Java - Convert to correct json format using Jackson

Question

I'm using Jackson to write a Java object to Json.

This is wath I am getting

{
"obj": [{
    "Id": 1,
    "type": "type1",
    "properties": [{
        "name": "PropN",
        "value": "ValN"
    }]
}, {
    "id": 2,
    "type": "type",
    "properties": [{
        "name": "Prop3",
        "value": "Val3"
    }]
}]

}

This is what i need to get:

{
    "obj": [{
            "id": 1,
            "type": "type",
            "properties": {
                "name": "Eb1"
            }
        },
        {
            "id": 2,
            "type": "type",
            "properties": {
                "name": "Eb2"
            }
        }
    ]
}

I dont know how to get the properties name and value "tags" from the json and also, remove the properties array to a list.

My Properties array is a simple POJO, and the Obj class has an ArrayList of properties.

Can someone tell me how to get this done?

Thanks.

Answer 1

You can use quicktype to generate the exact types you need. Here's what it produces with the JSON you require:

// Converter.java

// https://stackoverflow.com/questions/49055781/java-convert-to-correct-json-format-using-jackson
//     import io.quicktype.Converter;
//
// Then you can deserialize a JSON string with
//
//     StackOverflow data = Converter.fromJsonString(jsonString);

package io.quicktype;

import java.util.Map;
import java.io.IOException;
import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.core.JsonProcessingException;

public class Converter {
    // Serialize/deserialize helpers

    public static StackOverflow fromJsonString(String json) throws IOException {
        return getObjectReader().readValue(json);
    }

    public static String toJsonString(StackOverflow obj) throws JsonProcessingException {
        return getObjectWriter().writeValueAsString(obj);
    }

    private static ObjectReader reader;
    private static ObjectWriter writer;

    private static void instantiateMapper() {
        ObjectMapper mapper = new ObjectMapper();
        reader = mapper.reader(StackOverflow.class);
        writer = mapper.writerFor(StackOverflow.class);
    }

    private static ObjectReader getObjectReader() {
        if (reader == null) instantiateMapper();
        return reader;
    }

    private static ObjectWriter getObjectWriter() {
        if (writer == null) instantiateMapper();
        return writer;
    }
}

// StackOverflow.java

package io.quicktype;

import java.util.Map;
import com.fasterxml.jackson.annotation.*;

public class StackOverflow {
    private Obj[] obj;

    @JsonProperty("obj")
    public Obj[] getObj() { return obj; }
    @JsonProperty("obj")
    public void setObj(Obj[] value) { this.obj = value; }
}

// Obj.java

package io.quicktype;

import java.util.Map;
import com.fasterxml.jackson.annotation.*;

public class Obj {
    private long id;
    private String type;
    private Properties properties;

    @JsonProperty("id")
    public long getID() { return id; }
    @JsonProperty("id")
    public void setID(long value) { this.id = value; }

    @JsonProperty("type")
    public String getType() { return type; }
    @JsonProperty("type")
    public void setType(String value) { this.type = value; }

    @JsonProperty("properties")
    public Properties getProperties() { return properties; }
    @JsonProperty("properties")
    public void setProperties(Properties value) { this.properties = value; }
}

// Properties.java

package io.quicktype;

import java.util.Map;
import com.fasterxml.jackson.annotation.*;

public class Properties {
    private String name;

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