MalformedJsonException while converting JSON data to Java Object

Question

while using Postman to test the @POST method of RESTEasy, I got the error MalformedJsonException

My @POST method

@POST
    @Path("service/product")
    @Consumes("application/json")
    public Object setProductData(Product product) {
        String result = product.toString().trim();
        Gson gson = new Gson();
        Data.addProduct(gson.fromJson(result, Product.class));

        return Response.status(200).entity(result).build();
    }

My model

public class Product {
    private String id;
    private String name;
    private String image;
    private double price;
    private String catalogId;

    public Product(String id, String name, String image, double price, String catalogId) {
        this.id = id;
        this.name = name;
        this.image = image;
        this.price = price;
        this.catalogId = catalogId;
    }

    public Product() {
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getImage() {
        return image;
    }

    public void setImage(String image) {
        this.image = image;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public String getCatalogId() {
        return catalogId;
    }

    public void setCatalogId(String catalogId) {
        this.catalogId = catalogId;
    }

    @Override
    public String toString() {
        return "{" +
                "id='" + id + ',' +
                "name='" + name + ',' +
                "image='" + image + ',' +
                "price='" + price + ',' +
                "catalogId='" + catalogId + ',' + "}";
    }
}

This is what I want to add: https://i.sstatic.net/vaBSe.png

The data is in json format, {"id":"band1","name":"Mi Band 4","image":"https://i.imgur.com/7MLMnhW.jpg","price":30.0,"catalogId":"abc1"} for examle

The error: https://i.sstatic.net/eiFSj.png

Earlier I got the error Expected BEGIN_OBJECT but was STRING at line 1 column 1 path $ but then I realized toString() method in Product class was the problem, I fixed it and it produced the error in the question.

Please help me to fix this error.

Why would you use toString to convert your product to JSON (Gson has a toJson method) and then use fromJson to convert it back again to pass it to the Data.addProduct method? Couldn't you simply pass the product parameter to your Data.addProduct method? — Hopey One
– Hopey One, Commented May 12, 2021 at 2:42
Your data is in json format doesn't even have an end curly brace. That alone makes it invalid. Are you sure it's pasted correctly or is that actually your problem? — Atmas
– Atmas, Commented May 12, 2021 at 2:46

v2k · Accepted Answer · 2021-05-12 02:54:58Z

1

Your toString() is faulty to begin with - the Json formulation isn't correct. If you want to use toString() anyways to convert your POJO into JSON, use apache commons lang3's JSON style in the toString().

import com.google.gson.Gson;
import org.apache.commons.lang3.builder.ToStringBuilder;
import org.apache.commons.lang3.builder.ToStringStyle;

public class Test1 {

    public static void main(String[] args) {
        Product product = new Product("1", "someone", "https://url", 1.23, "11");
        System.out.println(product);

        Gson gson = new Gson();
        Product product1 = gson.fromJson(product.toString().trim(), Product.class);
        System.out.println(product1);
    }

    private static class Product {
        private String id;
        private String name;
        private String image;
        private double price;
        private String catalogId;

        public Product() {
        }

        public Product(String id, String name, String image, double price, String catalogId) {
            this.id = id;
            this.name = name;
            this.image = image;
            this.price = price;
            this.catalogId = catalogId;
        }

        @Override
        public String toString() {
            return new ToStringBuilder(this, ToStringStyle.JSON_STYLE)
                    .append("id", id)
                    .append("name", name)
                    .append("image", image)
                    .append("price", price)
                    .append("catalogId", catalogId)
                    .toString();
        }

        public String getId() {
            return id;
        }

        public Product setId(String id) {
            this.id = id;
            return this;
        }

        public String getName() {
            return name;
        }

        public Product setName(String name) {
            this.name = name;
            return this;
        }

        public String getImage() {
            return image;
        }

        public Product setImage(String image) {
            this.image = image;
            return this;
        }

        public double getPrice() {
            return price;
        }

        public Product setPrice(double price) {
            this.price = price;
            return this;
        }

        public String getCatalogId() {
            return catalogId;
        }

        public Product setCatalogId(String catalogId) {
            this.catalogId = catalogId;
            return this;
        }
    }
}

The output is as follows:-

{"id":"1","name":"someone","image":"https://url","price":1.23,"catalogId":"11"} {"id":"1","name":"someone","image":"https://url","price":1.23,"catalogId":"11"}

Now, coming to the usage. If you are taking the object as an input itself as a POST request body, then why not simply use 'Data.addProduct(product);'?

answered May 12, 2021 at 2:54

v2k

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3 Comments

Minh Nguyên Nguyễn Đức Over a year ago

I'm confused a bit, as I'm new to this. I can call data from mongodb to server as json, but I do not know how to get data input back to mongodb. Can I add data to mongodb with raw json data input? If yes, please tell me, I'm willing to know it

Minh Nguyên Nguyễn Đức Over a year ago

And thank you, I'm learning your code to find a way improving my code.

v2k Over a year ago

@MinhNguyênNguyễnĐức, in mongo, everything is in terms of document. You can add direct json as well to it. Sample would be: geeksforgeeks.org/…. The recommended way is to save the POJO in mongo. Follow the official documentation from mongodb site here: docs.mongodb.com/guides/server/insert You are welcome. Am happy that the code makes sense to you.

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