I have the following json file:

[{"name":"James","height":170.3,"weight":55.945535152517735,"items":[{"name":"Tickle","number":1000},{"name":"Greedy","number":1400}]},{"name":"Mary","height":150.43,"weight":55.943284737579376,"items":[{"name":"Happy","number":1400},{"name":"Nosey","number":1100}]},{"name":"Robert","height":167.21,"weight":55.94449876875712,"items":[{"name":"Sneeze","number":1400},{"name":"Bump","number":900}]},{"name":"John","height":134.32,"weight":55.94390696616939,"items":[{"name":"Snow","number":1400},{"name":"Messy","number":900}]}]

And have two classes for the data:

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

@JsonIgnoreProperties(ignoreUnknown = true)
public class People {
    private String name;
    private double height;
    private double weight;
    private Item item;


//setters and getters

}

...

    import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
    
    @JsonIgnoreProperties(ignoreUnknown = true)
    public class Item{
        private String name;
        private int number;

        //setters and getters
}

I used jackson to read the data:

import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;

public class TestClient {
    public static void main(String[] args)
    {

        ObjectMapper mapper = new ObjectMapper();
        try {
            People[] usrPost = mapper.readValue(new URL("https://mylink"), People[].class);
            System.out.println(usrPost[2]);
        } catch ( MalformedURLException e ) {
            e . printStackTrace ( ) ;
        } catch ( IOException e ) {
            e . printStackTrace ( ) ;
        }
    }
    }

For some reason I keep on getting the following error message:

com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize value of type ` ` from Array value (token `JsonToken.START_ARRAY`)
 at [Source: (URL); line: 1, column: 97] (through reference chain: java.lang.Object[][0]-> People["item"])
    at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:59)
    at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1741)
    at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1515)
    at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1462)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeFromArray(BeanDeserializer.java:648)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:211)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:187)
    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:129)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:314)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:177)
    at com.fasterxml.jackson.databind.deser.std.ObjectArrayDeserializer.deserialize(ObjectArrayDeserializer.java:214)
    at com.fasterxml.jackson.databind.deser.std.ObjectArrayDeserializer.deserialize(ObjectArrayDeserializer.java:24)
    at com.fasterxml.jackson.databind.deser.DefaultDeserializationContext.readRootValue(DefaultDeserializationContext.java:323)
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4674)
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3560)
    at uk.ac.ed.inf.TestClient.main(TestClient.java:21)

Any help would be greatly appreciated! Think there might be an issue with the second Item class and the fact that I'm reading an array.

CodePudding user response：

try this modified People class ... in your json, items is an array, so model must fit

@JsonIgnoreProperties(ignoreUnknown = true)
public class People {
    private String name;
    private double height;
    private double weight;
    private List<Item> items;

    // other getter/setter

    public List<Item> getItems() {
        return items;
    }

    public void setItems(List<Item> items) {
        this.items = items;
    }
}