%s\n",json_object_to_json_string(new_obj));
json_object_put(new_obj);
new_obj =json_tokener_parse("[\"abc\",null,\"def\",12]");
printf("new_obj.to_string()=%s\n",json_object_to_json_string(new_obj));
json_object_put(new_obj);
new_obj = json_tokener_parse("{}");
printf("new_obj.to_string()=%s\n",json_object_to_json_string(new_obj));
json_object_put(new_obj);
new_obj = json_tokener_parse("{ \"foo\":\"bar\" }");
printf("new_obj.to_string()=%s\n", json_object_to_json_string(new_obj));
json_object_put(new_obj);
new_obj = json_tokener_parse("{ \"foo\":\"bar\", \"baz\": null, \"bool0\": true }");
printf("new_obj.to_string()=%s\n",json_object_to_json_string(new_obj));
json_object_put(new_obj);
new_obj = json_tokener_parse("{ \"foo\": [null,\"foo\"] }");
printf("new_obj.to_string()=%s\n",json_object_to_json_string(new_obj));
json_object_put(new_obj);
new_obj = json_tokener_parse("{ \"abc\": 12,\"foo\": \"bar\", \"bool0\": false,\"bool1\": true, \"arr\": [ 1, 2, 3, null, 5 ] }");
printf("new_obj.to_string()=%s\n",json_object_to_json_string(new_obj));
json_object_put(new_obj);
new_obj = json_tokener_parse("{ foo }");
if(is_error(new_obj)) printf("got error as expected\n");
new_obj = json_tokener_parse("foo");
if(is_error(new_obj)) printf("got error as expected\n");
new_obj = json_tokener_parse("{ \"foo");
if(is_error(new_obj)) printf("got error as expected\n");
/*test incremental parsing */
tok= json_tokener_new();
new_obj = json_tokener_parse_ex(tok, "{\"foo", 6);
if(is_error(new_obj)) printf("got error as expected\n");
new_obj = json_tokener_parse_ex(tok, "\": {\"bar",8);
if(is_error(new_obj)) printf("got error as expected\n");
new_obj = json_tokener_parse_ex(tok, "\":13}}", 6);
printf("new_obj.to_string()=%s\n",json_object_to_json_string(new_obj));
json_object_put(new_obj);
json_tokener_free(tok);
json_object_put(my_string);
json_object_put(my_int);
json_object_put(my_object);
json_object_put(my_array);
/*如果前面没有添加到对象中，必须显示释放，
如果添加到对象中，已经释放对象，则无需调用， 在这务必小心，否则很容易内存泄漏*/
return 0;
}
输出结果：
my_string=
my_string.to_string()="\t"
my_string=\
my_string.to_string()="\\"
my_string=foo
my_string.to_string()="foo"
my_int=9
my_int.to_string()=9
my_array=
[0]=1
[1]=2
[2]=3
[3]=null
[4]=5
my_array.to_string()=[ 1, 2, 3, null, 5 ]
my_object=
abc: 12
foo: "bar"
bool0: false
bool1: true
my_object.to_string()={ "abc":12, "foo": "bar", "bool0": false,"bool1": true }
new_obj.to_string()="\u0003"
new_obj.to_string()="foo"
new_obj.to_string()="foo"
new_obj.to_string()="ABC"
new_obj.to_string()=null
new_obj.to_string()=true
new_obj.to_string()=12
new_obj.to_string()=12.300000
new_obj.to_string()=[ "\n" ]
new_obj.to_string()=[ "\nabc\n" ]
new_obj.to_string()=[ null ]
new_obj.to_string()=[ ]
new_obj.to_string()=[ false ]
new_obj.to_string()=[ "abc",null, "def", 12 ]
new_obj.to_string()={ }
new_obj.to_string()={ "foo":"bar" }
new_obj.to_string()={ "foo":"bar", "baz": null, "bool0": true }
new_obj.to_string()={ "foo": [null, "foo" ] }
new_obj.to_string()={ "abc": 12,"foo": "bar", "bool0": false, "bool1":true, "arr": [ 1, 2, 3, null, 5 ] }
got error as expected
got error as expected
got error as expected
new_obj.to_string()={ "foo": {"bar": 13 } }
备注
Json-c-0.8版本对0.7版本做的更新：
* 添加va_end 给指针至NULL 增加程序健壮性
* 添加宏使得能够编译出调试代码
* 解决个bug 在指数中使用大写字母E
* 添加 stddef.h 头文件
* 允许编译json-c 使用-Werror