Get the data for UI

[S Roberts]

i try to populate dropdownlist on gwt ui with data from tables in oracle database, and i have created following interfaces such a DataService

@RemoteServiceRelativePath("getData")
public interface DataService extends RemoteService {
	
	String [] getGroupData();	

}

and

public interface DataServiceAsync {
	

	void getChartGroupData(AsyncCallback<String[]> callback);


}

and within DataServiceImpl class i implement this method for getting an array of data from db table:

public class DataServiceImpl extends RemoteServiceServlet implements
		GetDataService {
	

	@Override
	public String[] getChartGroupData() {

		

		// load application settings from file
		String config = "loader.properties";
		Properties settings = new Properties();
		InputStream configFile = DataServiceImpl.class.getClassLoader()
				.getResourceAsStream(config);
		if (configFile != null) {
			try {
				settings.load(configFile);
			} catch (IOException e) {
				e.printStackTrace();
			
				System.exit(1);
			}
		}

		// connect to db
		DB connector = new DB();
		Connection connection = null;
		try {
			connection = connector.connect(
					settings.getProperty("db.type"),
					settings.getProperty("db.connectURL"),
					settings.getProperty("db.user"),
					settings.getProperty("db.password"));
		} catch (ClassNotFoundException e) {
			
			e.printStackTrace();
			System.exit(1);
		} catch (SQLException e) {
			
			e.printStackTrace();
			System.exit(1);
		}
	

		String name = null;
		String[] nameArray = new String[] { name };
		String query = "SELECT g.group_name " + "FROM "
				+ Meta.GROUP_TABLE + " g ";
		PreparedStatement stmt = null;
		ResultSet rs = null;

		try {

			stmt = connection.prepareStatement(query);

			rs = stmt.executeQuery();
			while (rs.next()) {
				Group group = new Group();

				group.setName(rs.getString("GROUP_NAME"));
				name = group.toString();

			}
		} catch (SQLException e) {

			e.printStackTrace();
		} finally {
			try {
				rs.close();
				stmt.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}

		return nameArray;

	}

in my gwt.xml file i wrote:

<servlet class="com.db.server.DataServiceImpl" path="/DataServiceImpl"/>

and in the web.xml

<servlet>
    <servlet-name>DataServiceImpl</servlet-name>
    <servlet-class>com.db.server.DataServiceImpl</servlet-class>
  </servlet>
  
  <servlet-mapping>
    <servlet-name>DataServiceImpl</servlet-name>
    <url-pattern>/app/DataServiceImpl</url-pattern>
  </servlet-mapping>

and then i write on the client side the asynccallback, to get all data from table in db in an array and then fill with it an dropdownlist on ui:

public class Application implements EntryPoint {

	private DataServiceAsync rpc;
	private ArrayList<String> list= new ArrayList<String>();
	public void onModuleLoad() {
		UI ui = new UI();
		RootLayoutPanel.get().add(ui);
	
	
		rpc = (DataServiceAsync) GWT.create(DataService.class);
		ServiceDefTarget target = (ServiceDefTarget) rpc;
		target.setServiceEntryPoint(com.google.gwt.core.client.GWT
				.getModuleBaseURL() + "getData");
		
		
		
		  AsyncCallback<String[]> callback = new AsyncCallback<String[]>() {
			public void onFailure(Throwable caught) {
				GWT.log("RPC error", caught);
			}

		
			@Override
			public void onSuccess(String[] result) {
		  
		
				for(int i=0;i<result.length;i++)
				{
					
					UI.listBoxGroups.addItem(result[i]);
					
				}
				GWT.log("RPC success", null);
			
			}

		};
		rpc.getGroupData(callback);
		

	}
	}

the data doesn't seem to be loaded, i can't get anything on my gwt gui on the dropdownlist. Any suggestions please, what i do wrong here?

[Vijitha Kumara]

In general this kind of issues best solved via narrowing down the issue at each layer, DB call, call to onSuccess() etc... Find out where you miss the data in first place, then you should be able to solve it easily.

[S Roberts]

thank you for answering, but i can't understand what did you ment