JPA Finding an Entity

by Online Tutorials Library July 14, 2022

Finding an entity

To find an entity, EntityManger interface provides find() method that searches an element on the basis of primary key.

JPA Entity Finding Example

Here, we will search a particular record and fetch it on the console.

This example contains the following steps: –

Create an entity class named as StudentEntity.java under com.tutoraspire.jpa.student package that contains attributes s_id, s_name, s_age.

StudentEntity.java

  package com.tutoraspire.jpa.student;  import javax.persistence.*;    @Entity  @Table(name=”student”)  public class StudentEntity {    @Id  private int s_id;  private String s_name;  private int s_age;    public StudentEntity(int s_id, String s_name, int s_age) {  super();  this.s_id = s_id;  this.s_name = s_name;  this.s_age = s_age;  }    public StudentEntity() {  super();  }    public int getS_id() {  return s_id;  }    public void setS_id(int s_id) {  this.s_id = s_id;  }    public String getS_name() {  return s_name;  }    public void setS_name(String s_name) {  this.s_name = s_name;  }    public int getS_age() {  return s_age;  }    public void setS_age(int s_age) {  this.s_age = s_age;  }    }  

Now, map the entity class and other databases confiuguration in Persistence.xml file.

Persistence.xml

  <persistence>  <persistence-unit name=”Student_details”>    <class>com.tutoraspire.jpa.student.StudentEntity</class>    <properties>  <property name=”javax.persistence.jdbc.driver” value=”com.mysql.jdbc.Driver”/>  <property name=”javax.persistence.jdbc.url” value=”jdbc:mysql://localhost:3306/studentdata”/>  <property name=”javax.persistence.jdbc.user” value=”root”/>  <property name=”javax.persistence.jdbc.password” value=””/>  <property name=”eclipselink.logging.level” value=”SEVERE”/>  <property name=”eclipselink.ddl-generation” value=”create-or-extend-tables”/>  </properties>    </persistence-unit>  </persistence>  

Create a persistence class named as FindStudent.java under com.tutoraspire.jpa.find package to persist the entity object with data.

FindStudent.java

  package com.tutoraspire.jpa.find;    import javax.persistence.*;    import com.tutoraspire.jpa.student.*;    public class FindStudent {  public static void main(String args[])  {  EntityManagerFactory emf=Persistence.createEntityManagerFactory(“Student_details”);  EntityManager em=emf.createEntityManager();        StudentEntity s=em.find(StudentEntity.class,101);    System.out.println(“Student id = “+s.getS_id());  System.out.println(“Student Name = “+s.getS_name());  System.out.println(“Student Age = “+s.getS_age());    }  }  

Output:

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