import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
//@Table(name="EMP", schema="HR")
@Table(name="EMP")
public class Professor {
@Id
@Column(name = "EMP_ID")
private int id;
@Column(name = "COMM")
private String name;
@Column(name = "SAL")
private long salary;
public Professor() {
}
public Professor(int id) {
this.id = id;
}
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 String toString() {
return "Professor id: " + getId() + " name: " + getName() + " salary: " + getSalary();
}
}
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(int id, String name, long salary) {
Professor emp = new Professor(id);
emp.setName(name);
emp.setSalary(salary);
em.persist(emp);
return emp;
}
public void removeProfessor(int id) {
Professor emp = findProfessor(id);
if (emp != null) {
em.remove(emp);
}
}
public Professor raiseProfessorSalary(int id, long raise) {
Professor emp = em.find(Professor.class, id);
if (emp != null) {
emp.setSalary(emp.getSalary() + raise);
}
return emp;
}
public Professor findProfessor(int id) {
return em.find(Professor.class, id);
}
public Collection
Query query = em.createQuery("SELECT e FROM Professor e");
return (Collection
}
}
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(); Professor emp = service.createProfessor(158, "AAA", 45000); em.getTransaction().commit(); System.out.println("Persisted " + emp); util.checkData("select * from EMP"); // remove an employee em.getTransaction().begin(); service.removeProfessor(158); em.getTransaction().commit(); System.out.println("Removed Professor 158"); util.checkData("select * from EMP"); em.close(); emf.close();
}
}
File: persistence.xml
