Static methods X Non-static methods for data access layer

The truth is that it depends on how "sophisticated" you are ...

In general I would say no , this is not good practice.

Using static methods in DAO , you can not modify its behavior (in cases of overloading, for example) ...

If you use 2 or more threads simultaneously, if one of the threads closes DAO before the others, which is very likely to happen, you will not get the result you expect, do you agree? Not to mention other cases like unit tests ... it's a lot more complicated ... then some disadvantages:

• Is not secure in a multi-threaded application.
• You can not inject dependencies into static classes.
• "Difficult" to implement unit tests ....

I recommend using the Singleton pattern for your DAO :

public class ClienteDAO { 
  private static final ClienteDAO SINGLETON = openInst(); 

  private static ClienteDAO openInst() { 
    // Iniciar o DAO
  } 

  public ClienteDAO getInstance() { 
    return SINGLETON; 
  } 
}