The new Gazetteer client offers the possibility to add new protocols. The idea is that anyone can add him own driver to manage its own protocol. 

To add a new gazetteer protocol the first step is to create a new driver that just is a class that has to inherit of the *IGazetteerServiceDriver* interface. This interface forces to implement the common methods that all the Gazetteer drivers have to had. There is also an abstract class named *AbstractGazetteerServiceDriver* than implements this interface and it has a default implementation for some of the driver methods (but the using of this class is not necessary). Next figure shows the hierarchy:

.. figure:: ./catalog-and-gazetteer.img/gazetteerDrivers.png
   :scale: 50
   :alt: TEXTO
   :align: center


Methods to implement
--------------------


The unique methods that are not implemented in AbstractGazetteerServiceDriver and they have to be implemented on every driver are:

.. code-block:: java

  GazetteerCapabilities getCapabilities(URI uri) throws Exception;

It sends a message to the server and tries to discover the server capabilities that will be used to create the queries.The driver has to discover if the server is ready an has to return a *GazetteerCapabilities* object.

*GazetteerCapabilities* is a class that has some methods that the user interface uses: the **isAvailable()** method is  used to know if the server is ready (it return true by deafult). The **getVersion()** method indicates the protocol version that has the server and the **getServerMessage()** is used to show a message that is written on the user interface.   

.. code-block:: java

  public Feature[] getFeature(URI uri, Query query) throws Exception;

This method sends a request to the server to search a geographic name. It has to return an array of *Feature*'s that is an object that contains a name and a position. The SRS actually is specified by the service (not for every feature).

*Query* is an object that contains the information to make the query (the searched name, the thesaurus selection, the selected area...). This query has been filled with the fields that the user has selected in the user interface.

.. code-block:: java

  public String getServiceName();

It has to return the service name that will be showed in the user interface to select this driver.


Driver register
---------------
To use a new driver, it has to be registered on the application using the *GazetteerDriverRegister* class. It implements the *Singleton* pattern: it has an static method to retrieve a register instance and this instance has a method to register the driver. Next fragment code can be used to register the *ExampleNewDriver*:

.. code-block:: java

  GazetteerDriverRegister register = GazetteerDriverRegister.getInstance();
  register.register(new ExampleNewDriver());



Adding a new field to make a search
-----------------------------------

The first step is to create a new *JPanel* that has to inherit from *SearchAditionalPropertiesPanel*. This class is a normal JPanel that has a method **getProperties()** that returns a *Properties* object. The created panel has to create a new *Properties* object and fill it with a set of key-value pairs where the key value will be used to retrieve the value that will be used to create the query.

This *Properties* object is retrieved from the panel and is added to the *Query* object that is a parameter in the **getFeature()** method. The driver can get it and used it to make its own requests. 

Next step is to implement the next method in the driver: 

.. code-block:: java

  public SearchAditionalPropertiesPanel getAditionalSearchPanel()

This method creates a *SearchAditionalPropertiesPanel* and return it. Every time that the driver that implements this method is selected on the connection window, this panel will be showed on the search window. 


Creating a thesaurus tree (searches by cathegory)
-------------------------------------------------

In the user interface there is a *JTree* that is used to make searches by cathegory. To fill this tree with a set of values it is necessary to fill the *GazetteerCapabilities* object returned in the **getCapabilities** method with a list of *FeatureType* Objects using the **setFeatureTypes()** method. A *FeatureType* object has basically a name, a description and a list of *FeatureType* objects that will be showed like children in the *JTree*.