DuplicateKeyException in mongodb and spring boot - spring

Question

I am using Spring Boot and MongoDB and I am able to store a document in MongoDB successfully. When I was trying to insert a second document, it is showing duplicatekeyexception. The total message of exception is as follows:
com.mongodb.DuplicateKeyException: Write failed with error code 11000
and error message 'E11000 duplicate key error collection:
Football_Admin.SignUp index: id dup key: { : 0 }'
The code is as follows:
SignUpRepository.java
package com.admin.Repository;
import org.springframework.data.mongodb.repository.MongoRepository;
import org.springframework.stereotype.Repository;
import com.admin.Model.SignUp;
#Repository
public interface SignUpRepository extends MongoRepository<SignUp,String>{
}
Controller
#Controller
#RequestMapping("/SignIn_Up")
public class HomeController {
#Autowired
SignUpRepository repository;
#RequestMapping(value = "/addadmin", method = RequestMethod.POST)
public String addAdmin(#ModelAttribute("SignUp") SignUp sign) throws NoSuchAlgorithmException,InvalidKeySpecException {
String originalPassword = sign.getPassword();
String generatedSecuredPasswordHash = generateStorngPasswordHash(originalPassword);
String email = sign.getEmail();
String fullname = sign.getFullName();
try {
sign.setEmail(email);
sign.setFullName(fullname);
sign.setPassword(generatedSecuredPasswordHash);
repository.save(sign);
}
catch (DuplicateKeyException e) {
e.printStackTrace();
}
System.out.println(generatedSecuredPasswordHash);
System.out.println("Email name is:"+sign.getEmail());
System.out.println("Full Name is:"+sign.getFullName());
System.out.println("Password is:"+sign.getPassword());
return "welcome";
}
Entity
package com.admin.Model;
import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;
#Document(collection="SignUp")
public class SignUp {
#Id
private int id;
private String fullName;
private String email;
private String password;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getFullName() {
return fullName;
}
public void setFullName(String fullName) {
this.fullName = fullName;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String toString() {
return id+""+fullName+""+password;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
}

Answer 1

MongoDb driver don't know how to create a unique Id of type int when inserting so you received unique index exception
So either you manually create and maintain your index (quite hard) or change your id field type to ObjectId