Department.java Source code

Introduction

Here is the source code for Department.java

Source

    File:Department.java

    import javax.persistence.Entity;
    import javax.persistence.GeneratedValue;
    import javax.persistence.GenerationType;
    import javax.persistence.Id;

@Entity
public class Department {
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private int id;

  private String name;

  public int getId() {
    return id;
  }

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

  public String getName() {
    return name;
  }

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

  public String toString() {
    return "Department id: " + getId() + ", name: " + getName();
  }
}

    File:Professor.java

    import java.util.ArrayList;
    import java.util.Collection;

    import javax.persistence.Column;
    import javax.persistence.Entity;
    import javax.persistence.EntityResult;
    import javax.persistence.FieldResult;
    import javax.persistence.Id;
    import javax.persistence.JoinColumn;
    import javax.persistence.ManyToOne;
    import javax.persistence.OneToMany;
    import javax.persistence.OneToOne;
    import javax.persistence.SqlResultSetMapping;
    import javax.persistence.SqlResultSetMappings;
    import javax.persistence.Table;

@Entity
@Table(name = "EMP")
@SqlResultSetMappings( { 
  
  @SqlResultSetMapping(
      name="ProfessorWithAddressColumnAlias",
      entities={@EntityResult(entityClass=Professor.class,
                              fields=@FieldResult(name="id", column="EMP_ID")),
                @EntityResult(entityClass=Address.class)}
  )

})
public class Professor {
  @Id
  @Column(name = "EMP_ID")
  private int id;

  private String name;

  private long salary;

  @OneToOne
  private Address address;

  @ManyToOne
  @JoinColumn(name = "DEPT_ID")
  private Department department;

  @ManyToOne
  @JoinColumn(name = "MANAGER_ID")
  private Professor manager;

  @OneToMany(mappedBy = "manager")
  private Collection<Professor> directs = new ArrayList<Professor>();

  public int getId() {
    return id;
  }

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

  public String getName() {
    return name;
  }

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

  public long getSalary() {
    return salary;
  }

  public void setSalary(long salary) {
    this.salary = salary;
  }

  public Address getAddress() {
    return address;
  }

  public void setAddress(Address address) {
    this.address = address;
  }

  public Department getDepartment() {
    return department;
  }

  public void setDepartment(Department department) {
    this.department = department;
  }

  public Collection<Professor> getDirects() {
    return directs;
  }

  public void addDirect(Professor employee) {
    if (!getDirects().contains(employee)) {
      getDirects().add(employee);
      if (employee.getManager() != null) {
        employee.getManager().getDirects().remove(employee);
      }
      employee.setManager(this);
    }
  }

  public Professor getManager() {
    return manager;
  }

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

  public String toString() {
    return "Professor id: " + getId() + " name: " + getName() + " with MgrId: "
        + (getManager() == null ? null : getManager().getId());
  }
}

    File:ProfessorService.java

    import java.util.List;

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

public class ProfessorService {
  protected EntityManager em;

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

  public List findWithAlias() {
    Query query = em.createNativeQuery(
        "SELECT emp.emp_id AS emp_id, name, salary, manager_id, dept_id, address_id, "
            + "address.id, street, city, state, zip " + "FROM emp, address "
            + "WHERE address_id = id", "ProfessorWithAddressColumnAlias");
    return query.getResultList();
  }

}

    File:Address.java

    import javax.persistence.Entity;
    import javax.persistence.Id;

@Entity
public class Address {
  @Id
  private int id;

  private String street;

  private String city;

  private String state;

  private String zip;

  public int getId() {
    return id;
  }

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

  public String getStreet() {
    return street;
  }

  public void setStreet(String address) {
    this.street = address;
  }

  public String getCity() {
    return city;
  }

  public void setCity(String city) {
    this.city = city;
  }

  public String getState() {
    return state;
  }

  public void setState(String state) {
    this.state = state;
  }

  public String getZip() {
    return zip;
  }

  public void setZip(String zip) {
    this.zip = zip;
  }

  public String toString() {
    return "Address id: " + getId() + ", street: " + getStreet() + ", city: " + getCity()
        + ", state: " + getState() + ", zip: " + getZip();
  }

}

    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.findWithAlias();

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

            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>