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		<title>Java/JPA/Many to One Mapping - История изменений</title>
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		<updated>2026-04-06T22:53:07Z</updated>
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	<entry>
		<id>http://jexp.ru/index.php?title=Java/JPA/Many_to_One_Mapping&amp;diff=9005&amp;oldid=prev</id>
		<title>Admin: 1 версия</title>
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				<updated>2010-06-01T07:23:14Z</updated>
		
		<summary type="html">&lt;p&gt;1 версия&lt;/p&gt;
&lt;table class=&quot;diff diff-contentalign-left&quot; data-mw=&quot;interface&quot;&gt;
				&lt;tr style=&quot;vertical-align: top;&quot; lang=&quot;ru&quot;&gt;
				&lt;td colspan=&quot;1&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;← Предыдущая&lt;/td&gt;
				&lt;td colspan=&quot;1&quot; style=&quot;background-color: white; color:black; text-align: center;&quot;&gt;Версия 07:23, 1 июня 2010&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; style=&quot;text-align: center;&quot; lang=&quot;ru&quot;&gt;&lt;div class=&quot;mw-diff-empty&quot;&gt;(нет различий)&lt;/div&gt;
&lt;/td&gt;&lt;/tr&gt;&lt;/table&gt;</summary>
		<author><name>Admin</name></author>	</entry>

	<entry>
		<id>http://jexp.ru/index.php?title=Java/JPA/Many_to_One_Mapping&amp;diff=9004&amp;oldid=prev</id>
		<title> в 18:01, 31 мая 2010</title>
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				<updated>2010-05-31T18:01:48Z</updated>
		
		<summary type="html">&lt;p&gt;&lt;/p&gt;
&lt;p&gt;&lt;b&gt;Новая страница&lt;/b&gt;&lt;/p&gt;&lt;div&gt;== One To Many And Many To One Mapping ==&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
   &lt;br /&gt;
  &amp;lt;!-- start source code --&amp;gt;&lt;br /&gt;
   &lt;br /&gt;
    &amp;lt;source lang=&amp;quot;java&amp;quot;&amp;gt;&lt;br /&gt;
&lt;br /&gt;
File: Department.java&lt;br /&gt;
&lt;br /&gt;
import java.util.HashMap;&lt;br /&gt;
import java.util.Map;&lt;br /&gt;
import javax.persistence.Entity;&lt;br /&gt;
import javax.persistence.GeneratedValue;&lt;br /&gt;
import javax.persistence.GenerationType;&lt;br /&gt;
import javax.persistence.Id;&lt;br /&gt;
import javax.persistence.MapKey;&lt;br /&gt;
import javax.persistence.OneToMany;&lt;br /&gt;
@Entity&lt;br /&gt;
public class Department {&lt;br /&gt;
    @Id @GeneratedValue(strategy=GenerationType.IDENTITY)&lt;br /&gt;
    private int id;&lt;br /&gt;
    private String name;&lt;br /&gt;
    @OneToMany(mappedBy=&amp;quot;department&amp;quot;)&lt;br /&gt;
    @MapKey(name=&amp;quot;name&amp;quot;)&lt;br /&gt;
    private Map&amp;lt;String, Professor&amp;gt; employees;&lt;br /&gt;
    public Department() {&lt;br /&gt;
        employees = new HashMap&amp;lt;String, Professor&amp;gt;();&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public int getId() {&lt;br /&gt;
        return id;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public void setId(int id) {&lt;br /&gt;
        this.id = id;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public String getName() {&lt;br /&gt;
        return name;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public void setName(String deptName) {&lt;br /&gt;
        this.name = deptName;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public void addProfessor(Professor employee) {&lt;br /&gt;
        if (!getProfessors().containsKey(employee.getName())) {&lt;br /&gt;
            getProfessors().put(employee.getName(), employee);&lt;br /&gt;
            if (employee.getDepartment() != null) {&lt;br /&gt;
                employee.getDepartment().getProfessors().remove(employee.getName());&lt;br /&gt;
            }&lt;br /&gt;
            employee.setDepartment(this);&lt;br /&gt;
        }&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public Map&amp;lt;String,Professor&amp;gt; getProfessors() {&lt;br /&gt;
        return employees;&lt;br /&gt;
    }&lt;br /&gt;
    public String toString() {&lt;br /&gt;
        return &amp;quot;Department id: &amp;quot; + getId() + &lt;br /&gt;
               &amp;quot;, name: &amp;quot; + getName();&lt;br /&gt;
    }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
File: Professor.java&lt;br /&gt;
&lt;br /&gt;
import javax.persistence.Entity;&lt;br /&gt;
import javax.persistence.GeneratedValue;&lt;br /&gt;
import javax.persistence.GenerationType;&lt;br /&gt;
import javax.persistence.Id;&lt;br /&gt;
import javax.persistence.ManyToOne;&lt;br /&gt;
@Entity&lt;br /&gt;
public class Professor {&lt;br /&gt;
    @Id @GeneratedValue(strategy=GenerationType.IDENTITY)&lt;br /&gt;
    private int id;&lt;br /&gt;
    private String name;&lt;br /&gt;
    private long salary;&lt;br /&gt;
    &lt;br /&gt;
    @ManyToOne&lt;br /&gt;
    private Department department;&lt;br /&gt;
    public int getId() {&lt;br /&gt;
        return id;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public void setId(int id) {&lt;br /&gt;
        this.id = id;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public String getName() {&lt;br /&gt;
        return name;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public void setName(String name) {&lt;br /&gt;
        this.name = name;&lt;br /&gt;
    }&lt;br /&gt;
    public long getSalary() {&lt;br /&gt;
        return salary;&lt;br /&gt;
    }&lt;br /&gt;
    public void setSalary(long salary) {&lt;br /&gt;
        this.salary = salary;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public Department getDepartment() {&lt;br /&gt;
        return department;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public void setDepartment(Department department) {&lt;br /&gt;
        this.department = department;&lt;br /&gt;
    }&lt;br /&gt;
    public String toString() {&lt;br /&gt;
        return &amp;quot;Professor id: &amp;quot; + getId() + &amp;quot; name: &amp;quot; + getName() + &lt;br /&gt;
               &amp;quot; with &amp;quot; + getDepartment();&lt;br /&gt;
    }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
File: ProfessorService.java&lt;br /&gt;
import java.util.Collection;&lt;br /&gt;
