Tech Blogs: February 2013

Before we start let me tell you this is not a best or even say a common practice in Hibernate but this approach is used when there is a sudden addition/change in requirements and you for unavoidable reasons do not want to add a new entity or change existing entities and you want to go ahead with your DTO/VO instead of Hibernate bean classes. One of the example is you are generating some report and client wants you to add few more fields that are not mapped to this entity bean so only option you have is to change your HQL to SQL and load this data in some DTO/VO and print it.

So let’s start with it. For the sack of brevity here we will use simple SQL query but you are free to use any complicated query with this approach. We have a table with following fields

· EMP_ID

· EMP_FIRST_NAME

· EMP_LAST_NAME

· EMP_DOB

· EMP_DOJ (Date of Joining)

· IS_ACTIVE (If employee is still part of organization)

So we have following data in our table.

Now we want to load data from this table to our VO class EmpUnmanagedVO which looks like Table 1

Table 1: VO Class

package com.study.hibernate.vo;

import java.util.Date;

public class EmpUnmanagedVO {

private String id;

private String name;

private String lastname;

private Date dob;

private Date doj;

private boolean isActive;

public String getId() {

return id;

}

public void setId(String id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getLastname() {

return lastname;

}

public void setLastname(String lastname) {

this.lastname = lastname;

}

public Date getDob() {

return dob;

}

public void setDob(Date dob) {

this.dob = dob;

}

public Date getDoj() {

return doj;

}

public void setDoj(Date doj) {

this.doj = doj;

}

public boolean isActive() {

return isActive;

}

public void setActive(boolean isActive) {

this.isActive = isActive;

}

public String toString() {

StringBuilder sbuild = new StringBuilder();

sbuild.append("Id:").append(id).append(", Name:").append(name).append(", Last Name:").append(lastname);

return sbuild.toString();

}

Now we will write our method to call a simple SQL query to get details from EMP_DETAILS table and load the data in this VO.

@SuppressWarnings("unchecked")

public List<EmpUnmanagedVO> getUnmanagedEmpDetails() throws DBException {

Session sess = null;

try

{

sess = HibernateUtil.getSession();

Query qry = sess.createSQLQuery("SELECT * FROM EMP_DETAILS");

qry.setResultTransformer(new ResultTransformer() {

public Object transformTuple(Object[] values, String[] colnames) {

EmpUnmanagedVO emp = new EmpUnmanagedVO();

emp.setId(String.valueOf(values[0]));

emp.setName(String.valueOf(values[1]));

emp.setLastname(String.valueOf(values[2]));

emp.setDob((Date)values[3]);

emp.setDoj((Date)values[4]);

emp.setActive("Y".equals(String.valueOf(values[5])));

return emp;

}

public List transformList(List arg0) {

return arg0;

}

});

return qry.list();

}

catch(HibernateException e)

{

throw new DBException("Error occured while loading unmanaged bean",e);

}

finally

{

HibernateUtil.closeSession(sess);

}

So when we call this method we will have following output.

Feb 28, 2013 7:22:52 AM org.hibernate.annotations.common.Version <clinit>

INFO: HCANN000001: Hibernate Commons Annotations {4.0.1.Final}

Feb 28, 2013 7:22:52 AM org.hibernate.Version logVersion

INFO: HHH000412: Hibernate Core {4.1.7.Final}

Feb 28, 2013 7:22:52 AM org.hibernate.cfg.Environment <clinit>

INFO: HHH000206: hibernate.properties not found

Feb 28, 2013 7:22:52 AM org.hibernate.cfg.Environment buildBytecodeProvider

INFO: HHH000021: Bytecode provider name : javassist

Feb 28, 2013 7:22:52 AM org.hibernate.cfg.Configuration configure

INFO: HHH000043: Configuring from resource: /hibernate.cfg.xml

Feb 28, 2013 7:22:52 AM org.hibernate.cfg.Configuration getConfigurationInputStream

INFO: HHH000040: Configuration resource: /hibernate.cfg.xml

Feb 28, 2013 7:22:52 AM org.hibernate.cfg.Configuration doConfigure

INFO: HHH000041: Configured SessionFactory: null