Message.java Source code

Introduction

Here is the source code for Message.java

Source

    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<Message>) 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

    <persistence xmlns="http://java.sun.com/xml/ns/persistence"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence"version="1.0"><persistence-unit name="JPAService"transaction-type="RESOURCE_LOCAL"><properties><property name="hibernate.dialect"value="org.hibernate.dialect.HSQLDialect"/><property name="hibernate.hbm2ddl.auto"value="update"/><property name="hibernate.connection.driver_class"value="org.hsqldb.jdbcDriver"/><property name="hibernate.connection.username"value="sa"/><property name="hibernate.connection.password"value=""/><property name="hibernate.connection.url"value="jdbc:hsqldb:data/tutorial"/></properties></persistence-unit></persistence>