How to fix Type definition error in Spring Boot application?

I am building a Spring Boot application that utilizes the com.explore.explore.entities.Spot class. but getting this error

Type definition error: [simple type, class com.explore.explore.entities.Spot]] with root cause

I have checked the Spot class and its dependencies, but I can't seem to find the issue. How can I fix this error and properly serialize the Spot object to JSON?

I have already tried the following steps:

Checked that the Spot class is defined correctly, with all fields and methods properly annotated.
Checked that any custom data types used in the Spot class are defined correctly and annotated properly.
Checked that any dependencies used by the Spot class are present and correctly configured.

MyController.java

package com.explore.explore.controller;

import java.util.ArrayList;
import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import com.explore.explore.entities.Spot;
import com.explore.explore.services.SpotService;

@RestController
public class MyController {

    @Autowired
    public SpotService SpotService;

    @GetMapping("/hello")
    public String home() {
        return "hello";
    }

    // get spots
    @GetMapping("/spots")
    // public List<Integer> getSpots() {
    // List<Integer> list;
    // list = new ArrayList<>();
    // list.add(3);
    // list.add(5);
    // return this.SpotService.getSpots();
    // }

    public List<Spot> getSpots() {
        
        List<Spot> list;
        list = new ArrayList<>();
        list.add(new Spot(1, "38 Block", "Near 38"));
        list.add(new Spot(0, "UNIMAll", "Near Me"));
        return list;
    }
}

Spot.java

package com.explore.explore.entities;

import org.springframework.http.converter.HttpMessageConversionException;

public class Spot {
    private long id;
    private String name;
    private String location;

    public Spot(long id, String name, String location) {
    
        super();
        this.id = id;
        this.name = name;
        this.location = location;
    
    }
    public Spot() {
        super();
    }
}

Solution

I needed to add annotations for serialization

@JsonAutoDetect, @JsonProperty, and @JsonInclude

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

@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY)
public class Spot {
    @JsonProperty("id")
    private long id;
    @JsonProperty("name")
    private String name;
    @JsonProperty("location")
    private String location;

    public Spot(long id, String name, String location) {
        super();
        this.id = id;
        this.name = name;
        this.location = location;
    }

    public Spot() {
        super();
    }

    // getters and setters here
}