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:

Database Table: student, create student table.
Model Class: Student.java, develop the model class.
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