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JPA read data from database example

                         

In this section, you will learn how to retrieve data from database using JPA. Create a "JPARead.java" file and follows the following steps to reading data from database.

  1. Create "JPARead" class file.

  2. Put the following text in "JPARead.java" file.

  3. JPARead.java
    /*
    * To change this template, choose Tools | Templates
    * and open the template in the editor.
    */

    package roseindia;

    import java.util.Iterator;
    import java.util.List;
    import javax.persistence.EntityManager;
    import javax.persistence.EntityManagerFactory;
    import javax.persistence.EntityTransaction;
    import javax.persistence.Persistence;
    import javax.persistence.Query;

    /**
    *
    * @author Administrator
    */
    public class JPARead {
    public static void main(String arg[]){
    EntityManagerFactory emf=Persistence.createEntityManagerFactory("netjpa");
    EntityManager em=emf.createEntityManager();
    try{
    EntityTransaction entr=em.getTransaction();
    entr.begin();
    Query query=em.createNamedQuery("readAllRecords");
    List stList=query.getResultList();
    Iterator stIterator=stList.iterator();
    while(stIterator.hasNext()){
    Student stu=(Student)stIterator.next();
    System.out.print("Name:"+stu.getSname());
    System.out.print(" Roll:"+stu.getSroll());
    System.out.print(" Course:"+stu.getScourse());
    System.out.println();
    }
    entr.commit();
    }
    catch(Exception e){
    System.out.println(e.getMessage());
    }
    finally{
    em.close();
    }

    }
    }

     

  4. Run it and get the following output:

                         

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