Question

如果我将获得不确定的行JSON数据。我应该如何设置我的课程？

这是我目前的课程

public class ChatMessage {

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

@JsonAnyGetter
public Map<String, String> any(){
    return this.message;
}

public Map<String, String> getMessage() {
    return this.message;
}

@JsonAnySetter
public void setMessage(String key, String value) {
    message.put(key, value);
}

@Override
public String toString() {
    return "Message [message=" + message + "]";
}
}

这是我从js发送的json

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

我现在出错了

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就像

{"type":"message",
 "user":"james",
 "to":"",
 "message":"Welcome james join the room",
 "xxx":"xxxxxxxxxxxxx"}

或

{"type":"message",
 "user":"james",
 "to":"",
 "message":"Welcome james join the room",
 "yyy":"xxxxxxxxxxxxx"}

我应该如何设置课程？谢谢

Answer 1

重命名json中的message字段或POJO中的message字段。根据您的POJO结构，杰克逊试图将"message":"Hi every"反序列化为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）。

您的代码将与以下json一起使用：

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

OR

遵循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 + "]";
}
}

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

1 个答案: