File: Professor.java
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.NamedQuery;
import javax.persistence.QueryHint;
@Entity
@NamedQuery(name="findProfessorNoCache",
query="SELECT e FROM Professor e WHERE e.id = ?1",
hints={@QueryHint(name="toplink.cache-usage", value="DoNotCheckCache")})
public class Professor {
@Id
private int id;
private String name;
private long salary;
public int getId() {
return id;
}
public String getName() {
return name;
}
public long getSalary() {
return salary;
}
public String toString() {
return "Professor " + getId() +
": name: " + getName() +
", salary: " + getSalary();
}
}
File: ProfessorService.java
import java.util.Collection;
import javax.persistence.EntityManager;
import javax.persistence.NoResultException;
import javax.persistence.Query;
public class ProfessorService {
protected EntityManager em;
public ProfessorService(EntityManager em) {
this.em = em;
}
public Professor findProfessor(int empId) {
Query q = em.createQuery("SELECT e FROM Professor e WHERE e.id = ?1");
q.setParameter(1, empId);
try {
return (Professor) q.getSingleResult();
} catch (NoResultException e) {
return null;
}
}
public Professor findProfessorNoCache(int empId) {
Query q = em.createQuery("SELECT e FROM Professor e WHERE e.id = ?1");
// force read from database
q.setHint("cacheUsage", oracle.toplink.essentials.queryframework.ObjectLevelReadQuery.DoNotCheckCache);
q.setParameter(1, empId);
try {
return (Professor) q.getSingleResult();
} catch (NoResultException e) {
return null;
}
}
public Professor findProfessorNoCacheNamed(int empId) {
Query q = em.createNamedQuery("findProfessorNoCache");
q.setParameter(1, empId);
try {
return (Professor) q.getSingleResult();
} catch (NoResultException e) {
return null;
}
}
public Collection findAllProfessors() {
return (Collection) em.createQuery("SELECT e FROM Professor e").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.removeDepartment2();
util.checkData("select * from Professor");
util.checkData("select * from Department");
em.getTransaction().commit();
em.close();
emf.close();
}
}
File: persistence.xml
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence" version="1.0">
JPA-QueryHintsExample.zip( 5,332 k)