context initialization Issue in Spring Boot

Question

am newbie to spring boot am trying to create a simple application using spring boot am getting the error as:

org.springframework.beans.factory.UnsatisfiedDependencyException:Error creating bean with name'carsApplication':Unsatisfied dependency expressed through field'carMongoRepository';

nested exception is org.springframework.beans.factory.BeanCreationException:Error creating bean with name'carMongoRepository':Invocation of init method failed;nested exception is org.springframework.data.mapping.model.MappingException:Could not lookup mapping metadata for domain class java.lang.Object!

This is the project structure

This is the Model class that I had implemented:

Model class for cars having id,make and model and it includes get and set method

package com.example.cars;

import org.springframework.data.mongodb.core.mapping.Document;
import org.springframework.stereotype.Component;


@Document(collection = "cars")
public class Car {

    private String id;
    private String make;
    private String model;

    public Car() {
    }

    public String getId() {
        return id;
    }

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

    public String getMake() {
        return make;
    }

    public void setMake(String make) {
        this.make = make;
    }

    public String getModel() {
        return model;
    }

    public void setModel(String model) {
        this.model = model;
    }


}

This is the Main class that I had implemented:

Main class for the spring boot application to run the application

package com.example.cars;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;

@SpringBootApplication
@EnableAutoConfiguration
@ComponentScan
public class CarsApplication {

    @Autowired
    CarMongoRepository carMongoRepository;

    public static void main(String[] args) {
        SpringApplication.run(CarsApplication.class, args);
    }
}

This is the Controller class that I had implemented:

Controller class for the API calls to add the car values like model and make.Include API call as shown below having the POST method implementation.

package com.example.cars;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;


@Controller
public class CarController {

    @Autowired
    CarMongoRepository carMongoRepository;

    @RequestMapping(value = "/addCar", method = RequestMethod.POST)
    public void addCar(@ModelAttribute Car car) {
        carMongoRepository.save(car);
    }

}

This is the repository that I had implemented

Implemented interface for the CRUD repository call for the application as shown below.Used @Repository annotation for this implementation. Class name is CarMongoRepository that extends CRUDRepository as shown below.

package com.example.cars;

import org.springframework.data.repository.CrudRepository;

import com.example.cars.Car;
import org.springframework.stereotype.Repository;

@Repository
public interface CarMongoRepository extends CrudRepository {
}

While am try to run the spring boot main class am getting the error as mentioned above.So, Please help me to solve this issue.

Answer 1

CrudRepository needs generic parameters to know which Entity (or Document) it should handle.

Make your CarMongoRepository extend CrudRepository<Car, String> and it should work.

The first parameter specifies the type of entity/document the repository should handle and the second parameter is the type of the id of this entity/document (i assume that it is the field id of type String inside your Car class)

If you dont specify any parameters it assumes your CarMongoRepository to extend CrudRepository<Object, Object> and that is what the error message tells you.

org.springframework.data.mapping.model.MappingException:Could not lookup mapping metadata for domain class java.lang.Object!

Your application trys to lookup mapping for an Entity/Document of type Object which is not definied.

I'm not very familiar to document store databases with spring but I think you have to annotate your id attribute in the Car class with @Id (At least thats the annotation for @Entity classes. Maybe there is a different equivalent for @Document classes.)