JSON 文件 - Java：编辑/更新字段值
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JSON File - Java: editing/updating fields values
提问by GrayFox
I have some JSONObject(s) in my workflow, and the same JSONObjects are stored by writting them into a json file.
我的工作流程中有一些 JSONObject(s)，并且通过将它们写入 json 文件来存储相同的 JSONObject。
I would like an efficient way to update the json file, only fields where is needed, with the content of newer JSONObjects instances.
我想要一种有效的方法来更新 json 文件，只有需要的字段，以及较新的 JSONObjects 实例的内容。
Eg:
例如：
On file I have
在文件中我有
ObjectOnFile = {key1:val1, key2:val2,...}
In memory I have
在记忆中我有
ObjectInMemory = {key1:val1_newer, key2:val2_newer,...}
The update will be like:
更新将类似于：
if (!(ObjectInMemory.get(key1).equals(ObjectOnFile.get(key1)))
// update file field value <--- how to?
In general I would like to update the value of every key where its content is newer (different).
一般来说，我想更新其内容较新（不同）的每个键的值。
Actually my code is:
其实我的代码是：
import org.json.JSONObject;
import com.fasterxml.Hymanson.databind.ObjectMapper;
ObjectMapper mapper = new ObjectMapper();
Sting key = "key1"; //whatever
JSONObject jo = new JSONObject("{key1:\"val1\", key2:\"val2\"}");
JSONObject root = mapper.readValue(new File(json_file), JSONObject.class);
JSONObject val_newer = jo.getJSONObject(key);
JSONObject val_older = root.getJSObject(key);
if(!val_newer.equals(val_older)){
root.put(key,val_newer);
/*write back root to the json file...how? */
}
采纳答案by PVR
Simply you can do like this:
你可以这样做：
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import org.json.JSONException;
import org.json.JSONObject;
import com.fasterxml.Hymanson.databind.ObjectMapper;
public class Test {
public static void main(String[] args) throws JSONException, IOException
{
ObjectMapper mapper = new ObjectMapper();
String key = "key1"; //whatever
JSONObject jo = new JSONObject("{key1:\"val1\", key2:\"val2\"}");
//Read from file
JSONObject root = mapper.readValue(new File("json_file"), JSONObject.class);
String val_newer = jo.getString(key);
String val_older = root.getString(key);
//Compare values
if(!val_newer.equals(val_older))
{
//Update value in object
root.put(key,val_newer);
//Write into the file
try (FileWriter file = new FileWriter("json_file"))
{
file.write(root.toString());
System.out.println("Successfully updated json object to file...!!");
}
}
}
}
