GWT RPC AsyncCallBack is always failing persistently.

I'm trying to retrieve data from database with GWT and RPC. 

public class MySQLConnection extends RemoteServiceServlet implements Connection{

private Connection conn = null;

private ResultSet rs = null;

    private PreparedStatement pstmt = null;

public static Connection getConnection() throws Exception {

   String driver = "com.mysql.jdbc.Driver";

   String url = "jdbc:mysql://localhost:3306/temperature";

   String username = "root";

   String password = "123456";

   Class.forName(driver);

   Connection conn = DriverManager.getConnection(url, username, password);

   return conn;

 }

public String[] sensor() throws Exception{

String [] user = null;

try {

     conn = getConnection();

     String query = "SELECT ID, times FROM sensor ORDER BY id DESC LIMIT 1;";

     pstmt = conn.prepareStatement(query); // create a statement

     pstmt.setInt(1, 1001); // set input parameter

     rs = pstmt.executeQuery();

     // extract data from the ResultSet

     while (rs.next()) {

       user = new String[] {rs.getString(1),rs.getString(2)};

     }

   } catch(SQLException e) {

     e.printStackTrace();

   } finally {

     try {

       rs.close();

       pstmt.close();

       conn.close();

     } catch (SQLException e) {

       e.printStackTrace();

     }

   }

   return user;

}

public String[] sensors() throws Exception{

return sensor();

}

This is the server side programming where I would return 2 parameters to the client side which will then be shown in the web application. However it is always unsuccessful as it is always onFailure that is occuring.

btnNewButton.addClickListener(new ClickListener() {

public void onClick(Widget event) {

ConnectionAsync Abra =(ConnectionAsync) GWT.create(Connection.class);

ServiceDefTarget target = (ServiceDefTarget) Abra;

String moduleRelativeURL = GWT.getModuleBaseURL() + "MySQLConnection";

target.setServiceEntryPoint(moduleRelativeURL);

AsyncCallback callback = new AsyncCallback(){

public void onSuccess (Object result){

textbox2.setText((String)result);

Hi.setText("You Pass!");

}

public void onFailure(Throwable caught) {

Hi.setText("You fail!");

}

};

Abra.sensors(callback);

}

});

This is my program on the client side.

Hope if anyone would help me with this

With Regards,

Zhen Liang

 

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