Hql query using dot´s in the response parameters

问题:

I am accesing to the database using a Dto with some entities and I want to improve the request without modifing my dto and removing the fetch so hibernate don´t return all the data from all the entities (hibernate is set to lazy), I tried with the next, but it´s not working:

    StringBuilder hql = new StringBuilder();
    hql.append(" select d.id as id, ce.cod as clasification.cod ");
    hql.append(" from Document d");
    hql.append(" join d.clasificacionEntity ce");

The working hql request:

    StringBuilder hql = new StringBuilder();
    hql.append(" select d");
    hql.append(" from Document d");
    hql.append(" join fetch  d.clasificacionEntity ce");

The problem is when I try to use "ce.cod as clasification.cod" the second dot gives me a error, there is other way to do that? , thanks a lot!!!

My dto result is:

  DocumentDto{
    private id
    private clasificacionEntityDto;
  }

  And 
 clasificacionEntityDto   {
     private cod
  }   

回答1:

When you write this code:

hql.append(" select d.id as id, ce.cod as clasification.cod ");

You tell on parser d.id named id and ce.cod named clasification.cod

The last alias is wrong! A correct name is clasification or cod.

If you want to point properties of ce.cod (cod which data type has?) you can point after extraction of your result.

回答2:

You don't mention how you are transforming the query result into your DTO entities. One simple solution that does not require you to alter your DTO classes.

// select only the fields you need from your query
StringBuilder hql = new StringBuilder();
hql.append(" select d.id as id, ce.cod as cod ");
hql.append(" from Document d");
hql.append(" join d.clasificacionEntity ce");

// ... etc. Then get back your results as raw type
List<Object[]> rows = crit.list();

Then loop through your results and create your DTOs manually. Note that this example assumes that your document has a single classification.

List<DocumentDTO> documents = new ArrayList<DocumentDTO>();
for ( Object[] row: rows ) {
    Long id = (Long)row[0];
    String cod = (String)row[1];
    ClassificationEntityDTO ce = new ClassificationEntityDTO(cod);
    DocumentDTO d = new DocumentDTO(id, ce);
    documents.add(d);
}

See this question

AliasToBeanResultTransformer(MyDTO.class) fails to instantiate MyDTO

回答3:

At the end I just create a dto like this:

DocumentDto{
     private id
     private String clasificacionEntityDtoCod;
  }

and set it like this:

   StringBuilder hql = new StringBuilder();
   hql.append(" select d.id as id, ce.cod as clasificacionEntityDtoCod ");
   hql.append(" from Document d");
   hql.append(" join d.clasificacionEntity ce");