import javax.persistence.EntityManager;&lt;br /&gt;
import javax.persistence.Query;&lt;br /&gt;
public class ProfessorService {&lt;br /&gt;
  protected EntityManager em;&lt;br /&gt;
  public ProfessorService(EntityManager em) {&lt;br /&gt;
    this.em = em;&lt;br /&gt;
  }&lt;br /&gt;
  public Department createDepartment(String name) {&lt;br /&gt;
    Department dept = new Department();&lt;br /&gt;
    dept.setName(name);&lt;br /&gt;
    em.persist(dept);&lt;br /&gt;
    return dept;&lt;br /&gt;
  }&lt;br /&gt;
  public Collection&amp;lt;Department&amp;gt; findAllDepartments() {&lt;br /&gt;
    Query query = em.createQuery(&amp;quot;SELECT d FROM Department d&amp;quot;);&lt;br /&gt;
    return (Collection&amp;lt;Department&amp;gt;) query.getResultList();&lt;br /&gt;
  }&lt;br /&gt;
  public Professor createProfessor(String name, long salary) {&lt;br /&gt;
    Professor emp = new Professor();&lt;br /&gt;
    emp.setName(name);&lt;br /&gt;
    emp.setSalary(salary);&lt;br /&gt;
    em.persist(emp);&lt;br /&gt;
    return emp;&lt;br /&gt;
  }&lt;br /&gt;
  public Professor setProfessorDepartment(int empId, int deptId) {&lt;br /&gt;
    Professor emp = em.find(Professor.class, empId);&lt;br /&gt;
    Department dept = em.find(Department.class, deptId);&lt;br /&gt;
    dept.addProfessor(emp);&lt;br /&gt;
    emp.setDepartment(dept);&lt;br /&gt;
    return emp;&lt;br /&gt;
  }&lt;br /&gt;
  public Collection&amp;lt;Professor&amp;gt; findAllProfessors() {&lt;br /&gt;
    Query query = em.createQuery(&amp;quot;SELECT e FROM Professor e&amp;quot;);&lt;br /&gt;
    return (Collection&amp;lt;Professor&amp;gt;) query.getResultList();&lt;br /&gt;
  }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
File: Main.java&lt;br /&gt;
import java.util.Collection;&lt;br /&gt;
import javax.persistence.EntityManager;&lt;br /&gt;
import javax.persistence.EntityManagerFactory;&lt;br /&gt;
import javax.persistence.Persistence;&lt;br /&gt;
public class Main {&lt;br /&gt;
  public static void main(String[] a) throws Exception {&lt;br /&gt;
    JPAUtil util = new JPAUtil();&lt;br /&gt;
    EntityManagerFactory emf = Persistence.createEntityManagerFactory(&amp;quot;ProfessorService&amp;quot;);&lt;br /&gt;
    EntityManager em = emf.createEntityManager();&lt;br /&gt;
    ProfessorService service = new ProfessorService(em);&lt;br /&gt;
    em.getTransaction().begin();&lt;br /&gt;
    Professor emp = service.createProfessor(&amp;quot;empName&amp;quot;,100L);&lt;br /&gt;
    Department dept = service.createDepartment(&amp;quot;deptName&amp;quot;);&lt;br /&gt;
    emp = service.setProfessorDepartment(emp.getId(),dept.getId());&lt;br /&gt;
    System.out.println(emp.getDepartment() + &amp;quot; with Professors:&amp;quot;);&lt;br /&gt;
    System.out.println(emp.getDepartment().getProfessors());&lt;br /&gt;
    Collection&amp;lt;Professor&amp;gt; emps = service.findAllProfessors();&lt;br /&gt;
    if (emps.isEmpty()) {&lt;br /&gt;
        System.out.println(&amp;quot;No Professors found &amp;quot;);&lt;br /&gt;
    } else {&lt;br /&gt;
        System.out.println(&amp;quot;Found Professors:&amp;quot;);&lt;br /&gt;
        for (Professor emp1 : emps) {&lt;br /&gt;
            System.out.println(emp1);&lt;br /&gt;
        }&lt;br /&gt;
    }&lt;br /&gt;
    Collection&amp;lt;Department&amp;gt; depts = service.findAllDepartments();&lt;br /&gt;
    if (depts.isEmpty()) {&lt;br /&gt;
        System.out.println(&amp;quot;No Departments found &amp;quot;);&lt;br /&gt;
    } else {&lt;br /&gt;
        System.out.println(&amp;quot;Found Departments:&amp;quot;);&lt;br /&gt;
        for (Department dept1 : depts) {&lt;br /&gt;
            System.out.println(dept1 + &amp;quot; with &amp;quot; + dept1.getProfessors().size() +&lt;br /&gt;
                    &amp;quot; employees &amp;quot; + dept1.getProfessors());&lt;br /&gt;
        }&lt;br /&gt;
    }&lt;br /&gt;
    util.checkData(&amp;quot;select * from Professor&amp;quot;);&lt;br /&gt;
    util.checkData(&amp;quot;select * from Department&amp;quot;);&lt;br /&gt;
    em.getTransaction().rumit();&lt;br /&gt;
    em.close();&lt;br /&gt;
    emf.close();&lt;br /&gt;
  }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
File: JPAUtil.java&lt;br /&gt;
import java.io.Reader;&lt;br /&gt;
import java.sql.Connection;&lt;br /&gt;
import java.sql.DriverManager;&lt;br /&gt;
import java.sql.ResultSet;&lt;br /&gt;
import java.sql.ResultSetMetaData;&lt;br /&gt;
import java.sql.Statement;&lt;br /&gt;
public class JPAUtil {&lt;br /&gt;
  Statement st;&lt;br /&gt;
  &lt;br /&gt;
  public JPAUtil() throws Exception{&lt;br /&gt;
    Class.forName(&amp;quot;org.hsqldb.jdbcDriver&amp;quot;);&lt;br /&gt;
    System.out.println(&amp;quot;Driver Loaded.&amp;quot;);&lt;br /&gt;
    String url = &amp;quot;jdbc:hsqldb:data/tutorial&amp;quot;;&lt;br /&gt;
    Connection conn = DriverManager.getConnection(url, &amp;quot;sa&amp;quot;, &amp;quot;&amp;quot;);&lt;br /&gt;
    System.out.println(&amp;quot;Got Connection.&amp;quot;);&lt;br /&gt;
    st = conn.createStatement();&lt;br /&gt;
  }&lt;br /&gt;
  public void executeSQLCommand(String sql) throws Exception {&lt;br /&gt;
    st.executeUpdate(sql);&lt;br /&gt;
  }&lt;br /&gt;
  public void checkData(String sql) throws Exception {&lt;br /&gt;
    ResultSet rs = st.executeQuery(sql);&lt;br /&gt;
    ResultSetMetaData metadata = rs.getMetaData();&lt;br /&gt;
    for (int i = 0; i &amp;lt; metadata.getColumnCount(); i++) {&lt;br /&gt;
      System.out.print(&amp;quot;\t&amp;quot;+ metadata.getColumnLabel(i + 1)); &lt;br /&gt;
    }&lt;br /&gt;
    System.out.println(&amp;quot;\n----------------------------------&amp;quot;);&lt;br /&gt;
    while (rs.next()) {&lt;br /&gt;
      for (int i = 0; i &amp;lt; metadata.getColumnCount(); i++) {&lt;br /&gt;
        Object value = rs.getObject(i + 1);&lt;br /&gt;
        if (value == null) {&lt;br /&gt;
          System.out.print(&amp;quot;\t       &amp;quot;);&lt;br /&gt;
        } else {&lt;br /&gt;
          System.out.print(&amp;quot;\t&amp;quot;+value.toString().trim());&lt;br /&gt;
