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JPA setMaxResults Example

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In this section, you will learn how to use the setMaxResults() method in your JPA application.

JPA setMaxResults Example

     

In this section, you will learn how to use the setMaxResults() method in your JPA application. The setMaxResults function is used to set a limit to restrict the number of objects returned from database.

setMaxResults(int maxResult): This method is used with query instance for setting the maximum number of results to be fetched from database. 

To test the setMaxResults with example follow the following steps:

  1. Database Table: student, create student table.
  2. Model Class: Student.java, develop the model class.
  3. Main Class: JPASetMaxResult.java, develop the program to run the application.

Database Table: student

CREATE TABLE `student` ( 
`id` int(11) NOT NULL auto_increment, 
`sname` varchar(100) NOT NULL, 
`sroll` int(11) NOT NULL, 
`scourse` varchar(10) NOT NULL, 
PRIMARY KEY (`id`) 
)

Then enter few records in student table.

Model Class: Student.java

Here is the code of the model class, which is mapped to student table in the database.

/**

*/
package roseindia;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;

/**
* @author Administrator
*
*/
@Entity
@Table(name="student")

public class Student {

@Id
@GeneratedValue
private int id;

/**
* @return the id
*/
public int getId() {
return id;
}

/**
* @param id the id to set
*/
public void setId(int id) {
this.id = id;
}

@Column(name="sname", length=100,nullable=false)
private String sname;

/**
* @return the sname
*/
public String getSname() {
return sname;
}

/**
* @param sname the sname to set
*/
public void setSname(String sname) {
this.sname = sname;
}

@Column(name="sroll",nullable=false)
private int sroll;

/**
* @return the sroll
*/
public int getSroll() {
return sroll;
}

/**
* @param sroll the sroll to set
*/
public void setSroll(int sroll) {
this.sroll = sroll;
}

@Column(name="scourse",length=10,nullable=false)
private String scourse;

/**
* @return the scourse
*/
public String getScourse() {
return scourse;
}

/**
* @param scourse the scourse to set
*/
public void setScourse(String scourse) {
this.scourse = scourse;
}

}

Main Class: JPASetMaxResult.java

/**

*/
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 JPASetMaxResult {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub

EntityManagerFactory emf=Persistence.createEntityManagerFactory("jpa");
EntityManager em=emf.createEntityManager();
try{
EntityTransaction entr=em.getTransaction();
entr.begin();
Query query=em.createQuery("SELECT st FROM Student st WHERE st.sroll > ?1");
query.setParameter(1, 100);
query.setMaxResults(3);
List stuList=query.getResultList();
Iterator stuIterator=stuList.iterator();
while(stuIterator.hasNext()){
Student st=(Student)stuIterator.next();
System.out.print("sname:"+st.getSname());
System.out.print(" sroll:"+st.getSname());
System.out.print(" scourse:"+st.getSname());
System.out.println();
}
entr.commit();
}
finally{
em.close();
}
}

}

You can run the example from eclipse ide.

Output:

log4j:WARN No appenders could be found for logger (org.hibernate.cfg.annotations.Version).

log4j:WARN Please initialize the log4j system properly.

Hibernate: select student0_.id as id0_, student0_.scourse as scourse0_, student0_.sname as sname0_, student0_.sroll as sroll0_ from student student0_ where student0_.sroll>? limit ?

sname:Vinod sroll:Vinod scourse:Vinod

sname:Ravi sroll:Ravi scourse:Ravi

sname:Suman sroll:Suman scourse:Suman

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Posted on: June 17, 2009

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