c json解析示例

json-c是最主流的json c库。
[root@hs-10-20-30-193 build]# cmake -DCMAKE_INSTALL_PREFIX=/usr/local ..
-- The C compiler identification is GNU 4.8.5
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc - works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Looking for sys/resource.h
-- Looking for sys/resource.h - found
-- Looking for getrusage
-- Looking for getrusage - found
-- Wrote /home/zjh/json-c-json-c-0.16-20220414/build/apps_config.h
-- Looking for fcntl.h
-- Looking for fcntl.h - found
-- Looking for inttypes.h
-- Looking for inttypes.h - found
-- Looking for stdarg.h
-- Looking for stdarg.h - found
-- Looking for strings.h
-- Looking for strings.h - found
-- Looking for string.h
-- Looking for string.h - found
-- Looking for syslog.h
-- Looking for syslog.h - found
-- Looking for 4 include files stdlib.h, ..., float.h
-- Looking for 4 include files stdlib.h, ..., float.h - found
-- Looking for unistd.h
-- Looking for unistd.h - found
-- Looking for sys/types.h
-- Looking for sys/types.h - found
-- Looking for dlfcn.h
-- Looking for dlfcn.h - found
-- Looking for endian.h
-- Looking for endian.h - found
-- Looking for limits.h
-- Looking for limits.h - found
-- Looking for locale.h
-- Looking for locale.h - found
-- Looking for memory.h
-- Looking for memory.h - found
-- Looking for stdint.h
-- Looking for stdint.h - found
-- Looking for stdlib.h
-- Looking for stdlib.h - found
-- Looking for sys/cdefs.h
-- Looking for sys/cdefs.h - found
-- Looking for sys/param.h
-- Looking for sys/param.h - found
-- Looking for sys/random.h
-- Looking for sys/random.h - not found
-- Looking for sys/stat.h
-- Looking for sys/stat.h - found
-- Looking for xlocale.h
-- Looking for xlocale.h - found
-- Looking for _isnan
-- Looking for _isnan - not found
-- Looking for _finite
-- Looking for _finite - not found
-- Looking for INFINITY
-- Looking for INFINITY - found
-- Looking for isinf
-- Looking for isinf - found
-- Looking for isnan
-- Looking for isnan - found
-- Looking for nan
-- Looking for nan - found
-- Looking for _doprnt
-- Looking for _doprnt - not found
-- Looking for snprintf
-- Looking for snprintf - found
-- Looking for vasprintf
-- Looking for vasprintf - found
-- Looking for vsnprintf
-- Looking for vsnprintf - found
-- Looking for vprintf
-- Looking for vprintf - found
-- Looking for arc4random
-- Looking for arc4random - not found
-- Looking for bsd/stdlib.h
-- Looking for bsd/stdlib.h - not found
-- Looking for open
-- Looking for open - found
-- Looking for realloc
-- Looking for realloc - found
-- Looking for setlocale
-- Looking for setlocale - found
-- Looking for uselocale
-- Looking for uselocale - found
-- Looking for strcasecmp
-- Looking for strcasecmp - found
-- Looking for strncasecmp
-- Looking for strncasecmp - found
-- Looking for strdup
-- Looking for strdup - found
-- Looking for strerror
-- Looking for strerror - found
-- Looking for vsyslog
-- Looking for vsyslog - found
-- Looking for strtoll
-- Looking for strtoll - found
-- Looking for strtoull
-- Looking for strtoull - found
-- Looking for stddef.h
-- Looking for stddef.h - found
-- Check size of int
-- Check size of int - done
-- Check size of int64_t
-- Check size of int64_t - done
-- Check size of long
-- Check size of long - done
-- Check size of long long
-- Check size of long long - done
-- Check size of size_t
-- Check size of size_t - done
-- Check size of ssize_t    // ssize_t这个数据类型用来表示可以被执行读写操作的数据块的大小。 它和size_t类似,但必需是signed.意即：它表示的是signed size_t类型的。
-- Check size of ssize_t - done
-- Performing Test HAS_GNU_WARNING_LONG
-- Performing Test HAS_GNU_WARNING_LONG - Failed
-- Performing Test HAVE_ATOMIC_BUILTINS
-- Performing Test HAVE_ATOMIC_BUILTINS - Success
-- Performing Test HAVE___THREAD
-- Performing Test HAVE___THREAD - Success
-- Wrote /home/zjh/json-c-json-c-0.16-20220414/build/config.h
-- Wrote /home/zjh/json-c-json-c-0.16-20220414/build/json_config.h
-- Performing Test REENTRANT_WORKS
-- Performing Test REENTRANT_WORKS - Success
-- Performing Test BSYMBOLIC_WORKS
-- Performing Test BSYMBOLIC_WORKS - Success
-- Performing Test VERSION_SCRIPT_WORKS
-- Performing Test VERSION_SCRIPT_WORKS - Success
-- Could NOT find Doxygen (missing: DOXYGEN_EXECUTABLE) 
Warning: doxygen not found, the 'doc' target will not be included
-- Configuring done
-- Generating done
-- Build files have been written to: /home/zjh/json-c-json-c-0.16-20220414/build
[root@hs-10-20-30-193 build]# make all install
Scanning dependencies of target json-c
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[ 16%] Linking C shared library libjson-c.so
[ 16%] Built target json-c
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Install the project...
-- Install configuration: "debug"
-- Installing: /usr/local/lib64/libjson-c.so.5.2.0
-- Up-to-date: /usr/local/lib64/libjson-c.so.5
-- Up-to-date: /usr/local/lib64/libjson-c.so
-- Installing: /usr/local/lib64/libjson-c.a
-- Installing: /usr/local/lib64/cmake/json-c/json-c-targets.cmake
-- Installing: /usr/local/lib64/cmake/json-c/json-c-targets-debug.cmake
-- Installing: /usr/local/lib64/cmake/json-c/json-c-config.cmake
-- Installing: /usr/local/lib64/pkgconfig/json-c.pc
-- Installing: /usr/local/include/json-c/json_config.h
-- Installing: /usr/local/include/json-c/json.h
-- Installing: /usr/local/include/json-c/arraylist.h
-- Installing: /usr/local/include/json-c/debug.h
-- Installing: /usr/local/include/json-c/json_c_version.h
-- Installing: /usr/local/include/json-c/json_inttypes.h
-- Installing: /usr/local/include/json-c/json_object.h
-- Installing: /usr/local/include/json-c/json_object_iterator.h
-- Installing: /usr/local/include/json-c/json_tokener.h
-- Installing: /usr/local/include/json-c/json_types.h
-- Installing: /usr/local/include/json-c/json_util.h
-- Installing: /usr/local/include/json-c/json_visit.h
-- Installing: /usr/local/include/json-c/linkhash.h
-- Installing: /usr/local/include/json-c/printbuf.h
-- Installing: /usr/local/include/json-c/json_pointer.h

// 解析字符串
    json_object* root = json_tokener_parse(json_str);
// 获取根节点里面的"C"属性
    json_object* changes = json_object_object_get(root, "C");
    
// 判断json属性值的类型
    if (json_object_get_type(changes) == json_type_null)
    {
        printf("empty xlog record, just a ddl or not supported dml(not insert/update/delete/truncate)\n");
        return OCI_SUCCESS;
    }
    else
    {
        int change_rows = json_object_array_length(changes); // 获取json数组的长度
        
        if (change_rows > 2)
            json_object_array_sort(changes, json_sort_by_obj_kind_func);  // json数组排序
......
    // 获取json数组中某个成员的值
                record = json_object_array_get_idx(changes, i);
                record_attr = json_object_object_get(record, "K");
                const char* dml_type = json_object_get_string(record_attr);   // json对象转字符串
    json_object_put(root); // 最后必须调用json_object_put(root)解除对root对象的引用，否则会导致内存泄露

void json_object_array_sort(struct json_object *jso, int (*sort_fn)(const void *, const void *))
{
    assert(json_object_get_type(jso) == json_type_array);
    array_list_sort(JC_ARRAY(jso)->c_array, sort_fn);
}

// 排序函数
static int json_sort_by_obj_kind_func(const void* j1, const void* j2)
{
    json_object* const* jso1, * const* jso2;
    char str1[65] = { 0 }, str2[65] = { 0 };

    jso1 = (json_object* const*)j1;
    jso2 = (json_object* const*)j2;

    if (!*jso1 && !*jso2)
        return 0;
    if (!*jso1)
        return -1;
    if (!*jso2)
        return 1;

    snprintf(str1, 64, "%s %s %s",
        json_object_get_string(json_object_object_get(*jso1, "K")),
        json_object_get_string(json_object_object_get(*jso1, "T")),
        json_object_get_string(json_object_object_get(*jso1, "S")));
    snprintf(str2, 64, "%s %s %s",
        json_object_get_string(json_object_object_get(*jso2, "K")),
        json_object_get_string(json_object_object_get(*jso2, "T")),
        json_object_get_string(json_object_object_get(*jso2, "S")));

    return strcmp(str1, str2);
}