        }&lt;br /&gt;
      }&lt;br /&gt;
      System.out.println(&amp;quot;&amp;quot;);&lt;br /&gt;
    }&lt;br /&gt;
  }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
File: persistence.xml&lt;br /&gt;
&amp;lt;persistence xmlns=&amp;quot;http://java.sun.ru/xml/ns/persistence&amp;quot;&lt;br /&gt;
             xmlns:xsi=&amp;quot;http://www.w3.org/2001/XMLSchema-instance&amp;quot;&lt;br /&gt;
             xsi:schemaLocation=&amp;quot;http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence&amp;quot; version=&amp;quot;1.0&amp;quot;&amp;gt;&lt;br /&gt;
  &amp;lt;persistence-unit name=&amp;quot;JPAService&amp;quot; transaction-type=&amp;quot;RESOURCE_LOCAL&amp;quot;&amp;gt;&lt;br /&gt;
    &amp;lt;properties&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.dialect&amp;quot; value=&amp;quot;org.hibernate.dialect.HSQLDialect&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.hbm2ddl.auto&amp;quot; value=&amp;quot;update&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.connection.driver_class&amp;quot; value=&amp;quot;org.hsqldb.jdbcDriver&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.connection.username&amp;quot; value=&amp;quot;sa&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.connection.password&amp;quot; value=&amp;quot;&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.connection.url&amp;quot; value=&amp;quot;jdbc:hsqldb:data/tutorial&amp;quot;/&amp;gt;&lt;br /&gt;
    &amp;lt;/properties&amp;gt;&lt;br /&gt;
  &amp;lt;/persistence-unit&amp;gt;&lt;br /&gt;
&amp;lt;/persistence&amp;gt;&lt;br /&gt;
           &lt;br /&gt;
       &amp;lt;/source&amp;gt;&lt;br /&gt;
    &lt;br /&gt;
   &lt;br /&gt;
  &amp;lt;!-- end source code --&amp;gt;&lt;br /&gt;
   &lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
== Persisting With Relationships Using GetReference ==&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
   &lt;br /&gt;
  &amp;lt;!-- start source code --&amp;gt;&lt;br /&gt;
   &lt;br /&gt;
    &amp;lt;source lang=&amp;quot;java&amp;quot;&amp;gt;&lt;br /&gt;
&lt;br /&gt;
File: Department.java&lt;br /&gt;
&lt;br /&gt;
import java.util.ArrayList;&lt;br /&gt;
import java.util.Collection;&lt;br /&gt;
import javax.persistence.Entity;&lt;br /&gt;
import javax.persistence.Id;&lt;br /&gt;
import javax.persistence.OneToMany;&lt;br /&gt;
@Entity&lt;br /&gt;
public class Department {&lt;br /&gt;
    @Id&lt;br /&gt;
    private int id;&lt;br /&gt;
    private String name;&lt;br /&gt;
    @OneToMany(mappedBy=&amp;quot;department&amp;quot;)&lt;br /&gt;
    private Collection&amp;lt;Professor&amp;gt; employees;&lt;br /&gt;
    public Department() {&lt;br /&gt;
        employees = new ArrayList&amp;lt;Professor&amp;gt;();&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public int getId() {&lt;br /&gt;
        return id;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public void setId(int id) {&lt;br /&gt;
        this.id = id;&lt;br /&gt;
    }&lt;br /&gt;
    public String getName() {&lt;br /&gt;
        return name;&lt;br /&gt;
    }&lt;br /&gt;
    public void setName(String name) {&lt;br /&gt;
        this.name = name;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public Collection&amp;lt;Professor&amp;gt; getProfessors() {&lt;br /&gt;
        return employees;&lt;br /&gt;
    }&lt;br /&gt;
    public String toString() {&lt;br /&gt;
        return &amp;quot;Department no: &amp;quot; + getId() + &lt;br /&gt;
               &amp;quot;, name: &amp;quot; + getName();&lt;br /&gt;
    }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
File: Professor.java&lt;br /&gt;
&lt;br /&gt;
import javax.persistence.Entity;&lt;br /&gt;
import javax.persistence.Id;&lt;br /&gt;
import javax.persistence.ManyToOne;&lt;br /&gt;
@Entity&lt;br /&gt;
public class Professor {&lt;br /&gt;
    @Id&lt;br /&gt;
    private int id;&lt;br /&gt;
    private String name;&lt;br /&gt;
    &lt;br /&gt;
    @ManyToOne&lt;br /&gt;
    private Department department;&lt;br /&gt;
    &lt;br /&gt;
    public int getId() {&lt;br /&gt;
        return id;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public void setId(int id) {&lt;br /&gt;
        this.id = id;&lt;br /&gt;
    }&lt;br /&gt;
    public String getName() {&lt;br /&gt;
        return name;&lt;br /&gt;
    }&lt;br /&gt;
    public void setName(String name) {&lt;br /&gt;
        this.name = name;&lt;br /&gt;
    }&lt;br /&gt;
    public Department getDepartment() {&lt;br /&gt;
        return department;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public void setDepartment(Department dept) {&lt;br /&gt;
        this.department = dept;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public String toString() {&lt;br /&gt;
        return &amp;quot;Professor &amp;quot; + getId() + &lt;br /&gt;
               &amp;quot;: name: &amp;quot; + getName() +&lt;br /&gt;
               &amp;quot;, dept: &amp;quot; + ((getDepartment() == null) ? null : getDepartment().getName());&lt;br /&gt;
    }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
File: ProfessorService.java&lt;br /&gt;
import java.util.Collection;&lt;br /&gt;
import javax.persistence.EntityManager;&lt;br /&gt;
public class ProfessorService {&lt;br /&gt;
  protected EntityManager em;&lt;br /&gt;
  public ProfessorService(EntityManager em) {&lt;br /&gt;
    this.em = em;&lt;br /&gt;
  }&lt;br /&gt;
  public Professor createProfessor(int empId, String empName, int deptId) {&lt;br /&gt;
    Department dept = em.getReference(Department.class, deptId);&lt;br /&gt;
    Professor emp = new Professor();&lt;br /&gt;
    emp.setId(empId);&lt;br /&gt;
    emp.setName(empName);&lt;br /&gt;
    emp.setDepartment(dept);&lt;br /&gt;
    dept.getProfessors().add(emp);&lt;br /&gt;
    em.persist(emp);&lt;br /&gt;
    return emp;&lt;br /&gt;
  }&lt;br /&gt;
  public Collection&amp;lt;Professor&amp;gt; findAllProfessors() {&lt;br /&gt;
    return (Collection&amp;lt;Professor&amp;gt;) em.createQuery(&amp;quot;SELECT e FROM Professor e&amp;quot;).getResultList();&lt;br /&gt;
  }&lt;br /&gt;
