无法读取 JSON：无法构造`java.util.LinkedHashMap` 的实例

Question

如果我得到了不确定的行 JSON 数据。我应该如何设置我的班级？这是我现在的班级public class ChatMessage {private Map<String, String> message = new HashMap<>();@JsonAnyGetterpublic Map<String, String> any(){    return this.message;}public Map<String, String> getMessage() {    return this.message;}@JsonAnySetterpublic void setMessage(String key, String value) {    message.put(key, value);}@Overridepublic String toString() {    return "Message [message=" + message + "]";}}这是我从 js 发送的 json{"type":"message","user":"james","to":"","message":"Hi every"}我现在有错误org.springframework.messaging.converter.MessageConversionException: Could not read JSON: Cannot construct instance of `java.util.LinkedHashMap` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('Welcome james join the room')at [Source: (byte[])" . {"type":"message","user":"james","to":"","message":"Welcome james join the room"}"; line: 1, column: 52] (through reference chain: chat.model.ChatMessage["message"]); nested exception is         com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct         instance of `java.util.LinkedHashMap` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('Welcome james join the room')at [Source: (byte[])" . {"type":"message","user":"james","to":"","message":"Welcome james join the room"}"; line: 1, column: 52] (through reference chain: chat.model.ChatMessage["message"])因为我的 json 会像{"type":"message", "user":"james", "to":"", "message":"Welcome james join the room", "xxx":"xxxxxxxxxxxxx"}或者{"type":"message", "user":"james", "to":"", "message":"Welcome james join the room", "yyy":"xxxxxxxxxxxxx"}我应该如何设置我的班级？谢谢

Answer 1

重命名messagejson 中的字段或messagePOJO 中的字段。根据您的 POJO 结构，jackson 试图反序列化"message":"Hi every"到您的 POJO 中的消息字段，并且无法从中创建 Map（因为它只是一个字符串）。

您的代码将使用以下 json：

{"type":"message","user":"james","to":"","json-message":"Hi every"}

或者

以下POJO：

public class ChatMessage {

private Map<String, String> map = new HashMap<>();

@JsonAnyGetter

public Map<String, String> any(){

    return this.map;

}

public Map<String, String> getMap() {

    return this.map;

}

@JsonAnySetter

public void setMap(String key, String value) {

    map.put(key, value);

}

@Override

public String toString() {

    return "Map [map=" + map + "]";

}

}