Hibernate: How can I reuse an alias on the same criteria?

Question

I am trying to convert HQL queries to criteria and create aliases to perform join on a criteria as follows:

public List<Patient> getPatients(String ssn, String phone, String zipCode) { Criteria c = getCurrentSession().createCriteria(Patient.class); if(ssn != null) { c.add(Restrictions.eq("ssn", ssn)); } if(phone != null) { c.createAlias("contact", "contactAlias1") c.add(Restrictions.eq("contactAlias1.phone", phone)); } if(zipCode != null) { c.createAlias("contact", "contactAlias2") c.add(Restrictions.eq("contactAlias2.zipCode", zipCode)); } }

When I run this code I got the following error:

org.hibernate.QueryException: duplicate association path

Of course I can always add another if condition as follows and use single alias:

if(phone != null || zipCode != null) { c.createAlias("contact", "contactAlias") }

However, the actual code has thousands of lines like this. Using this approach would be tedious and make the code unreadable.

So I want to know if I can detect a previously created alias for the same mapping and reuse it for other restrictions.

Thierry · Accepted Answer · 2014-09-24 09:55:33Z

use a Set to store already defined aliases :

public List<Patient> getPatients(String ssn, String phone, String zipCode) { Set<String> definedAliases = new HashSet<String>(); Criteria c = getCurrentSession().createCriteria(Patient.class); if(ssn != null) { c.add(Restrictions.eq("ssn", ssn)); } if(phone != null) { if (!definedAliases.contains("contact")) { c.createAlias("contact", "contactAlias"); definedAliases.add("contact"); } c.add(Restrictions.eq("contactAlias.phone", phone)); } if(zipCode != null) { if (!definedAliases.contains("contact")) { c.createAlias("contact", "contactAlias"); definedAliases.add("contact"); } c.add(Restrictions.eq("contactAlias.zipCode", zipCode)); } }

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