  public Collection&amp;lt;Department&amp;gt; findAllDepartments() {&lt;br /&gt;
    return (Collection&amp;lt;Department&amp;gt;) em.createQuery(&amp;quot;SELECT d FROM Department d&amp;quot;).getResultList();&lt;br /&gt;
  }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
File: JPAUtil.java&lt;br /&gt;
import java.io.Reader;&lt;br /&gt;
import java.sql.Connection;&lt;br /&gt;
import java.sql.DriverManager;&lt;br /&gt;
import java.sql.ResultSet;&lt;br /&gt;
import java.sql.ResultSetMetaData;&lt;br /&gt;
import java.sql.Statement;&lt;br /&gt;
public class JPAUtil {&lt;br /&gt;
  Statement st;&lt;br /&gt;
  &lt;br /&gt;
  public JPAUtil() throws Exception{&lt;br /&gt;
    Class.forName(&amp;quot;org.hsqldb.jdbcDriver&amp;quot;);&lt;br /&gt;
    System.out.println(&amp;quot;Driver Loaded.&amp;quot;);&lt;br /&gt;
    String url = &amp;quot;jdbc:hsqldb:data/tutorial&amp;quot;;&lt;br /&gt;
    Connection conn = DriverManager.getConnection(url, &amp;quot;sa&amp;quot;, &amp;quot;&amp;quot;);&lt;br /&gt;
    System.out.println(&amp;quot;Got Connection.&amp;quot;);&lt;br /&gt;
    st = conn.createStatement();&lt;br /&gt;
  }&lt;br /&gt;
  public void executeSQLCommand(String sql) throws Exception {&lt;br /&gt;
    st.executeUpdate(sql);&lt;br /&gt;
  }&lt;br /&gt;
  public void checkData(String sql) throws Exception {&lt;br /&gt;
    ResultSet rs = st.executeQuery(sql);&lt;br /&gt;
    ResultSetMetaData metadata = rs.getMetaData();&lt;br /&gt;
    for (int i = 0; i &amp;lt; metadata.getColumnCount(); i++) {&lt;br /&gt;
      System.out.print(&amp;quot;\t&amp;quot;+ metadata.getColumnLabel(i + 1)); &lt;br /&gt;
    }&lt;br /&gt;
    System.out.println(&amp;quot;\n----------------------------------&amp;quot;);&lt;br /&gt;
    while (rs.next()) {&lt;br /&gt;
      for (int i = 0; i &amp;lt; metadata.getColumnCount(); i++) {&lt;br /&gt;
        Object value = rs.getObject(i + 1);&lt;br /&gt;
        if (value == null) {&lt;br /&gt;
          System.out.print(&amp;quot;\t       &amp;quot;);&lt;br /&gt;
        } else {&lt;br /&gt;
          System.out.print(&amp;quot;\t&amp;quot;+value.toString().trim());&lt;br /&gt;
        }&lt;br /&gt;
      }&lt;br /&gt;
      System.out.println(&amp;quot;&amp;quot;);&lt;br /&gt;
    }&lt;br /&gt;
  }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
File: Main.java&lt;br /&gt;
import java.util.Collection;&lt;br /&gt;
import java.util.Iterator;&lt;br /&gt;
import javax.persistence.EntityManager;&lt;br /&gt;
import javax.persistence.EntityManagerFactory;&lt;br /&gt;
import javax.persistence.Persistence;&lt;br /&gt;
public class Main {&lt;br /&gt;
  public static void main(String[] a) throws Exception {&lt;br /&gt;
    JPAUtil util = new JPAUtil();&lt;br /&gt;
    EntityManagerFactory emf = Persistence.createEntityManagerFactory(&amp;quot;ProfessorService&amp;quot;);&lt;br /&gt;
    EntityManager em = emf.createEntityManager();&lt;br /&gt;
    ProfessorService service = new ProfessorService(em);&lt;br /&gt;
    em.getTransaction().begin();&lt;br /&gt;
    service.createProfessor(1, &amp;quot;empName&amp;quot;, 1);&lt;br /&gt;
    util.checkData(&amp;quot;select * from Professor&amp;quot;);&lt;br /&gt;
    em.getTransaction().rumit();&lt;br /&gt;
    em.close();&lt;br /&gt;
    emf.close();&lt;br /&gt;
  }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
File: persistence.xml&lt;br /&gt;
&amp;lt;persistence xmlns=&amp;quot;http://java.sun.ru/xml/ns/persistence&amp;quot;&lt;br /&gt;
             xmlns:xsi=&amp;quot;http://www.w3.org/2001/XMLSchema-instance&amp;quot;&lt;br /&gt;
             xsi:schemaLocation=&amp;quot;http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence&amp;quot; version=&amp;quot;1.0&amp;quot;&amp;gt;&lt;br /&gt;
  &amp;lt;persistence-unit name=&amp;quot;JPAService&amp;quot; transaction-type=&amp;quot;RESOURCE_LOCAL&amp;quot;&amp;gt;&lt;br /&gt;
    &amp;lt;properties&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.dialect&amp;quot; value=&amp;quot;org.hibernate.dialect.HSQLDialect&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.hbm2ddl.auto&amp;quot; value=&amp;quot;update&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.connection.driver_class&amp;quot; value=&amp;quot;org.hsqldb.jdbcDriver&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.connection.username&amp;quot; value=&amp;quot;sa&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.connection.password&amp;quot; value=&amp;quot;&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.connection.url&amp;quot; value=&amp;quot;jdbc:hsqldb:data/tutorial&amp;quot;/&amp;gt;&lt;br /&gt;
    &amp;lt;/properties&amp;gt;&lt;br /&gt;
  &amp;lt;/persistence-unit&amp;gt;&lt;br /&gt;
&amp;lt;/persistence&amp;gt;&lt;br /&gt;
           &lt;br /&gt;
       &amp;lt;/source&amp;gt;&lt;br /&gt;
    &lt;br /&gt;
   &lt;br /&gt;
  &amp;lt;!-- end source code --&amp;gt;&lt;br /&gt;
   &lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
== Use One Joined Column ==&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
   &lt;br /&gt;
  &amp;lt;!-- start source code --&amp;gt;&lt;br /&gt;
   &lt;br /&gt;
    &amp;lt;source lang=&amp;quot;java&amp;quot;&amp;gt;&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
File: Department.java&lt;br /&gt;
&lt;br /&gt;
import javax.persistence.Entity;&lt;br /&gt;
import javax.persistence.GeneratedValue;&lt;br /&gt;
import javax.persistence.GenerationType;&lt;br /&gt;
import javax.persistence.Id;&lt;br /&gt;
@Entity&lt;br /&gt;
public class Department {&lt;br /&gt;
    @Id @GeneratedValue(strategy=GenerationType.IDENTITY)&lt;br /&gt;
    private int id;&lt;br /&gt;
    private String name;&lt;br /&gt;
    public int getId() {&lt;br /&gt;
        return id;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public void setId(int id) {&lt;br /&gt;
        this.id = id;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public String getName() {&lt;br /&gt;
        return name;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public void setName(String deptName) {&lt;br /&gt;
        this.name = deptName;&lt;br /&gt;
    }&lt;br /&gt;
