Question

How to excecute join queries in hibernate?

Answer 1

@Entity
@Table(name="TEAM")
class Book {
    int id;
    string book_name;
    @ManyToOne
    Lib lib;
    public int getId(){ return this.id;}
    public void setId(int id){ this.id = id; }
    public string getBook_name(){ return this.book_name;}
    public void setBook_name(string book_name){ this.book_name = book_name; }
    public Lib getLib(){ return this.lib;}
    public void setLib(Lib lib){ this.lib = lib; }
}
class Lib {
    int id;
    string lib_name;
    Set<book> books;
    public int getId(){ return this.id;}
    public void setId(int id){ this.id = id; }
    public string getLib_name(){ return this.lib_name;}
    public void setLib_name(string lib_name){ this.lib_name = lib_name; }
    public Set<book> getBooks(){ return this.books;}
    public void setBooks(Set<book> books){ this.books = books; }
}

How to execute join queries in hibernate?

There are three ways:

1) SQL:

SQLQuery query = session.createSQLQuery("SELECT {b.*}, {l.*} FROM book b INNER JOIN lib l ON l.id = b.lib.id");
query.addEntity("p", Book.class);
query.addJoin("l", "b.lib");
... = query.list();

2) HQL:

Query query = session.createQuery("FROM Book as b INNER JOIN FETCH b.lib as l");
... = query.list();

3) Criteria

Criteria criteria = session.createCriteria(Book.class, "b");
criteria.createAlias("b.lib", "l");
... = criteria.list();