Hibernate Example queries

Question

I will explain the problem with an example.
I have a Vehicle object which has a model name and a make. When the make is given, relevant vehicle should be listed. when both make and model is given,then suitable vehicles should be listed.

For example: There is an entity called 'Vehicle' .It has a proxy called makeModel whose Entity name is MakeModel . MakeModel has proxies which are 'make' and 'model' whose entity names are Model and Make.Both Entititiyes 'Model' and 'Make' have String variable 'name'.Here are classes

class Vehicle{
 private Integer vehicleId;  
 private MakeModel makeMOdel;
 //getters and setters  
}

class MakeModel {
 private Make make;
 private Model model;  
 //getters and setters  
}  

class Make{
 private Integer mid;
 private String make;
}  
class Model{  
 private Integer mdlid;
 private String modelName;
}

Here is how I tried to get vehicle list. Here, session is Hibernate Session.

Criteria cr= session.createCriteria(Vehicle.class);  

MakeModel mkmd=new MakeModel();  
if( /* if only the make is give */){  
 Make mk=new Make();  
 mk.setMake("Toyota");  
 mkmd.setMake(mk);
}  
else if(if both make and and model given){  
 Make mk=new Make();  
 mk.setMake("Toyota");  
 mkmd.setMake(mk);  
 Model md=new Model("Venus");  
 mkmd.setModel(md);
 }  

cr.createCriteria("makeModel").add(Example.create(mkmd));List l=cr.list();  

But this returns all vehicles. I want to get all vehicles using hibernate criteria not HQL.

A same question can be found here and referred this also. Any one let me know where is wrong and how to retrieve vehicle list according to given criteria.

Answer 1

Supposing that you are passing to your function makeValue and modelValue, which are the make and the model you want, you would have:

Criteria cr = session.createCriteria(Vehicle.class);  // Create the criteria on desired class
cr.createAlis("makeModel", "makeModel")
  .createAlias("makeModel.make", "make")
  .createAlias("makeModel.model", "model");  // Creating aliases makes a join on those tables 
if (makeValue != null){
    cr.add(Restrictions.eq("make.make", makeValue))  // If you have a makeValue passed, filter by it
}
if (makeModel != null){
    cr.add(Restrictions.eq("model.modelName", modelValue));  // If you have a makeModel passed, filter by it
}

return cr.list();    // Return the list

The result will be a List<Vehicle>. You can add a @SuppressWarnings("unchecked") to your method to avoid seeing unchecked cast warnings.