网络传输中，数据交互也需要一些自定义协议，其实json就是最好用之一。
使用cjson进行json字符串的构造，以及对其进行对应解析的测试代码。
1：背景介绍
JSNON作为一种轻量级的数据交互格式，易于阅读和编写，易于解析和生成。
日常开发中对json的使用次数也越来越多。
我常用的就是使用cjon以及jsoncpp对数据进行构造以及解析。
cjson因为直接包含一个头文件和.c文件就可以使用，特别方便，这里整理一些使用cjson进行构造与解析的实例，做代码备份。
2：测试代码
2.1：构造json格式的数据，返回json字符串
/********************* { "name": "test", "age": 80, "languages": ["C++", "Java"], "phone": { "number": "1867216i144", "type": "home" }, "languages": [{ "name": "Linux kernel development", "price": "7.7" }, { "name": "Linux server development", "price": "8.0" }], "vip": true, "address": "" } *********************/ char * make_json_str() { // 创建json对象 cJSON *root = cJSON_CreateObject(); // 添加键值对 cJSON_AddItemToObject(root, "name", cJSON_CreateString("test")); cJSON_AddItemToObject(root, "age", cJSON_CreateNumber(80)); // 创建json数组 cJSON *languages = cJSON_CreateArray(); cJSON_AddItemToArray(languages, cJSON_CreateString("C++")); cJSON_AddItemToArray(languages, cJSON_CreateString("Java")); cJSON_AddItemToObject(root, "languages", languages); cJSON *phone = cJSON_CreateObject(); cJSON_AddItemToObject(phone, "number", cJSON_CreateString("1867216i144")); cJSON_AddItemToObject(phone, "type", cJSON_CreateString("home")); cJSON_AddItemToObject(root, "phone", phone); cJSON *book0 = cJSON_CreateObject(); cJSON_AddItemToObject(book0, "name", cJSON_CreateString("Linux kernel development")); cJSON_AddItemToObject(book0, "price", cJSON_CreateNumber(7.7)); cJSON *book1 = cJSON_CreateObject(); cJSON_AddItemToObject(book1, "name", cJSON_CreateString("Linux server development")); cJSON_AddItemToObject(book1, "price", cJSON_CreateNumber(8.0)); // 创建json数组 cJSON *books = cJSON_CreateArray(); cJSON_AddItemToArray(books, book0); cJSON_AddItemToArray(books, book1); cJSON_AddItemToObject(root, "books", books); cJSON_AddItemToObject(root, "vip", cJSON_CreateBool(1)); cJSON_AddItemToObject(root, "address", cJSON_CreateString("")); // NULL值的问题 //格式化json对象 并返回 char *jsonstr = cJSON_Print(root); //注意释放 内部会释放其子节点的 cJSON_Delete(root); printf("make json str is [%lu][%s] \n", strlen(jsonstr), jsonstr); return jsonstr; }
2.2：json字符串对应的解析
void printCJson(cJSON *root); int parse_json_str(const char * jsonstr) { if(jsonstr == NULL) { printf("parse json error: jsonstr is null \n"); return -1; } cJSON *root = cJSON_Parse(jsonstr); if(root == NULL) { printf("parse json error: cJSON_Parse error \n"); return -1; } //获取对应的字段并进行打印 printCJson(root); cJSON_Delete(root); return 0; } void printCJson(cJSON *root) { //获取到各个子对象 cJSON *name = cJSON_GetObjectItem(root, "name"); cJSON *age = cJSON_GetObjectItem(root, "age"); cJSON *languages = cJSON_GetObjectItem(root, "languages"); cJSON *phone = cJSON_GetObjectItem(root, "phone"); cJSON *books = cJSON_GetObjectItem(root, "books"); cJSON *vip = cJSON_GetObjectItem(root, "vip"); cJSON *address = cJSON_GetObjectItem(root, "address"); printf(" name: %s\n", name->valuestring); printf(" age: %d\n", age->valueint); printf(" languages: "); for (int i = 0; i < cJSON_GetArraySize(languages); i++) { cJSON *lang = cJSON_GetArrayItem(languages, i); if (i != 0) { printf(", "); } printf("%s", lang->valuestring); } printf("\n"); cJSON *number = cJSON_GetObjectItem(phone, "number"); cJSON *type = cJSON_GetObjectItem(phone, "type"); printf(" phone number: %s, type: %s\n", number->valuestring, type->valuestring); for (int i = 0; i < cJSON_GetArraySize(books); i++) { cJSON *book = cJSON_GetArrayItem(books, i); cJSON *name = cJSON_GetObjectItem(book, "name"); cJSON *price = cJSON_GetObjectItem(book, "price"); printf(" book name: %s, price: %lf\n", name->valuestring, price->valuedouble); } printf(" vip: %d\n", vip->valueint); if (address && !cJSON_IsNull(address)) { printf(" address: %s\n", address->valuestring); } else { printf(" address is null\n"); } }
2.3：测试调用主函数
#include <stdio.h> #include <stdlib.h> #include <string.h> #include "cJSON.h" //需要包含cjson的头文件 以及编译时要编译对应的cjson.c一起 int main() { //构造json字符串 内部会对json字符串申请内存 要释放 char * strjson = make_json_str(); //解析构造的json字符串 打印对应的字段 parse_json_str(strjson); free(strjson); return 0; }
3：执行结果
make json str is [286][{ "name": "test", "age": 80, "languages": ["C++", "Java"], "phone": { "number": "1867216i144", "type": "home" }, "books": [{ "name": "Linux kernel development", "price": 7.7 }, { "name": "Linux server development", "price": 8 }], "vip": true, "address": "" }] name: test age: 80 languages: C++, Java phone number: 1867216i144, type: home book name: Linux kernel development, price: 7.700000 book name: Linux server development, price: 8.000000 vip: 1 address:
我开始试着积累一些常用代码：自己代码库中备用
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