Question

我正在构建一个更新我的应用程序的updater工具。我需要保存以前版本的配置文件。一些配置文件是JSON文件。有没有办法以我保留旧值的方式更新JSON文件但如果有新的物品或钥匙，他们也会被保存吗？

例如：版本1 json文件：

{
    "name": "demo",
    "description": "Parse some JSON data",
    "location": "New York"
}

版本2 json文件：

{
    "name": "demo",
    "description": "Parse some JSON data",
    "location": "London",
    "day": "Monday"
}

合并后的预期json文件：

{
    "name": "demo",
    "description": "Parse some JSON data",
    "location": "New York",
    "day": "Monday"
}

有没有办法在没有任何外部库的情况下这样做？

Answer 1

正如@ cricket_007所建议的，这个解决方案对我有用：

public void mergeJsonsFiles(File newJson, File oldJson) throws Exception {
    HashMap<String, Object> newMap = convertJsonToMap(newJson);
    HashMap<String, Object> oldMap = convertJsonToMap(oldJson);

    for (Entry<String, Object> entry : oldMap.entrySet()) {
        if (newMap.get(entry.getKey()) == null) {
            newMap.put(entry.getKey(), entry.getValue());
        }
    }

    ObjectMapper mapper = new ObjectMapper();
    String jsonFromMap = mapper.writeValueAsString(newMap);

    PrintWriter writer = new PrintWriter(newJson);
    writer.write(jsonFromMap);
    writer.close();
}

private HashMap<String, Object> convertJsonToMap(File json) {
    ObjectMapper mapper = new ObjectMapper();
    HashMap<String, Object> map = new HashMap<String, Object>();
    try {
        map = mapper.readValue(json, new TypeReference<HashMap<String, Object>>(){});
    } catch (IOException e) {
        map.clear();
    }
    return map;
}

Java - 合并JSON文件

1 个答案: