Help me for Joinin two tables.

[Gokul Kesavalu]

Hi everybody,


I am a newbie to Hibernate. I have two tables Application and ApplicationUser.

Application - fields(id(primary key),application-name,description,application_url,app_id)

ApplicationUser - fields(id(primary key),user_id,app_id,date_of_request, application_name,status)


I created a method as follows to retrieve data.

                  public static List loadApplications(int user_id) {

		Session session = HibernateUtil.getSessionFactory().openSession();
		Transaction transaction = null;
		Application application = null;
		List apps = null;
		int id = 12;
		try {
			transaction = session.beginTransaction();
			String hql = "select application.application_name,application.app_id,application.application_url from Application as application,ApplicationUser applicationuser where application.id=applicationuser.app_id and applicationuser.status=1 and applicationuser.user_id ="
					+ user_id;
			Query query = session.createQuery(hql);
			apps = query.list();

			for (Iterator iterator = apps.iterator(); iterator.hasNext();) {
				application = (Application) iterator.next();
				System.out.println("App ID is : " + application.getApp_id());
				System.out.println("Application Name is : "
						+ application.getApplication_name());
				System.out.println("Application URL is : "
						+ application.getApplication_url());
			}
			transaction.commit();

		} catch (HibernateException he) {
			// TODO: handle exception
			transaction.rollback();
			he.printStackTrace();
		} finally {
			session.close();
		}
		return apps;
	}

My POJO classes are as follows,


Application.java

package com.action;

import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;

import org.hibernate.annotations.Fetch;

@Entity
@Table(name = "application")
public class Application {
	
	private int id;
	private String application_name;
	private String description;
	private String application_url;
	private String app_id;
	
	@Id
	@GeneratedValue
	@Column(name = "id")
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	
	@Column(name = "application_name", nullable = false)
	public String getApplication_name() {
		return application_name;
	}
	public void setApplication_name(String applicationName) {
		application_name = applicationName;
	}
	
	@Column(name = "description", nullable = false)
	public String getDescription() {
		return description;
	}
	public void setDescription(String description) {
		this.description = description;
	}
	
	@Column(name = "application_url", nullable = false)
	public String getApplication_url() {
		return application_url;
	}
	public void setApplication_url(String applicationUrl) {
		application_url = applicationUrl;
	}
	
	@Column(name = "app_id", nullable = false)
	public String getApp_id() {
		return app_id;
	}
	public void setApp_id(String appId) {
		app_id = appId;
	}
}

ApplicationUser.java

package com.action;

import java.sql.Date;

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

@Entity
@Table(name = "applicationuser")
public class ApplicationUser {
	
	private long id;
	private long user_id;
	private long app_id;
	private Date date_of_request;		
	private String application_name;
	private int status;	

	@Id
	@GeneratedValue
	@Column(name = "id")
	public long getId() {
		return id;
	}
	public void setId(long id) {
		this.id = id;
	}
	
	
	@Column(name = "user_id", nullable = false)
	public long getUser_id() {
		return user_id;
	}
	public void setUser_id(long userId) {
		user_id = userId;
	}
	
	
	@Column(name = "app_id", nullable = false)
	public long getApp_id() {
		return app_id;
	}
	public void setApp_id(long appId) {
		app_id = appId;
	}
	
	
	@Column(name = "date_of_request", nullable = false)
	public Date getDate_of_request() {
		return date_of_request;
	}
	public void setDate_of_request(Date dateOfRequest) {
		date_of_request = dateOfRequest;
	}
	
	
	@Column(name = "application_name", nullable = false)
	public String getApplication_name() {
		return application_name;
	}
	public void setApplication_name(String applicationName) {
		application_name = applicationName;
	}
	
	
	@Column(name = "status", nullable = false)
	public int getStatus() {
		return status;
	}
	public void setStatus(int status) {
		this.status = status;
	}
}

But it shows me the following error.
java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.action.Application

But my query works fine in query browser. please help me to fix it out..

[Vicky Vijay]

Hi Gokul,

QUERY:
select application.application_name,application.app_id,application.application_url from Application as application,ApplicationUser applicationuser


Here you are using two tables,

1.Application
2.ApplicationUser

I hope, Retrieving the data using SELECT a.field1, a.field2..........

would return as Object[]

[Gokul Kesavalu]

Hi Guru, Thanks for the reply. Yes it return as Object. I have a pojo class for Application. How to set this in that Pojo so that i can retrieve from that. or any other modifications need to be done in query...

[Vicky Vijay]

Hello Gokul,

Refer the below link,

Iterate the Object[]

Hope, This helps you !!