Professor.java Source code

Introduction

Here is the source code for Professor.java

Source

    File:Professor.java

    import javax.persistence.Basic;
    import javax.persistence.Column;
    import javax.persistence.Entity;
    import javax.persistence.FetchType;
    import javax.persistence.Id;
    import javax.persistence.IdClass;
    import javax.persistence.JoinColumn;
    import javax.persistence.JoinColumns;
    import javax.persistence.Lob;
    import javax.persistence.ManyToOne;
    import javax.persistence.PrimaryKeyJoinColumn;
    import javax.persistence.SecondaryTable;
    import javax.persistence.SecondaryTables;

@Entity
@SecondaryTables( {
    @SecondaryTable(name = "COMPANY", pkJoinColumns = {
        @PrimaryKeyJoinColumn(name = "ID", referencedColumnName = "ID") })
        
})
public class Professor {
  private String country;

  @Id
  private int id;

  private String name;

  @ManyToOne
  @JoinColumns( {
      @JoinColumn(name = "MGR_ID", referencedColumnName = "ID", table = "COMPANY") })
  private Professor manager;

  public int getId() {
    return id;
  }

  public void setId(int id) {
    this.id = id;
  }

  public String getCountry() {
    return country;
  }

  public void setCountry(String country) {
    this.country = country;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public Professor getManager() {
    return manager;
  }

  public void setManager(Professor manager) {
    this.manager = manager;
  }

  public String toString() {
    return "Professor id: " + getId() + " name: " + getName() + " country: " + getCountry();
  }
}

    File:ProfessorId.java

    import java.io.Serializable;

public class ProfessorId implements Serializable {
  private String country;

  private int id;

  public ProfessorId() {
  }

  public ProfessorId(String country, int id) {
    this.country = country;
    this.id = id;
  }

  public String getCountry() {
    return country;
  }

  public int getId() {
    return id;
  }

  public boolean equals(Object o) {
    return ((o instanceof ProfessorId) && country.equals(((ProfessorId) o).getCountry()) && id == ((ProfessorId) o)
        .getId());

  }

  public int hashCode() {
    return country.hashCode() + id;
  }
}

    File:ProfessorService.java

    import java.util.Collection;

    import javax.persistence.EntityManager;
    import javax.persistence.Query;

public class ProfessorService {
  protected EntityManager em;

  public ProfessorService(EntityManager em) {
    this.em = em;
  }

  public Professor createProfessor(String country, int id, String name) {
    Professor emp = new Professor();
    emp.setCountry(country);
    emp.setId(id);
    emp.setName(name);
    em.persist(emp);

    return emp;
  }

  public Professor findProfessor(String country, int id) {
    return em.find(Professor.class, new ProfessorId(country, id));
  }

  public Collection<Professor> findAllProfessors() {
    Query query = em.createQuery("SELECT e FROM Professor e");
    return (Collection<Professor>) query.getResultList();
  }
}

    File:JPAUtil.java

    import java.io.Reader;
    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.ResultSet;
    import java.sql.ResultSetMetaData;
    import java.sql.Statement;

public class JPAUtil {
  Statement st;
  
  public JPAUtil() throws Exception{
    Class.forName("org.hsqldb.jdbcDriver");
    System.out.println("Driver Loaded.");
    String url = "jdbc:hsqldb:data/tutorial";

    Connection conn = DriverManager.getConnection(url, "sa", "");
    System.out.println("Got Connection.");
    st = conn.createStatement();
  }
  public void executeSQLCommand(String sql) throws Exception {
    st.executeUpdate(sql);
  }
  public void checkData(String sql) throws Exception {
    ResultSet rs = st.executeQuery(sql);
    ResultSetMetaData metadata = rs.getMetaData();

    for (int i = 0; i < metadata.getColumnCount(); i++) {
      System.out.print("\t"+ metadata.getColumnLabel(i + 1)); 
    }
    System.out.println("\n----------------------------------");

    while (rs.next()) {
      for (int i = 0; i < metadata.getColumnCount(); i++) {
        Object value = rs.getObject(i + 1);
        if (value == null) {
          System.out.print("\t       ");
        } else {
          System.out.print("\t"+value.toString().trim());
        }
      }
      System.out.println("");
    }
  }
}

    File:Main.java

    import javax.persistence.EntityManager;
    import javax.persistence.EntityManagerFactory;
    import javax.persistence.Persistence;

    public class Main {
        public static void main(String[] a) throws Exception {
            JPAUtil util = new JPAUtil();

            EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
            EntityManager em = emf.createEntityManager();
            ProfessorService service = new ProfessorService(em);

            em.getTransaction().begin();

            service.createProfessor("country", 1, "name");
            System.out.println("Professors:");
            for (Professor emp : service.findAllProfessors()) {
                System.out.print(emp);
                System.out.print(emp.getManager());
            }

            util.checkData("select * from Professor");

            em.getTransaction().commit();
            em.close();
            emf.close();
        }
    }

    File:persistence.xml

    <persistence xmlns="http://java.sun.com/xml/ns/persistence"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence"version="1.0"><persistence-unit name="JPAService"transaction-type="RESOURCE_LOCAL"><properties><property name="hibernate.dialect"value="org.hibernate.dialect.HSQLDialect"/><property name="hibernate.hbm2ddl.auto"value="update"/><property name="hibernate.connection.driver_class"value="org.hsqldb.jdbcDriver"/><property name="hibernate.connection.username"value="sa"/><property name="hibernate.connection.password"value=""/><property name="hibernate.connection.url"value="jdbc:hsqldb:data/tutorial"/></properties></persistence-unit></persistence>