I use TomCat 8.0 server, h2 database and IntelliJ IDEA 14 for my WebApplication, but when I run app(button event) I receive
java.lang.NullPointerException image. I have successful connection to Database like this(it's already tested):
public class DbConnection {
private static final String DRIVER = "org.h2.Driver";
private static final String URL = "jdbc:h2:tcp://localhost/~/Students";
private static final String USER_NAME = "doncho";
private static final String PASS = "";
private static DbConnection instance;
private static Connection conn;
private DbConnection(){
}
public static DbConnection getInstance(){
if(instance == null){
instance = new DbConnection();
}
return instance;
}
public Connection getConnect() throws SQLException{
Connect();
return conn;
}
private void Connect() throws SQLException {
if (conn == null) {
try {
Class.forName(DRIVER);
} catch (ClassNotFoundException e) {
System.out.println("Driver isn't found");
e.printStackTrace();
}
DriverManager.getConnection(URL, USER_NAME, PASS);
}
}
public void Disconnect() throws SQLException{
if(conn != null){
conn.close();
conn=null;
}
}
I have create class RegisterDao which must insert data into table with name "Name" and just one column - "name"
public class RegisterDAO {
Connection conn = null;
PreparedStatement state = null;
public StudentBean registerStudent(String userName) throws SQLException{
StudentBean result = null;
String sql = "INSERT INTO Name VALUES(?)";
try {
conn = DbConnection.getInstance().getConnect();
state = conn.prepareStatement(sql);
state.setString(1, userName);
state.execute();
} catch (SQLException e) {
e.printStackTrace();
}finally {
if(state != null){
state.close();
}
}
DbConnection.getInstance().Disconnect();
return result;
}}
And this is my class (java bean) StudentBean
@javax.ejb.Stateless(name = "StudentEJB")
public class StudentBean {
private String name;
public StudentBean() {
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}}
I use thеsе classes to insert data in table "Name" through servlet - RegisterServlet
public class RegisterServlet extends HttpServlet {
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try {
Connection conn = DbConnection.getInstance().getConnect();
System.out.println("It Works");
} catch (SQLException e) {
e.printStackTrace();
}
String username = request.getParameter("usernameReg");
StudentBean student;
try {
student = new RegisterDAO().registerStudent(username);
request.getServletContext().getRequestDispatcher("/index.jsp").forward(request, response);
} catch (SQLException e) {
e.printStackTrace();
}
try {
DbConnection.getInstance().Disconnect();
} catch (SQLException e) {
e.printStackTrace();
}
}}
But I get the upper error. I am confused because I tested source in Eclipse and there it works, but in IntelliJ it doesn't. I'm new in IntelliJ so I hope that some with more experience will give me an idea to resolve the problem.
P.S. System.out.println("It Works"); from servlet works and I guarantee that I call servlet into "index.jsp" correct.
Sorry for this long post and best regards, D.Balamjiev.
