java.math.BigInteger cannot be cast to java.util.List in Spring project

Question

I have the code:

public Student LoginStudent(Student student) {              
    List<Student> students = new ArrayList<Student>();
    sessionFactory.getCurrentSession().getTransaction().begin();
    String hql = "select stu_id,name from  student  where username = \"[email protected]\"";
    students = (List<Student>) sessionFactory.getCurrentSession().createSQLQuery(hql).uniqueResult();               
    if (students.size() > 0) {
        return students.get(0);
    } else {
        return null;
    }
}

I am getting error:

java.lang.ClassCastException: java.math.BigInteger cannot be cast to java.util.List

I searched Google, someone suggests:

return ((BigInteger)LoginStudent.get(0)).longValue();

But how can I use this?

When you run the sql "select stu_id,name from student where username = "[email protected]" what is the result you are getting? — Lucky
– Lucky, Commented Aug 9, 2015 at 10:03

Roman C · Accepted Answer · 2015-08-09 09:23:54Z

2

Change hql to

String hql = "from Student where username = '[email protected]'";
students = (List<Student>) sessionFactory.getCurrentSession().createQuery(hql).list();

the javadoc for uniqueResult says

Convenience method to return a single instance that matches the query, or null if the query returns no results.

But you need a List<Student> to retrieve, so use list().

edited Aug 9, 2015 at 9:23

answered Aug 8, 2015 at 14:24

Roman C

1

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4 Comments

Salini Over a year ago

I have used list().....I am getting error:---java.math.BigInteger cannot be cast to com.student.pack.Student

Salini Over a year ago

return students.get(0);-----this line

Roman C Over a year ago

students is a List<Student>, and you return the first element of it which is a Student. There's no BigInteger here, unless you manually cast it. Don't cast an object which is not instance of a BigInteger to this type. And use proper naming in code, if you write hql then use HQL, if you want to use SQL, then write sql. I will add the line to execute HQL instead of SQL, and read this if you still want to use SQL.

Nathan Hughes Over a year ago

@Salini: sounds like you didn't use Roman's change to the hql, try that first.

Shadow Droid · Accepted Answer · 2015-08-08 15:19:39Z

0

Please change the line from

students = (List<Student>) sessionFactory.getCurrentSession().createSQLQuery(hql).uniqueResult();

to

students = (List<Student>) (sessionFactory.getCurrentSession().createSQLQuery(hql).uniqueResult());

Give a try, it should work if uniqueResult() returns a list of student objects

answered Aug 8, 2015 at 15:19

Shadow Droid

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Comments

carbontax · Accepted Answer · 2015-08-10 12:53:14Z

To get your hql to work you need to do something like this:

Student student = null;

sessionFactory.getCurrentSession().getTransaction().begin();
String hql = "select stu_id,name from  student  where username = :username";

Object[] result = sessionFactory.getCurrentSession()
    .createSQLQuery(hql)
    .setParameter("username", "[email protected]")
    .uniqueResult();

if(result != null) {
   // manually convert your selection into a Student
   student = new Student();
   s.setId((Long) result[0]);
   s.setName((String) result[1]);
}

return student;

The reason you have to do this is because you are selecting certain field from Student in your hql query. See https://docs.jboss.org/hibernate/orm/3.3/reference/en/html/queryhql.html#queryhql-select

Kikin-Sama · Accepted Answer · 2015-08-10 14:29:46Z

0

Or declare a constructor so your query works like this:

select new Student(s.stu_id,s.name) from  Student s where...

That should do it.

answered Aug 10, 2015 at 14:29

Kikin-Sama

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