CentOS 7 使用cJSON 库

小鱼儿 2024-02-17 09:16 74阅读 0赞

## 什么是JSON ##

JSON是一种轻量级的数据交换格式，可读性强、编写简单。键值对组合编写规则，键名使用双引号包裹，冒号：分隔符后面紧跟着数值，有两种常用的数据类型是对象和数组。

对象：使用花括号\{\}包裹起来的内容，数据结构\{“key1”: “value1”, “key2”:“value2” …\}，key为对象的属性，value为对象的值。

数值：使用中括号\[\]包裹起来的内容，数据结构\{“key”: \[“value1”, “value2”, “value3” …\]\}。

## CentOS 7 安装cJSON 库 ##

cJSON Github 地址：[https://github.com/DaveGamble/cJSON][https_github.com_DaveGamble_cJSON]

步骤1：首先，你需要下载cJSON的源代码。你可以从[https://github.com/DaveGamble/cJSON][https_github.com_DaveGamble_cJSON]或者源代码官方网站下载。并上传至/usr/local/source\_code/

![828da76057214d31b55ffef966bbe3c4.png][]

步骤2：下载完成后，需要将源代码解压，可以使用以下命令：

[root@localhost source_code]# tar -zxvf cJSON-1.7.15.tar.gz

![07db4c08719f49f7aa369105b83d34bf.png][]

步骤3：解压后，切换到源代码目录：

[root@localhost source_code]# cd cJSON-1.7.15

步骤4：生成cJSON动态/[静态库][Link 1]，执行如下指令：

[root@localhost cJSON-1.7.15]# mkdir build
    [root@localhost cJSON-1.7.15]# cd build/
    [root@localhost build]# cmake ..
    CMake Deprecation Warning at CMakeLists.txt:2 (cmake_minimum_required):
      Compatibility with CMake < 2.8.12 will be removed from a future version of
      CMake.
    
      Update the VERSION argument <min> value or use a ...<max> suffix to tell
      CMake that the project does not need compatibility with older versions.
    
    
    -- The C compiler identification is GNU 8.3.1
    -- Detecting C compiler ABI info
    -- Detecting C compiler ABI info - done
    ******
    [root@localhost build]# make && make install
    [  2%] Building C object CMakeFiles/cjson.dir/cJSON.c.o
    [  4%] Linking C shared library libcjson.so
    [  4%] Built target cjson
    [  6%] Building C object CMakeFiles/cJSON_test.dir/test.c.o
    [  8%] Linking C executable cJSON_test
    [  8%] Built target cJSON_test
    [ 11%] Building C object tests/CMakeFiles/unity.dir/unity/src/unity.c.o
    [ 13%] Linking C static library libunity.a
    [ 13%] Built target unity
    [ 15%] Building C object tests/CMakeFiles/print_number.dir/print_number.c.o
    [ 17%] Linking C executable print_number
    -- 省略--
    [100%] Built target fuzz_main
    Install the project...
    -- Install configuration: ""
    -- Installing: /usr/local/include/cjson/cJSON.h
    -- Installing: /usr/local/lib64/pkgconfig/libcjson.pc
    -- Installing: /usr/local/lib64/libcjson.so.1.7.15
    -- Installing: /usr/local/lib64/libcjson.so.1
    -- Installing: /usr/local/lib64/libcjson.so
    -- Installing: /usr/local/lib64/cmake/cJSON/cjson.cmake
    -- Installing: /usr/local/lib64/cmake/cJSON/cjson-noconfig.cmake
    -- Installing: /usr/local/lib64/cmake/cJSON/cJSONConfig.cmake
    -- Installing: /usr/local/lib64/cmake/cJSON/cJSONConfigVersion.cmake

### 遇到的问题及解决办法 ###

编译执行./test\_cjson,提示如下截图错误信息：

[root@localhost cJSON_demo]# ./test_cjson
    ./test_cjson: error while loading shared libraries: libcjson.so.1: cannot open shared object file: No such file or directory

从报错的原因上看，本机上没有找到cJOSN类库的静态库/动态库libcjson.so。

首先检查/usr/local/lib 和/usr/local/include 目录中是否包含cjson 静态或动态库，可以执行如下指令：

ls /usr/local/lib | grep cjson
    ls /usr/local/include | grep cjson

![3f3fca54571c4969bf500c48061f5a3e.png][]

从上面分组 查询结果可知：cjson 没有在/usr/local/lib 库中生成cjson 静态/动态库链接。

再次查看cJOSN 在执行make && make install 指令时，对应cJSON 静态/动态库生成链接存放目录地址。

![07cc32c34521450192772e6282ece7d2.png][]

从上述截图可知cJSON 静态/动态库被安装到了/usr/local/lib64 目录中。

将/usr/local/lib64 目录添加至本机静态/动态库链接目录文件中，执行如下指令：

[root@localhost cJSON_demo]# cat /etc/ld.so.conf.d/usr-libs.conf
    /usr/local/lib
    [root@localhost cJSON_demo]# vi /etc/ld.so.conf.d/usr-libs.conf
    [root@localhost ~]#  cat /etc/ld.so.conf.d/usr-libs.conf
    /usr/local/lib
    /usr/local/lib64
    [root@localhost cJSON_demo]# sudo ldconfig

