Parsing JSON and Converting in List Of Object

Question

I have a json response received from API Call the sample response is something like this

{
 "meta": {
   "code": "200"
  },
 "data": [
   {
    "Id": 44,
    "Name": "Malgudi ABC"
  },
  {
    "Id": 45,
    "Name": "Malgudi, DEF"
  }
]
}

I am trying to make List of Object from it, the code that i've written for this is

private static List<TPDetails> getListOfTpDetails(ResponseEntity<?> responseEntity){
       ObjectMapper objectMapper = new ObjectMapper();
        List<TPDetails> tpDetailsList = objectMapper.convertValue(responseEntity.getBody().getClass(), new TypeReference<TPDetails>(){});
        return tpDetailsList;
    }

Where TPDetails Object is Like this

public class TPDetails {
    int Id;
    String Name;
}

the code which i have used is resulting in

java.lang.IllegalArgumentException: Unrecognized field "meta" (class com.sbo.abc.model.TPDetails), not marked as ignorable (2 known properties: "Id", "Name"])
 at [Source: UNKNOWN; line: -1, column: -1] (through reference chain: com.sbo.abc.model.TPDetails["meta"])

I want to convert the Above JSON response in List

List<TPDetails> abc = [
{"Id": 44, "Name": "Malgudi ABC"},
{"Id": 45,"Name": "Malgudi DEF"}
]

Any help would be highly appreciable.Thanks well in advance

What libraries are you wanting to use, or do you have no preference? — BeUndead
– BeUndead, Commented Mar 29, 2019 at 10:34

Syed Khalid Ahmed · Accepted Answer · 2019-03-29 11:54:59Z

1

Create 2 more classes like

public class Temp {
    Meta meta;
    List<TPDetails> data;
}

public class Meta {
    String code;
}

and now convert this json to Temp class.

Temp temp = objectMapper.convertValue(responseEntity.getBody().getClass(), new TypeReference<Temp>(){});

UPDATED :

Make sure responseEntity.getBody() return the exact Json String which you mentioned above.

Temp temp = objectMapper.readValue(responseEntity.getBody(), new TypeReference<Temp>(){});

edited Mar 29, 2019 at 11:54

answered Mar 29, 2019 at 10:35

Syed Khalid Ahmed

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3 Comments

N Tanwar Over a year ago

java.lang.IllegalArgumentException: Cannot deserialize instance of java.util.ArrayList out of START_OBJECT token at [Source: UNKNOWN; line: -1, column: -1] (through reference chain: com.sbo.abc.model.TPWrapper["data"]) null, is what i'm getting while parsing the data

Syed Khalid Ahmed Over a year ago

@NTanwar use responseEntity.getBody() instead of responseEntity.getBody().getClass(). and are you sure convertValue is the function you want to use. I think readValue is the function

N Tanwar Over a year ago

Cannot resolve method 'readValue(capture<?>, anonymous com.fasterxml.jackson.core.type.TypeReference<com.sbo.abc.model.TPWrapper>)' is what i am getting TPWrapper class is like this ``` @Data @JsonInclude(JsonInclude.Include.NON_NULL) @JsonPropertyOrder({ "meta", "data" }) public class TPWrapper { @JsonIgnoreProperties("meta") TPMeta meta; @JsonProperty("data") List<TPDetails> data; } ```

Syed Khalid Ahmed · Accepted Answer · 2019-03-29 10:44:08Z

0

The format of your java class does not reflect the json you are parsing. I think it should be:

class Response {
    Meta meta;
    List<TPDetails> data;
}

class Meta {
    String code;
}

You should then pass Response to your TypeReference: new TypeReference<Response>(){}

If you don't care about the meta field, you can add @JsonIgnoreProperties to your response class and get rid of the Meta class and field.

edited Mar 29, 2019 at 10:44

Syed Khalid Ahmed

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answered Mar 29, 2019 at 10:37

burm87

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4 Comments

N Tanwar Over a year ago

java.lang.IllegalArgumentException: Cannot deserialize instance of java.util.ArrayList out of START_OBJECT token at [Source: UNKNOWN; line: -1, column: -1] (through reference chain: com.sbo.abc.model.TPWrapper["data"]) null is something which i have got

burm87 Over a year ago

@NTanwar do you have getters, setters and empty constructor on the classes?

N Tanwar Over a year ago

@Data @JsonInclude(JsonInclude.Include.NON_NULL) @JsonPropertyOrder({ "meta", "data" }) public class TPWrapper { @JsonIgnoreProperties("meta") TPMeta meta; @JsonProperty("data") List<TPDetails> data; } i am using lombok and annotations, so need not to write it explicitly

burm87 Over a year ago

I have noticed now, why are you using the convertValue method instead of the readValue? Also, I have added this configuration to the objectmapper and it working properly: objectMapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)

dkb · Accepted Answer · 2019-03-29 11:12:28Z

Create/update following class, I am storing JSON file, since do not have service, but should be fine and Able to parse it and read it from the following model.

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;

import java.util.List;

@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonPropertyOrder({
        "meta",
        "data"
})
public class OuterPoJo {

    @JsonProperty("meta")
    private Meta meta;
    @JsonProperty("data")
    private List<TPDetails> data = null;

    @JsonProperty("meta")
    public Meta getMeta() {
        return meta;
    }

    @JsonProperty("meta")
    public void setMeta(Meta meta) {
        this.meta = meta;
    }

    @JsonProperty("data")
    public List<TPDetails> getData() {
        return data;
    }

    @JsonProperty("data")
    public void setData(List<TPDetails> data) {
        this.data = data;
    }
}

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;

@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonPropertyOrder({
        "code"
})
public class Meta {

    @JsonProperty("code")
    private String code;

    @JsonProperty("code")
    public String getCode() {
        return code;
    }

    @JsonProperty("code")
    public void setCode(String code) {
        this.code = code;
    }

}

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;

@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonPropertyOrder({
        "Id",
        "Name"
})
public class TPDetails {

    @JsonProperty("Id")
    private Integer id;
    @JsonProperty("Name")
    private String name;

    @JsonProperty("Id")
    public Integer getId() {
        return id;
    }

    @JsonProperty("Id")
    public void setId(Integer id) {
        this.id = id;
    }

    @JsonProperty("Name")
    public String getName() {
        return name;
    }

    @JsonProperty("Name")
    public void setName(String name) {
        this.name = name;
    }

}


import java.io.File;
public class App {
public static void main(String[] args) throws Exception {
    ObjectMapper objectMapper = new ObjectMapper();
    OuterPoJo myPoJo = objectMapper.readValue(
            new File("file.json"),
            OuterPoJo.class);

    for (TPDetails item : myPoJo.getData()) {
        System.out.println(item.getId() + ":" + item.getName());
    }

}
}

output:

44:Malgudi ABC
45:Malgudi, DEF

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