[FIXED] Java Stream "Cannot resolve method 'map' in 'T'" error

Issue

I cannot map entity to dto by using map() method of Java Stream API.

public EmployeeDto create(EmployeeRequest request) {
    final Employee employee = EmployeeRequestMapper.mapToEntity(request);
    return employeeRepository.save(employee)
            .map(EmployeeDto::new);
}

But I get "Cannot resolve method 'map' in 'T'" error for the map method in my service. Here are the related classes below:

public class EmployeeRequestMapper {

    public static Employee mapToEntity(EmployeeRequest request) {
        return new Employee(
                request.getName(),
                request.getEmail(),
                request.getCountry(),
                request.getAge()
        );
    }
}

@Data
@NoArgsConstructor
public class EmployeeDto {
    private Long id;
    private String name;
    private String email;
    private String country;
    private int age;

    public EmployeeDto(Employee employee) {
        this.id = employee.getId();
        this.name = employee.getName();
        this.email = employee.getEmail();
        this.country = employee.getCountry();
        this.age = employee.getAge();
    }
}

So, what is the problem?

Solution

save returns an Employee, not an Optional<Employee>. And Employee doesn't appear to have a map method.

So your method return new EmployeeDto(employeeRepository.save(employee)); instead.

Answered By - Federico klez Culloca
Answer Checked By - Katrina (JavaFixing Volunteer)