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.
Create "JPARead" class file.
Put the following text in "JPARead.java" file.
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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(); } } }Run it and get the following output:
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