如何使用 Jackson 解析具有不同类型的无名数组

Question

I have some json data that looks like

"value": [ 1572553480.732, "118" ]

And the parser is choking with a "Cannot construct instance of Value (no Creators, like default construct, exist): no double/Double-argument constructor/factory method to deserialize from Number value (1.572553780732E9)"

My data class looks like:

public class Value {
  private double uTime;
  private String count;
  public Value() { super(); }
  public Value(double uTime, String count) {...}
  // also getters and setters for both
}

Answer 1

You can use @JsonFormat annotation with JsonFormat.Shape.ARRAY shape:

import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JsonPathApp {

    public static void main(String[] args) throws Exception {
        ObjectMapper mapper = new ObjectMapper();

        String json = "{\"value\": [ 1572553480.732, \"118\" ]}";
        System.out.println(mapper.readValue(json, Root.class));
    }
}

class Root {

    @JsonFormat(shape = JsonFormat.Shape.ARRAY)
    private Value value;

    // getters, setters, toString
}

Above code prints:

Root{value=Value{uTime=1.572553480732E9, count='118'}}

Answer 2

Your json is not correct. You have a field 'value' with an array as value with a long and a String.

Try the following Json that should map in a Value object:

{"uTime":1572553480.732,"count":"118"}

If the 'value' is part of a bigger json then do the following:

{<other json string>, "value":{"uTime":1.572553480732E9,"count":"118"}, <otherjson>}