在Jackson中反序列化具有相同名称但不同类型的属性？

问题描述

我有一个REST API，它返回的JSON响应为：

  {
 channel： JHBHS  
} 
  

有时返回：

  {
 channel：{
 id：12321，
 name：某些频道 
 } 
} 
  

我有一个POJO，如：

  public class Event {
 private String channel; 
 @JsonProperty（ channel）
私人频道channelObj; 
} 
 
公共类频道{
 private int id; 
私有字符串名称； 
} 
  

那么，有没有办法（除了编写自己的自定义反序列化器）在中，这将帮助我映射频道为 String 类型的 String 和 Channel 是JSON对象时的类型？

换句话说，在Jackson中，有没有一种方法可以通过类型进行映射变量而不仅仅是 name ？

解决方案

我建议您使用像这样：

  class事件{
 
 @JsonProperty（ channel） 
私人JsonNode channelInternal; 
 
私人频道； 
 
私有字符串channelStr; 
 
 / ** 
 *带有通道解析的自定义获取器
 * @return channel 
 * / 
 public Channel getChannel（）{
 if （channel == null&& channelInternal！= null）{
 if（channelInternal.isObject（））{
 int id = channelInternal.get（ id）。intValue（）; 
字符串名称= channelInternal.get（名称）.asText（）; 
 channel = new Channel（id，name）; 
} 
} 
返回频道； 
} 
 
 / ** 
 *自定义带有通道字符串解析的吸气剂
 * @返回通道字符串
 * / 
 public String getChannelStr（ ）{
 if（channelStr == null&& channelInternal！= null）{
 if（channelInternal.isTextual（））{
 channelStr = channelInternal.asText（）; 
} 
} 
返回channelStr; 
} 
} 
  

或类似的：

 类事件{
 
私人频道； 
 
私有字符串channelStr; 
 
 @JsonSetter（ channel）
 public void setChannelInternal（JsonNode channelInternal）{
 if（channelInternal！= null）{
 if（channelInternal.isTextual（） ）{
 channelStr = channelInternal.asText（）; 
}否则if（channelInternal.isObject（））{
 int id = channelInternal.get（ id）。intValue（）; 
字符串名称= channelInternal.get（名称）.asText（）; 
 channel = new Channel（id，name）; 
} 
} 
} 
 
 public Channel getChannel（）{
返回频道； 
} 
 
 public String getChannelStr（）{
 return channelStr; 
} 
} 
  

但我认为使用自定义反序列化器更为常见。 / p>

这里是测试代码

  public static void main（String [] args）引发IOException {
 ObjectMapper objectMapper = new ObjectMapper（）; 
字符串source1 = {\n + 
 \ channel\：\ JHBHS\ \n + 
}; 
字符串source2 = {\n + 
 \ channel\：{\n + 
 \ id\：12321，\ n + 
 \ name\：\某些频道\ \n + 
} \n + 
}; 
 
 //测试对象解析
事件结果= objectMapper.readValue（source2，Event.class）; 
 System.out.println（String.format（％s：％s，result.getChannel（）。getId（），result.getChannel（）。getName（）））; 
 
 //测试字符串解析
结果= objectMapper.readValue（source1，Event.class）; 
 System.out.println（result.getChannelStr（））; 
} 
  

输出：

  12321：某些频道
 JHBHS 
  

I have a REST API which returns a JSON response as:

{
    "channel" : "JHBHS"
}

and sometimes it returns:

{
    "channel": {
                    "id": 12321,
                    "name": "Some channel"
               }
}

I have a POJO like:

public class Event {
    private String channel;
    @JsonProperty("channel")
    private Channel channelObj;
}

public class Channel {
    private int id;
    private String name;
}

So, is there a way (other than writing your own custom deserializer) in Jackson2 which will help me map channel in JSON to String type when it's a String and Channel type when it's a JSON Object?

Or in other words, is there a way in Jackson which maps by type of the variable and not just by name?

解决方案

I can suggest you to use JsonNode like this:

class Event {

    @JsonProperty("channel")
    private JsonNode channelInternal;

    private Channel channel;

    private String channelStr;

    /**
     * Custom getter with channel parsing
     * @return channel
     */
    public Channel getChannel() {
        if (channel == null && channelInternal != null) {
            if (channelInternal.isObject()) {
                int id = channelInternal.get("id").intValue();
                String name = channelInternal.get("name").asText();
                channel = new Channel(id, name);
            }
        }
        return channel;
    }

    /**
     * Custom getter with channel string parsing
     * @return channel string
     */
    public String getChannelStr() {
        if (channelStr == null && channelInternal != null) {
            if (channelInternal.isTextual()) {
                channelStr = channelInternal.asText();
            }
        }
        return channelStr;
    }
}

or like this:

class Event {

    private Channel channel;

    private String channelStr;

    @JsonSetter("channel")
    public void setChannelInternal(JsonNode channelInternal) {
        if (channelInternal != null) {
            if (channelInternal.isTextual()) {
                channelStr = channelInternal.asText();
            } else if (channelInternal.isObject()) {
                int id = channelInternal.get("id").intValue();
                String name = channelInternal.get("name").asText();
                channel = new Channel(id, name);
            }
        }
    }

    public Channel getChannel() {
        return channel;
    }

    public String getChannelStr() {
        return channelStr;
    }
}

But I think using custom deserializer is more common.

Here is test code

public static void main(String[] args) throws IOException {
    ObjectMapper objectMapper = new ObjectMapper();
    String source1 = "{\n" +
            "    \"channel\" : \"JHBHS\"\n" +
            "}";
    String source2 = "{\n" +
            "    \"channel\": {\n" +
            "                    \"id\": 12321,\n" +
            "                    \"name\": \"Some channel\"\n" +
            "               }\n" +
            "}";

    //Test object parsing
    Event result = objectMapper.readValue(source2, Event.class);
    System.out.println(String.format("%s : %s", result.getChannel().getId(), result.getChannel().getName()));

    //Test string parsing
    result = objectMapper.readValue(source1, Event.class);
    System.out.println(result.getChannelStr());
}

And the output:

12321 : Some channel
JHBHS

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