    public String toString() {&lt;br /&gt;
        return &amp;quot;Department id: &amp;quot; + getId() + &lt;br /&gt;
               &amp;quot;, name: &amp;quot; + getName();&lt;br /&gt;
    }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
File: Professor.java&lt;br /&gt;
&lt;br /&gt;
import javax.persistence.Entity;&lt;br /&gt;
import javax.persistence.GeneratedValue;&lt;br /&gt;
import javax.persistence.GenerationType;&lt;br /&gt;
import javax.persistence.Id;&lt;br /&gt;
import javax.persistence.JoinColumn;&lt;br /&gt;
import javax.persistence.ManyToOne;&lt;br /&gt;
@Entity&lt;br /&gt;
public class Professor {&lt;br /&gt;
    @Id @GeneratedValue(strategy=GenerationType.IDENTITY)&lt;br /&gt;
    private int id;&lt;br /&gt;
    private String name;&lt;br /&gt;
    private long salary;&lt;br /&gt;
    &lt;br /&gt;
    @ManyToOne&lt;br /&gt;
    @JoinColumn(name=&amp;quot;DEPT_ID&amp;quot;)&lt;br /&gt;
    private Department department;&lt;br /&gt;
    public int getId() {&lt;br /&gt;
        return id;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public void setId(int id) {&lt;br /&gt;
        this.id = id;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public String getName() {&lt;br /&gt;
        return name;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public void setName(String name) {&lt;br /&gt;
        this.name = name;&lt;br /&gt;
    }&lt;br /&gt;
    public long getSalary() {&lt;br /&gt;
        return salary;&lt;br /&gt;
    }&lt;br /&gt;
    public void setSalary(long salary) {&lt;br /&gt;
        this.salary = salary;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public Department getDepartment() {&lt;br /&gt;
        return department;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public void setDepartment(Department department) {&lt;br /&gt;
        this.department = department;&lt;br /&gt;
    }&lt;br /&gt;
    public String toString() {&lt;br /&gt;
        return &amp;quot;Professor id: &amp;quot; + getId() + &amp;quot; name: &amp;quot; + getName() + &lt;br /&gt;
               &amp;quot; with &amp;quot; + getDepartment();&lt;br /&gt;
    }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
File: ProfessorService.java&lt;br /&gt;
import java.util.Collection;&lt;br /&gt;
import javax.persistence.EntityManager;&lt;br /&gt;
import javax.persistence.Query;&lt;br /&gt;
public class ProfessorService {&lt;br /&gt;
  protected EntityManager em;&lt;br /&gt;
  public ProfessorService(EntityManager em) {&lt;br /&gt;
    this.em = em;&lt;br /&gt;
  }&lt;br /&gt;
  public Professor createProfessor(String name, long salary) {&lt;br /&gt;
    Professor emp = new Professor();&lt;br /&gt;
    emp.setName(name);&lt;br /&gt;
    emp.setSalary(salary);&lt;br /&gt;
    em.persist(emp);&lt;br /&gt;
    return emp;&lt;br /&gt;
  }&lt;br /&gt;
  public Professor setProfessorDepartment(int empId, int deptId) {&lt;br /&gt;
    Professor emp = em.find(Professor.class, empId);&lt;br /&gt;
    Department dept = em.find(Department.class, deptId);&lt;br /&gt;
    emp.setDepartment(dept);&lt;br /&gt;
    return emp;&lt;br /&gt;
  }&lt;br /&gt;
  public Collection&amp;lt;Professor&amp;gt; findAllProfessors() {&lt;br /&gt;
    Query query = em.createQuery(&amp;quot;SELECT e FROM Professor e&amp;quot;);&lt;br /&gt;
    return (Collection&amp;lt;Professor&amp;gt;) query.getResultList();&lt;br /&gt;
  }&lt;br /&gt;
  public Department createDepartment(String name) {&lt;br /&gt;
    Department dept = new Department();&lt;br /&gt;
    dept.setName(name);&lt;br /&gt;
    em.persist(dept);&lt;br /&gt;
    return dept;&lt;br /&gt;
  }&lt;br /&gt;
  public Collection&amp;lt;Department&amp;gt; findAllDepartments() {&lt;br /&gt;
    Query query = em.createQuery(&amp;quot;SELECT d FROM Department d&amp;quot;);&lt;br /&gt;
    return (Collection&amp;lt;Department&amp;gt;) query.getResultList();&lt;br /&gt;
  }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
File: JPAUtil.java&lt;br /&gt;
import java.io.Reader;&lt;br /&gt;
import java.sql.Connection;&lt;br /&gt;
import java.sql.DriverManager;&lt;br /&gt;
import java.sql.ResultSet;&lt;br /&gt;
import java.sql.ResultSetMetaData;&lt;br /&gt;
import java.sql.Statement;&lt;br /&gt;
public class JPAUtil {&lt;br /&gt;
  Statement st;&lt;br /&gt;
  &lt;br /&gt;
  public JPAUtil() throws Exception{&lt;br /&gt;
    Class.forName(&amp;quot;org.hsqldb.jdbcDriver&amp;quot;);&lt;br /&gt;
    System.out.println(&amp;quot;Driver Loaded.&amp;quot;);&lt;br /&gt;
    String url = &amp;quot;jdbc:hsqldb:data/tutorial&amp;quot;;&lt;br /&gt;
    Connection conn = DriverManager.getConnection(url, &amp;quot;sa&amp;quot;, &amp;quot;&amp;quot;);&lt;br /&gt;
    System.out.println(&amp;quot;Got Connection.&amp;quot;);&lt;br /&gt;
    st = conn.createStatement();&lt;br /&gt;
  }&lt;br /&gt;
  public void executeSQLCommand(String sql) throws Exception {&lt;br /&gt;
    st.executeUpdate(sql);&lt;br /&gt;
  }&lt;br /&gt;
  public void checkData(String sql) throws Exception {&lt;br /&gt;
    ResultSet rs = st.executeQuery(sql);&lt;br /&gt;
    ResultSetMetaData metadata = rs.getMetaData();&lt;br /&gt;
    for (int i = 0; i &amp;lt; metadata.getColumnCount(); i++) {&lt;br /&gt;
      System.out.print(&amp;quot;\t&amp;quot;+ metadata.getColumnLabel(i + 1)); &lt;br /&gt;
    }&lt;br /&gt;
    System.out.println(&amp;quot;\n----------------------------------&amp;quot;);&lt;br /&gt;
    while (rs.next()) {&lt;br /&gt;
      for (int i = 0; i &amp;lt; metadata.getColumnCount(); i++) {&lt;br /&gt;
        Object value = rs.getObject(i + 1);&lt;br /&gt;
        if (value == null) {&lt;br /&gt;
          System.out.print(&amp;quot;\t       &amp;quot;);&lt;br /&gt;
        } else {&lt;br /&gt;
          System.out.print(&amp;quot;\t&amp;quot;+value.toString().trim());&lt;br /&gt;
        }&lt;br /&gt;
      }&lt;br /&gt;
      System.out.println(&amp;quot;&amp;quot;);&lt;br /&gt;
    }&lt;br /&gt;
  }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
File: Main.java&lt;br /&gt;
import java.util.Collection;&lt;br /&gt;
import javax.persistence.EntityManager;&lt;br /&gt;
import javax.persistence.EntityManagerFactory;&lt;br /&gt;
import javax.persistence.Persistence;&lt;br /&gt;
public class Main {&lt;br /&gt;
  public static void main(String[] a) throws Exception {&lt;br /&gt;
    JPAUtil util = new JPAUtil();&lt;br /&gt;
    EntityManagerFactory emf = Persistence.createEntityManagerFactory(&amp;quot;ProfessorService&amp;quot;);&lt;br /&gt;
    EntityManager em = emf.createEntityManager();&lt;br /&gt;
    ProfessorService service = new ProfessorService(em);&lt;br /&gt;
    em.getTransaction().begin();&lt;br /&gt;
    Professor emp = service.createProfessor(&amp;quot;empName&amp;quot;, 100);&lt;br /&gt;
    &lt;br /&gt;
    &lt;br /&gt;
    &lt;br /&gt;
    Department dept = service.createDepartment(&amp;quot;deptName&amp;quot;);&lt;br /&gt;
    &lt;br /&gt;
    &lt;br /&gt;
    &lt;br /&gt;
    service.setProfessorDepartment(emp.getId(), dept.getId());&lt;br /&gt;
    &lt;br /&gt;
    Collection&amp;lt;Professor&amp;gt; emps = service.findAllProfessors();&lt;br /&gt;
    for (Professor emp1 : emps) {&lt;br /&gt;
      System.out.println(emp1);&lt;br /&gt;
    }&lt;br /&gt;
    Collection&amp;lt;Department&amp;gt; depts = service.findAllDepartments();&lt;br /&gt;
    for (Department dept1 : depts) {&lt;br /&gt;
      System.out.println(dept1);&lt;br /&gt;
    }&lt;br /&gt;
    util.checkData(&amp;quot;select * from Professor&amp;quot;);&lt;br /&gt;
    util.checkData(&amp;quot;select * from Department&amp;quot;);&lt;br /&gt;
    em.getTransaction().rumit();&lt;br /&gt;
    em.close();&lt;br /&gt;
    emf.close();&lt;br /&gt;
  }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
File: persistence.xml&lt;br /&gt;
&amp;lt;persistence xmlns=&amp;quot;http://java.sun.ru/xml/ns/persistence&amp;quot;&lt;br /&gt;
             xmlns:xsi=&amp;quot;http://www.w3.org/2001/XMLSchema-instance&amp;quot;&lt;br /&gt;
             xsi:schemaLocation=&amp;quot;http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence&amp;quot; version=&amp;quot;1.0&amp;quot;&amp;gt;&lt;br /&gt;
  &amp;lt;persistence-unit name=&amp;quot;JPAService&amp;quot; transaction-type=&amp;quot;RESOURCE_LOCAL&amp;quot;&amp;gt;&lt;br /&gt;
    &amp;lt;properties&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.dialect&amp;quot; value=&amp;quot;org.hibernate.dialect.HSQLDialect&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.hbm2ddl.auto&amp;quot; value=&amp;quot;update&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.connection.driver_class&amp;quot; value=&amp;quot;org.hsqldb.jdbcDriver&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.connection.username&amp;quot; value=&amp;quot;sa&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.connection.password&amp;quot; value=&amp;quot;&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.connection.url&amp;quot; value=&amp;quot;jdbc:hsqldb:data/tutorial&amp;quot;/&amp;gt;&lt;br /&gt;
    &amp;lt;/properties&amp;gt;&lt;br /&gt;
  &amp;lt;/persistence-unit&amp;gt;&lt;br /&gt;
&amp;lt;/persistence&amp;gt;&lt;br /&gt;
           &lt;br /&gt;
       &amp;lt;/source&amp;gt;&lt;br /&gt;
    &lt;br /&gt;
   &lt;br /&gt;
  &amp;lt;!-- end source code --&amp;gt;&lt;br /&gt;
   &lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
== Use Two Joined Columns for Many to one Mapping ==&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
   &lt;br /&gt;
  &amp;lt;!-- start source code --&amp;gt;&lt;br /&gt;
   &lt;br /&gt;
    &amp;lt;source lang=&amp;quot;java&amp;quot;&amp;gt;&lt;br /&gt;
&lt;br /&gt;
File: Professor.java&lt;br /&gt;
&lt;br /&gt;
import java.util.ArrayList;&lt;br /&gt;
import java.util.Collection;&lt;br /&gt;
import javax.persistence.Column;&lt;br /&gt;
import javax.persistence.Entity;&lt;br /&gt;
import javax.persistence.Id;&lt;br /&gt;
import javax.persistence.IdClass;&lt;br /&gt;
import javax.persistence.JoinColumn;&lt;br /&gt;
import javax.persistence.JoinColumns;&lt;br /&gt;
import javax.persistence.JoinTable;&lt;br /&gt;
import javax.persistence.ManyToMany;&lt;br /&gt;
import javax.persistence.ManyToOne;&lt;br /&gt;
import javax.persistence.OneToMany;&lt;br /&gt;
@Entity &lt;br /&gt;
@IdClass(ProfessorId.class)&lt;br /&gt;
public class Professor {&lt;br /&gt;
    @Id private String country;&lt;br /&gt;
    @Id&lt;br /&gt;
    @Column(name=&amp;quot;EMP_ID&amp;quot;)&lt;br /&gt;
    private int id;&lt;br /&gt;
    private String name;&lt;br /&gt;
    private long salary;&lt;br /&gt;
    @ManyToOne &lt;br /&gt;
    @JoinColumns({&lt;br /&gt;
        @JoinColumn(name=&amp;quot;MGR_COUNTRY&amp;quot;, referencedColumnName=&amp;quot;COUNTRY&amp;quot;),&lt;br /&gt;
        @JoinColumn(name=&amp;quot;MGR_ID&amp;quot;, referencedColumnName=&amp;quot;EMP_ID&amp;quot;)&lt;br /&gt;
    })&lt;br /&gt;
    private Professor manager;&lt;br /&gt;
    @OneToMany(mappedBy=&amp;quot;manager&amp;quot;)&lt;br /&gt;
    private Collection&amp;lt;Professor&amp;gt; directs;&lt;br /&gt;
    @ManyToMany &lt;br /&gt;
    @JoinTable(&lt;br /&gt;
        name=&amp;quot;EMP_PROJECT&amp;quot;, &lt;br /&gt;
        joinColumns={&lt;br /&gt;
            @JoinColumn(name=&amp;quot;EMP_COUNTRY&amp;quot;, referencedColumnName=&amp;quot;COUNTRY&amp;quot;),&lt;br /&gt;
            @JoinColumn(name=&amp;quot;EMP_ID&amp;quot;, referencedColumnName=&amp;quot;EMP_ID&amp;quot;)},&lt;br /&gt;
        inverseJoinColumns=@JoinColumn(name=&amp;quot;PROJECT_ID&amp;quot;))&lt;br /&gt;
    private Collection&amp;lt;Project&amp;gt; projects;&lt;br /&gt;
    public Professor() {&lt;br /&gt;
        directs = new ArrayList&amp;lt;Professor&amp;gt;();&lt;br /&gt;
        projects = new ArrayList&amp;lt;Project&amp;gt;();&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public int getId() {&lt;br /&gt;
        return id;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public void setId(int id) {&lt;br /&gt;
        this.id = id;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public String getCountry() {&lt;br /&gt;
        return country;&lt;br /&gt;
    }&lt;br /&gt;
