There were times when I had to use an Entity without a primary Key in the DB.
I was trying to get it work thru the Result Set Mapper functionality which was provided for Hibernate. I had faced some issues and here are my alternatives.
Step-1
Create a transformer which extends the org.hibernate.transform.ResultTransformer
Step-2
Look at the place where I catch the PropertyNotFoundException. There is a reason for the same
Step-3
There are 2 ways of implementing the ResultSet Transformer
Create the POJO which resembles the DB Table
Create an SQL Query as
sqlQuery.append(" SELECT column1 as col1, column2 as cl2 ");
sqlQuery.append(" FROM table tbl ");
col1 and col2 should be defined as variables (case sensitive)
private String col1;
private String col2;
in yur POJO with SETTER and GETTER methods.
If you are using Hibernate here is the way
If you are using JPA mode then there is n direct way to invoke ResultSetTransformer. So what I have dne is as follows
Thats all. Now instetad of those annoying Object[] which comes as RESULT SET, we will be able to get POJO objects just like resulr Hibernate / JPA modes.
Happy hunting.
I was trying to get it work thru the Result Set Mapper functionality which was provided for Hibernate. I had faced some issues and here are my alternatives.
Step-1
Create a transformer which extends the org.hibernate.transform.ResultTransformer
import java.lang.reflect.Field;
import java.util.List;
import org.hibernate.HibernateException;
import org.hibernate.PropertyNotFoundException;
import org.hibernate.property.ChainedPropertyAccessor;
import org.hibernate.property.PropertyAccessor;
import org.hibernate.property.PropertyAccessorFactory;
import org.hibernate.property.Setter;
import org.hibernate.transform.ResultTransformer;
public class AdvancedSearchResultTransformer implements ResultTransformer {
private final Class resultClass;
private final PropertyAccessor propertyAccessor;
private Setter[] setters;
private Field[] fields;
private static final long serialVersionUID = -3489302728091710568L;
public AdvancedSearchResultTransformer(Class resultClass) {
if ( resultClass == null ) {
throw new IllegalArgumentException( "resultClass cannot be null" );
}
this.resultClass = resultClass;
propertyAccessor = new ChainedPropertyAccessor(
new PropertyAccessor[] {
PropertyAccessorFactory.getPropertyAccessor( resultClass, null ),
PropertyAccessorFactory.getPropertyAccessor( "field" )
}
);
}
public Object transformTuple(Object[] tuple, String[] aliases) {
Object result;
try {
fields = resultClass.getDeclaredFields();
if ( setters == null ) {
setters = new Setter[aliases.length];
for ( int i = 0; i < aliases.length; i++ ) {
String alias = aliases[i];
if ( alias != null ) {
Setter setter;
try {
setter = propertyAccessor.getSetter(resultClass, alias);
} catch (PropertyNotFoundException e) {
for (Field field : this.fields) {
String fieldName = field.getName();
if (fieldName.equalsIgnoreCase(alias)) {
alias = fieldName;
break;
}
}
setter = propertyAccessor.getSetter(resultClass, alias);
}
setters[i] = setter;
}
}
}
result = resultClass.newInstance();
for ( int i = 0; i < aliases.length; i++ ) {
if ( setters[i] != null ) {
setters[i].set( result, tuple[i], null );
}
}
}
catch ( InstantiationException e ) {
throw new HibernateException( "Could not instantiate resultclass: " + resultClass.getName() );
}
catch ( IllegalAccessException e ) {
throw new HibernateException( "Could not instantiate resultclass: " + resultClass.getName() );
}
return result;
}
public List transformList(List collection) {
return collection;
}
public int hashCode() {
int result;
result = resultClass.hashCode();
result = 31 * result + propertyAccessor.hashCode();
return result;
}
}
Step-2
Look at the place where I catch the PropertyNotFoundException. There is a reason for the same
Step-3
There are 2 ways of implementing the ResultSet Transformer
Create the POJO which resembles the DB Table
Create an SQL Query as
sqlQuery.append(" SELECT column1 as col1, column2 as cl2 ");
sqlQuery.append(" FROM table tbl ");
col1 and col2 should be defined as variables (case sensitive)
private String col1;
private String col2;
in yur POJO with SETTER and GETTER methods.
If you are using Hibernate here is the way
public List executeReadAllSQLQuery(String queryString, Object[] values,
Object[] aliasInputs, Class transformerClass) throws ORMException {
SQLQuery sqlQuery = null;
try {
sessionObj = getHibSession();
sqlQuery = sessionObj.createSQLQuery(queryString);
sqlQuery.setResultTransformer(new AdvancedSearchResultTransformer(transformerClass));
if(aliasInputs != null){
for (int i = 0; i < aliasInputs.length; i++) {
sqlQuery.addScalar(aliasInputs[i].toString());
}
}
if (values != null) {
for (int i = 0; i < values.length; i++) {
sqlQuery.setParameter(i, values[i]);
}
}
return sqlQuery.list();
}
If you are using JPA mode then there is n direct way to invoke ResultSetTransformer. So what I have dne is as follows
Query sqlQuery = null;
try {
entityMgrObj = getHibJpaEntityManager();
sqlQuery = entityMgrObj.createNativeQuery(queryString);
sqlQuery.unwrap(SQLQuery.class).setResultTransformer(new AdvancedSearchResultTransformer(transformerClass));
if(aliasInputs != null){
for (int i = 0; i < aliasInputs.length; i++) {
sqlQuery.unwrap(SQLQuery.class).addScalar(aliasInputs[i].toString());
}
}
if (values != null) {
for (int i = 0; i < values.length; i++) {
sqlQuery.setParameter(i, values[i]);
}
}
return sqlQuery.getResultList();
}
Look at the place where I tweak JPA to forcibly use Hibernate ResultSet Mapper.Thats all. Now instetad of those annoying Object[] which comes as RESULT SET, we will be able to get POJO objects just like resulr Hibernate / JPA modes.
Happy hunting.
