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: -

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

StudentEntity.java

package com.javahubpoint.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;  
    }  
      
}

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

Persistence.xml

<persistence>  
<persistence-unit name="Student_details">  
<class>com.javahubpoint.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>

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

FindStudent.java

package com.javahubpoint.jpa.find;  
  
import javax.persistence.*;
import com.javahubpoint.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: