Java null pointer exception in REST API

Question

I am actually using postman to send login request to my REST API but it's giving me a javaNullpointer exception. It's because in model class one of my variables is not getting a value. setPhone_Number() function is not called in my model class. So the phone_number variable is empty.

Help is appreciated.

Here is my error screnshot eclipse error for null pointer here is what i am sending through postman Postman

here is the login dao class.

 public class LoginDao {

 private String password;
 private String phone_number;


    public LoginDao(){
        phone_number = null;
        password = null;
    }

    public Response doLogin(login logg, String user_type) throws SQLException{
        ResultSet rs = null;
        boolean userType = true;        
        //if userType is resource then boolean is false, if userType is user then boolean is true.
        //logg.setPhone_Number(phone_number);

        DBConnection dbConnection = new DBConnection();
        //Connection connection = dbConnection.getConnection();
        this.phone_number = logg.getPhone_Number();
        this.password = logg.getPassword();


        try{
            if(user_type.equalsIgnoreCase("Rider")) {
                rs = dbConnection.runSql("select rider_id, phone_number, password from rider");
                userType = true;

            }
            else if(user_type.equalsIgnoreCase("Driver")) {
                rs = dbConnection.runSql("select driver_id, phone_number, password from driver");   
                userType = false;
            }

            while(rs.next()){
                System.out.println(phone_number);
                System.out.println(rs.getString("phone_number"));
                System.out.println("user"+user_type);

                if((this.phone_number.equals(rs.getString("phone_number"))) && (this.password.equals(rs.getString("password")))){

Here is model class login

 public class login {

private String phone_number;
private String password;

public login(){

}

public String getPhone_Number() {

    System.out.println("getting "+phone_number);
    return phone_number;
}

public void setPhone_Number(String phone_number) {

    System.out.println("seting "+phone_number);
    this.phone_number = phone_number;
}

public String getPassword() {
    return password;
}

public void setPassword(String password) {

    System.out.println("seting "+password);
    this.password = password;
}

}

Here is loginResource.java

 import javax.ws.rs.POST;

 import javax.ws.rs.Path;
 import javax.ws.rs.Produces;
 import javax.ws.rs.QueryParam;
 import javax.ws.rs.core.MediaType;
 import javax.ws.rs.core.Response;

 import static javax.ws.rs.core.MediaType.APPLICATION_JSON;

 import java.sql.SQLException;

  import javax.ws.rs.Consumes;

  import io.github.yasirfaisal21.schoolvan.schoolvan.dao.LoginDao;
 import io.github.yasirfaisal21.schoolvan.schoolvan.model.login;

  @Path("login")


 public class loginResource {
@Produces(MediaType.APPLICATION_JSON)
@Consumes(APPLICATION_JSON)
@POST
public Response doLogin(login log,@QueryParam("user_type") String user_type ) 
        throws SQLException{


LoginDao loginDao = new LoginDao();
if(user_type.equalsIgnoreCase("Rider"))
        return loginDao.doLogin(log,"Rider");
else
    return loginDao.doLogin(log,"Driver");
 }

}

Answer 1

In your login.java class, replace:

private String phone_number;
with
private String phoneNumber;

and update its getters and setters according like so:

public String getPhoneNumber() {
    return phoneNumber;
}

public void setPhoneNumber(String phoneNumber) {
    this.phoneNumber = phoneNumber;
}   

Answer 2

In loginResource.java, the line

LoginDao loginDao = new LoginDao();

calls this method in LoginDao:

public LoginDao(){
        phone_number = null;
        password = null;
    }

where you have explicitly set phone_number = null

now on Line 52 of LoginDao

if((this.phone_number.equals(rs.getString("phone_number"))) && (this.password.equals(rs.getString("password"))))

this.phone_number corresponds to the LoginDao object most recently constructed, which has phone_number set to null. Even before values can be compared with rs, the equals function fails and you get a null pointer exception.

You should instead take in the values phone_number and password from the request. Try creating a parametrized constructor and assigning them the values you pass, like so:

public LoginDao(String number, String password){
         this.phone_number = number;
         this.password = password;
}

and calling it from loginResource like so:

if(user_type.equalsIgnoreCase("Rider"))
        return new loginDao(number,password).doLogin(log,"Rider");
else
    return new loginDao(number,password).doLogin(log,"Driver");
 }

Alternatively, I think you are trying to save parameters into Login object, but you haven't done that anywhere in loginResource. You should change your constructor in loginDao to

public loginDao() { }

and write the following in loginResource :

Login login = new Login();
if(user_type.equalsIgnoreCase("Rider")){
       login.setPhone_number("your phone number from request");
        return loginDao.doLogin(log,"Rider");
 }
else
  {
   login.setPhone_number("your phone number from request");
  return loginDao.doLogin(log,"Driver");
 }