    public void setCountry(String country) {&lt;br /&gt;
        this.country = country;&lt;br /&gt;
    }&lt;br /&gt;
    public String getName() {&lt;br /&gt;
        return name;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public void setName(String name) {&lt;br /&gt;
        this.name = name;&lt;br /&gt;
    }&lt;br /&gt;
    public long getSalary() {&lt;br /&gt;
        return salary;&lt;br /&gt;
    }&lt;br /&gt;
    public void setSalary(long salary) {&lt;br /&gt;
        this.salary = salary;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public Collection&amp;lt;Professor&amp;gt; getDirects() {&lt;br /&gt;
        return directs;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public Professor getManager() {&lt;br /&gt;
        return manager;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public void setManager(Professor manager) {&lt;br /&gt;
        this.manager = manager;&lt;br /&gt;
    }&lt;br /&gt;
    &lt;br /&gt;
    public Collection&amp;lt;Project&amp;gt; getProjects() {&lt;br /&gt;
        return projects;&lt;br /&gt;
    }&lt;br /&gt;
    public String toString() {&lt;br /&gt;
        return &amp;quot;Professor id: &amp;quot; + getId() + &amp;quot; name: &amp;quot; + getName() +&lt;br /&gt;
               &amp;quot; country: &amp;quot; + getCountry();&lt;br /&gt;
    }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
File: ProfessorId.java&lt;br /&gt;
import java.io.Serializable;&lt;br /&gt;
import javax.persistence.Column;&lt;br /&gt;
import javax.persistence.Embeddable;&lt;br /&gt;
@Embeddable&lt;br /&gt;
public class ProfessorId implements Serializable{&lt;br /&gt;
  private String country;&lt;br /&gt;
  @Column(name = &amp;quot;EMP_ID&amp;quot;)&lt;br /&gt;
  private int id;&lt;br /&gt;
  public ProfessorId() {&lt;br /&gt;
  }&lt;br /&gt;
  public ProfessorId(String country, int id) {&lt;br /&gt;
    this.country = country;&lt;br /&gt;
    this.id = id;&lt;br /&gt;
  }&lt;br /&gt;
  public String getCountry() {&lt;br /&gt;
    return country;&lt;br /&gt;
  }&lt;br /&gt;
  public int getId() {&lt;br /&gt;
    return id;&lt;br /&gt;
  }&lt;br /&gt;
  public boolean equals(Object o) {&lt;br /&gt;
    return ((o instanceof ProfessorId) &amp;amp;&amp;amp; country.equals(((ProfessorId) o).getCountry()) &amp;amp;&amp;amp; id == ((ProfessorId) o)&lt;br /&gt;
        .getId());&lt;br /&gt;
  }&lt;br /&gt;
  public int hashCode() {&lt;br /&gt;
    return country.hashCode() + id;&lt;br /&gt;
  }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
File: ProfessorService.java&lt;br /&gt;
import java.util.Collection;&lt;br /&gt;
import javax.persistence.EntityManager;&lt;br /&gt;
import javax.persistence.Query;&lt;br /&gt;
public class ProfessorService {&lt;br /&gt;
  protected EntityManager em;&lt;br /&gt;
  public ProfessorService(EntityManager em) {&lt;br /&gt;
    this.em = em;&lt;br /&gt;
  }&lt;br /&gt;
  public Professor createProfessor(String country, int id, String name, long salary) {&lt;br /&gt;
    Professor emp = new Professor();&lt;br /&gt;
    emp.setCountry(country);&lt;br /&gt;
    emp.setId(id);&lt;br /&gt;
    emp.setName(name);&lt;br /&gt;
    emp.setSalary(salary);&lt;br /&gt;
    em.persist(emp);&lt;br /&gt;
    return emp;&lt;br /&gt;
  }&lt;br /&gt;
  public void createProject(String projName) {&lt;br /&gt;
    Project proj = new Project();&lt;br /&gt;
    proj.setName(projName);&lt;br /&gt;
    em.persist(proj);&lt;br /&gt;
  }&lt;br /&gt;
  public void setProfessorManager(String country, int id, String mgrCountry, int mgrId) {&lt;br /&gt;
    Professor emp = findProfessor(country, id);&lt;br /&gt;
    Professor mgr = findProfessor(mgrCountry, mgrId);&lt;br /&gt;
    emp.setManager(mgr);&lt;br /&gt;
    mgr.getDirects().add(emp);&lt;br /&gt;
  }&lt;br /&gt;
  public void addProfessorProject(String country, int id, int projId) {&lt;br /&gt;
    Professor emp = findProfessor(country, id);&lt;br /&gt;
    Project proj = em.find(Project.class, projId);&lt;br /&gt;
    emp.getProjects().add(proj);&lt;br /&gt;
    proj.getProfessors().add(emp);&lt;br /&gt;
  }&lt;br /&gt;
  public Professor findProfessor(String country, int id) {&lt;br /&gt;
    return em.find(Professor.class, new ProfessorId(country, id));&lt;br /&gt;
  }&lt;br /&gt;
  public Collection&amp;lt;Professor&amp;gt; findAllProfessors() {&lt;br /&gt;
    Query query = em.createQuery(&amp;quot;SELECT e FROM Professor e&amp;quot;);&lt;br /&gt;
    return (Collection&amp;lt;Professor&amp;gt;) query.getResultList();&lt;br /&gt;
  }&lt;br /&gt;
  public Collection&amp;lt;Project&amp;gt; findAllProjects() {&lt;br /&gt;
    Query query = em.createQuery(&amp;quot;SELECT p FROM Project p&amp;quot;);&lt;br /&gt;
    return (Collection&amp;lt;Project&amp;gt;) query.getResultList();&lt;br /&gt;
  }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
File: Project.java&lt;br /&gt;
import java.util.ArrayList;&lt;br /&gt;
import java.util.Collection;&lt;br /&gt;
import javax.persistence.Entity;&lt;br /&gt;
import javax.persistence.Id;&lt;br /&gt;
import javax.persistence.ManyToMany;&lt;br /&gt;
@Entity&lt;br /&gt;
public class Project {&lt;br /&gt;
  @Id&lt;br /&gt;
  protected int id;&lt;br /&gt;
  protected String name;&lt;br /&gt;
  @ManyToMany(mappedBy = &amp;quot;projects&amp;quot;)&lt;br /&gt;
  protected Collection&amp;lt;Professor&amp;gt; employees = new ArrayList&amp;lt;Professor&amp;gt;();&lt;br /&gt;
  public int getId() {&lt;br /&gt;
    return id;&lt;br /&gt;
  }&lt;br /&gt;
  public void setId(int projectNo) {&lt;br /&gt;
    this.id = projectNo;&lt;br /&gt;
  }&lt;br /&gt;
  public String getName() {&lt;br /&gt;
    return name;&lt;br /&gt;
  }&lt;br /&gt;
  public void setName(String projectName) {&lt;br /&gt;
    this.name = projectName;&lt;br /&gt;
  }&lt;br /&gt;
  public Collection&amp;lt;Professor&amp;gt; getProfessors() {&lt;br /&gt;
    return employees;&lt;br /&gt;
  }&lt;br /&gt;
  public void addProfessor(Professor employee) {&lt;br /&gt;
    if (!getProfessors().contains(employee)) {&lt;br /&gt;
      getProfessors().add(employee);&lt;br /&gt;
