SpringBoot #OneToMany Postman Request not working - json

Question

1.User Class with OneToMany Annotation in relation to Roles class that can be many
2.Roles Class with #ManyToOne and #JoinColumn Annotation
3.Controller class with the endpoint
4.Postman request with Json Object throws an Exception, JSON parse error: Cannot deserialize instance of com.cvt.programmingTask.model.User out of START_ARRAY token
Class User()
package com.cvt.programmingTask.model;
import java.util.Set;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
#Entity
#Table(name = "user")
public class User {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
#Column(name = "first_name")
private String firstName;
#Column(name = "last_name")
private String lastName;
#Column(name = "email_id", unique=true)
private String emailId;
#OneToMany(mappedBy = "user")
private Set<Roles> roles;
public User() {
}
public User(String firstName, String lastName, String emailId, Set<Roles> roles) {
super();
this.firstName = firstName;
this.lastName = lastName;
this.emailId = emailId;
this.roles = roles;
}
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getEmailId() {
return emailId;
}
public void setEmailId(String emailId) {
this.emailId = emailId;
}
public Set<Roles> getRoles() {
return roles;
}
public void setRoles(Set<Roles> roles) {
this.roles = roles;
}
}
Class Roles :
package com.cvt.programmingTask.model;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
#Entity
#Table(name="roles")
public class Roles {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
#Column(name = "name")
private String name;
#ManyToOne(cascade = CascadeType.ALL)
#JoinColumn(name="user_id", nullable=false)
private User user;
public Roles() {
}
public Roles(Long id, String name, User user) {
super();
this.id = id;
this.name = name;
this.user = user;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
}
User Controller Java File
package com.cvt.programmingTask.controller;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import com.cvt.programmingTask.exception.ResourceNotFoundException;
import com.cvt.programmingTask.model.User;
import com.cvt.programmingTask.repository.UserRepository;
/**
* #author edibi
*
*/
//#CrossOrigin(origins = "http://localhost:4200")
#RestController
#RequestMapping("/api/v1")
public class UserController {
#Autowired
private UserRepository userRepository;
//get all users
#GetMapping("/users")
public List<User> getAllUsers(){
return userRepository.findAll();
}
//create user rest api
#PostMapping("/users")
public User createUser(#RequestBody User user) {
return userRepository.save(user);
}
//get user
#GetMapping ("/users/{id}")
public ResponseEntity<User> getUserById(#PathVariable Long id) {
User user = userRepository.findById(id)
.orElseThrow(()->new ResourceNotFoundException("User does not exist with id : " +id));
return ResponseEntity.ok(user);
}
//update user
#PutMapping("/users/{id}")
public ResponseEntity<User> updateUser(#PathVariable Long id, #RequestBody User userDetails){
User user = userRepository.findById(id)
.orElseThrow(()->new ResourceNotFoundException("User does not exist with id : " +id));
user.setFirstName(userDetails.getFirstName());
user.setLastName(userDetails.getLastName());
user.setEmailId(userDetails.getEmailId());
user.setRoles(userDetails.getRoles());
User updatedUser = userRepository.save(user);
return ResponseEntity.ok(updatedUser);
}
//delete User rest api
#DeleteMapping("/users/{id}")
public ResponseEntity< Map<String, Boolean> >deleteUser(#PathVariable Long id){
User user = userRepository.findById(id)
.orElseThrow(()->new ResourceNotFoundException("User does not exist with id : " +id));
userRepository.delete(user);
Map<String, Boolean> response = new HashMap<>();
response.put("deleted", Boolean.TRUE);
return ResponseEntity.ok(response);
}
}
Can you help me out really don't know what'S wrong. Thanks