问题描述
所以在运行代码之前,这是example.json:
fetch_object()
当我执行此代码时:
{
"example1": 5
}
然后这发生在example.json:
JsonWriter exampleWriter = new JsonWriter(new FileWriter(examplePath));
exampleWriter.beginobject();
exampleWriter.name("example2").value(13);
exampleWriter.endobject();
exampleWriter.close();
我希望example.json包含example1和example2的数据,我该怎么做?
解决方法
尝试 JsonWriter exampleWriter =新的JsonWriter(新的FileWriter(examplePath,true));
,您可以将整个JSON
有效负载读取为JsonObject
并添加新属性。之后,您可以将其序列化回JSON
。
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonObject;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
public class GsonApp {
public static void main(String[] args) throws IOException {
Path pathToJson = Paths.get("./resource/test.json");
Gson gson = new GsonBuilder().setPrettyPrinting().create();
try (BufferedReader reader = Files.newBufferedReader(pathToJson);
BufferedWriter writer = Files.newBufferedWriter(pathToJson,StandardOpenOption.WRITE)) {
JsonObject root = gson.fromJson(reader,JsonObject.class);
root.addProperty("example2",13);
gson.toJson(root,writer);
}
}
}
上面的代码生成:
{
"example1": 5,"example2": 13
}
另请参阅: