File: Main.java
import java.util.Date;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.TemporalType;
public class Main {
static EntityManagerFactory emf = Persistence.createEntityManagerFactory("JPAService");
static EntityManager em = emf.createEntityManager();
public static void main(String[] a) throws Exception {
em.getTransaction().begin();
Date start = new Date();
Date end = new Date();
em.createQuery("SELECT e " + "FROM Student e " + "WHERE e.startDate BETWEEN :start AND :end")
.setParameter("start", start, TemporalType.DATE)
.setParameter("end", end, TemporalType.DATE).getResultList();
em.getTransaction().commit();
em.close();
emf.close();
Helper.checkData();
}
}
File: Project.java
import java.util.ArrayList;
import java.util.Collection;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.ManyToMany;
@Entity
public class Project {
@Id
protected int id;
protected String name;
@ManyToMany(mappedBy="projects")
private Collection students;
public Project() {
students = new ArrayList();
}
public int getId() {
return id;
}
public String getName() {
return name;
}
public Collection getStudents() {
return students;
}
public String toString() {
return "Project id: " + getId() + ", name: " + getName();
}
}
File: Student.java
import java.util.ArrayList;
import java.util.Collection;
import java.util.Date;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.ManyToMany;
import javax.persistence.ManyToOne;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.OneToMany;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
@Entity
@NamedQueries({
@NamedQuery(name="findStudentAboveSal",
query="SELECT e " +
"FROM Student e " +
"WHERE e.department = :dept AND " +
" e.salary > :sal"),
@NamedQuery(name="findHighestPaidByDepartment",
query="SELECT e " +
"FROM Student e " +
"WHERE e.department = :dept AND " +
" e.salary = (SELECT MAX(e2.salary) " +
" FROM Student e2 " +
" WHERE e2.department = :dept)")
})
public class Student {
@Id
private int id;
private String name;
private long salary;
@Temporal(TemporalType.DATE)
private Date startDate;
@ManyToOne
private Student manager;
@OneToMany(mappedBy="manager")
private Collection directs;
@ManyToOne
private Department department;
@ManyToMany
private Collection projects;
public Student() {
projects = new ArrayList();
directs = new ArrayList();
}
public int getId() {
return id;
}
public String getName() {
return name;
}
public long getSalary() {
return salary;
}
public Date getStartDate() {
return startDate;
}
public Department getDepartment() {
return department;
}
public Collection getDirects() {
return directs;
}
public Student getManager() {
return manager;
}
public Collection getProjects() {
return projects;
}
public String toString() {
return "Student " + getId() +
": name: " + getName() +
", salary: " + getSalary() +
", dept: " + ((getDepartment() == null) ? null : getDepartment().getName());
}
}
File: Department.java
import java.util.ArrayList;
import java.util.Collection;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.OneToMany;
@Entity
public class Department {
@Id
private int id;
private String name;
@OneToMany(mappedBy="department")
private Collection students;
public Department() {
students = new ArrayList();
}
public int getId() {
return id;
}
public String getName() {
return name;
}
public Collection getStudents() {
return students;
}
public String toString() {
return "Department no: " + getId() +
", name: " + getName();
}
}
File: Helper.java
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class Helper {
public static void checkData() throws Exception {
Class.forName("org.hsqldb.jdbcDriver");
Connection conn = DriverManager.getConnection("jdbc:hsqldb:data/tutorial", "sa", "");
Statement st = conn.createStatement();
ResultSet mrs = conn.getMetaData().getTables(null, null, null, new String[] { "TABLE" });
while (mrs.next()) {
String tableName = mrs.getString(3);
System.out.println("\n\n\n\nTable Name: "+ tableName);
ResultSet rs = st.executeQuery("select * from " + tableName);
ResultSetMetaData metadata = rs.getMetaData();
while (rs.next()) {
System.out.println(" Row:");
for (int i = 0; i < metadata.getColumnCount(); i++) {
System.out.println(" Column Name: "+ metadata.getColumnLabel(i + 1)+ ", ");
System.out.println(" Column Type: "+ metadata.getColumnTypeName(i + 1)+ ": ");
Object value = rs.getObject(i + 1);
System.out.println(" Column Value: "+value+"\n");
}
}
}
}
}
File: persistence.xml
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence" version="1.0">