Get single row in JPA

Question

How to get single row from entity in JPA?

Table: Employee

    @Id
    private int empId;
    private String empName;
    ...    

JPA by default return List. I`m trying to fetch single row.

EmployeeRepository :-

    public Employee findByEmpName(String empName);

Another way is to do it, @Query should be use.

    @Query(value="select e from Employee e where empName = ?1 limit 1", nativeQuery=true)
    public Employee findByEmpName(String empName);

How can i ensure that it return single row and correct result. Any help appreciated.. Thanks in advance.

Answer 1

You don't need to "ensure" anything.

If you dont have a collection of sort specified as return (e.g. List<Employee> instead of Employee ) and your query return more than one result it will launch a javax.persistence.NonUniqueResultException: result returns more than one elements.

If your query return more rows and you want only one of those either add a condition to differentiate which one of those rows you actually want or, if they are the same, add a good old distinct

How can i ensure that it return single row and correct result.

That's your job when writing the query

Answer 2

There is an out of the box solution, in repository you can name method as findFirstBy... or findTopBy..., that should do the thing.

You can find more in Spring reference documentation

Answer 3

JPA have a method to fetch a single row getSingleResult, but it's recommended to fetch a list and extract the first element over getResultList.

See: Example