File: Message.java
import java.util.Date;
import javax.persistence.Basic;
import javax.persistence.Entity;
import javax.persistence.Id;
@Entity
public class Message {
@Id
private long id = System.currentTimeMillis();
@Basic
private String message;
@Basic
private Date created = new Date();
public Message() {
}
public Message(String msg) {
message = msg;
}
public void setId(long val) {
id = val;
}
public long getId() {
return id;
}
public void setMessage(String msg) {
message = msg;
}
public String getMessage() {
return message;
}
public void setCreated(Date date) {
created = date;
}
public Date getCreated() {
return created;
}
}
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 void messageCreateAndList() {
em.persist(new Message("Hello Persistence!"));
Query q = em.createQuery("select m from Message m");
for (Message m : (List) q.getResultList()) {
System.out.println(m.getMessage()
+ " (created on: " + m.getCreated() + ")");
}
}
}
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.messageCreateAndList();
util.checkData("select * from Message");
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-UsingSystemMiliSecondsAsKey.zip( 5,333 k)