    }&lt;br /&gt;
    if (!employee.getProjects().contains(this)) {&lt;br /&gt;
      employee.getProjects().add(this);&lt;br /&gt;
    }&lt;br /&gt;
  }&lt;br /&gt;
  public String toString() {&lt;br /&gt;
    return getClass().getName().substring(getClass().getName().lastIndexOf(&amp;quot;.&amp;quot;) + 1) + &amp;quot; no: &amp;quot;&lt;br /&gt;
        + getId() + &amp;quot;, name: &amp;quot; + getName();&lt;br /&gt;
  }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
File: JPAUtil.java&lt;br /&gt;
import java.io.Reader;&lt;br /&gt;
import java.sql.Connection;&lt;br /&gt;
import java.sql.DriverManager;&lt;br /&gt;
import java.sql.ResultSet;&lt;br /&gt;
import java.sql.ResultSetMetaData;&lt;br /&gt;
import java.sql.Statement;&lt;br /&gt;
public class JPAUtil {&lt;br /&gt;
  Statement st;&lt;br /&gt;
  &lt;br /&gt;
  public JPAUtil() throws Exception{&lt;br /&gt;
    Class.forName(&amp;quot;org.hsqldb.jdbcDriver&amp;quot;);&lt;br /&gt;
    System.out.println(&amp;quot;Driver Loaded.&amp;quot;);&lt;br /&gt;
    String url = &amp;quot;jdbc:hsqldb:data/tutorial&amp;quot;;&lt;br /&gt;
    Connection conn = DriverManager.getConnection(url, &amp;quot;sa&amp;quot;, &amp;quot;&amp;quot;);&lt;br /&gt;
    System.out.println(&amp;quot;Got Connection.&amp;quot;);&lt;br /&gt;
    st = conn.createStatement();&lt;br /&gt;
  }&lt;br /&gt;
  public void executeSQLCommand(String sql) throws Exception {&lt;br /&gt;
    st.executeUpdate(sql);&lt;br /&gt;
  }&lt;br /&gt;
  public void checkData(String sql) throws Exception {&lt;br /&gt;
    ResultSet rs = st.executeQuery(sql);&lt;br /&gt;
    ResultSetMetaData metadata = rs.getMetaData();&lt;br /&gt;
    for (int i = 0; i &amp;lt; metadata.getColumnCount(); i++) {&lt;br /&gt;
      System.out.print(&amp;quot;\t&amp;quot;+ metadata.getColumnLabel(i + 1)); &lt;br /&gt;
    }&lt;br /&gt;
    System.out.println(&amp;quot;\n----------------------------------&amp;quot;);&lt;br /&gt;
    while (rs.next()) {&lt;br /&gt;
      for (int i = 0; i &amp;lt; metadata.getColumnCount(); i++) {&lt;br /&gt;
        Object value = rs.getObject(i + 1);&lt;br /&gt;
        if (value == null) {&lt;br /&gt;
          System.out.print(&amp;quot;\t       &amp;quot;);&lt;br /&gt;
        } else {&lt;br /&gt;
          System.out.print(&amp;quot;\t&amp;quot;+value.toString().trim());&lt;br /&gt;
        }&lt;br /&gt;
      }&lt;br /&gt;
      System.out.println(&amp;quot;&amp;quot;);&lt;br /&gt;
    }&lt;br /&gt;
  }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
File: Main.java&lt;br /&gt;
import javax.persistence.EntityManager;&lt;br /&gt;
import javax.persistence.EntityManagerFactory;&lt;br /&gt;
import javax.persistence.Persistence;&lt;br /&gt;
public class Main {&lt;br /&gt;
  public static void main(String[] a) throws Exception {&lt;br /&gt;
    JPAUtil util = new JPAUtil();&lt;br /&gt;
    EntityManagerFactory emf = Persistence.createEntityManagerFactory(&amp;quot;ProfessorService&amp;quot;);&lt;br /&gt;
    EntityManager em = emf.createEntityManager();&lt;br /&gt;
    ProfessorService service = new ProfessorService(em);&lt;br /&gt;
    em.getTransaction().begin();&lt;br /&gt;
    service.createProfessor(&amp;quot;country&amp;quot;, 1, &amp;quot;name&amp;quot;, 100);&lt;br /&gt;
    service.createProfessor(&amp;quot;mgrcountry&amp;quot;, 2, &amp;quot;mgrName&amp;quot;, 100);&lt;br /&gt;
    service.createProject(&amp;quot;proj&amp;quot;);&lt;br /&gt;
    service.addProfessorProject(&amp;quot;empCountry2&amp;quot;, 1, 1);&lt;br /&gt;
    service.setProfessorManager(&amp;quot;Country&amp;quot;, 1, &amp;quot;mgrCountry&amp;quot;, 1);&lt;br /&gt;
&lt;br /&gt;
    System.out.println(&amp;quot;Professors:&amp;quot;);&lt;br /&gt;
    for (Professor emp : service.findAllProfessors()) {&lt;br /&gt;
      System.out.println(emp + &amp;quot; &amp;quot; + emp.getProjects().size());&lt;br /&gt;
      System.out.println(emp + &amp;quot; &amp;quot; + emp.getManager());&lt;br /&gt;
    }&lt;br /&gt;
    System.out.println(&amp;quot;Projects:&amp;quot;);&lt;br /&gt;
    for (Project p : service.findAllProjects()) {&lt;br /&gt;
      System.out.print(p + &amp;quot; &amp;quot; + p.getProfessors().size());&lt;br /&gt;
    }&lt;br /&gt;
    util.checkData(&amp;quot;select * from Professor&amp;quot;);&lt;br /&gt;
    em.getTransaction().rumit();&lt;br /&gt;
    em.close();&lt;br /&gt;
    emf.close();&lt;br /&gt;
  }&lt;br /&gt;
}&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
File: persistence.xml&lt;br /&gt;
&amp;lt;persistence xmlns=&amp;quot;http://java.sun.ru/xml/ns/persistence&amp;quot;&lt;br /&gt;
             xmlns:xsi=&amp;quot;http://www.w3.org/2001/XMLSchema-instance&amp;quot;&lt;br /&gt;
             xsi:schemaLocation=&amp;quot;http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence&amp;quot; version=&amp;quot;1.0&amp;quot;&amp;gt;&lt;br /&gt;
  &amp;lt;persistence-unit name=&amp;quot;JPAService&amp;quot; transaction-type=&amp;quot;RESOURCE_LOCAL&amp;quot;&amp;gt;&lt;br /&gt;
    &amp;lt;properties&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.dialect&amp;quot; value=&amp;quot;org.hibernate.dialect.HSQLDialect&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.hbm2ddl.auto&amp;quot; value=&amp;quot;update&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.connection.driver_class&amp;quot; value=&amp;quot;org.hsqldb.jdbcDriver&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.connection.username&amp;quot; value=&amp;quot;sa&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.connection.password&amp;quot; value=&amp;quot;&amp;quot;/&amp;gt;&lt;br /&gt;
      &amp;lt;property name=&amp;quot;hibernate.connection.url&amp;quot; value=&amp;quot;jdbc:hsqldb:data/tutorial&amp;quot;/&amp;gt;&lt;br /&gt;
    &amp;lt;/properties&amp;gt;&lt;br /&gt;
  &amp;lt;/persistence-unit&amp;gt;&lt;br /&gt;
&amp;lt;/persistence&amp;gt;&lt;br /&gt;
           &lt;br /&gt;
       &amp;lt;/source&amp;gt;&lt;br /&gt;
    &lt;br /&gt;
   &lt;br /&gt;
  &amp;lt;!-- end source code --&amp;gt;&lt;/div&gt;</summary>
			</entry>

	</feed>