java - 为什么没有写JSON？

Question

这是代码:

public static void init() {
    File file = new File(SimpleMessagesAPI.getMainAPI().getDataFolder(), "config.json");
    try {

        ObjectMapper objectMapper = new ObjectMapper();
        ArrayNode arrayNode = objectMapper.createArrayNode();
        ObjectNode firstObjectNode = objectMapper.createObjectNode();
        ObjectNode secondObjectNode = objectMapper.createObjectNode();

        firstObjectNode.put("period", 5);
        firstObjectNode.put("async", true);
        firstObjectNode.put("country", "Europe/Bucharest");

        secondObjectNode.putArray("broadcast")
                .add("&7Hello players! Now is %server_online players!")
                .add("&eNow is %time")
                .add("&6Thanks for playing on that server!")
                .add("&cHave fun guys! %motd");

        ArrayNode firstArrayNode = objectMapper.createArrayNode();
        firstArrayNode.add(firstObjectNode);

        ArrayNode secondArrayNode = objectMapper.createArrayNode();
        secondArrayNode.add(secondObjectNode);

        ObjectNode principalObjectNode = objectMapper.createObjectNode();
        principalObjectNode.putPOJO("mechanic", firstArrayNode);

        ObjectNode secondarObjectNode = objectMapper.createObjectNode();
        secondarObjectNode.putPOJO("messages", secondArrayNode);

        arrayNode.add(principalObjectNode);
        arrayNode.add(secondarObjectNode);

        if (!file.exists()) {
                file.createNewFile();
                objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(arrayNode);
        }

        /*String json = file.toString();
        JsonNode jsonNode = objectMapper.readTree(json);
        String messages = jsonNode.get("messages").asText();
        String mechanic = jsonNode.get("mechanic").asText();
        System.out.println("Messages: " + messages + "\n\n\n" + "Mechanic: " + mechanic + "\n\n");*/
        //ObjectConfig config = new ObjectConfig(messages, mechanic);
        //objectMapper.writeValue(new File(SimpleMessagesAPI.getMainAPI().getDataFolder() + "config.json"), config);

    } catch (IOException e) {
            e.printStackTrace();
    }
}

这就是我想要创建的 JSON:

{
  "mechanic": {
    "period"          : 5,
    "async"           : true,
    "country"         : "Europe/Bucharest"
  },
  "messages": {
    "broadcast"       : [
      "&7Hello players! Now is %server_online players!",
      "&eNow is %time",
      "&6Thanks for playing on that server!",
      "&cHave fun guys! %motd"
    ]
  }
}

但是当我执行代码时，这创建了一个空的 JSON 对象，为什么？

并且 file.createNewFile(); 表示“结果被忽略”。

非常感谢大家的帮助

Answer 1

您的代码行有 2 个问题

file.createNewFile();
objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(arrayNode);

1. 您在 file.createNewFile(); 上收到编译器警告: 结果被忽略，因为您忽略了返回的 boolean 结果 file.createNewFile().

   你最好应该这样做:

   if (!file.createNewFile())
       throw new IOException("could not create file " + file);
   

2. 您的方法调用.writeValueAsString(arrayNode)只是 生成一个 JSON 字符串，但它不会将此字符串写入任何地方。

   您需要使用.writeValue(file, arrayNode)相反。