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2026-06-18

获取JSON对象中的字符串值 - JsonGetString ​

函数简介 ​

获取JSON对象中指定键对应的字符串值。

接口名称 ​

JsonGetString

DLL调用 ​

c
long JsonGetString(long obj, string key, int* err);

参数说明 ​

参数名类型说明
obj长整数型JSON对象句柄。
key字符串键名。
err整数型指针错误码输出参数，可为0。

示例 ​

SDK 调用 ​

cpp
#include "OLAPlugServer.h"

OLAPlugServer ola;
// 假设 jsonStr 来自 HTTP 响应、文件读取或 MatchImage 等接口
const char* jsonStr = "{\"username\":\"ola\",\"enabled\":true,\"vip\":false,\"level\":10}";
int32_t err = 0;
int64_t root = ola.JsonParse(jsonStr, &err);
if (root != 0 && err == 0) {
    int32_t getErr = 0;
    std::string username = ola.JsonGetString(root, "username", &getErr);
    ola.JsonFree(root);
}
csharp
using OLAPlug;

var ola = new OLAPlugServer();
// 假设 jsonStr 来自 HTTP 响应、文件读取或 MatchImage 等接口
string jsonStr = "{\"username\":\"ola\",\"enabled\":true,\"vip\":false,\"level\":10}";
int err;
long root = ola.JsonParse(jsonStr, out err);
if (root != 0 && err == 0)
{
    int getErr;
    string username = ola.JsonGetString(root, "username", out getErr);
    ola.JsonFree(root);
}
python
from OLAPlugServer import OLAPlugServer

ola = OLAPlugServer()
# 假设 json_str 来自 HTTP 响应、文件读取或 MatchImage 等接口
json_str = '{"username":"ola","enabled":true,"vip":false,"level":10}'
root, err = ola.JsonParse(json_str)
if root != 0 and err == 0:
    username, get_err = ola.JsonGetString(root, "username")
    ola.JsonFree(root)
java
import com.olaplug.OLAPlugServer;
import com.sun.jna.ptr.IntByReference;

OLAPlugServer ola = new OLAPlugServer();
// 假设 jsonStr 来自 HTTP 响应、文件读取或 MatchImage 等接口
String jsonStr = "{\"username\":\"ola\",\"enabled\":true,\"vip\":false,\"level\":10}";
IntByReference err = new IntByReference(0);
long root = com.olaplug.OLAPlugDLLHelper.JsonParse(jsonStr, err);
if (root != 0 && err.getValue() == 0) {
    com.sun.jna.ptr.IntByReference getErr = new com.sun.jna.ptr.IntByReference(0);
    String username = com.olaplug.OLAPlugServer.PtrToStringUTF8(
        com.olaplug.OLAPlugDLLHelper.JsonGetString(root, "username", getErr));
    ola.JsonFree(root);
}
cpp
var ola = com("OlaPlug.OlaSoft")
// 假设 jsonStr 来自 HTTP 响应等接口
var jsonStr = "{\"username\":\"ola\",\"enabled\":true,\"vip\":false,\"level\":10}"
var err = 0
var root = ola.JsonParse(jsonStr, err)
if(root && err == 0) {
    var getErr = 0
    var username = ola.JsonGetString(root, "username", getErr)
    ola.JsonFree(root)
}
vbscript
Set ola = CreateObject("OlaPlug.OlaSoft")
' 假设 jsonStr 来自 HTTP 响应等接口
jsonStr = "{""username"":""ola"",""enabled"":true,""vip"":false,""level"":10}"
err = 0
root = ola.JsonParse(jsonStr, err)
If root <> 0 And err = 0 Then
    getErr = 0
    username = ola.JsonGetString(root, "username", getErr)
    ola.JsonFree(root)
End If
text
.局部变量 ola, OLAPlug
ola.创建 ()
' 假设 jsonStr 来自 HTTP 响应等接口
jsonStr ＝ “{“username“:“ola“,“enabled“:true,“vip“:false,“level“:10}“
err ＝ 0
root ＝ ola.JsonParse (jsonStr, err)
.如果真 (root ≠ 0 且 err ＝ 0)
    getErr ＝ 0
    username ＝ ola.JsonGetString (root, "username", getErr)
    ola.JsonFree (root)
.如果真结束
aardio
import OLAPlugServer;
var ola = OLAPlugServer();
// 假设 jsonStr 来自 HTTP 响应等接口
var jsonStr = "{\"username\":\"ola\",\"enabled\":true,\"vip\":false,\"level\":10}";
var err = 0;
var root = ola.JsonParse(jsonStr, err);
if(root && !err){
    var getErr = 0;
    var username = ola.JsonGetString(root, "username", getErr);
    ola.JsonFree(root);
}
text
变量 ola <类型 = OLAPlugServer>
ola = 新建 OLAPlugServer
// 假设 jsonStr 来自 HTTP 响应等接口
文本型 jsonStr = "{\"username\":\"ola\",\"enabled\":true,\"vip\":false,\"level\":10}"
整数 err = 0
长整数 root = ola.JsonParse(jsonStr, err)
如果真 (root ≠ 0 且 err ＝ 0)
{
    整数 getErr = 0
    文本型 username = ola.JsonGetString(root, "username", getErr)
    ola.JsonFree(root)
}
cpp
#include "OLAPlugServer.h"

OLAPlugServer ola;
// 假设 jsonStr 来自 HTTP 响应、文件读取或 MatchImage 等接口
const char* jsonStr = "{\"username\":\"ola\",\"enabled\":true,\"vip\":false,\"level\":10}";
int32_t err = 0;
int64_t root = ola.JsonParse(jsonStr, &err);
if (root != 0 && err == 0) {
    int32_t getErr = 0;
    std::string username = ola.JsonGetString(root, "username", &getErr);
    ola.JsonFree(root);
}

原生 DLL 调用 ​

cpp
long instance = CreateCOLAPlugInterFace();
const char* jsonStr = "{\"username\":\"ola\",\"enabled\":true,\"vip\":false,\"level\":10}";
int err = 0;
long root = JsonParse(instance, jsonStr, &err);
if (root != 0 && err == 0) {
long instance = CreateCOLAPlugInterFace();
const char* jsonStr = "{\"username\":\"ola\",\"enabled\":true,\"vip\":false,\"level\":10}";
int err = 0;
long root = JsonParse(instance, jsonStr, &err);
if (root != 0) {
    long ptr = JsonGetString(instance, root, "username", 0);
    if (ptr != 0) {
        char username[256] = {0};
        GetStringFromPtr(ptr, username, sizeof(username));
        FreeStringPtr(ptr);
    }
    JsonFree(instance, root);
}
    JsonFree(instance, root);
}
csharp
using System.Runtime.InteropServices;
using System.Text;

[DllImport("OLAPlug_x64.dll", CallingConvention = CallingConvention.StdCall)]
static extern long CreateCOLAPlugInterFace();

long instance = CreateCOLAPlugInterFace();
string jsonStr = "{\"username\":\"ola\",\"enabled\":true,\"vip\":false,\"level\":10}";
int err = 0;
long root = JsonParse(instance, jsonStr, err);
if (root != 0 && err == 0)
{
using System.Runtime.InteropServices;
using System.Text;

[DllImport("OLAPlug_x64.dll", CallingConvention = CallingConvention.StdCall)]
static extern long CreateCOLAPlugInterFace();
[DllImport("OLAPlug_x64.dll", CallingConvention = CallingConvention.StdCall)]
static extern int GetStringFromPtr(long ptr, StringBuilder lpString, int size);
[DllImport("OLAPlug_x64.dll", CallingConvention = CallingConvention.StdCall)]
static extern int FreeStringPtr(long ptr);
[DllImport("OLAPlug_x64.dll", CallingConvention = CallingConvention.StdCall)]
static extern int GetStringSize(long ptr);
[DllImport("OLAPlug_x64.dll", CallingConvention = CallingConvention.StdCall)]
static extern long JsonGetString(long ola, long obj, string key, int err);
[DllImport("OLAPlug_x64.dll", CallingConvention = CallingConvention.StdCall)]
static extern long JsonParse(long ola, string str, int err);
[DllImport("OLAPlug_x64.dll", CallingConvention = CallingConvention.StdCall)]
static extern int JsonFree(long ola, long obj);

long instance = CreateCOLAPlugInterFace();
string jsonStr = "{\"username\":\"ola\",\"enabled\":true,\"vip\":false,\"level\":10}";
long root = JsonParse(instance, jsonStr, 0);
if (root != 0) {
    long ptr = JsonGetString(instance, root, "username", 0);
    if (ptr != 0) {
        StringBuilder sb = new StringBuilder(GetStringSize(ptr) + 1);
        GetStringFromPtr(ptr, sb, sb.Capacity);
        FreeStringPtr(ptr);
    }
    JsonFree(instance, root);
}
python
from ctypes import CDLL, c_int, c_int64, create_string_buffer

ola = CDLL("OLAPlug_x64.dll")
ola.CreateCOLAPlugInterFace.restype = c_int64
instance = ola.CreateCOLAPlugInterFace()
json_str = b'{"username":"ola","enabled":true,"vip":false,"level":10}'
err = c_int(0)
root = ola.JsonParse(instance, json_str, err)
if root and err.value == 0:
    get_err = c_int(0)
    ptr = ola.JsonGetString(instance, root, b"username", get_err)
    if ptr:
        buf = create_string_buffer(256)
        ola.GetStringFromPtr(ptr, buf, 256)
        ola.FreeStringPtr(ptr)
        username = buf.value.decode("utf-8")
    ola.JsonFree(instance, root)

返回值 ​

返回值说明
（返回值）返回字符串指针，失败时返回0。需调用 FreeStringPtr 释放内存。

注意事项 ​

项目说明
释放内存返回的字符串需要调用 FreeStringPtr 释放内存。
如果键不存在或值不是字符串类型如果键不存在或值不是字符串类型，返回0。