如何将JsonNode实例转换为实际的Pojo [英] How to convert a JsonNode instance to an actual pojo

问题描述

在代码的特定位置，我已经将一个表示为字符串的JSON文档解析为 JsonNode ，因为我还不知道实际的目标pojo类类型.

At a certain point in my code, I have parse a JSON document, represented as a string, to a JsonNode, because I don't know yet the actual target pojo class type.

现在，一段时间后，我知道了pojo的 Class 实例，我想将此 JsonNode 转换为该类的实际pojo(用注释正确的 @JsonProperty 注释).能做到吗?如果可以，怎么办?

Now, some time later, I know the Class instance of the pojo and I want to convert this JsonNode to an actual pojo of that class (which is annotated with the proper @JsonProperty annotations). Can this be done? If so, how?

我正在使用Jackson 2.10.x.

I am working with Jackson 2.10.x.

推荐答案

在这种情况下，您可以使用两种方法:

In this case you can use two methods:

• 请参见以下示例:

  import com.fasterxml.jackson.databind.JsonNode;
  import com.fasterxml.jackson.databind.ObjectMapper;
  
  import java.io.File;
  import java.util.StringJoiner;
  
  public class JsonNodeConvertApp {
  
      public static void main(String[] args) throws Exception {
          File jsonFile = new File("./resource/test.json").getAbsoluteFile();
  
          ObjectMapper mapper = new ObjectMapper();
          JsonNode node = mapper.readTree(jsonFile);
  
          System.out.println(mapper.treeToValue(node, Message.class));
          System.out.println(mapper.convertValue(node, Message.class));
      }
  }
  
  class Message {
      private int id;
      private String body;
  
      // getters, setters, toString
  }
  

  上面的 JSON 有效负载的代码如下:

  Above code for JSON payload like below:

  {
    "id": 1,
    "body": "message body"
  }
  

  打印:

  Message[id=1, body='message body']
  Message[id=1, body='message body']
  

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