No operations defined in spec! I get this error when I try to run spring boot application using swagger

Question

I'm working with ecommerce spring boot application using swagger. When I try to run my application I get message as "No operations defined in spec!"

This is Api code:

package com.ecommerce.demo.repository;

import com.ecommerce.demo.model.Category;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface CategoryRepo extends JpaRepository<Category, Integer> {

}

Configuration file :

import org.springframework.web.servlet.config.annotation.CorsRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
class Webconfig {

    @Bean
    public WebMvcConfigurer corsConfigurer() {
        return new WebMvcConfigurer() {
            @Override
            public void addCorsMappings(CorsRegistry registry) {
                registry.addMapping("/**")
                        .allowedOrigins("*")
                        .allowedMethods("GET", "PUT", "POST", "PATCH", "DELETE", "OPTIONS");
            }
        };
    }
}

Here is the dependencies that I'm using:

<dependency>
    <groupId>io.springfox</groupId>
    <artifactId>springfox-swagger2</artifactId>
    <version>2.9.2</version>
</dependency>
<dependency>
    <groupId>io.springfox</groupId>
    <artifactId>springfox-swagger-ui</artifactId>
    <version>2.9.2</version>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-test</artifactId>
    <scope>test</scope>
</dependency>

Here is my model :

package com.ecommerce.demo.model;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.validation.constraints.NotBlank;

@Entity
@Table(name="categories")
public class Category {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @Column(name = "category_name")
    private @NotBlank String categoryName;

    private @NotBlank String description;

    @Column(name = "image_url")
    private @NotBlank String imageUrl;

    public Integer getId() {
        return id;
    }

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

    public String getCategoryName() {
        return categoryName;
    }

    public void setCategoryName(String categoryName) {
        this.categoryName = categoryName;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public String getImageUrl() {
        return imageUrl;
    }

    public void setImageUrl(String imageUrl) {
        this.imageUrl = imageUrl;
    }
}

Repository :

package com.ecommerce.demo.repository;

import com.ecommerce.demo.model.Category;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface CategoryRepo extends JpaRepository<Category, Integer> {

}

Here is Service :

package com.ecommerce.demo.service;

import com.ecommerce.demo.model.Category;
import com.ecommerce.demo.repository.CategoryRepo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class CategoryService {
    @Autowired
    CategoryRepo categoryRepo;

    public void createCategory(Category category){
        categoryRepo.save(category);

    }
}

And Controller :

package com.ecommerce.demo.controller;

import com.ecommerce.demo.model.Category;
import com.ecommerce.demo.service.CategoryService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("category")
public class CategoryController {

    @Autowired
    CategoryService categoryService;

    @PostMapping("/create")
    public String createCategory(@RequestBody Category category){
        categoryService.createCategory(category);
        return "success";
    }
}

Swagger doesn't recognise the api.What's the problem in this code?