how can i concatenate two properties into one property using hibernate criteria query

Question

for example there are 2 properties house number and pincode and i want a single property as address like house number is 10 and pincode is 110064 and combine address property is 10,110064 this is my code

  final Criteria criteria= getDatabaseSession().createCriteria(Application.class, "application");
 final ProjectionList projectionList=Projections.projectionList();
 criteria.setProjection(projectionList);

projectionList.add(Projections.property("address.street"), "street");
 projectionList.add(Projections.property("address.postcode"), "postcode");
 projectionList.add(Projections.property("address.houseNumber"), "houseNumber");

 criteria.createAlias("application.applicationCase", "applicationCase", JoinType.INNER_JOIN);
 criteria.createAlias("applicationCase.property", "property");
 criteria.createAlias("property.address", "address");
 criteria.setResultTransformer(Criteria.ALIAS_TO_ENTITY_MAP);
 return (Map<String, Object>) criteria.uniqueResult(); 

and i want to do something like this

   projectionList.add(Projections.property("address.street"+"address.houseNumber"+"address.postcode"),"address");

can somebody help.

Answer 1

Using HQL

You can use the concat expression, but it can be used only with HQL

select concat(address.street, address.houseNumber, address.postcode) as fullAddress from ...

Using @Formula

If you want to use Criteria, you can use @Formula. It is need to add additional property to the persistent

@Formula(value = "concat(f_street, f_houseNumber, f_postcode)")
private String fullAddress;

You need to specify column names (not property names), because of Hibernate adds them to the SQL as is. It is not very convenient when you use joins — you need to specify aliases, generated by Hibernate, in the formula.

You can refer to the fullAddress in the Projection

projectionList.add(Projections.property("fullAddress"), "fullAddress");

I have tested it with MySQl. For Oracle you can try to use

@Formula(value = "f_street || f_houseNumber || f_postcode")
private String fullAddress;

Extending Hibernate

I have tried to extend the Projection to add concat function to the Criteria. I test it for the simplest case.

public class ConcatProjection extends SimpleProjection {

    private static final String CONCAT_FUNCTION_NAME = "concat";

    private final String[] properties;

    public ConcatProjection(String... properties) {
        this.properties = properties;
    }

    @Override
    public String toSqlString(Criteria criteria, int loc, CriteriaQuery criteriaQuery)
            throws HibernateException {
        String result = getFunction(criteriaQuery).render(StringType.INSTANCE,
                propertiesToColumns(criteria, criteriaQuery), criteriaQuery.getFactory());
        return result + " as y" + loc + '_';
    }

    private List<String> propertiesToColumns(Criteria criteria, CriteriaQuery criteriaQuery) {
        List<String> result = new ArrayList<String>(properties.length);

        for (String property : properties) {
            result.add(criteriaQuery.getColumn(criteria, property));
        }

        return result;
    }

    private SQLFunction getFunction(CriteriaQuery criteriaQuery) {
        return criteriaQuery.getFactory().getSqlFunctionRegistry()
                .findSQLFunction(CONCAT_FUNCTION_NAME);
    }

    @Override
    public Type[] getTypes(Criteria criteria, CriteriaQuery criteriaQuery)
            throws HibernateException {
        return new Type[] { StringType.INSTANCE };
    }

}

Using

projectionList.add(
    new ConcatProjection("address.street", 
        "address.houseNumber",  "address.postcode"), "fullAddress");