再次编译执行./test\_cjson, Main 函数正确输出。

## cJSON快速入门 ##

在/usr/local/source\_code 新增 cJSON\_demo目录并新增test\_cjson.c 文件，文件内容如下：

#include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <cjson/cJSON.h>
    
    int main()
    {
        cJSON *json = NULL;
        cJSON *node = NULL;
        cJSON *tnode = NULL;
        cJSON *tnode2 = NULL;
        char *json_data = NULL;
        int i, j, size, size2;
    
        char *data = "{\"serialNumber\":\"212089842348362300\", \
                       \"cellularInfo\":\
                          [\
                               {\"name\":\"ethernet0/0/1\",\
                               \"switch\":\"0\"},\
                               {\"name\":\"ethernet0/0/2\",\
                               \"switch\":\"1\"},\
                               {\"name\":\"ethernet0/0/3\",\
                               \"switch\":\"0\"}\
                           ],\
                           \"family\":[\"father\",\"mother\",\"brother\",\"sister\",\"somebody\"]\
                       }";
    
        json = cJSON_Parse(data);
        json_data = cJSON_Print(json);
        printf("data: %s\n", json_data);
        free(json_data);
    
        node = cJSON_GetObjectItem(json,"serialNumber");
        if(node == NULL)
            printf("serialNumber: no\n");
        else
            printf("serialNumber: ok\n");
    
        node = cJSON_GetObjectItem(json, "family");
        if (node == NULL)
             printf("family: no\n");
         else
             printf("family: ok\n");
         if (node->type == cJSON_Array)
        {
            printf("family array size is %d\n", cJSON_GetArraySize(node));
    
            size = cJSON_GetArraySize(node);
            for (i=0; i<size; i++)
            {
                tnode = cJSON_GetArrayItem(node, i);
    
                if (tnode->type == cJSON_String)
                    printf("%d: %s\n", i, tnode->valuestring);
                else
                    printf("node type is not string, value = %d\n", tnode->type);
              }
        }
    
        node = cJSON_GetObjectItem(json, "cellularInfo");
        if(node == NULL)
             printf("cellularInfo: no\n");
         else
             printf("cellularInfo: ok\n");
        if (node->type == cJSON_Array)
        {
            printf("cellularInfo array size is %d\n", cJSON_GetArraySize(node));
    
            size = cJSON_GetArraySize(node);
            for (i=0; i<size; i++)
            {
                tnode = cJSON_GetArrayItem(node, i);
    
                if (tnode->type == cJSON_String)
                    printf("%d: %s\n", i, tnode->valuestring);
                else if (tnode->type == cJSON_Object)
                {
                    size2 = cJSON_GetArraySize(tnode);
                    for (j=0; j<size2; j++)
                    {
                        tnode2 = cJSON_GetArrayItem(tnode, j);
                        if (tnode2->type == cJSON_String)
                            printf("%d-%d: %s\n", i, j, tnode2->valuestring);
                        else
                            printf("tnod2 type is err\n");
                     }
                 }
                 else
                    printf("node type is not string, value = %d\n", tnode->type);
              }
         }
    
        cJSON_Delete(json);
    
        return 0;
    }

编译源码并执行：

[root@localhost cJSON_demo]# gcc -o test_cjson test_cjson.c -lcjson
    [root@localhost cJSON_demo]# ./test_cjson
    data: {
            "serialNumber": "212089842348362300",
            "cellularInfo": [{
                            "name": "ethernet0/0/1",
                            "switch":       "0"
                    }, {
                            "name": "ethernet0/0/2",
                            "switch":       "1"
                    }, {
                            "name": "ethernet0/0/3",
                            "switch":       "0"
                    }],
            "family":       ["father", "mother", "brother", "sister", "somebody"]
    }
    serialNumber: ok
    family: ok
    family array size is 5
    0: father
    1: mother
    2: brother
    3: sister
    4: somebody
    cellularInfo: ok
    cellularInfo array size is 3
    0-0: ethernet0/0/1
    0-1: 0
    1-0: ethernet0/0/2
    1-1: 1
    2-0: ethernet0/0/3
    2-1: 0

## cJSON 参考资料 ##

cJSON Github 官网地址：[https://github.com/DaveGamble/cJSON][https_github.com_DaveGamble_cJSON]

cJSON 开发参考: [https://zhuanlan.zhihu.com/p/55095477?utm\_oi=892471685738024960][https_zhuanlan.zhihu.com_p_55095477_utm_oi_892471685738024960]

[https_github.com_DaveGamble_cJSON]: https://github.com/DaveGamble/cJSON
[828da76057214d31b55ffef966bbe3c4.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/02/06/b199cde1d4be4332ab2899adf3159f9a.png
[07db4c08719f49f7aa369105b83d34bf.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/02/06/de466f88dc7e4b61908a9d66752dcdfd.png
[Link 1]: https://so.csdn.net/so/search?q=%E9%9D%99%E6%80%81%E5%BA%93&spm=1001.2101.3001.7020
[3f3fca54571c4969bf500c48061f5a3e.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/02/06/0bbb05f6c14748b7bebbdfa1feea50e9.png
[07cc32c34521450192772e6282ece7d2.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/02/06/ff17d6a34738474cb7feca595062b7ff.png
[https_zhuanlan.zhihu.com_p_55095477_utm_oi_892471685738024960]: https://zhuanlan.zhihu.com/p/55095477?utm_oi=892471685738024960