How to enforce 1 to Many and zero to Many relationship in Hibernate and retrieve the items?

My requirement is to have items that can be in different categories.

Each item must have 1 to Many categories

Each category can have 0 to Many items.

I followed this question and to implement that I did the following, but with following code I cannot add many categories and cannot retrieve the items of each category.

Sample

Item table

item1
item2

Category table

cat1
cat2
cat3
cat4
cat5

Relationship

item1 cat1
item2 cat1
item1 cat2
item1 cat3
item2 cat2

I need to make sure there would not be any duplicate. For example, adding item1 cat1 to the above output that already have item1 cat1 should be failed.

@Entity
public class Item {

    @Id
    @GeneratedValue
    long id;
    @Column(unique = true)
    String name;
    @OneToMany
    Set<Category> category = new HashSet<>();
    ....

@Entity
public class Category {

    @Id
    @GeneratedValue
    long id;
    private String name;
    ...

To retrieve items I have following code which returns following error

ERROR: No value specified for parameter 1
org.hibernate.exception.SQLGrammarException: could not extract ResultSet

Criteria criteria = session.createCriteria(Item.class);
            crit.add(Restrictions.eq("category", "cat1"));
            return crit.list();