java.lang.IllegalArgumentException: Unknown entity: com.prithvi.thoughtprocess.beans.dao.impl.User
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.persist(AbstractEntityManagerImpl.java:1149) ~[hibernate-entitymanager-5.0.12.Final.jar:5.0.12.Final]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_51]
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_51]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_51]
at java.lang.reflect.Method.invoke(Unknown Source) ~[na:1.8.0_51]

package com.prithvi.thoughtprocess.beans.domain;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="user")
public class User  implements Serializable {

    /**
     *
     */
    private static final long serialVersionUID = 3367865397662004005L;

    @Id
    @GeneratedValue(strategy =  GenerationType.SEQUENCE)
    @Column(name = "id")
    private Integer id;

    @Column(name = "name")
    private String name;
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    }

package com.prithvi.thoughtprocess.beans.dao.impl;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

import org.springframework.stereotype.Repository;

import com.prithvi.thoughtprocess.beans.dao.UserDAO;
import com.prithvi.thoughtprocess.beans.domain.User;

@Repository
public class UserDAOImpl  implements UserDAO{

    @PersistenceContext
    private EntityManager entityManager;

    @Override
    public <S extends User> S save(S entity) {
        entityManager.persist(entity);
        return null;
    }}

spring.datasource.url=jdbc:mysql://localhost:3306/bookbank
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.tomcat.max-wait=20000
spring.datasource.tomcat.max-active=50
spring.datasource.tomcat.max-idle=20
spring.datasource.tomcat.min-idle=15

spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQLDialect
spring.jpa.properties.hibernate.id.new_generator_mappings = false
spring.jpa.properties.hibernate.format_sql = true

logging.level.org.hibernate.SQL=DEBUG
logging.level.org.hibernate.type.descriptor.sql.BasicBinder=TRACE

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import com.prithvi.thoughtprocess.dto.BookDto;

@ComponentScan(basePackages = {"com.prithvi.thoughtprocess.beans"})
@SpringBootApplication
public class Example {

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

}

package com.prithvi.thoughtprocess.beans.controller;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import com.prithvi.thoughtprocess.beans.service.UserService;
import com.prithvi.thoughtprocess.dto.UserDto;

@RestController
public class UserController {

    @Autowired
    private UserService userService;


    @RequestMapping(value = "user/save", method = RequestMethod.POST)
    String save(@RequestBody UserDto userDto) {
        userService.saveUser(userDto);
        return "User save successfully";
    }

    @RequestMapping(value = "user/list", method = RequestMethod.GET)
    List<UserDto> list() {
        return userService.listUser();
    }

}

package com.prithvi.thoughtprocess.beans.service.impl;

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


import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import com.prithvi.thoughtprocess.beans.dao.UserDAO;
import com.prithvi.thoughtprocess.beans.domain.User;
import com.prithvi.thoughtprocess.beans.service.UserService;
import com.prithvi.thoughtprocess.dto.UserDto;

@Service
@Transactional
public class UserServiceImpl implements UserService {

    @Autowired
    private UserDAO userDAO;

    @Override

    public void saveUser(UserDto userDto) {
        userDAO.save(convertToEntity(userDto));
    }

    public User convertToEntity(UserDto userDto){
        User user = new User();
        user.setId(userDto.getId());
        user.setName(userDto.getName());
        return user;
    }

    public UserDto convertToDto(User user){
        UserDto userDto = new UserDto();
        userDto.setId(user.getId());
        userDto.setName(user.getName());
        return userDto;
    }

    @Override
    public List<UserDto> listUser() {
        //List<User> users = userDAO.list();
        List<UserDto> userDtos = new ArrayList<>();
        /*for (User user : users) {
            userDtos.add(convertToDto(user));
        }*/
        return userDtos;
    }

}